SRS Labs PTC10 User Manual

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Version 4.2 (May 14, 2019)

User Manual

PTC10

Programmable Temperature Controller

PTC10 Programmable Temperature Controller

Certification

Stanford Research Systems certifies that this product met its published specifications at the time of shipment.

Warranty

This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of one (1) year from the date of shipment.

Service

For warranty service or repair, this product must be returned to a Stanford Research Systems authorized service facility. Contact Stanford Research Systems or an authorized representative before returning this product for repair.

1290-C Reamwood Avenue Sunnyvale, California 94089 Phone: (408) 744-9040 Fax: (408) 744-9049

www.thinkSRS.com

Printed in the USA

Contents i

PTC10 Programmable Temperature Controller

Contents

Safety and preparation for use....................................................................................... v

Specifications .................................................................................................................. vii

Introduction 1

I/O cards ............................................................................................................................ 2

PTC320 thermistor/diode/RTD card .................................................................................... 2

PTC321 RTD reader ................................................................................................................ 5

PTC323 2-channel thermistor/diode/RTD card ................................................................... 6

PTC330 thermocouple reader .............................................................................................. 11

PTC420 AC output card........................................................................................................ 13

PTC430 50 W DC output card ............................................................................................. 14

PTC431 100W DC output card ............................................................................................ 15

PTC440 TEC driver ............................................................................................................... 17

PTC510 analog I/O card ....................................................................................................... 20

PTC520 digital I/O card ........................................................................................................ 20

Operation 23

Quick start tutorial ........................................................................................................ 24

Turn the instrument on .......................................................................................................... 24

The Select screen ................................................................................................................... 24

Configure the sensor inputs ................................................................................................... 24

If the sensor reading does not appear ................................................................................... 25

Plot data .................................................................................................................................. 25

Test the outputs ..................................................................................................................... 26

Set the data logging rate ......................................................................................................... 27

Save data to and retrieve data from a USB memory device ................................................ 27

Interface with a computer ...................................................................................................... 28

Control a temperature........................................................................................................... 29

Acquiring and logging data ........................................................................................... 36

Input filters .............................................................................................................................. 36

Custom calibration tables ...................................................................................................... 36

Virtual channels ...................................................................................................................... 38

Logging data to internal memory ........................................................................................... 39

Logging data to USB ............................................................................................................... 39

ADC sampling and logged data ............................................................................................. 39

Format of PTC10 log files ...................................................................................................... 40

Using the system fan ..................................................................................................... 41

Using PID feedback ........................................................................................................ 42

...................................................................... 42

Basic PID feedback concepts ................................................................................................. 42

Manual tuning .......................................................................................................................... 43

Automatic tuning algorithms .................................................................................................. 46

Using the automatic tuner...................................................................................................... 49

Front-panel controls ................................................................................................ ...... 52

Contents ii

PTC10 Programmable Temperature Controller

USB logging indicator ............................................................................................................. 52

.............................................................................................................................. 52

.............................................................................................................. 52

....................................................................................................................... 53

.................................................................................................................. 54

........................................................................................................................... 54

................................................................................................................... 59

................................................................................................................... 64

..................................................................................................................... 78

Firm ware updates .......................................................................................................... 85

Replacing the clock battery .......................................................................................... 86

Remote programm ing 87

Connecting to the PTC10 ...................................................................................................... 87

Communication, assembly, and run-time errors .................................................................. 90

Concurrent macros ................................................................................................................ 90

Macro names .......................................................................................................................... 91

Command syntax ................................................................................................................... 91

Rem ote instructions ...................................................................................................... 95

General instructions ............................................................................................................... 95

IEEE 488.2 Instructions ........................................................................................................... 99

Program submenu ................................................................................................................ 103

System submenu ................................................................................................................... 106

<channel> submenu ............................................................................................................ 110

Error codes ........................................................................................................................... 121

Startup macro ....................................................................................................................... 122

Sam ple m acros ............................................................................................................. 123

Temperature profiles ........................................................................................................... 123

Control a feedback setpoint with an analog input .............................................................. 124

PID input scheduling ............................................................................................................. 124

Show channels with tripped alarms on the Numeric screen ............................................. 125

Make a virtual channel show the PID setpoint ................................................................ .... 125

Linearizing outputs when interfacing with external power supplies .................................. 125

Control instrument functions with the digital IO lines ....................................................... 126

Drive a solid state relay with the digital IO lines ................................................................. 127

PC applications 129

PTCFileConverter ....................................................................................................... 130

FileGrapher ................................................................................................................... 132

File menu ................................ ............................................................................................... 132

Edit menu .............................................................................................................................. 132

Process menu ....................................................................................................................... 134

Special menu ......................................................................................................................... 136

Command line and macro instructions ............................................................................... 137

Circuit description 141

Core system cards ....................................................................................................... 142

PTC212 CPU board ............................................................................................................. 142

PTC221 backplane ............................................................................................................... 142

Contents iii

PTC10 Programmable Temperature Controller

PTC231 front panel .............................................................................................................. 144

PTC240 GPIB card ............................................................................................................... 145

I/O cards ........................................................................................................................ 146

PTC320 1-channel thermistor/diode/RTD reader ........................................................... 146

PTC321 4-channel RTD reader ........................................................................................... 147

PTC330 thermocouple reader ............................................................................................ 148

PTC420 AC output card...................................................................................................... 149

PTC430 50W DC output card ............................................................................................ 149

PTC431 100W DC output card .......................................................................................... 150

PTC440 TEC driver ............................................................................................................. 151

PTC510 analog I/O card ..................................................................................................... 152

PTC520 digital I/O card ...................................................................................................... 153

Parts List 155

PTC212 CPU board ............................................................................................................. 155

PTC221 backplane ............................................................................................................... 165

PTC231 front panel .............................................................................................................. 167

PTC240 GPIB option ........................................................................................................... 169

PTC320 1-channel thermistor, diode, and RTD reader .................................................... 170

PTC321 4-channel RTD reader ........................................................................................... 173

PTC330 thermocouple reader ............................................................................................ 176

PTC420 AC output card...................................................................................................... 180

PTC430 50W DC output card ............................................................................................ 182

PTC440 TEC driver ............................................................................................................. 184

PTC510 analog I/O card ..................................................................................................... 187

PTC520 digital I/O card ...................................................................................................... 189

Schematics 193

Safety and Preparation for Use v

PTC10 Programmable Temperature Controller

Line voltage

The PTC10 operates from an 88 to 264 VAC power source having a line frequency between 47

and 63 Hz.

Power entry module

A power entry module, labeled AC POWER on the back panel of the PTC10, provides

connection to the power source and to a protective ground.

Power cord

The PTC10 package includes a detachable, three-wire power cord for connection to the power

source and protective ground.

The exposed metal parts of the box are connected to the power ground to protect against electrical shock. Always use an outlet which has a properly connected protective ground. Consult with an electrician if necessary.

Grounding

A chassis grounding lug is available on the back panel of the PTC10. Connect a heavy duty ground wire, #12AWG or larger, from the chassis ground lug directly to a facility earth ground to provide additional protection against electrical shock.

Line fuse

Use a 10 A/250 V 3AB Slo-Blo fuse.

Operate only with covers in place

To avoid personal injury, do not remove the product covers or panels. Do not operate the product without all covers and panels in place.

Serviceable parts

The PTC10 does not include any user serviceable parts inside. Refer service to a qualified technician.

Specifications vii

PTC10 Programmable Temperature Controller

PTC10 temperature controller

Maximum PID rate 50 or 60 Hz, depending on AC line frequency Data logging rate 10 samples/second/channel 1 sample/hour/channel (can be set

independently for each channel or globally for all channels) Display resolution 0.001 °C, °F, K, V, A, W, etc. if 1000 < displayed value < 1000; 6 significant figures otherwise PID feedback auto-tuning Single step response or relay tuning with conservative, moderate, and

aggressive response targets Display 320 × 240 pixel touchscreen; numeric and graphical data displays. Alarms Upper and lower temperaturelimits or rate-of-change limits can be set on each

channel. If exceeded, an audio alarm and a relay closure occur. Computer interface USB, Ethernet, and RS-232; optional GPIB (IEEE488.2) Power 10 A, 88 to 132 VAC or 176 to 264 VAC, 47 to 63 Hz or DC Dimensions 17"× 5" × 18" (WHL) Weight 25 lbs. Warranty One year parts and labor on defects in material and workmanship.

PTC320 thermistor, diode, and RTD reader

Inputs One input for 2-wire or 4-wire thermistor, diode, or RTD Connector 6-pin 240° push-pull DIN socket

Thermistors Range 0 30, 100, 300 ; 1, 3, 10, 30, 100, 300 k ; 2.5 M Excitation current 30 range 200 µA 100 range 100 µA 300 range 50 µA 1 k range 30 µA 3 k range 20 µA 10 k range 10 µA 30 k range 5 µA 100 k range 3 µA 300 k range 2 µA

2.5 M range 1 µA Initial accuracy 30 range ±0.025 100 range ±0.06 300 range ±0.1 1 k range ±0.2 3 k range ±0.6 10 k range ±1.3 30 k range ±4 100 k range ±10 300 k range ±250

2.5 M range ±30 k Drift due to temperature 30 range ±0.002 /°C 100 range ±0.006 /°C 300 range ±0.006 /°C 1 k range ±0.01 /°C

Specifications viii

PTC10 Programmable Temperature Controller

3 k range ±0.03 /°C 10 k range ±0.1 /°C 30 k range ±0.15 /°C 100 k range ±0.5 /°C 300 k range ±3 /°C

2.5 M range ±2000 /°C RMS noise 30 range 0.003 100 range 0.006 300 range 0.012 1 k range 0.02 (= 2 mK for 300 thermistor at 25°C) 3 k range 0.03 (= 0.8 mK for 1 k thermistor at 25°C) 10 k range 0.06 (= 0.6 mK for 2252 thermistor at 25°C) 30 k range 0.1 (= 0.3 mK for 10 k thermistor at 25°C) 100 k range 0.3 (= 0.2 mK for 30 k thermistor at 25°C) 300 k range 3 (= 0.7 mK for 100 k thermistor at 25°C)

2.5 M range 25 (= 1.8 mK for 300 k thermistor at 25°C) Diodes

Excitation current output 10 µA Initial accuracy ± 100 ppm Drift ±5 ppm/°C Voltage input 0 2.5 V Initial accuracy 10 µV + 0.01% of reading Drift ±5 ppm/°C RMS noise 1.5 µV

RTDs Range 0 30, 100, 300 ; 1, 3, 10, 30, 100, 250 k , 2.5 M Excitation 30 range 3 mA 100 range 2 mA 300 range 1 mA 1 k range 500 µA 3 k range 200 µA 10 k range 100 µA 30 k range 50 µA 100 k range 10 µA 300 k range 5 µA

2.5 M range 1 µA Initial accuracy 30 range ±0.004 100 range ±0.008 300 range ±0.02 (=±50 mK for Pt100 RTD at 25°C) 1 k range ±0.04 3 k range ±0.1 10 k range ±0.2 30 k range ±1 100 k range ±2.5 300 k range ±16

2.5 M range ±30 k Drift due to temperature 30 range ±0.0006 /°C 100 range ±0.001 /°C 300 range ±0.0015 /°C (=±5 mK/°C for Pt100 RTD at 25°C) 1 k range ±0.005 /°C 3 k range ±0.01 /°C 10 k range ±0.03 /°C

Specifications ix

PTC10 Programmable Temperature Controller

30 k range ±0.06 /°C 100 k range ±0.2 /°C 300 k range ±3 /°C

2.5 M range ±2000 /°C RMS noise 30 range 0.00012 100 range 0.0003 300 range 0.0006 ( = 1.4 mK for Pt100 RTD at 25°C) 1 k range 0.0013 3 k range 0.003 10 k range 0.006 30 k range 0.012 100 k range 0.07 300 k range 0.25

2.5 M range 25

PTC321 Pt RTD reader

Inputs Four 4-wire inputs for 100 Pt RTDs Connector 5-pin, 3.5mm header Range 0 400 IEC751 Pt100 RTDs 215 °C to 850 °C Excitation current 1 mA Initial accuracy ±30 mK Drift due to temperature 1.4 mK/°C Drift due to time ±15 mK/year (at 25°C ambient temperature) Noise 2 mK RMS (at 25°C sensor temperature and 10 samples/s) Signal detection Card detects open and short circuit conditions

PTC323 thermistor, diode, and RTD reader

Inputs Two inputs for 4-wire thermistor, diode, or RTD Connectors One 9-pin D-sub socket

RTDs and thermistors Range 0 10, 30, 100, 300 ; 1, 3, 10, 30, 100, 300 k ; 2.5 M , or auto Excitation current Low power High power 10 range 1 mA 3 mA 30 range 300 µA 3 mA 100 range 100 µA 2 mA 300 range 30 µA 1 mA 1 k range 10 µA 500 µA 3 k range 3 µA 200 µA 10 k range 1 µA 50 µA 30 k range 300 nA 50 µA 100 k range 100 nA 5 µA 300 k range 30 nA 5 µA

2.5 M range 1 µA 1 µA Initial accuracy (AC current, at midrange) 10 range ±0.007 ±0.005 30 range ±0.03 ±0.005 100 range ±0.07 ±0.008 300 range ±0.25 ±0.015 (=±40 mK for Pt100 RTD at 25°C) 1 k range ±0.6 ±0.05 3 k range ±2 ±0.1

Specifications x

PTC10 Programmable Temperature Controller

10 k range ±6 ±0.25 30 k range ±25 ±1 100 k range ±150 ±4 300 k range ±1 k ±13

2.5 M range ±3 k ±3 k Typical drift due to temperature (at midrange) 10 range ±0.0002 /°C ±0.0001 /°C 30 range ±0.0004 /°C ±0.0001 /°C 100 range ±0.002 /°C ±0.0002 /°C 300 range ±0.004 /°C ±0.0004 /°C 1 k range ±0.01 /°C ±0.001 /°C 3 k range ±0.06 /°C ±0.003 /°C 10 k range ±0.2 /°C ±0.01 /°C 30 k range ±1 /°C ±0.02 /°C 100 k range ±3 /°C ±1 /°C 300 k range ±20 /°C ±2 /°C

2.5 M range ±30 /°C ±50 /°C RMS noise (DC current, at midrange) 10 range 0.0003 0.0001 30 range 0.001 0.0001 100 range 0.002 0.0002 300 range 0.006 0.0003 ( = 0.8 mK for Pt100 RTD at 25°C) 1 k range 0.02 0.0007 3 k range 0.06 0.002 10 k range 0.2 0.007 30 k range 1.0 0.008 100 k range 6 0.12 300 k range 40 0.2

2.5 M range 10 10 Diodes

Excitation current output 10 µA Initial accuracy ± 100 ppm Drift ±5 ppm/°C Voltage input 0 2.5 V Initial accuracy 10 µV + 0.01% of reading Drift ±5 ppm/°C RMS noise 3 µV

PTC330 thermocouple reader

Inputs Four optoisolated thermocouple inputs Connector Mini thermocouple jacks Thermocouple types E, J, K, N, or T Range ±500 mV Type E 270 °C to 980 °C (range of calibration table with cold junction at 25°C) Type J 210 °C to 1177 °C Type K 270 °C to 1342 °C Type N 270 °C to 1281 °C Type T 270 °C to 383 °C Input capacitance <1 pF Accuracy ±500 mK (over 12 months) Noise 20 mK RMS (at 10 samples/s) Drift due to temperature 20 mK/°C (type K thermocouple at 164.0 K) CMRR 100 dB Common mode isolation 250 VAC

Specifications xi

PTC10 Programmable Temperature Controller

PTC420 AC output card

Output One line voltage output switched by solid-state relay Connector NEMA 5-15 (3-prong North American wall socket); a heater cable with a

mating plug on one side and stripped ends on the other is included Output voltage 120/240 VAC Max. output current 5 A On/off cycle time Adjustable between 1 and 240 s Max. line voltage 250 VAC Surge current 100 A max. (non-repetitive) Output resolution 0.1% at 10 s cycle time Heater resistance (min.) 24 (110 VAC), 46 (230 VAC)

PTC430 50 W DC output card

Output One linear, unipolar DC current source Connector Two banana jacks, 0.75 inch center-to-center spacing Range 50 V 1A, 20 V 2 A, 50 V 0.5A, 20 V 0.5 A,50 V 0.1A, or 20 V 0.1 A Output resolution 24 bits with dithering enabled or 16 bits with dithering disabled Accuracy ±1 mA (1 A range) ±0.1 mA (0.5 A range) ±0.01 mA (0.1 A range) Noise (rms), 50 load, 6 µA (50 V 1 A and 20 V 2 A ranges) DC 10 Hz 1.5 µA (0.5 A range)

0.2 µA (0.1 A range)

PTC431 100W DC output card

Output One unipolar DC current source Connector #6 screw terminals. Accepts 12 22 AWG wire or #6 spade terminals up to

-lb. Range 50 V 2A, 50V 0.6A, 50V 0.2A, 20V 2A, 20V 0.6A, 20V 0.2A Output resolution 16 bits Accuracy ±1 mA (2 A range) ±0.5 mA (0.6 A range) ±0.2 mA (0.2 A range) Noise (rms), 25 load, 5 µA (2 A range) DC 10 Hz 1.5 µA (0.6 A range)

0.5 µA (0.2 A range)

PTC440 TEC driver

Output One linear, bipolar DC current source Input One 2- or 4-wire thermistor/RTD/IC temperature sensor input Connector One 15-pin DB15-F

TEC driver

Output current -5 A +5A Maximum power 50W Compliance voltage 12 V (at 0 A current) Output resolution 0.15 mA Accuracy ±5 mA Current noise 0.02 mA (at 0.5A current, 22 ohm resistive load, 0.01-10 Hz bandwidth)

Specifications xii

PTC10 Programmable Temperature Controller

Temperature sensor input

Compatible sensors Thermistors 2 or 4-wire NTC thermistors RTDs 4-wire platinum RTDs, 100 1000 at 0°C IC sensors LM335, AD590, or equivalent Excitation current 10 µA, 100 µA, or 1 mA Input range Resistance 1 250 k Voltage 0 2.5V Current 0 1 mA RMS electronic noise (sensor at 25°C) 10 µA excitation 1 k thermistor 0.7 = 15 mK 2252 thermistor 0.6 = 5 mK 10 k thermistor 1 = 4 mK 100 µA excitation 1 k thermistor 0.1 = 1.5 mK 2252 k thermistor 0.1 = 0.7 mK 10 k thermistor 0.2 = 0.5 mK 1 mA excitation 100 Pt RTD 0.003 = 8 mK LM135/235/335 4 mK RMS AD590/592 6 mK RMS Initial accuracy 10 µA excitation 1 k thermistor 1.2 = 30 mK 2252 thermistor 10 = 100 mK 10 k thermistor 66 = 150 mK 100 µA excitation 1 k thermistor 0.06 = 1.6 mK 2252 k thermistor 0.1 = 10 mK 10 k thermistor 0.5 = 1.1 mK 1 mA excitation 100 Pt RTD 0.004 = 5 mK LM135/235/335 70 mK AD590/592 400 mK (sensor at 25°C) Thermal drift 10 µA excitation 100 µA excitation 1 mA excitation LM135/235/335 AD592/592

Analog I/O

Inputs/outputs 4 voltage I/O channels, independantly configurable as inputs or outputs Connector 4 BNC jacks Range ±10 V Resolution 24-bit input, 16-bit output ADC noise 30 µV RMS = 100 µV p-p (10 samples/s)

Digital I/O

Inputs/outputs 8 optoisolated TTL lines, configurable as either 8 inputs or 8 outputs

Specifications xiii

PTC10 Programmable Temperature Controller

Connector One DB-25F

Relays

Outputs 4 independent SPDT relays Connector One 12-pin 3.5mm header Maximum current 5 A Maximum voltage 250 VAC

Introduction 1

PTC10 Programmable Temperature Controller

Introduction

The PTC10 is a high-performance, general-purpose laboratory temperature controller that can

monitor and control temperatures with millikelvin resolution. Its features include:

Modular design

The PTC10 can accept up to four I/O cards, each of which can read up to four temperature sensors and/or drive one heater. The instrument can be customized by selecting the I/O cards best suited to your application. The PTC10 also comes standard with four ±10V I/O channels that can be used with external amplifiers to read signals and drive heaters.

Reads up to 16 tem perature sensors

Temperature input cards are available for reading thermocouples, RTDs, thermistors, and diodes. For optimal signal-to-noise ratio, each temperature input channel has its own 24-bit ADC.

Drives up to 6 heaters

Three kinds of heater driver cards are available for driving resistive heaters and thermoelectric devices. Depending on the model of driver card used, two or three heaters can be directly driven at full power. In addition, the unpowered voltage I/O channels included as standard equipment can be used to drive heaters with the help of an external amplifier.

Graphical touchscreen display

The PTC10 can display temperature measurements and heater output on graphs or numeric displays. Any combination of channels can be displayed, and four different channel combinations can be saved and recalled. Touchscreen operation makes the instrument versatile and easy to use.

Logs data to USB memory devices

Up to 10 data points/second/channel can be logged to standard USB memory sticks and hard drives. The data can be transferred to a computer by simply plugging the USB device into a PC and copying the log files. Windows applications are included to graph PTC10 log files and to convert them to various ASCII text formats.

Up to 6 feedback loops

The PTC10 can control up to six different temperatures (one for each heater output) by continually adjusting the amount of power supplied to heaters. Each feedback loop can run as fast as 50 or 60 Hz, depending on the frequency of your AC power.

Runs user programs

A macro programming language makes it possible to customize the functionality of the instrument. Conditional statements, variables, and subroutine calls are supported. Up to 10 user programs can run concurrently.

Computer com m unications

The PTC10 can receive text commands and send responses over USB, RS-232, Ethernet, and an optional GPIB interface. All aspects of PTC10 operation can be controlled over these interfaces. Eight digital I/O lines are also provided; these can interact with user programs to control most aspects

Introduction 2

PTC10 Programmable Temperature Controller

on removable circuit boards. The chassis has four wide and two narrow slots for these I/O cards. The wide slots (which are labeled 1 4 on the back panel) can be occupied by optional temperature input and/or heater driver cards. The narrow slots (slots 5 and 6) are occupied by general-purpose analog and digital I/O cards included as standard equipment.

Replacing I/O cards

Cards can be added, removed, or rearranged by the user. No firmware setup is needed; the system automatically recognizes the new cards. For most purposes, the six slots are identical and cards do not need to be arranged in any particular order. However, the lower-numbered slots are preferred for output cards because these slots get the most cooling from the fan. In addition, alarms can only activate relays on a digital I/O card if the card is installed in slot 6.

Some channel-specific settings (PID feedback parameters, alarm settings, sensor type, custom calibration data, and filter settings) may be lost when I/O cards are replaced or rearranged. However, factory calibration is stored on the card and is not lost.

To add or replace an I/O card:

1. Unplug the PTC10 from the wall; otherwise, even if the instrument is switched off, live line voltage could be present. Removing and installing I/O cards while the power is turned on may permanently damage the instrument.

large Philips head screws on the

sides of the cover and lifting the cover straight up.

3. Remove the two flathead Phillips screws immediately t back panel.

4. Remove the I/O card by pulling up alternately on the front and back of the card.

5. Install the new I/O card. Put the back of the card in place first, then press firmly down on the front of the card. Ensure that the top of the card is level with the tops of all the other cards.

6. Re-install the two back-panel screws and re-attach the top cover. The card can be damaged if the screws are not installed.

7. Turn the PTC10 on. The new card should automatically appear on the Select screen, and remote commands for the new card should automatically become available.

PTC320 thermistor/diode/RTD card

The PTC320 is a single-channel, multi-range input card that can read a variety of temperature sensors. It can read resistances between 1 and 2.5 M , and can also read diode temperature sensors.

Standard calibration curves are included for the following sensors. the range of the standard calibration curve; outside this range, no reading appears for the sensor. It may be possible to obtain a larger range by uploading a custom calibration curve.

Introduction 3

PTC10 Programmable Temperature Controller

Sensor

class

Manufacturer

Calibration

type

Range,

Diode

Scientific Instruments

Si410

1.0 450

Si430

1.0 400 Si440

1.0 500

LakeShore; Omega

DT-470 (=CY7)

1.4 475

DT-670 (=CY670)

1.4 500

Cryo-Con

S700

1.5 475

S800

1.4 385

S900

1.5 500

Ruthenium

oxide

LakeShore RX-102A

0.050 40

RX-103A

1.2 40

RX-202A

0.050 40

Scientific Instruments

RO600

1.0 300

Cryo-Con

R400

2.0 273

R500

0.050 20

RTD

All

IEC751 (DIN43760)

48.15 1173.15

Thermistor

Measurement

Specialties,

Inc.

(formerly YSI);

Omega

100 

193.15 373.15

300 

193.15 373.15

1000 

193.15 373.15

2252 

193.15 523.15

3000 

193.15 523.15

5000 

193.15 523.15

6000 

193.15 523.15

10000  type B

193.15 523.15

10000  type H

193.15 523.15

30 k

233.15 523.15

100 k

233.15 423.15

300 k

298.15 423.15

1 M

298.15 423.15

Other resistive and diode sensors can be used with the PTC320, but require custom calibration curves. For example, rhodium-iron, germanium, and carbon-glass sensors have too much sensorto-sensor variability to use a standard curve, and therefore must be custom-calibrated.

Connecting the sensor

The PTC320 has a 6-pin DIN socket that mates with standard 6-pin push-pull DIN plugs (i.e. Digi-Key CP-1060-ND). This is the pinout of the socket, as it appears when looking at the back panel:

Not connected

Excitation +Sense +

Ground

Excit

Introduction 4

PTC10 Programmable Temperature Controller

chassis.

The PTC320 passes an excitation current through the attached RTD, thermistor, or diode, and senses the induced voltage. For the most accurate results all sensors should be read with a four-wire configuration, using separate sense and excitation leads. However, for convenience the PTC320 can also read sensors attached with only two leads.

To make a two-wire measurement, connect one end of the sensor to pin 1 (Excitation ) and the other to pin 5 (Excitation +). An inaccuracy is introduced because the resistance of the leads affects the measurement; however, some thermistors have such a high resistance that the lead resistance may be negligible in comparison.

A four-wire measurement eliminates the effect of lead resistance. In the four-wire configuration, two of the wires carry the excitation current, while the other two wires sense the voltage that the current produces across the sensor. RTDs sold with four wires normally have two wires of one color, both attached to one side of the RTD, and two of a different color attached to the other side. In this case, the RTD should be wired to the PTC320 in one of the following two ways (assuming the leads are white and black):

Pin 1

Pin 2

Pin 3

Pin 4

Pin 5

Option 1

White

Unconnected

Black

Option 2

Black

Unconnected

White

RTDs with two wires can be modified by connecting two additional wires, one on each side of the sensing element and as close to the sensing element as possible.

The higher the resistance of a sensor, the more its leads pick up noise from ambient electromagnetic radiation. The noise level of high-resistance thermistors in particular can often be improved by using a shielded cable and connecting the shield to pin 3.

Excitation current

The excitation current provided to the sensor is automatically determined by the PTC320. For resistive sensors, the current is determined by the type of sensor and the measurement range as shown in the table below. When a diode sensor is in use, the card always produces a 10 µA excitation.

Measurem ent

range

RTD

excitation

Therm istor

excitation

Diode

excitation

5 mA

200 µA

100

2 mA

100 µA

300

1 mA

50 µA

1 k

500 µA

30 µA

3 k

200 µA

20 µA

10 k

100 µA

10 µA

30 k

50 µA

5 µA

100 k

10 µA

3 µA

300

5 µA

2 µA

2.5 V ( )

1 µA

10 µA

Excitation current produced by the PTC320

The thermistor excitation current results in about 1 µW of power being dissipated in the thermistor at the high end of each measurement range. Therefore, if the dissipation constant of the thermistor is above 1 mW/°C, the measurement error due to self-heating should be less than 1 mK.

Introduction 5

PTC10 Programmable Temperature Controller

PTC321 RTD reader

Resistance temperature detectors (RTDs) use the resistance of a metal wire or film to indicate temperature. RTDs are usually made of platinum which, being very non-reactive, produces sensors with exceptional long-term stability. However, platinum RTDs are also expensive and have a limited temperature range.

Typically, the resistance is measured by passing an excitation current through it and measuring the resulting voltage drop. A four-wire RTD has two wires to carry the current and two to measure the voltage. Negligible current flows through the voltage-measuring wires, ensuring that the resistance of the wires does affect the measured voltage.

RTDs usually have the °C (IEC751 standard). The cient of 0.00392 °C is less common, even in America.

The PTC321 RTD reader reads up to four 100 ohm platinum RTDs with a 1 mA excitation current. The current through the RTD can be reversed with each reading to null out parasitic thermocouple voltages.

The PTC321 has a range of 10 , allowing it to read 100 European-type platinum RTDs in the temperature range 215 to 850°C. RTDs with other base resistances can also be used, but over a smaller temperature range.

The PTC321 is calibrated at ambient temperatures of 25 and 35°C. An on-board temperature sensor continuously interpolates between these two calibrations to account for thermal drift of the

electronic components. Since the PTC10 enclosure is usually elevated 2 to 3 degrees above ambient temperature, the accuracy of the PTC321 may be reduced if the ambient temperature rises above about 32°C.

To further improve measurement stability, the PTC321 can control the main enclosure fan to

keep the card at a constant temperature (see the Channel.PCB button).

A narrow flange is available for the PTC321. With this flange mounted, the card can be plugged into either slot 5 (normally occupied by the analog I/O card) or slot 6 (normally occupied by the digital I/O card). Since all six slots of the PTC are identical except for their width, the I/O cards can be arranged in any order as long as they fit into the slots. To order the narrow flange from SRS, contact sales and ask for part number 7-01920-720.

Connecting the RTDs

RTDs are connected to the PTC321 with removable 5-pin, 3.5 mm terminal plugs (e.g., Weidmüller part number 169045). The supplied plugs use a tension clamp to hold the RTD wires. To install the RTD wires:

1. Hold the plug such that the row of five small holes is on the right and the five larger holes are on the left.

2. Each pair of holes is blocked by a metal clip. Place a small screwdriver into one of the small holes and firmly push it into the narrow gap to the right of the clip. The screwdriver should go in about half an inch and push the clip to the left.

3. The larger hole should open up. Place a stripped wire into the hole and remove the screwdriver.

Plugs with screw clamps (e.g., nnect the RTD wires to these plugs, but the wires often come loose, resulting in noisy temperature measurements. The tension clamps are a little more difficult to install but produce a more reliable connection.

Introduction 6

PTC10 Programmable Temperature Controller

On each connector, the top two pins receive the resistance signal, the middle pin is a ground that can be connected to a shield or left unconnected, and the lower two pins provide the excitation current.

Commercial 4-wire RTDs usually have two wires of the one color connected to one end of the resistive sensor, and two of a different color connected to the other end. There is normally no shield. In this case, the RTD plug should be wired in one of the following ways (assuming black and white wires):

Pin 1

Pin 2

Pin 3

Pin 4

Pin 5

Option 1

White

Black

Unconnected

White

Black

Option 2

Black

White

Unconnected

Black

White

If the plug is wired any other way, no reading appears when the sensor is plugged into the RTD reader.

RTDs with two wires must be modified by soldering two additional wires to the existing wires, one on each side of the sensing element and as close to the sensing element as possible. The diagram below shows how to connect the wires to the PTC321.

Connecting a 2-wire RTD to the PTC321 RTD reader

PTC323 2-channel thermistor/diode/RTD card

The PTC323 is a two-channel, multi-range input card that can read a variety of temperature sensors. It can read resistances between 1 and 2.5 M , and can also read diode temperature sensors.

Standard calibration curves are included for the follo the range of the standard calibration curve; outside this range, no reading appears for the sensor. It may be possible to obtain a larger range by uploading a custom calibration curve.

Connect the two wires that

came with the sensor (thin lines)

to the Signal inputs

Solder two additional wires (thick lines)

to the sensor and connect them

to the Excitation inputs

RTD

sensing

element

Signal Signal Ground Excitation Excitation

Introduction 7

PTC10 Programmable Temperature Controller

Sensor

class

Manufacturer

Calibration

type

Range,

Diode

Scientific Instruments

Si410

1.0 450

Si430

1.0 400 Si440

1.0 500

LakeShore; Omega

DT-470 (=CY7)

1.4 475

DT-670 (=CY670)

1.4 500

Cryo-Con

S700

1.5 475

S800

1.4 385

S900

1.5 500

Ruthenium

oxide

LakeShore

RX-102A

0.050 40

RX-103A

1.2 40

RX-202A

0.050 40

Scientific Instruments

RO600

1.0 300

Cryo-Con

R400

2.0 273

R500

0.050 20

RTD

All

IEC751 (DIN43760)

48.15 1173.15 US

48.15 1173.15

Thermistor

Measurement

Specialties,

Inc.

(formerly YSI);

Omega

100 

193.15 373.15

300 

193.15 373.15

1000 

193.15 373.15

2252 

193.15 523.15

3000 

193.15 523.15

5000 

193.15 523.15

6000 

193.15 523.15

10000  type B (32.66 k at 0°C)

193.15 523.15

10000  type H (29.49 k at 0°C)

193.15 523.15

30 k

233.15 523.15

100 k

233.15 423.15

300 k

298.15 423.15

1 M

298.15 423.15

Connecting the sensor

The sensors are connected via a 9-pin D-sub (DB9) socket that mates with any standard DB9 plug, such as Amphenol L717SDE09P with backshell 17E-1657-09. One plug and backshell is provided with each PTC323. Here is a wiring diagram of the socket as it appears when looking at the PTC10

Introduction 8

PTC10 Programmable Temperature Controller

A four-wire connection is used so that the PTC323 measures the resistance of the sensor and not the wires going to the sensor. The +I and I pins provide a small current and should be connected to the temperature sensor with two wires, preferably a shielded twisted pair. The +V and V pins measure the voltage produced across the sensor and should be connected to +I and -I as close as possible to the sensor.

Resistive sensors: Four-wire resistive sensors usually have two wires of one color attached to one side of the RTD, and two of a second color attached to the other side. Two wires of the same co wires of the other color should be connected to the V and I pins.

Two-wire sensors can be converted to four-wire sensors by soldering two additional wires to the existing leads, one on each side of the sensing element and as close to the sensing element as possible. Soldering is essential; the wires should not be connected to the sensor by pressure alone (e.g. crimping or clamping), as any resistance within the joint becomes part of the measured sensor resistance.

The higher the resistance of an RTD or thermistor, the more sensitive it is to ambient electromagnetic noise and the greater the need for shielded cables.

Diode sensors: Diode sensors can be connected in either direction. If no reading appears, change the current direction from Forward to Reverse.

Diode sensors are especially susceptible to electromagnetic noise because the diode rectifies any noise picked up by the sensor leads, increasing the measured voltage. It may be necessary to place the sample within an electromagnetically shielded enclosure and to put EMI filters not only the on the sensor leads but also on all other leads entering the enclosure. The filters should be located at the point where the wires enter the enclosure, and the enclosure itself should be grounded. D-sub and circular connectors with built-in filters, as well as individual filters, can be obtained from Spectrum Advanced Specialty Products. We have found their 4000 pF pi filters to be effective. These filters include capacitors to ground, which should be connected either to the ground pin (pin

3) of the sensor input connector or to chassis ground.

AD590 sensors: The PTC323 can read AD590 sensors if the sensor is connected in series with a 2 k resistor as shown below. Note that the diagram shows the sensor connected to channel A, but it can also be connected to channel B. The diagram shows the back of the DB9 connector, that is, the side that you solder to, with pin 1 in the bottom-right corner.

sistors have a TCR of about 100 ppm/°C, which means that the sensor reading will drift upward by about 30 mK for each 1°C rise in ambient temperature. Thermal drift can be reduced substantially by

AD590

Introduction 9

PTC10 Programmable Temperature Controller

using a 5 ppm/°C resistor available from SRS; ask for part number 4-02502-457. For even better stability, a 1 ppm/°C resistor such as the Riedon USR2G-2KX1, available from Digi-Key, can be used. In any case, to minimize noise and drift, the resistor should be soldered directly to the pins on the DB9 plug and covered up with the backshell.

Because AD590 sensors are highly sensitive to electromagnetic interference, the AD590 wires

and package must be shielded, with the shield connected to pin 3 of the DB9 connector.

Excitation current

The PTC323 measures the resistance of the sensor by passing an excitation current through it. The larger the excitation, the less noise the temperature reading will have. However, if the excitation is too large it will heat the sensor and cause higher than expected readings. Therefore, e

Low power: minimizes sensor heating. This option is mainly for use with thermistors in

cryogenic applications. To compensate for the fact that heat conductivity decreases (and thermistor resistance increases) as the temperature approaches absolute zero, the amount of power that the sensor dissipates decreases as the measurement range is increased.

High power: minimizes noise. Power dissipation is kept roughly constant as the

measurement range is increased. This option is for use with RTDs or with any kind of sensor at non-cryogenic temperatures.

Auto power: uses low power if the sensor type is set to thermistor or ROX, or high power

if the sensor type is set to RTD.

The PTC323 has 12 measurement ranges. Within any given range, it generates a constant excitation current as shown in the table below. Note that the range has to be greater than the sensor resistance, so if the sensor resistance is 10 k , for example, the range should be 30 k .

For diode sensors the range is always 2.5V and the excitation current is always 10 µA.

The graph below shows how the amount of power dissipated by the sensor depends on the range and power settings. Sensor heating (degrees above the ambient temperature) is proportional to power dissipation.

Left: the amount of current passed through the sensor by the PTC10; right:

the amount of power that the sensor dissipates due to that current

Introduction 10

PTC10 Programmable Temperature Controller

The table below shows some representative noise, electronic accuracy, and self-heating values for free-standing sensors at room temperature. Note that the amount of self-heating can vary dramatically depending on the thermal conductivity of whatever the sensor is attached to or immersed in.

Noise

Accuracy

Self-heating

Low

power

High

power

Low

power

High

power

Low

power

High

Power

100 RTD

20 mK

0.8 mK

640 mK

40 mK

0.09 mK

100 mK

1 k thermistor

2 mK

0.08 mK

60 mK

3 mK

0.009 mK

40 mK

10 k thermistor

2 mK

0.02 mK

50 mK

2 mK

0.0009 mK

25 mK

100 k thermistor

9 mK

0.04 mK

220 mK

3 mK

0.00009 mK

2.5 mK

Noise, accuracy, and amount of self-

accuracy of the PTC10 immediately after calibration and does not account for self-heating or the accuracy

- above ambient temperature of a ~1 mm diameter sensor hanging by its leads in still air (dissipation constant 1 mW/°C).

The graphs below show how electronic noise varies with temperature for several types of

sensors.

RMS noise levels for 100Ω and 1000Ω platinum RTD sensors as a function of temperature. At low power, the 100Ω

and 1000Ω sensors have about the same noise level.

Introduction 11

PTC10 Programmable Temperature Controller

RMS noise levels for 100Ω, 10kΩ, and 1MΩ (at 25°C) thermistors as a function of temperature

RMS noise for DT-670 diode sensor as a function of temperature.

The direction of the excitation current can be set by the user to forward, reverse, or AC (switching between forward and reverse with each sample). AC current is recommended for resistive sensors to reduce noise and drift. AC current cannot be used with diode sensors.

PTC330 thermocouple reader

How thermocouples work

If the two ends of a metal wire are held at different temperatures, the electrons at the hot end move faster than those at the cold end. Since the electrons are free to diffuse throughout the wire, they behave somewhat like a ga the hot end of the wire develops a lower density of electrons relative to the cold end. As a result, the hot end has a slight positive

Introduction 12

PTC10 Programmable Temperature Controller

charge and the cold end a slight negative charge, producing a voltage difference. The exact voltage depends on the temperature at each end and the composition of the wire.

A thermocouple has two wires that develop different voltages in response to a given temperature difference. The wires are welded together at one end ) and the voltage difference is measured at the other junction . If we know the cold junction temperature and if each wire has a perfectly homogeneous composition, we can calculate the hot junction temperature. Normally, we measure the cold junction temperature with another sensor such as an RTD or a thermistor.

Thermocouple calibration tables generally assume that the cold junction is at 0 °C. Therefore, to convert the thermocouple voltage to a temperature, to calculate what the thermocouple voltage would be if the cold junction were at 0°C. For example, say a type K thermocouple is used to measure the temperature of some liquid nitrogen. The thermocouple reader measures a voltage of -6.829 mV and also determines that the cold junction is at 25°C. The calibration table indicates that the voltage of a type K thermocouple at 25°C is 1.000 mV. So we add 1 mV to the reading and look up the result, -5.829 mV, in the calibration table. The result is the temperature of the inaccurately named -196°C.

Choosing a thermocouple

Thermocouples are inexpensive and can sense a wide range of temperatures, but without frequent calibration they are accurate to no more than 1°C, partly because they tend to oxidize or otherwise react with gases in their environment. Thermocouples made from thinner wires oxidize more quickly and therefore exhibit more calibration drift than heavier-gauge thermocouples.

When selecting a thermocouple type, t s generally a tradeoff between sensitivity and stability. That is, thermocouples that produce the largest voltages also have the most calibration drift. With the excep he letters that describe thermocouples (E, J, K, etc.) appear to be assigned in order of increasing long-term stability, with type C being the least stable and type T the most. Therefore, if your application requires low noise, it might be best to choose type E; for the best absolute accuracy, type T might be more appropriate.

Each PTC330 input supports one of the following thermocouple types:

Type E thermocouples have one chromel (90% nickel, 10% chromium) and one constantan (60% copper, 40% nickel) wire. It has a large voltage change per degree (68 µV/°C), resulting in excellent signal-to-noise ratio. However, its long-term stability is not very good. Type E thermocouples are resistant to oxidation, but corrode if used in a vacuum or other reduced-oxygen environment.

Type J thermocouples have one iron and one constantan wire. Above 500°C, oxidation of the iron results in poor stability. This thermocouple is mainly used in legacy applications.

Type K thermocouples have one chromel and one alumel (95% nickel, 2% manganese, 2% aluminum, 1% silicon) wire. With a wide temperatur s the most popular type of thermocouple. Type K thermocouples are resistant to oxidation, but corrode if used in a vacuum or other reduced-oxygen environment.

Type N thermocouples and 1% silicon) and one

and 0.1% magnesium) wire. They are designed for high stability,

especially at temperatures above 500°C. However, their sensitivity is low.

Type T thermocouples have one copper and one constantan wire. They are very accurate and can be used in reducing atmospheres, but their temperature range is limited.

The following table summarizes some properties of thermocouples. Two temperature ranges are given: the range that the thermocouple itself can withstand without losing its calibration, and the

built-in calibration tables, assuming that the cold junction

Introduction 13

PTC10 Programmable Temperature Controller

appears on the display and any feedback loops for which the thermocouple is an input do not function.

-2 standard for thermocouple-to-thermocouple material variation. Not all commercial thermocouples may follow this standard; for example, Omega specifies an accuracy of 2.2°C for its type J and K thermocouples. Greater accuracy is possible if your thermocouple is custom calibrated. The accuracy values in this table only apply to the thermocouple itself and

Tem perature range, °C

Accuracy

Type

Thermocouple

PTC10, cold

junction at 25°C

Sensitivity,

µV/°C at 25°C

Standard

calibration,

°C, at 0°C

Custom

calibration,

°C, <300°C

200 to 870

245 to 1025

60.9

1.7

0 to 760

185 to 1225

51.7

1.5

0.1

200 to1260

245 to 1395

40.6

1.5

0.1

270 to 1300

245 to 1325

26.5

1.5

200 to 350

245 to 425

40.6

0.5

0.1

Connecting thermocouples to the PTC330

The PTC330 thermocouple reader is factory-configured to read one of the above thermocouple types. The thermocouple must be equipped with a miniature jack such as Omega part number SMPW-J-M for type J, SMPW-K-M for type K, etc. The jacks on the PTC330 are color coded according to the American (ANSI) color coding scheme, i.e. type J jacks are black, type K jacks are yellow, etc. The colors may not conform to the standard colors used in other countries.

The thermocouple jacks are connected with thermocouple extension wires to a cold junction block inside the PTC10. The cold junction temperature is measured with a platinum RTD temperature sensor. The cold junction temperature is recorded so that if unexpected drift or other artifacts appear in the thermocouple readings, it can be determined whether the artifacts are due to erratic behavior of the cold junction. If readings are displayed in sensor units (see the System.Other.Units button), the raw thermocouple EMFs are displayed in millivolts, not corrected for the cold junction temperature, and the cold junction temperature is displayed in ohms.

inputs are optically isolated and the thermocouples can come in direct contact with electrically live metal. In this case, however, the noise level and accuracy of the measurement may be affected.

The PTC330 hardware is calibrated at ambient temperatures of 25 and 35°C. An on-board

temperature sensor continuously interpolates between these two calibrations to account for

is usually elevated 2 to 3 degrees above ambient temperature, the accuracy of the PTC330 may be compromised if the ambient temperature rises above about 32°C.

To further improve measurement stability, the PTC330 can control the main enclosure fan to

keep the card at a constant temperature (see the manual entry for the Channel.PCB control).

PTC420 AC output card

The PTC420 AC output card has a solid-state relay that delivers mains current to the heater. It is intended for control of large heaters including heating mantles, heating tape, and heating blankets. The relay is either on or off; when on, the full AC mains voltage appears on the output. To vary the output power, the PTC420 switches the relay on and then off once every 10 seconds (by default) with a variable duty cycle.

Introduction 14

PTC10 Programmable Temperature Controller

The card can deliver at most 5 A of current. If the resistance of the heater is too small, the card delivers more than its rated current and may be shut down by its internal protection circuitry. In some cases the card may be damaged. The minimum permissible heater resistance depends on the AC line voltage as shown in the table below. The table also shows the maximum power that the card can deliver.

Line

voltage,

Exam ple

locations

Min heater

resistance,

ohm s

Max power at

min heater

resistance, W

Max power

at heater

resistance R, W

100

Japan

500

10000 / R

120

Canada, US

600

14400 / R

220

Russia

1100

48400 / R

230

Europe

1150

52900 / R

240

China, Australia

1200

57600 / R

The total AC current delivered at any one time by the all the PTC420 cards in a single chassis cannot exceed 10 A

PTC430 50 W DC output card

The PTC430 DC output card can deliver up to 50 W of power and is intended for precise control of small heaters. The card offers two voltage ranges (50 V and 20 V) and three current ranges (1A, 0.5A, and 0.1A). An auto-range feature continuously adjusts the current and voltage ranges to the smallest values needed to achieve the power specified with the channel Hi Lmt setting.

The depends on the resistance of the heater; see the table below.

Heater resistance

(R),

Optimum

output

range

Maximum power, W

> 500

50 V 0.1 A

2500/R

500

50 V 0.1 A

100 500

50 V 0.5 A

2500/R

100

50 V 0.5 A

50 100

50 V 1 A

2500/R

50 V 1 A

20 50

50 V 1 A

20 V 2 A

10 20

20 V 2 A

400/R

20 V 2 A

< 10

20 V 2 A

Maximum output power and optimum output range as a function of

heater resistance

, the heater must have a resistance of 50 ohms. If the

produces about 265W at 115V or 1060W

at 230V.

If the heatsink temperature of a DC output card exceeds 60 circuitry shuts down the output. This is likely to occur if one of the 50V output ranges is used when the heater resistance is under 20 ; if the ambient temperature outside the chassis is above 30°C; if

Introduction 15

PTC10 Programmable Temperature Controller

and/or if the system fan is turned off or not working. If the heater resistance is less than 20 , select the 20 V ranges to prevent thermal shutdown.

The temperature of the heatsink can be monitored by setting the System.Display.Monitors

PCB temperature display should appear on the Select screen directly underneath the current value of the DC output card. If the temperature

If the 50 V 1 A range is used and the average heater resistance is less than 65 , up to three DC output cards can be installed in a single chassis and run at full power simultaneously. If four DC output cards are installed and the average output current at any given moment exceeds 0.8A, a system reset may occur to protect the power supply from overload.

If any other range is used or the average heater resistance is greater than 65 , up to four DC output cards can be installed in a single chassis and run at full power.

Hardware faults

The PTC430 continuously monitors for unsafe operating conditions. If such a condition occurs and persists for more than 2 seconds, the In addition, one of the following error messages appears in a pop- :

Ground fault: on, and the current s

positive terminal is not the same as the current flowing into the negative terminal. This error can occur if one of the leads is shorted to an external ground.

Unexpected output current off, but current is flowing into

the negative terminal anyway. This error may indicate that the heater is shorted to a power source other than the PTC430. It can also i circuitry.

DC output card overheated: Either the resistance of the heater is too low; the positive

and negative terminals are shorted to each other off; or the chassis fan is no longer functioning. Try reducing the maximum output voltage or current, and make sure the front panel fan is running.

To re- key, then

re-enable the outputs by pressing the Output Enable key twice.

PTC431 100W DC output card

The PTC431 DC output card can deliver up to 100 W of power and is intended for precise control of small heaters. The card offers two voltage ranges (50 V and 20 V) and three current ranges (2A, 0.6A, and 0.2A). An auto-range feature continuously adjusts the current and voltage ranges to the smallest setting.

The 20V range can be used to limit the output voltage for safety purposes. Selecting this range does not otherwise affect the performance of the card. On the other hand, the 0.6A and 0.2A current ranges offer lower noise levels and are intended to be used when very precise temperature control is needed.

The maximum power that the PTC431 can deliver depends on the resistance of the heater as shown below.

Introduction 16

PTC10 Programmable Temperature Controller

Maximum output power as a function of output range and heater resistance

at 230V. circuitry shuts down the output. This is likely to occur if the heater resistance is under 10 ; if the

ambient temperature outside the chassis is above 30°C; and/or if the system fan is turned off or not working. The PCB temperatures can be monitored by going to the System screen and setting the Monitors control to Show.

Although up to four PTC431 cards can be installed in a chassis, only two can be run at full power at any given time. If more than two PTC431 cards are installed, their output should be limited to half their maximum value, either by using the 20V range or by setting the upper limit to 50W.

Hardware faults

The PTC431 can detect certain unsafe operating conditions. If such a condition occurs and

-enable the output, disable all outputs by pressing the Output Enable key, then re-enable the outputs by pressing the Output Enable key twice). In addition, one of the following error messages appears in a pop-up

Measured heater current differs from desired value: The ,

and the current at the positive terminal differs from the desired current by more than 0.25A. This error can occur if the card is out of calibration. It can also mean that the card has been damaged and is no longer capable of correctly regulating its output current or of producing its rated output current.

Current at + and heater terminals is different , and the

current at the positive terminal differs from the current at the negative terminal by more than 0.25A. This error can occur if one of the leads is shorted to an external ground.

Output is off but heater current was detected: current is flowing into the negative

. This error may indicate that the heater is shorted to a power source other than the PTC10. It can also i

Output card overheated: Either the resistance of the heater is less than 10 ohms; the

positive and negative terminals are shorted to each other; the ambient temperature is too

Introduction 17

PTC10 Programmable Temperature Controller

or current, and make sure the front panel fan is running.

PTC440 TEC driver

The PTC440 includes a current source to drive a thermoelectric cooler and a sensor input for a thermistor, RTD, or IC temperature sensor. The card has a single 15-pin D-sub connector for both sections. The pinout and wiring diagram are shown below. Only pins 1 and 3 need to be connected to power a TEC device, and only pins 8 and 14 need to be connected to read a temperature sensor. The other pins are optional.

TEC driver section

A thermoelectric cooler (TEC), also referred to as a Peltier device, is a solid-state electric heat pump that can both heat and cool, depending on the direction of current flow. Thermoelectric coolers are generally used for precise temperature control of small objects in the range of -100 100°C.

With its high-current, low-voltage output, its ability to change the direction of current flow, and circuitry to protect the TEC from excessive voltages, the PTC440 is primarily intended to drive TEC devices. However, it can also drive low-resistance (optimally 2.4 ohm) resistive heaters. In this case, the lower output limit should be set to 0 A and the heater should be connected to pins 1 and 3.

If the TEC is unplugged while current is flowing, or if the current is turned on when no TEC is

is feature ensures that the voltage between the output terminals is always zero when a TEC is plugged in. A nonzero voltage would produce a destructive current spike when the TEC is plugged in.

Therefore, if the PTC440 does not produce any output current, turn the current off and back on

three times or setting the output

value to zero with the Channel.value control.

Connecting the TEC

Connect the + and leads of the TEC to pins 1 and 3, respectively. Pins 2 and 4 can also be

connected to reduce contact resistance.

The PTC440 is a current source, that is, it has direct control over the current that passes through the TEC but not the voltage. Since thermoelectric coolers are easily destroyed by both voltages and currents even slightly above their rated maximum, the PTC440 provides a voltage input (Vmon) to

Introduction 18

PTC10 Programmable Temperature Controller

monitor the TEC voltage. The connections for this input are the TEC sense + and TEC sense pins. If these leads are connected to the TEC + and leads, as close to the TEC as possible, Vmon shows the voltage across the TEC. If the leads are not connected, Vmon shows the voltage at the

If only a small current passes through the TEC even at its maximum voltage, the TEC may have

been damaged by excessive current or voltage.

Maximum TEC voltage

The TEC driver has four voltage ranges: 3, 6, 9, and 12V. In general, the lowest possible voltage range should be used; besides potentially damaging the TEC, the larger voltage ranges create excess heat inside the PTC chassis and ca

However, when selecting a voltage range, it's important to account for the resistance of the wires you've used to connect the TEC. This resistance can significantly reduce the voltage available to the TEC. For example, if the wires have a resistance of 0.5 ohms and a 5A current is flowing through them, the wires will reduce the available voltage by 2.5V. Therefore, if the 3V range is selected, the maximum voltage across the TEC will only be 0.5V. If the TEC sense leads have been connected, this is the maximum voltage that will appear in the Vout display.

To minimize such voltage losses, heavy-gauge wires should be used to connect the TEC. Standard DB-15 cables in particular should not be used because their thin wires absorb most of the PTC440's output power.

The Vmon channel has a voltage limit, Vmax. If the voltage at the TEC exceeds Vmax, the PTC440's output is shut off. The output will remain disabled until it is set to zero using either the Output Enable key or the If the sense leads have been connected, the lead resistance does not have to be taken into account when setting Vmax.

In some cases, the output may exceed Vmax every time the PID feedback is enabled. To avoid this, temporarily set the ramp rate to a low value (i.e. 1 °C/s) when enabling the feedback.

Temperature input section

The PTC440 has a sensor input that can read thermistors, RTDs, AD590, and LM135/LM235/LM335 temperature sensors. t is not intended for precision applications and should only be used when temperature stability of ~0.1°C is acceptable. For more demanding applications the sensor should be read with a dedicated input card such as the PTC320 (for thermistors, RTDs, and diodes), PTC321 (for 100 RTDs only), or PTC330 (thermocouples). These cards provide lower noise and greater accuracy than the PTC440.

Connecting the temperature sensor

RTDs: 4-wire RTDs should be used to ensure accuracy. Two of the wires are normally white and are connected to one end of the resistive sensor, while the other two are black, red, or yellow and are connected to the other end. There is normally no shield. In this case, the RTD should be wired in one of the following ways (assuming black and white wires):

Pin 7

Pin 8

Pin 14

Pin 15

Option 1

White

Black

White

Black

Option 2

Black

White

Black

White

Thermistors: Two-wire thermistors should be connected to pins 8 and 14.

Introduction 19

PTC10 Programmable Temperature Controller

LM135/LM235/LM335: The LM135, LM235, and LM335 are integrated circuit temperature sensors. If an excitation current between 400 µA and 5 mA is passed through the sensor, the voltage drop across the sensor is 10 mV/K. The three models have different temperature ranges, with the LM135 having the largest range and the LM335 the smallest. For the best possible accuracy the sensors can be connected in a 4-wire configuration, just like an RTD. However, it is more common to connect the device in a 2-wire configuration, leavings pins 14 and 15 of the PTC440 unconnected. The first row of the table below lists the four sensor input pins on the

s show which leads of the LM135/235/335

should connect to those pins.

Pin 7

Pin 8

Pin 14

(optional)

Pin 15

(optional)

8-pin SOIC

Pin 8

Pin 4

Pin 8

Pin 4

Other packages

+ +

AD590/AD592: The AD590 and AD592 are an integrated circuit temperature sensors. When a

/K flows through the device. The two models have different packages and temperature ranges, with the AD590 having a range of -55 150°C and the AD592 a range of -25 125°C. The AD590/592 can be connected in a 2- or 4- wire configuration as shown in the table below. For the 2-wire configuration, leave PTC440 pins 14 and 15 disconnected.

Pin 7

Pin 8

Pin 14

(optional)

Pin 15

(optional)

8-pin SOIC

Pin 2

Pin 3

Pin 2

Pin 3

Other packages

+ +

Sensor excitation current

The excitation current provided to resistive sensors can be set to 10 µA, 100 µA, 1 mA, or auto. In auto current mode, the sensor resistance is continuously monitored and the excitation current is adjusted whenever the sensor resistance rises above or drops below the levels shown in the table

ion when a diode sensor is in use, or 1

mA when an LM335 or AD590 sensor is in use.

Sensor

resistance

Excitation

current

<2 k

1 mA

1 20 k

100 µA

>10 k

10 µA

TEC driver (for resistive sensors only)

Note that the resistance ranges overlap; if the sensor resistance is between 1 and 2 k , for example, the TEC driver can use either 1 mA or 100 µA excitation. If possible, the excitation current is kept at its previous value.

A slight temperature glitch may occur when the PTC440 switches from one range to the next. If these glitches could disrupt your experiment, set the excitation current manually.

Introduction 20

PTC10 Programmable Temperature Controller

A/D rate

Some TECs are capable of very fast response rates. If the temperature of your TEC changes very quickly (on the order of 1 second) when a current is passed through it reduce the system A/D rate (set with the System.Other.A/D rate command) from its default 100 ms to 50 ms. Operating the PID feedback loop at a faster rate allows it to more precisely control the system temperature and, therefore, results in a more stable temperature.

PTC510 analog I/O card

This card is included as standard equipment and fits in either of the two narrow I/O card slots. Each of its four channels can be either an input (±10V, 24-bit ADC) or an output (±10V, 16-bit DAC). Each channel has a red back-panel LED that lights up when the channel is an output.

The analog I/O channels can be used as PID inputs or outputs. Since each channel can only connected to an external amplifier.

PID feedback appear on the Channel Setup screen. The corresponding remote

available and the PID feedback loop is disabled. Instead, controls and remote instructions for an alarm, lowpass filter, difference filter, time derivative, and offset/gain calibration appear. These controls disappear, the remote instructions are not available, and the functions are disabled when the channel is an output.

PTC520 digital I/O card

This card is included as standard equipment and fits in either of the two narrow I/O card slots, although for compatibility with should be installed in slot 6. It offers four relays, each capable of passing up to 5A of current. It also has eight isolated TTL I/O lines on a 25pin connector compatible with the pinout of the standard PC parallel port. The TTL lines can be used as inputs or outputs, but all eight must have the same direction.

The relays are hosted on a single 12-pin pluggable terminal block. The four rel (comm state when the

PTC is turned off, when its outputs are not enabled, or when the relay is set to 0. In this state, the

pin a

1 and the outputs are enabled, the relay is activated: the

The relays appear on the PTC10 display as a single 4-bit integer value between 0 and 15. If no relays are activated, the value is 0. Each relay, if activated, adds the following to the displayed value:

Relay

B C D

Value

1 2 4 8

Therefore, if the relay channel 2 , only relay B is activated. If the channel read 6 , relays B and C are activated. Conversely, setting the relay channel to 6 activates relays B and C, and

Introduction 21

PTC10 Programmable Temperature Controller

deactivates the other relays. To set an individual relay from a macro or serial port without affecting the states of other relays, use a bitwise operator; for example, the remote command

relays |= 4

activates relay C, while the remote command

relays &= 11

remote commands.

The eight TTL lines are located on a standard 25-pin D-sub connector with the following pinout

(the pin numbers are usually printed next to the pins on D-sub connectors):

1 Unconnected 2 D0 3 D1 4 D2 5 D3 6 D4 7 D5 8 D6 9 D7 10 +5V 11 +5V 12 Gnd 13 Unconnected

14 Unconnected 15 Unconnected 16 Unconnected 17 Unconnected 18 Unconnected 19 Gnd 20 Gnd 21 Gnd 22 Gnd 23 Gnd 24 Gnd 25 Gnd

ground of whatever system the digital I/O is interfaced with. Alternatively, if the digital I/O lines are configured as inputs, a +5V pin can be shorted to any of the inputs D0 to D7 to pull them high,

-limited with 4.7

k resistors and are not intended to power a remote system.

The status of the eight digital I/O lines is reported on the PTC10 display as a single eight-bit

integer value. Each I/O line is assigned an integer value as shown in the following table:

Bit

D0 D1 D2 D3 D4 D5 D6 D7

Value

1 2 4

8 16 32 64

128

example, if only bits D1 and D3 are set, a DIO value of 2 + 8 = 10 is displayed.

Using the remote interface, macros can be defined that associate the digital I/O lines with most functions of the PTC10. The remote interface provides bitwise operators to set and query the relays and digital I/O lines.

Introduction 22

PTC10 Programmable Temperature Controller

The DIO lines can be used to pass a single, 8-bit value into or out of the PTC. The PTC treats the DIO like any other channel; for example, its value can be plotted or used in a PID feedback loop.

Virtual channels

The digital I/O card has three virtual channels with the default names V1, V2, and V3. These channels are not connected to any physical inputs or outputs. Instead, macros or remote commands can assign arbitrary values to these channels, or the channels can automatically follow the value of another channel. Like , the values of virtual channels can be plotted on the Plot screen, displayed on the Numeric screen, and logged to RAM and USB.

Each virtual channel can either an input or an output (see the Channel.IO Type button) input, a virtual channel can follow the value of another channel (see the Channel.Follow button), and its value can be modified by applying a lowpass filter, subtracting a difference channel, taking its derivative with respect to time, or applying offset/gain factors. By doing these calculations on a virtual channel that has been configured to follow a sensor input (instead of doing them directly on the sensor input channel), the raw sensor input is preserved and can still be viewed.

If the virtual channel is an output, it has a PID feedback loop that can be used for cascade control (see the description of the Channel.PID.Casc button in the Operation section). Unlike other

with the Output Enable button. However, virtual PID feedback loops do are disabled.

When the value of a virtual channel is changed by a macro or from the front panel, the new value does not become effective until an ADC conversion occurs. Therefore, if a macro sets the value of a virtual channel and then immediately reads the value back, the old value may be returned.

Operation 23

PTC10 Programmable Temperature Controller

Operation

Operation 24

PTC10 Programmable Temperature Controller

Turn the instrument on

Plug the PTC10 in and turn it on with the power switch located next to the AC power inlet.

If the PTC10 does not turn on, a fuse may have blown. Check the fuse holder just above the on/off switch.

If the instrument turns on but does not respond to button or touchscreen presses, the most likely cause is that the ground prong of the electrical socket is not connected to ground. A three-prong plug must be used and all three prongs must be connected.

The Select screen

Each of the green buttons on this screen represents one I/O channel. The buttons are arranged in roughly the same order as the connectors on the back of the PTC10. Each button shows the

ected, the value may be blank.

Some of the buttons represent internal data channels. In the figure above, for example, the channels that can be used for c isplay heater current, voltage, and

bold if the channel uses a custom calibration table.

Touch one or more buttons to select which channels to show on the Numeric, Plot, and Channel screens.

Configure the sensor inputs

thermistor/diode/RTD input card, it may be necessary to

select the sensor type and calibration curve.

1. Select one or more inputs on the Select screen.

Operation 25

PTC10 Programmable Temperature Controller

The top of this screen has one

tab for each selected channel. Touch one of the tabs to display the settings for that channel.

3. T etc.)

5. In the

If the sensor reading does not appear

The sensor reading is blank whenever it falls outside the limits of the calibration data or input hardware. This normally occurs when no sensor is connected, but can also occur if the sensor is incorrectly configured. In this case, try the following steps:

1. Ensure that the sensor is correctly connected. Thermistors and RTDs should normally be connected with four wires. Thermocouples and diodes must not be connected backwards.

2. Measure the resistance of the sensor with an ohmmeter to ensure that one of the wires is not broken.

3. Bring up the channel setup screen for the input channel and check the following settings:

Sensor: must agree with the type of sensor that is in use. Range: set to Auto or, if a fixed range is selected, ma

resistance.

Current: Forward, Reverse, or AC. If the current is off, no sensor reading will appear. Cal Type: must agree with the type of sensor that is in use. Cal R0: for RTDs only; must agree with the type of sensor that is in use.

appear in ohms or volts instead of degrees. Is the value correct?

5. If nce or voltage is within the range of the calibration table.

instead connect a resistor of about the same value to the PTC10. If the reading is still incorrect, the unit may need to be returned to SRS for recalibration.

Plot data

To plot data on-screen:

1. On the Select screen, touch the buttons to highlight the .

Once the Plot screen is showing, press the Plot key repeatedly to cycle between four screen

arrangements:

One plot for each channel All channels on a single plot Ponytail plot: all channels on a single plot, offset such that each channel starts at zero Custom: channels are assigned to plots with

described on page 65.

Operation 26

PTC10 Programmable Temperature Controller

Touch anywhere within the right half of the plot to zoom in. To zoom out, touch the left half of the plot (but not left of the Y axis in the bottom-left corner of the screen to return to viewing real-time data.

Test the outputs

Before trying to run a PID feedback loop for the first time, i elpful to verify that your heater is working by setting its current or power to a low value and seeing if any current flows. To do this, plug your heater i

1. Enable the outputs by pressing the Output Enable key twice. The red Output Enable light should turn on.

2. Select the output channel on the Select screen, then press the Channel key to display the channel setup screen.

make the channel

4 t

damage your system).

5. The Value button should display the value that you entered. If blank or displays zero, the PTC is not detecting the heater.

6. Verify that your heater is warming up.

7. To turn the current off, touch the Off button on the channel setup screen.

If the Value button is blank or try the following:

Verify that the heater leads are not shorted to ground or to each other. If the heater is resistive, unplug it from the PTC10 and measure its resistance with a

multimeter. Make sure that the resistance is appropriate for the output card:

PTC420 AC output card: 24 300 (120VAC), 46 600 (230VAC) PTC430 50W DC output card: 1 1k PTC431 100W DC output card: 10 1k

Display the

Monitors to the Select screen. Underneath the heater

tput card

resistance the same as what you measured with a multimeter? Is the voltage or current at the maximum that the output can produce?

Verify that the PID mode is set to off.

that the output value that you entered.

If the output is a PTC440 TEC driver, disable and re-enable the outputs.

output is automatically disabled if you try to output a current when no TEC device is connected, or if the voltage exceeds the Vmax setting.

disabling

the output. For example, if you move a sensor from one input to another, remember to disable the alarm on the old input.

Operation 27

PTC10 Programmable Temperature Controller

Set the data logging rate

By default, the PTC10 records ten data points per second . To change this rate, press the System key on the and select from the list of available options

The log interval determines the maximum l plot screen. The PTC10 stores up to one million data points for each channel in its on-board memory, while older data points are erased. At the default logging interval of 0.1 seconds, the

graph can display about the last 27 hours of data. If the logging interval is 1 second, up to 11 days of data can be displayed. The logging interval has to be set before the data is acquired; all on-board data is erased when the logging interval is changed.

The log interval also determines how much time a single log file can cover; see the next section

below.

It s also possible to assign a different log interval to each channel; see the description of the

Channel.Logging control on page 65.

Save data to and retrieve data from a USB memory device

A USB memory stick can be used to keep a permanent record of logged data. Data is logged to an ASCII file. The default name of the log file is \Log\00\Log00.csv (the top-

front panel). The file is an ASCII CSV

(comma-separated value) file that can be read with spreadsheet software.

The maximum size of the file is 2GB for FAT-formatted USB devices or 4 GB for FAT32 devices. The file can reach this size in as little as 6 days, but more typically it should take about 30 days. When the file fills up, Log00.csv is closed and the PTC10 automatically begins writing data to a new file named Log01.csv. If Log99.csv fills up, the PTC10 begins logging to a new directory

\Log\01 -level directory name).

Save data to a USB device

1. Plug the USB memory stick into the port on the back of the instrument. ars

on-screen. The message stays on-screen for several seconds while the log files are opened, then the message disappears.

3. Look for a small, dark red circle in the upper-right corner of the screen. This is the USB

logging indicator. Touch the circle. When it turns light red, the PTC10 is saving data to the USB device.

4. Before turning the instrument off or removing the USB device, touch the USB logging

indicator again and wait for it to turn dark. This step is very important to prevent damage to the USB device. If this step is skipped, the USB device should be re-formatted in a PC before using it again.

View saved data on a PC

A software package that can be downloaded from the SRS website (www.thinksrs.com, click Downloads > Software) includes a program that plots log files. No installation is required; just double-

Operation 28

PTC10 Programmable Temperature Controller

Interface with a computer

front panel, has -232, USB, GPIB, and Ethernet interfaces

The USB port uses an FTDI USB chip. If the PC asks for a driver, follow these instructions:

Install the USB driver for Windows PCs

1. Download and install the appropriate FTDI Virtual Com Port (VCP) driver from:

http://www.ftdichip.com/Drivers/VCP.htm

2. Optional: the default baud rate for the FTDI driver is 9600. For faster communication,

change the baud rate to 230400 on both the PC and the PTC10. On the PTC10, press the Setup key, touch the On the PC,

setting, open the Device Manager and expand the Ports line. Plug the PTC10 into the PC and look for a new port to appear. Double-click that port, select the Port Settings tab, and

3. The PTC10 should now appear as a COM port on your computer, and your programs can

use the USB connection in the same way that they use an RS-232 connection.

Read data from the PTC10

All RS-232, GPIB, USB, and Ethernet messages sent to the PTC10 must end with a linefeed

\ ntil the linefeed is

received. Instructions are not case-sensitive.

The most recent value (i.e., the value read at the most recent ADC conversion) of a single

channel can be queried by sending the name of the channel, followed by a question mark.

3A?

29.9313

the command:

Out1?

0.00000

The most recent value of all channels can be retrieved with a single getOutput instruction (the

question mark is optional in this case):

getOutput?

0.000000, 0.000000, 29.98424, 25.86019, 27.49236, NaN, 27.45483, NaN, 268.9367, NaN, NaN, 0.000000, 10.04576, 10.04574, 10.04572, NaN, NaN, NaN, 0, 0

Sensors that are disconnected or out of range (not a number). To determine the order of the channels in the getOutput response, send the getOutputNames query:

getOutputNames?

Operation 29

PTC10 Programmable Temperature Controller

Out 1, Out 2, 3A, 3B, 3C, 3D, Cold J 3, 4A, 4B, 4C, 4D, 5A, 5B, 5C, 5D, V1, V2, V3, DIO, Relays

This order does not change unless I/O cards are added, removed, or rearranged.

A third option for reading data is the getLog instruction, which returns the latest data point written to the log. By default, a logged value is the average of ten ADC conversions. Therefore the values returned by getLog are not as noisy as the values returned by the getOutput and <channel>? instructions, both of which return the result from the most recent ADC conversion only. In addition, getLog makes it easier to retrieve data acquired at consistent time intervals. For example, begin by sending this

getLog "3A", last

27.53936

Note that the channel name must be in quotes if it contains a space. Next, send the following command:

getLog "3A", next

27.57375

Each time then returns the new data point.

Control a temperature

The PTC10 can control the temperature of one or more external devices. Each device must include a heater or cooler, and a temperature sensor that monitors the temperature of whatever is being heated or cooled.

-integral-differential (PID) feedback algorithm that can monitor a temperature reading and determine how much power to send to the heater or cooler. The algorithm uses a set of three gain factors to determine how much and how quickly the heater or cooler power should be adjusted when the temperature deviates from its desired value. These gain factors must be properly set before the PTC10 can control the temperature of your system.

Start by plugging the heater and must be in thermal contact with the heater the better the thermal contact is, the more precise the temperature control will be.

Enable the lowpass filter

Adding a lowpass filter to the temperature input usually improves feedback performance. On the Select screen, touch the buttons for the heater output and the sensor input that you plan to use, making sure that they and no other channels are highlighted. er

2 thermocouple input

Operation 30

PTC10 Programmable Temperature Controller

ey. At the top of the screen are two tabs, one for each of the two channels

you selected. Touch the tab for the temperature sensor.

to display the list of available lowpass filter time constants. To get

, which displays a pop-up window with a brief description o press the Help key again to dismiss the help window.

In the Lopass menu, select one of the six options. Select the largest value that is less than the response time of your heater. The lowpass filter reduces noise, improving the accuracy of the PID tuning process and the performance of the tuned PID feedback loop.

Operation 31

PTC10 Programmable Temperature Controller

Configure the alarm

To protect your system from runaway feedback (overheating that can occur if, for example, the PID feedback is configured incorrectly or the se up an alarm. The alarm automatically shuts off the heater whenever the temperature exceeds limits that you specify, whenever the sensor becomes disconnected, and whenever the temperature becomes too high or low for the sensor to measure. On the Setup screen for your temperature sensor, under the Alarm heading, set the options as follows:

Status: This button indicates if the alarm is currently triggered. It can be used to turn off

latching alarms, but it effect on non-latching alarms. Mode Latch Sound: 1 beep. Output: select the heater output channel. The selected channel will be forced to zero

overheating your

system if the sensor is disconnected or incorrect feedback parameters are entered. Relay: For the best possible security, the output should be routed through one of the four

relays (A, B, C, or D) and the Relay button should be set to A, B, C, or D accordingly. The

relay will physically disconnect the heater whenever the alarm is beeping.

Operation 32

PTC10 Programmable Temperature Controller

Min: If the PTC10 is controlling a thermoelectric cooler, set the min to the lower

temperature limit of your system. Otherwise, this value should be set well below the lowest temperature that could normally be produced, so that the min setting can only be exceeded

if something is wrong with the sensor. Max: Set to the upper temperature limit of your system. Lag: Set to 1 s. This will prevent small glitches, such as those caused by autoranging, from

triggering the alarm.

Configure the PID feedback loop

The next step is to tell the instrument which temperature sensor to control and the desired

temperature of that sensor.

The PID loop is configured from setup screen of whichever channel you want to use as the heater output make sure the output that you want to use is selected. configuration.

and touch the blue tab for the output channel that you want to

use, Out 2 . You should see the channel setup screen for channel Out 2:

Operation 33

PTC10 Programmable Temperature Controller

Select which temperature sensor you want to control: in the umn, touch the

window showing all available input channels appears. Touch the button for the temperature that you want to control . Sensor 3A is now the PID input for heater Out 2.

Next, touch the value that you want the temperature to be

driven to

Configure the feedback autotuner

The feedback tuner changes the heater output and measures how much the temperature changes in response. Before this can be done, the PTC10 needs to be told how much the heater output should be changed and indicate how long it should wait for the temperature to change.

Go to the Channel setup screen for the hea

damage your system? Change these values if necessary. feedback, which makes the feedback faster but can also add noise. If D is set to zero, the tuner uses

Operation 34

PTC10 Programmable Temperature Controller

a different tuning algorithm that leaves derivative feedback disabled. This is sometimes necessary to reduce noise in the feedback output.

Start the feedback autotuner

If the system has never been tuned, start with the feedback turned off and the heater at ambient temperature. temperature to stabilize at the setpoint. In either case, the key to successful autotuning is to start with a stable temperature.

If starting at ambient temperature, ensure that the feedback is turned off before enabling the the tab for the output

If the outputs are disabled, enable t Output Enable LED turns on and the PTC10 beeps (if pressed again, the Output Enable key immediately turns all the PTC10 ts off; inputs are not affected).

to start the autotuner. A status window appears and is

updated every few seconds.

Before it begins the actual tuning process, the PTC10 verifies that the Step Y and Lag settings actually change the temperature by a significant amount, and cancels tuning i The figure below shows how this is done.

During the first stage of autotuning, the PTC10 compares how much the

temperature changes before vs. after turning the heater on. Autotuning is

ter the heater is

turned on.

The PTC10 first locks the heater output at its current value for one-third of the Lag time and measures how much the temperature changes. This measurement is the noise and drift. It then increases the heater output by Step Y and waits for the Lag time to elapse. If the temperature

heater output is returned to its original value, and no changes are made to the feedback gains. If the

Tuning was cancelled because the response was less than 10 times the noise and drift one or more of the following:

Operation 35

PTC10 Programmable Temperature Controller

significantly increase the temperature, in which

case Step Y should be increased; increased; or

The temperature was drifting up or down as the test began, in which case the heater should

be left to stabilize at room temperature before trying to tune again.

PTC10 during tuning; tuning will continue unless you turn tuning off or disable the outputs with the Outpu good idea to display a graph of heater output and temperature while autotuning (select the two

button in the bottom-right corner.

When tuning is finished, the PTC10 beeps and the PID feedback is automatically enabled. If the temperature is still below the setpoint, the PTC10 starts increasing power to the heater. The temperature may overshoot the setpoint, but should eventually stabilize at the setpoint.

The feedback should be re-tuned when:

The temperature units are changed (e.g. from °C to °F) The output units are changed (e.g. from W to A) The lowpass filter setting is changed

Operation 36

PTC10 Programmable Temperature Controller

Input filters

The PTC10 offers several numeric filters for processing sensor readings. Except for the sensor calibration, the filters are disabled by default and can be enabled by the user. In the order in which they are applied, the filters are:

1. Sensor calibration (converts sensor reading in ohms, volts, etc. to temperature)

2. Follow filter (virtual channels only; makes the channel equal to another channel. Not the same as the PID follow mode.)

3. Offset/gain (multiplies a channel by a gain and adds an offset)

4. Difference (subtracts the value of another channel)

5. Lowpass (filters out noise)

6. Derivative (takes the derivative of the signal with respect to time)

The filters can interact with each other. For example:

If the settings of filters 1 4 are changed and the lowpass filter is enabled, the effect of the

new setting on the sensor reading is lowpass filtered.

Changing the gain may have unpredictable results if the difference filter is enabled, and

changing the offset has no effect if the derivative filter is enabled.

Custom calibration tables have no effect if the follow filter is enabled.

Custom calibration tables

-in sensor calibration curves are appropriate for your sensors, a custom calibration table can be used to convert the raw sensor reading in ohms, volts, etc. to a temperature. Each channel can have its own custom calibration table.

Custom calibration tables can be loaded with a remote command or with a USB memory stick.

Format of custom calibration tables

bration table for a 100 platinum RTD that at 0°C has a resistance of 100 ohms:

units = °C 0, 100.00 10, 103.90 20, 107.79 30, 111.67 40, 115.54 50, 119.40 60, 123.24 70, 127.08 80, 130.90 90, 134.71 100, 138.51

Units: units that this table converts readings to. If omitted, assumed to be Kelvins. The units can be any string of 4 or fewer characters but must not contain any spaces, periods, plus or minus signs, or numbers. To

Operation 37

PTC10 Programmable Temperature Controller

type the degree sig number pad.

If the sensor readings will be converted to the units specified

by the System.Display.Units setting. If any other units are specified, System.Display.Units is

All other text before the first numeric value is ignored.

Calibration data: The data contains pairs of numeric values: the value to be displayed on the front panel, followed by the value For example, the sample table above tells the PTC10 to display 0 °C when the sensor resistance is 100 ohms.

The numeric values may be separated from each other with one or more commas, spaces, tabs, and/or newlines. to put each calibration point on a separate line as in the example.

The first value in each pair must be expressed in the units declared at the beginning of the calibration table, or in Kelvins if no units are declared.

The second value must be in ohms for resistive sensors, volts for diode sensors and analog I/O channels, or millivolts for thermocouples. For heater driver channels, the native units are by default watts, but can be changed to percent, volts, or amps with the If in doubt, look at which units the reading is displayed in when System.Display.is set to

A calibration table must contain at least two calibration points, and the entire file cannot contain more than 16384 characters (about 400 800 calibration points). Commas should not be used within numeric values.

The data points do t have to be equally spaced; they can be closely spaced in critical temperature areas and more widely spaced in outlying areas. For RTDs, the interval between data points should be 10°C or less to ensure the best possible (0.1 mK) interpolation accuracy. For thermistors, an interval of 1°C or less should be used.

The displayed value must constantly increase or decrease throughout the entire file, and there

. Likewise, the measured value also has to increase or decrease

monotonically. However, the displayed and measured values can go in opposite directions.

The calibration data must cover at least the entire expected range of measurements, which in the example above is 0 to 100°C. When readings fall outside the range of the calibration file, no data appears on the display, and any PID feedback loops that use the affected channel are frozen.

Furthermore, while the PTC10 normally uses a cubic spline algorithm to interpolate between the calibration points, between the first and last two points a less accurate linear interpolation algorithm is used. So the calibration table should ideally extend at least one point beyond the range that you expect to use.

The order of the data points can be reversed (measured value first, displayed value second) by adding a tilde to the beginning of the file. The tilde must be the first character in the file, appearing before the units declaration and any other header information.

How to load custom calibration tables

USB memory stick: create a text file containing the calibration information as described above. The name of the file should be the name of the channel plus the extension directory -level directory of a USB storage device, and copy the .txt file into the directory. Plug the storage device into the PTC10, and the PTC10 automatically loads the files. The device can then be removed.

Remote command: send the command:

Customcal <channel> <calibration data>

Operation 38

PTC10 Programmable Temperature Controller

where <channel> is a channel name and <calibration data> is the calibration information as described below. The data must be on a single line and the entire command must not contain more than 4092 characters.

How to verify that a custom calibration table is loaded

If a channel uses a custom calibration, th name appears in bold on the Select screen.

For more details, go to the Channel Setup screen and press the Channel.Cal.Details button to see

, a

description of the problem. file has any values after the header with no numeric characters, if the values are not monotonically

increasing or decreasing, or if the file ends with a temperature value.

Once a custom calibration table is loaded, it remains in effect until one of the following occurs:

A different calibration table is applied to the same channel, using either a USB memory stick

or remote command.

The calibration type (set with the Channel.Cal.Type button

The following have no effect on custom calibration tables:

Unplugging the USB device with the calibration tables. Plugging in a USB device that does not contain a calibration file for the channel. Restarting the PTC10.

Virtual channels

The PTC10 has three virtual channels named V1, V2, and V3. You can set these channels to any value or make their value follow the value of another channel. The value can then be graphed or saved to the log like any other channel. Here are some uses of virtual channels:

Show the rate of change o

You could just do this in the original channel, but using a virtual

channel lets you display both the original data and the rate of change side-by-side.

Show the d

virtual channel lets you keep the original data.

Run this macro to continuously set the value of a virtual channel to a feedback setpoint:

[waitForSample V1=#Out1.PID.actual]-1

Now the setpoint can be plotted on-screen and logged to USB.

Run this macro to show the value of channel 3A divided by the value of channel 3B:

[waitForSample #a=#3A #a/=#3B V1=#a]-1

Operation 39

PTC10 Programmable Temperature Controller

Logging data to internal memory

The most recent one million readings from each channel are saved in internal RAM and can be

plotted on-screen or retrieved using the getLog instruction. The amount of time that the internal

Log

interval

Time span of

internal log

0.1 second

1.2 days

0.3 second

3.6 days

1 second

12.1 days

3 seconds

36.4 days

10 seconds

121 days

30 seconds

1 year

1 minute

2 years

3 minutes

6 years

10 minutes

20 years

30 minutes

60 years

1 hour

120 years

All saved readings are erased when the log interval is changed.

Data from a single sensor can be logged at two different intervals by configuring one of the virtual channels (V1, V2, or V3) to follow an existing channel (set the IO type of the virtual channel to Input, then touch the Follow button) and then setting its log interval to a different value.

Logging data to USB

The PTC10 can record channel readings on removable USB memory devices such as USB hard drives or flash memory keys. When a USB device is plugged in, it takes the PTC10 several seconds (normally about 5 seconds) to recognize the device and for the USB logging feature to become available.

A small dark-red circle in the upper-right corner of the screen appears when a USB device is present but USB logging is turned off. The circle turns light red whenever data is being logged to USB. If no USB stick is present, the circle disappears completely. To log data to a USB device, plug the device into the PTC, touch the dark-red circle, and wait a few seconds until it turns light red. Touch the circle again to stop logging.

The PTC10 cannot read logged data from the USB memory. Data shown on the plot screen always comes from RAM.

Do not unplug a USB device or switch the PTC10 off while the PTC10 is logging to the device. Either of these actions causes off, touch the USB logging indicator in the upper-right corner of the screen and wait for it to turn dark.

ADC sampling and logged data

The PTC10 has two different sampling rate settings: one controls how often data is acquired, and another con

Operation 40

PTC10 Programmable Temperature Controller

A/D rate

The A/D (analog-to-digital conversion) rate controls how often a data point is acquired from each channel. All channels are read at the same A/D interval, which by default is 300 ms. This setting mainly affects the performance of feedback loops: the faster the A/D rate is, the more quickly the PID loops can respond to changing temperatures; the slower the A/D rate, the less noise there is in the PID output.

By default, the A/D conversion process is synchronized with the AC line voltage and the A/D rate can only be set to multiples of the AC line period. For example, if the A/D rate is set to 100 ms, A/D conversions occur every six cycles of the AC voltage if the PTC10 is plugged into a 60 Hz AC wall socket, or every five cycles for 50 Hz AC. This prevents 60 Hz noise from aliasing into temperature readings, which would cause a slow sinusoidal variation in the readings. 60 Hz noise still creates a constant offset in temperature readings, but the offset is usually too small to be of concern with thermocouple readings and can be removed from RTD readings using current reversal.

jumper on the motherboard s possible to set the A/D rate to any value between 10 and 1000 ms with a resolution of 1 µs (note that the jumper should only be moved while the system is switched off). However, the A/D conversions will no longer be perfectly synchronized to the AC line voltage, even if the A/D rate is set to a multiple of the line period. As a result, low-frequency sinusoidal interference may appear in your temperature sensor readings. The frequency of the noise is the difference between the AC line frequency and the closest multiple of the ADC conversion rate in Hertz. For example, if the A/D conversion rate is 10 Hz and the AC line frequency is 60.1 Hz, a sine wave with a frequency of 60.1

(6·10) = 0.1 Hz may be superimposed on all temperature readings.

This interference can be minimized by setting the A/D rate to either 90 Hz (if the line frequency is 60 Hz) or 75 Hz (for a 50 Hz line frequency) and then setting the lowpass filter to a value of at least 3 seconds on all input channels.

Log rate

The log rate controls how often channel readings are logged. The log rate can be set independently for each channel; the default is a point every 0.3 seconds. Normally the time between log points should be longer than the time between A/D samples, in which case multiple A/D readings are averaged together to create each logged value. If, on the other hand, the time between log points is shorter than the time between A/D samples, each A/D reading is recorded more than once in the log.

The plot screen always displays logged data. Therefore, a slow log rate reduces the noise visible in the graphs and may produce a stairstep appearance, while a fast log rate produces graphs with more detail.

Format of PTC10 log files

The PTC10 are in a .CSV format that s compatible with most spreadsheet programs. The first line contains a comma-separated list of channel names and each subsequent line contains a comma-separated list of values. The first value in each line is the time in milliseconds since 2000.

The data readings are sav changed while logging, there will be a discontinuity in the data.

If a sensor was disconnected, its reading was out of range, or no reading was acquired at the indicated time, then its value is empty and two consecutive commas appear.

Operation 41

PTC10 Programmable Temperature Controller

of the I/O cards.

Automatic fan control

At every A/D conversion, each I/O card reads internal temperature sensors and determines how fast it needs the system fan to run. The main system processor reads the desired fan speed from each I/O card and, if the System.Other.Fan contr , sets the fan to the fastest requested speed.

For the PTC430 DC output card and PTC440 TEC driver, the requested fan speed depends on the temperature of the amount of current being delivered, the voltage range, and the voltage drop across the heater.

For the PTC320 thermistor/diode/RTD reader, PTC321 RTD reader, and PTC330 thermocouple temperature specified with the Channel.PCB control. If the card temperature is below its Channel.PCB setting, the card Since the default PCB setting is 30°C, the temperature is normally regulated only if the PTC10 gets unusually warm.

To improve the thermal stability of the input cards, the Channel.PCB setting of one card can be reduced to a value just below its normal temperature, such that the fan is always running and the

kept at the Channel.PCB value. However, if the PTC10 outputs a large heater current, the fan speed increases to keep the output card cool and the temperature of the input cards may fall out of regulation.

Manual fan control

he fan speed can be manually set by changing the System.Other.Fan control to a value other than auto. In this case, the fan speed requested by the I/O cards is ignored. If the fan is turned off completely, the user must ensure that the temperature inside the PTC10 does not exceed 35°C or damage to the PTC10 may occur. In addition, temperature inputs may not be accurate at elevated temperatures.

The PTC430 DC output card and PTC440 TEC driver are prone to overheating if the fan speed is manually set to a value that is too low, especially if the card is operated at a high voltage range and heater resistance is low. If the PCB temperature of one of these cards exceeds 60°C, its output is automatically shut off. Set the output to zero to re-enable it, for example, by pressing the Output Enable key (which will disable all

Besides the main system fan, the PTC10 also has an internal fan that periodically turns on to keep the main power supply cool. This fan is unaffected by any user-accessible setting.

Operation 42

PTC10 Programmable Temperature Controller

To control a temperature, the PTC10 must be connected to a temperature sensor that measures the temperature in question, and to a heater or cooler that raises or lowers the temperature when power is applied. Although the heater/cooler will just be cal following principles apply whether it is a resistive heater, a thermoelectric device that can both heat and cool, or a cooling-only device such as a fan.

How sta

Under ideal conditions, when equipped with a PTC320, 321, or 323 input card, the PTC10 can regulate temperatures to within 1 mK. In practice, though, the level of stability mainly depends on external factors such as the amount of ambient temperature variation, the size of the sample being heated, and the type of sensor and heater used. To achieve optimum stability:

An appropriate thermistor, RTD, or diode for your temperature range must be used. Divide

the noise specification of the PTC10 input card (shown in the front of this manual) by the

estimate the

best-case stability for that sensor.

The sample should be small compared to the heater, and the sample and heater should be in

good thermal contact.

The system must be able to cool down as fast as it can be heated up. Cooling rates can be

very slow if the setpoint is close to the ambient temperature or the sample is thermally insulated. Under these conditions, thermoelectric devices generally produce more stable temperatures than resistive heaters since they can actively cool the sample.

If the PTC10 is controlling the temperature of an environmental chamber, the response time

can be improved (at the expense of added vibration) by using a flow-through configuration in which moving air is heated or cooled before it enters the chamber.

Ambient temperature variations must be minimized. It may be necessary to enclose the

temperature-

Basic PID feedback concepts

The PTC10 supplies a varying current, voltage, or power to the heater, and assumes that the measured temperature will increase or decrease in a roughly linear fashion with this output signal.

on external factors that vary unpredictably such as, for example, the ambient room temperature. Therefore, to maintain a consistent temperature, the heater power has to be determined by an algorithm that can monitor the temperature (T) and continually adjust its heater output (Y) with

the amount of heater output required to maintain that temperature.

In the PTC10, as in most other temperature controllers, the algorithm used is PID feedback, which is actually a combination of three algorithms.

The proportional feedback algorithm determines the error, i.e. the difference between the desired temperature (the setpoint) and the actual temperature T. The output Yp of the proportional feedback algorithm is just the error multiplied by a constant, P:

E(t) = (setpoint T(t))

Operation 43

PTC10 Programmable Temperature Controller

Yp(t) = P · E(t)

As the actual temperature approaches the setpoint, the proportional output Yp decreases to zero, at which point no power is supplied to the heater.

Normally, however, some power is required to keep the heater at the setpoint, which is why the integral feedback algorithm is needed. It multiplies the error by a constant (I) and adds the result to the previous integral output:

Yi(t) = I · E(t) + Yi(t 1)

As the actual temperature approaches the setpoint, the rate of change of the integral output Yi drops to zero. In effect, integral feedback sets the steady-state heater power.

Derivative feedback tries to predict what the temperature will be in the future by multiplying the rate of temperature change by a constant, D:

Yd(t) = D * (T(t 1) T(t))

If the temperature is increasing (and D is positive), derivative feedback reduces power to the heater; if the temperature is decreasing, derivative feedback increases power to the heater.

The output of the PID feedback loop (i.e., the heater power) is the sum of the three feedback algorithms:

Heater power = Yp(t) + Yi(t) + Yd(t)

The key challenge to using a PID feedback loop is determining the best feedback gains. The constants P, I, and D are different for every apparatus and must be determined experimentally. As a

variations; if they are too high, the feedback responds too much and overshoots the setpoint, and both heater power and temperature may begin to oscillate. The faster the temperature changes in response to the heater, the larger the gains can be.

Manual tuning

In this section we will use step response curves to illustrate some basic aspects of how the three feedback parameters P, I, and D affect feedback performance.

Proportional: the figure below illustrates the effect of changing the proportional gain P. The top graph shows the power being delivered to a heater by a PID feedback loop during four separate tests, while the bottom graph shows the temperature of the heater during the same tests. Each test is identical except for the value of P. At 1 minute, the setpoint is increased from 60 to 70°C. When P = 1 W/°C (second curve from top), the feedback loop exhibits a perfect response; that is, the temperature rapidly increases to 70°C with a slight overshoot that serves to minimize the settling time. If P is increased to 2 W/°C, the temperature responds more quickly but then overshoots the setpoint by an excessive amount, causing the system to oscillate.

Operation 44

PTC10 Programmable Temperature Controller

Interestingly, decreasing the proportional gain to 0.5 or 0.25 W/°C also results in more overshoot and can even cause oscillations, despite the fact that the heater response is smaller and the temperature rise integral feedback to take more responsibility for raising the heater power and as the next figure illustrates, the integral feedback has a greater tendency to overshoot and oscillate.

Integral: as with proportional gain, increasing the integral gain I also results in a larger heater

feedback is slow because it works by adjusting its previous output, rather than re-calculating its output from scratch at each feedback cycle. Therefore, integral feedback has a tendency to overshoot the setpoint and cause oscillations.

When I is reduced to 0.001 W/°C/s, the temperature at first responds quickly due to the action

of the proportional feedback. However, close inspection (see the lowest trace in the bottom graph)

time period shown. Without enough integral gain, temperature errors tend to persist. As an approximate guide, the integral gain should be about one-tenth the proportional gain.

Operation 45

PTC10 Programmable Temperature Controller

Derivative: derivative feedback reduces the heater output whenever the temperature is rising rapidly. In the example below, when the derivative gain D is increased from 3 to 6 W·s/°C, the amount of overshoot and oscillation decreases. The temperature rise is also a little slower, but because there is less oscillation the system stabilizes at 70°C sooner.

However, if the derivative gain is too large, it too can produce oscillations because when the temperature is rising rapidly, derivative feedback reduces the heater output, which causes the temperature to rise more slowly, which makes the derivative feedback increase the heater output, and so on.

Operation 46

PTC10 Programmable Temperature Controller

With the right amount of derivative feedback, we can increase P and I to levels that would

otherwise cause oscillations, and thereby obtain faster, more responsive feedback control.

Automatic tuning algorithms

During automatic tuning, the PTC10 changes the heater power, measures how much and how quickly the temperature changes in response, and then estimates the optimum values of the gain factors P, I, and D. Two tuning algorithms are available on the PTC10: the relay tuner and the step response tuner.

Relay tuner

Heater power (top) and sensor temperature (bottom) during relay

autotuning. Step Y is 1 W, Lag is 30 s, feedback is initially on, and the

system starts with the temperature stabilized at the 50°setpoint. After the

tuning has finished, the feedback turns on and re-stabilizes the system at

50°C after a few cycles of oscillation.

The relay tuner creates a temperature oscillation by switching the heater between two output values:

Output

high

= OutputI + (Step Y)/2

Output

low

= OutputI (Step Y)/2

where OutputI that the relay tuner cannot be started unless the output is greater than (Step Y)/2. For best results, the output should be greater than Step Y.

The relay tuner begins by disabling the feedback (if the feedback was on) and measuring the drift and noise of the feedback input signal in the absence of any changes to the feedback output. The drift-and-noise measurement continues for one-third the amount of time specified with control; the resulting drift-and-noise value is the difference between the largest and smallest input signal observed during this time.

After the drift and noise measurement, the relay tuner sets the heater output to Output

low

for the Lag time to start the oscillation. If during this period the feedback input does not change by at least ten times the drift-and-noise value, an error message is displayed in the Status window and tuning is

Operation 47

PTC10 Programmable Temperature Controller

cancelled. If this occurs, either 1) ensure that the temperature is stable before starting the step respond, increase the Lag time.

The tuner then sets the output to the Output

high

value. Then, each time the temperature crosses its initial value (50 °C in the figure above), the output is switched from high to low or low to high. This produces a temperature oscillation 180° out of phase with the output oscillation. The tuner performs two oscillation cycles, not including the kick start, and measures the period and amplitude of the second oscillation.

The relay tuner has to wait several times for the temperature to cross its initial value. If the temperature measurement is disturbed during this time (for example, if the temperature sensor is moved, or if the sensor is in an oven and the oven door is opened), the temperature may never cross its initial value and the tuner may run indefinitely without finishing.

Step response tuner

Heater power (top) and sensor temperature (bottom) during step response

autotuning. Step Y is 2.5 W, Lag is 45 s, feedback is initially off, and the

system starts at room temperature. After the step response is complete,

the feedback turns on and the temperature drops before stabilizing at the

50°C setpoint.

The step response tuner makes a single change to the amount of power delivered to the heater, and measures how much and how quickly the temperature changes in response.

The step response tuner begins by disabling the feedback (if the feedback was on), and measuring the drift and noise of the feedback input in the absence of any changes to the output. The drift-andnoise measurement takes one- and-noise value is the difference between the largest and smallest input signal during this time.

period the feedback input does not change by at least ten times the drift-and-noise value, an error that the temperature is stable before starting the step response; or 2) increase step Y; or 3) if it

The tuner continuously measures how quickly the feedback input changes, (i.e., the slope of the feedback input with respect to time). Tuning ends once the lag period has passed and the most

Operation 48

PTC10 Programmable Temperature Controller

recent slope is less than half the largest slope. The tuner then calculates the maximum slope, the lag time, and the total response, and uses these values to calculate the PID gains.

the feedback input channel to achieve accurate tuning results. Since the relay tuner does not require

sensitive to noise than the step response tuner.

if both its high and low

; otherwise, it selects the step response tuner. For example, if the out o negative) when autotuning is started, the step response tuner runs because the relay tuner would require a negative output.

Aggressive, moderate, and conservative tuning

Both the step response and relay tuners offer aggressive, moderate, and conservative tuning options. Conservative tuning theoretically produces zero overshoot and is usually the best choice when the temperature needs to follow a changing setpoint. The aggressive tuning option theoretically produces 25% overshoot (although in fact it tends to be larger) and is usually the best choice for applications in which the setpoint is constant. Moderate tuning produces a very stable feedback loop that behaves reasonably in a wide variety of situations.

The figure below compares when we change the setpoint from 60 to 70°C after relay tuning with the aggressive, moderate, and conservative options. In this case, conservative tuning produces the best response.

However, the results are much different if we look at how the system responds to a thermal disturbance. The next figure shows how well the system recovers when we start blowing air over the heater with a fan. The setpoint is a constant 60°C. In this case, aggressive tuning produces the best response.

Operation 49

PTC10 Programmable Temperature Controller

The actual behavior of your system might vary significantly from the behavior shown in these figures. In any event, the feedback gains determined by the automatic tuning algorithms should generally be regarded as only a starting point. In critical applications, the gains normally need to be manually adjusted to achieve good feedback performance.

Using the automatic tuner

Start with a stable temperature. Before the autotuner is started, the temperature must be

he easiest way to get a stable temperature is to let the system sit undisturbed for a long period of time with the heater off. On the other hand, if the PID gains have been set before and just need to be re-optimized, it may be easier to turn the feedback loop on and let the feedback stabilize the temperature. The autotuner can be started with the feedback either on or off.

Disable or enable derivative feedback. Because derivative feedback can amplify sensor noise, it may sometimes be preferable to disable it. If the derivative feedback gain is set to zero before autotuning begins, derivative feedback is disabled and the autotuner calculates P and I feedback gains, leaving the derivative feedback set to zero. In contrast, if the derivative feedback gain is initially nonzero, the autotuner calculates P, I, and D feedback gains using a more aggressive

autotuning produces faster-acting feedback but more noise. If your temperature sensor is noisy or

Set the step size and lag time.

controls how long the PTC10 waits for a response. If either value is too small, the PTC10 may, after attempting to tune, display a message saying that there was an insufficient response. If the values are too large, tuning will take longer than necessary and your heater will get excessively hot.

Start tuning. To begin tuning, go to the channel setup screen and set the tuning mode to

If the tuner finishes successfully, a high-pitched tone plays and the feedback loop starts running. If the tuner was unsuccessful (because Output Enable was off, the heater was unplugged, the temperature sensor was unplugged, the heater was out of range, or the response was too small), a low-pitched tone plays and the feedback loop is turned off.

When PID tuning is start ars.

Operation 50

PTC10 Programmable Temperature Controller

window does not cancel autotuning; to cancel autotuning, either 1) ;

2) touch th or 3) disable all out If the status window is dismissed, it can be displayed

Explanation of error messages produced by the autotuner

One of the following messages appears in the Tuning Status window if tuning was unsuccessful. If

Tuning was cancelled because the response was less than 10 tim es the noise and

drift

This message indicates that the heater produced an insufficient temperature response. It can

result from any of the following factors:

The temperature was not stable before the autotuner was started, or the temperature was

changed by some external factor after the autotuner was started. In particular, after running

-stabilize before running the

autotuner again.

The autotuner disturbance size (Step Y) was not large enough to create a noticeable change

in the temperature.

The autotuner wait time (Lag) was not long enough for the heater to change the

temperature.

To determine the source of the problem, look at a dual plot with the heater output on one plot

and the sensor temperature on the other. Make sure that the temperature was stable before the heater turned on and that it changed significantly after the heater was turned on.

Autotuning was cancelled because the Tune->Mode control was set to "Off"

This message indicates that the user turned off autotuning (by setting the autotuning mode to

Autotuning was cancelled because the PID mode was set to m anual.

The user turned off PID feedback while the tuner is running. The tuner is unable to run when

PID feedback is turned off.

Autotuning was cancelled because the PID mode was set to \"follow\"

Tuning was cancelled because the input was disconnected

No sensor signal was detected. Ensure that a sensor is plugged in and that its reading is not blank.

If the reading is blank, an incorrect sensor range, sensor type, or calibration may be selected.

Unable to tune feedback because the outputs are disabled. Press the Output Enable

button to enable outputs.

The outputs must be enabled before autotuning, or else the PTC10 will not be able to provide

any power to the heaters.

Operation 51

PTC10 Programmable Temperature Controller

Unable to tune feedback because the heater is disconnected

This message appears when the heater is connected to channels Out 1 or Out 2 and the measured

heater resistance is less than 1 ohm or greater than 10,000 ohms.

Unable to tune feedback due to a hardware fault in the heater output

This message appears when the heater is connected to channels Out 1 or Out 2 and the current at the + and terminals is not equal, or current was detected when the heater was supposed to be off, or the measured current differs from the expected current. Make sure that the heater is not shorted to ground or to another power supply.

Unable to tune feedback because the heater is under range Unable to tune feedback because the heater is over range

If Step tuning is selected, the heater output must be less than the maximum output minus Step Y. If Relay tuning is selected, the heater output must be less than the maximum output minus Step Y/, and greater than the minimum output plus Step Y/2.

Suggestions for best tuning results

mperature on

separate graphs. Make sure that you can see the temperature begin to rise or fall after the heater output changes.

If tuning fails, let the temperature stabilize and try increasing the step Y or lag before

attempting to tune again. You may also need to increase the lowpass filter time constant.

The temperature must be stable when tuning is started. Either the feedback must be running

and stabilized at the setpoint, or the heater must be off and the temperature stabilized at the ambient temperature.

Set the lowpass filter on the input (temperature) channel to a value just below the expected

response time of the system. The step response tuner in particular requires adequate lowpass filtering to produce accurate results.

Make sure the syst

process.

Since the ideal feedback parameters usually vary with temperature, run the tuning algorithm

at about the temperature at which the feedback will be used. If the system has never been tuned before you may need to tune at room temperature, then let the feedback bring the system to its working temperature, and re-tune at the working temperature.

The autotuning algorithm assumes that the temperature is a linear function of heater power.

y the algorithm may not be

perfectly accurate and may need to be manually adjusted.

Operation 52

PTC10 Programmable Temperature Controller

The front panel has six menu keys to the left of the display . These keys can be pressed at any time to display one of the six main screens. Each of the main screens except for the Program screen has six columns of buttons, usually with a column name at the top of each column. Each button has a name in large text and, usually, a value beneath the name in smaller text.

In this manual, buttons are referred to by the name of the screen (Select, Numeric, Plot, etc.), the name of the column (if any), and the name of the button, separated by dots. For example,

of the System screen. The

(RS-232, USB, etc.) as a remote command.

USB logging indicator

If a USB memory stick is plugged into the PTC10, a small dark-red circle appears in the upperright corner of the screen. Touch the circle to turn USB logging on; the circle will turn light red to indicate that data is being logged to USB. Touch the circle again to turn USB logging off.

Removing the USB memory device or powering down the PTC10 without first ejecting the device causes loss of data and corruption of the memory device. A corrupted device should be repaired by plugging it into a PC and running a program such as chkdsk (Windows) or fsck (Linux).

information about whichever window

bring up the Value inpu with pop-

When the PTC is turned on, all outputs are disabled (however, inputs function normally). This

vide power to

the heaters. To turn on the outputs, press that were previously running begin to provide power to the heaters.

If the outputs are enabled, pressing them to zero. Inputs continue to function normally. In an emergency situation, the Output Enable key is the quickest way to turn off the PT -enabling the outputs immediately returns all outputs to their previous values.

In certain cases it may be desirable to have the PTC power up with the outputs enabled to ensure that feedback loops automatically resume after a power failure. This can be accomplished with a

Operation 53

PTC10 Programmable Temperature Controller

The Output Enable key is not intended to prevent electric shocks. When handling exposed

heater wires, always disconnect the wires from the PTC10 or unplug the PTC10 from the wall.

Press and hold the "Output Enable" key for 3 seconds to put the PTC10 into standby mode. In standby mode, the outputs are turned off, data acquisition and macros are paused, the front panel display and system fan are shut off, and the system does not respond to remote commands. RTD excitation currents are still on, and an internal cooling fan may switch on occasionally. Press the "Output Enable" key again to leave standby mode.

Each column of buttons on this screen represents one I/O card, and each button shows the name and the current value of an I/O channel. The value may not appear if no sensor or heater is connected to the channel.

The PTC10 includes two I/O cards as standard equipment: a 4-channel, ±10V analog I/O (AIO) card in slot 5, and a digital I/O (DIO) card in slot 6. These cards appear in the two rightmost columns of the Select screen. The remaining four columns show any optional I/O cards that have been installed.

Buttons turn red at is, if the alarm is enabled and the reading is outside of the alarm limits or no sensor is connected. The name of the channel appears in bold if the channel uses a custom calibration table.

o view on the Numeric, Plot,

and Channel screens. The top of the Select screen has four Group tabs that let you save and recall button to change the selection group.

Operation 54

PTC10 Programmable Temperature Controller

This screen displays the current values of the selected channels as numbers. The more channels that are selected, the smaller the displays are. If enough space is available, an annunciator may appear that indicates whether the sensor or heater is disconnec u outputs are disabled

Input displays turn red whenever the alarm is triggered. The name of the channel appears in bold if the channel uses a custom calibration table.

Repea Touch one of the channel displays to show setup menu for the channel.

This screen shows logged data from the selected channels on one or more graphs. Press the Plot key repeatedly to cycle between the four formats described below (single, multi, custom, and ponytail).

The Plot screen always shows logged data. If, for example, the log interval is set to 10 s, the graph will have a very 10 seconds.

Operation 55

PTC10 Programmable Temperature Controller

Touch the tabs at the top of the screen to change the selection group. Each of the four groups remembers its graph format (single, multi, etc.), X range, and Y range. Therefore, when you change the selec so change.

Single plot

Up to eight selected channels are shown together on one graph with a single Y axis. If more than

eight channels are selected, only the first eight are shown.

Single plot mode showing the ambient temperature measured by two

thermocouples (channels 3B and 3C) and one Pt100 RTD (4B). RTDs

have a much lower noise level than thermocouples.

Multi plot

Each channel is shown in its own graph with an independent Y axis. If more than eight channels

are selected, only the first eight are shown.

In multi plot mode, each sensor gets its own graph. The X scale is the

same for all 3 graphs, but the Y scale is different.

Operation 56

PTC10 Programmable Temperature Controller

Custom plot

Each channel is assigned to a plot according to its Channel.Plot setting.

In custom plot mode, the user can manually assign each channel to a

graph. Here the thermocouple inputs have been assigned to plot 1 and the

RTD input to plot 2.

Ponytail plot

Like Single plot, up to eight selected channels are shown together on one graph. Each trace is offset by its initial value so that the trace begins at zero. The offset is recalculated whenever you touch the graph to zoom or pan, or whenever you switch to another screen and back to the Plot screen. If , the offset is never recalculated.

Using the ponytail plot does not affect how channel values are logged; the offsets are only applied to the plots, not to the log files.

In ponytail plot mode, all traces are offset so that they start at zero.

Operation 57

PTC10 Programmable Temperature Controller

Zooming and panning

To change the X axis scale of a plot, touch anywhere inside the plot:

Touch the right half of the plot to zoom in Touch the left half to zoom out Drag to pan.

Whenever the most recent data is visible on the graph, the graph automatically scrolls to keep the most recent data bottom-left corner of the screen to indicate that scrolling is disabled. To show current data and

Graphs that appear together on a screen always have the same X axis range. However, each selection group has its own, independent X axis range.

How to change the X axis scale

How to pan the graph horizontally

Operation 58

PTC10 Programmable Temperature Controller

By default, the PTC10 continually adjusts the Y-axis scale to accommodate all the data on the graph. Each graph has its own, independent Y axis scale. To change the Y axis scale for a particular graph, touch the area to the left of its Y axis.

Touch the top third of the Y axis to zoom out. Automatic scaling is disabled, so the Y axis

scale no longer changes as new data is acquired.

Touch the middle third to 1) re-enable automatic scaling and 2) reset automatic scaling, that

is, ignore previously-acquired data and adjust the Y range to accommodate only new data. Touch the bottom third to zoom in. Automatic scaling is disabled. Drag to pan.

How to change the Y scale of the bottom graph

How to pan the bottom graph vertically

Operation 59

PTC10 Programmable Temperature Controller

Program

A program is a set of one or more instructions that can be used to customize the behavior of the instrument. Programs can be input over the RS-232, GPIB, USB, or Ethernet interface, from the program screen, or as a files on a USB memory device. Regardless of how a program was input, its progress can be monitored from the program screen.

The Program screen has an Input window, which shows text received over RS-232 or GPIB; a Messages window, which shows responses and error messages from the PTC10; and a Progress window, which shows the list of instructions that make up the current program.

If a program is not running, you can compose or modify a program by touching a line in the Progress window. Touching a blank line brings up a list of possible commands. Touching a line that already contains an instruction brings up a list of three options: you can add a new instruction on the line above the one that was touched; delete the instruction that was touched; or replace the instruction that was touched.

The Program screen has six buttons:

Play sym bol

If a program is displayed but not running, press this button to start the program. If a program is running in the currently-selected tab, the button is highlighted and pressing it stops the program.

Pause symbol

Press this button to temporarily pause the program running in the currently-selected tab. Press the button again to resume running the program.

Clear

Erases all text from the Input, Messages, and Progress windows. Unless it has previously been saved, the current program is lost. This button cannot be pressed while a program is running in the current tab.

Load

Touch this button and a list of programs stored in memory is displayed. Programs can be stored in memory with the Program.Save or by attaching a USB device with text file the list and its component instructions are displayed in the Progress window, replacing whatever was previously in the window.

Operation 60

PTC10 Programmable Temperature Controller

The Program.Load button can be used to edit a previously-saved program: load the program,

then edit it in the Progress window, and finally re-save the program with the Save button.

To call a previously-

use the Program.Load button, since it would erase the rest of the program. Instead, touch the

Progress window and select the saved program from the list of commands. The Program.Load

button cannot be pressed while a program is running in the current tab.

Save

Saves the current program, as shown in the Inpu a name for the program. Up to 15 programs can be saved. If 15 programs are already saved, the Save button will have no effect.

hing a line in

any other

instruction) over one of the remote interfaces.

Delete

Touch this button to display a list of programs stored in memory. Select a program from the list and it will be deleted from memory. The Program.Delete button does not affect the status of currently-running macros.

Sending programs over RS-232, USB, GPIB, or Ethernet

Programs can be entered from a remote interface such as RS-232, USB, Ethernet, or the optional GPIB port. Each line of text sent to the PTC10 is run as a separate program (the entire program must be on a single line). If two or more lines are sent to the PTC10 in quick succession, the programs may run concurrently; that is, the PTC10 does not finish running the first program before beginning the second. However, the first program sent will always begin running before the

instruction.

Preparing programs as files on USB memory devices

The PTC10 can also read programs that are stored as text files in a USB memory device. This is the best way to enter longer programs.

program in a word processor or text editor device into the PTC10. To verify that the program is available, look for its name in the Macros column of the System Setup screen. The program can be run just as if it were saved in the memory; however, after the USB device is unplugged, the program can no longer be started.

While the PTC10 is running you can unplug the USB device, use a PC to edit a program stored

on the device, plug the USB device back into the PTC10, and run the new version of the program. button to re-load the program.

Program files can contain up to 16384 characters, and may include multiple lines and comments (an apostrophe, i.e. a single quote mark, indicates that the rest of the line is a comment). Except for the first newline after a comment, all whitespace is ignored; each line can be empty or can contain one or more instructions.

Operation 61

PTC10 Programmable Temperature Controller

Preparing programs from the front panel

Simple programs, such as a series of temperature ramps, can be entered from the front panel. To enter a program f

Progress window. A list of available top-level commands appears.

Any button with a name ending in a dot brings up a sub-menu when pressed. For example, the

commands to change the feedback setpoint or alarm limits for a channel are accessed by first

Touch the left square bracket (the button in the upper-left corner). Square brackets surround

Program screen, where the first line in the

Progress window is now a left square bracket.

Touch the Progress window again, anywhere beneath the first line. The list of possible

list of

Operation 62

PTC10 Programmable Temperature Controller

the

Touch the OK button. You are returned to the Program screen and the instruction

Operation 63

PTC10 Programmable Temperature Controller

e pause instruction has two arguments that

instruction will pause the program for one second.

three times.

Press the start button. While the program is running, the current instruction is highlighted and

the total number of repetitions as well as the number of repetitions remaining appears next to the appears at the top of the screen. By touching this tab, you can enter and start a second program

while the first program is still running.

Messages window.

Once the program is finished you can press the start button to run the prog

Running concurrent macros

Since a macro can run for a long period of time or even indefinitely, macro before macro simultaneously.

The PTC can run at most ten concurrent macros (including the startup macro, macros received over all I/O ports, and macros started from the Program screen). If an eleventh macro is started, a

message appears and the macro does not run.

If the PTC10 is turned off and turned back on again, macros that were running when the PTC10 was turned off are not restarted.

Operation 64

PTC10 Programmable Temperature Controller

screen

The Channel screen includes controls for all settings that affect individual data channels. Sensor calibration, PID feedback parameters, and alarms are all set up through this screen. Note that the layout of the screen varies depending on which channel is selected; for example, only output channels have PID controls, while only input channels have alarm controls.

Only one channel can be set up at a time. One tab appears at the top of the screen for each channel in the current selection group; select the tab for the channel you want to set up.

Name

Sets the name of the channel. The name must have 10 or fewer characters.

Value

If the channel is an input, this button shows the most recent reading but is grayed out, indicating

not grayed out and pressing this button allows you to enter a new output value. However, if PID feedback is turned on or Output Enable is off, changing the value will have no effect.

Off

Sets the PID feedback mode to Off, cancels any PID tuning processes currently operating on the

whichever is higher. This

button is only available for output channels.

Low lm t

This control, which is only available for output channels, sets the minimum output. However, if

the minimum is greater than zero, the output is still set to zero whenever outputs are disabled with should normally be changed when the output units are changed, since the limits are not

automatically converted to the new units.

Hi lm t

This control, which is only available for output channels, sets a maximum limit on the output.

ter. If

the high limit is less than the low limit, the low limit takes precedence.

Operation 65

PTC10 Programmable Temperature Controller

Range

If the I/O card has more than one range, pressing this button displays a menu of available ranges.

If the card only has a single range, this button is grayed out.

IO type

Each output channel has an ADC that can measure the actual

-purpose analog and digital I/O channels are bidirectional, i.e. they can be

used to monitor external signals, or to produce signals. In these cases, the IO type button has three

ts a voltage and the value you see on-screen is the

value you a external voltage, and the channel will measure that voltage.

Plot

Indicates which plot the channel will appear in when the Plot screen is showing, the plot type is

Choose one of eight plots for the channel to appear in, where plot 1 is the uppermost plot. If no

Plot screen. For example, if all

selected channels are assigned to plot 4, only one plot appears on the Custom plot screen.

Logging

By default, each chann once every second. This global log rate can be changed on the System screen (System.Log.Interval). The Logging button makes it possible to override the global log rate for individual channels.

Figures

Sets the maximum number of digits that are shown after the decimal point for all channel values. Fewer digits may be shown if the value wouldn fit into the available space. This setting does not affect logged data, PID feedback, or plots.

If th the System screen.

Cycle (AC output card only)

The PTC420 has a solid-state relay that can either deliver full power or no power to the heater. To more precisely control the power delivered to the heater, power is switched on for some fraction of a preset cycle time, then switched off for the remainder of the cycle. For example, if the cycle time is 10 seconds, the relay might switch on at time t = 0 s, off at t = 1 s, on at 10 s, off at 11 s, on at 20 s, and so on. This would produce 10% of the maximum output.

The Cycle instruction sets the on/off cycle time. Shortening the cycle period will reduce temperature swings associated with switching the current on and off, but will also reduce the lifetime of the relay. The cycle time must be between 1 and 240 seconds inclusive.

Dither (DC output card only)

The DC output card has a 16 bit DAC. For greater resolution, the least significant bit can be dithered. Dithering is enabled by default.

Operation 66

PTC10 Programmable Temperature Controller

Current (4-channel RTD reader and 1-channel thermistor/diode/RTD reader only)

Controls the direction of the sensor excitation current. Reverse the current to detect offsets due to parasitic thermocouple EMFs or 60 Hz noise. In AC mode, these offsets are automatically removed by reversing the current at each ADC reading; each reported temperature is based on the average of the last two ADC readings (cutting measurement bandwidth in half). The PTC320 thermistor excitation current can be turned off entirely with this control.

Current (TEC driver card only)

Controls the amount of excitation current (1 mA, 100 µA, 10 µA, or auto) provided to the temperature sensor. The sensor excitation current on the TEC driver card cannot be reversed.

PTC440 TEC driver when a resistive sensor is in use. The sensor resistance is continuously monitored and the excitation current is adjusted whenever the sensor resistance rises above or drops below the levels shown in the table. T always produces 1 mA when an LM335 or AD590 sensor is in use.

Sensor

resistance

Excitation

current

<2 k

1 mA

1 20 k

100 µA

>10 k

10 µA

TEC driver (for resistive sensors only)

The overlap of the resistance ranges keeps the PTC440 from rapidly switching back and forth between two excitation currents. If, for example, the sensor resistance is between 1 and 2 k , the PTC440 can select either 1 mA or 100 µA excitation, and if possible, it keeps the excitation at its previous value.

Slew (Only appears on the Out channel of TEC driver cards)

Sets the maximum positive and negative rate of change of the TEC driver output. The rate must be between 0 and 1000 amps per second, and the default value is 100 amps per second (which corresponds to an unlimited slew rate at 10 samples/second). Each time the TEC current is set (either by a PID feedback loop or with the Channel.value control), it ramps to the new value at this slew rate.

Rapid changes in the TEC current can create electromagnetic interference (EMI) in the temperature sensor and any other sensors near the TEC. The resulting spikes in the temperature reading can cause feedback oscillations or noisy temperature readings.

For the slew rate setting to be effective, the A/D rate (set with the System.Other.A/D rate control) should less than or equal to 100 ms. The slew rate is implemented with a software algorithm that runs at each A/D conversion, and the TEC driver output has a 13 Hz lowpass filter. If the A/D rate is set (for example) to 1000 ms, the algorithm only changes the TEC output current once each second and the output current therefore changes in discrete steps, each of which may exceed the desired slew rate.

remote command, the TEC output turns off immediately, regardless of the slew rate setting. When outputs are re-enabled, the TEC output ramps up to its previous value at the desired slew rate.

Operation 67

PTC10 Programmable Temperature Controller

Vm ax (Only appears on the Vmon channel of TEC driver cards)

Sets the maximum voltage that the PTC440 TEC driver can output. This control is intended to protect thermoelectric coolers from damaging voltages. If the measured voltage across the TEC is above Vmax for more than one second, current to the TEC is automatically shut off. The first time

-panel

display. To turn the current back on again, set the output to zero (for example, by

el menu, or by disabling and re-enabling all outputs with

the Output Enable button).

If the output current suddenly increases and the slew rate setting is too high, it is still possible to damage the TEC even if Vmax is set to an appropriate value. To prevent such damage, the output voltage should, if possible, also be limited by setting the output range to the lowest possible value (e.g., 3V 5A, 6V 5A, or 9V 5A) controls for the output channel to current values that do not produce excessive voltages.

The TEC voltage can also be limited using Channel.Alarm.Mode control level Channel.Alarm.Latch control , and the min and max to the desired voltage limits. Touch the Channel.Alarm.Output button and select the TEC output channel. The Channel.Alarm.Lag control can be set to 1 s to prevent noise spikes from inadvertently triggering the alarm, or left at 0 s to better protect the TEC from rapid voltage increases.

PCB (RTD, thermistor, and thermocouple readers only)

Sets the maximum printed circuit board (PCB) temperature for all channels on the selected card.

System.Other.Fan is set , the PTC10

temperature. The PCB control only appears for I/O

cards that have internal temperature sensors.

The PCB temperature is always in °C, regardless of the System.Display.Units setting. The default setting is 30°C.

Thermal drift of the RTD or thermocouple inputs can be reduced by setting the PCB temperature of one card to a lower value. This value should be a few degrees above room temperature, (i.e., 25°C). Reducing the maximum PCB temperature results in tighter regulation

articularly of the selected card, at the expense of more fan

noise.

However, if a DC output card is being used the system might sometimes turn up the fan speed to prevent thermal damage to the output card, causing larger internal temperature variations.

Diff (input channels only)

whichever channel is selected in the tab bar at the top of the Channel menu. To turn the difference feature off, touch Diff , then touch whatever channel is currently selected. The Diff button then shows an empty value.

Channels with a difference filter can be used as the input for PID feedback loops, in which case the feedback maintains a constant temperature differential between two locations, rather than a constant absolute temperature.

Lopass (input channels only)

If a non-zero value is selected, a 6th-order RC lowpass filter is applied to the selected channel. The lowpass filter removes noise with a period shorter than the indicated time constant but also increases the effective response time of a sensor.

The lowpass filter should always be enabled on the temperature inputs of all PID control loops. This is especially true when using step response PID tuning or when derivative feedback is enabled

Operation 68

PTC10 Programmable Temperature Controller

(i.e., the derivative gain is nonzero), since these algorithms calculate the change in temperature over time and therefore produce poor results if highconstant should be just below the response time of the system. When using an AC output card for PID control, the filter constant should be longer than the cycle time of the output.

When a sensor is disconnected and then reconnected to a lowpass-filtered channel, the PTC allows one second for the reading to settle. During this time, no reading appears. The output of the lowpass fil reading to gradually settle to its new value.

Units (PTC420 AC output card and PTC430 DC output card only)

By default, the output of these heater driver cards is measured output) and the output units of the DC output

(heater voltage).

d/dt (input channels only)

with respect to time. Since the derivative is normally somewhat noisy, the lowpass filter should be enabled when the derivative filter is used.

Follow (virtual input channels only)

This button only appears for virtual channels that are configured as inputs. Once a channel is

continuously follows the value of the selected channel.

Difference, derivative, or other filters may be applied to the virtual channel to modify the value. (assuming that channel 3A exists). The virtual channel now echoes the value of channel 3A. Next difference between channels 3A and 3B.

Sensor (input channels only)

Selects the sensor type. The button only appears on input channels that support more than one sensor type. The list of available sensor types varies with the I/O card.

Changing the sensor type has three effects. First, it changes the calibration curve that the PTC10 uses to convert raw sensor readings into temperature. Second, changing the sensor type may affect how the PTC hardware acquires data from the sensor. For example, if the sensor type of a PTC320 I/O card is changed from Thermistor to Diode, the PTC acquires voltage instead of resistance readings.

Finally, changing the sensor type affects which buttons appear in the Channel.Cal column as well as the list of options that the Channel.Cal.Type button offers. For example, if the sensor type is

, the Channel.Cal.Type button offers a list of standard RTD types, Callendarvan Dusen coefficients appear in the Channel. (thermistor), the Channel.Cal.Type button offers a list of standard thermistor types, and the

-Hart coefficients appear in the Channel.Cal column. of thermocouple can be

read, the thermocouple type cannot be changed on this card.

Some resistive cryogenic temperature sensors such as Rhodium-Iron, Germanium, and CarbonGlass are not included in the list of available sensor types because they do not have standard calibration curves. To use these sensors, set the Sensor type to thermistor, RTD, or ROX and load

Operation 69

PTC10 Programmable Temperature Controller

manual for more information on custom calibration tables.

Polarity (relays channel of digital I/O card only)

This setting only applies to the Relays channel on the digital I/O card. Changing the polarity

reverses the state of all four relays.

The Polarity setting ensures that the relays are in an acceptable state when the PTC10 is switched

off. When the Polarity is 0, the relays r

f four individual relay values: relay A can have a value of 0 or 1, relay B can have a value of 0 or 2, relay C can have a value of 0 or 4, and relay D can have a value of 0 or 8. When the polarity is changed, the value of each relay stays the same, but its meaning changes as shown in the table below.

Relay state →

Default

(power off)

Relay value

= 0

(alarm off)

Relay value

= 1, 2, 4, or 8

(alarm on)

Back panel pin →

Polarity = 0

Closed

Open

Closed

Open

Closed

Polarity = 1

Closed

Open

Closed

Open

what the relays revert to when the PTC10 is switched off. If no alarms are

configured, they will stay in that state when the PTC10 is turned back on again.

Channel screen: Alarm column

Each input channel has an alarm. If enabled, the alarm is triggered if any of the following

conditions occur:

The input (or its rate of change) exceeds the user-specified minimum and maximum values The input exceeds the measurement range of the I/O card The sensor is disconnected (except on analog I/O channels, which cannot detect

disconnected sensors)

When an alarm is triggered, it can do any of the following:

Play a sound Trigger a relay on the digital I/O card Shut off an output channel

The alarm can be programmed to remain triggered until it is manually shut off (latching alarm), or to shut itself off as soon as the input returns to a value within the alarm limits (non-latching alarm). The alarm can also be programmed to ignore momentary glitches.

To determine which alarms are currently triggered, look at the Select screen. A small white dot in the upper-

output enough power to damage

your system. The alarm should be configured to disable the heater output when triggered. For relay associated with the alarm. Wit ossible for the PTC10 to

Operation 70

PTC10 Programmable Temperature Controller

feedback is incorrectly set up.

The following controls are available for input channels only:

Status

Indicates if an alarm condition is currently present on this channel. If a latching alarm has been

also be used to artificially turn the alarm on to test the sound, output channel disabling, and GPIB status reporting.

alarm immediately turns on. If the alarm is non-latching, it turns off in less than a second; if it is latching, it stays on unt

Mode

Enables or disables the alarm. The following three alarm modes can be selected:

Off: the alarm never sounds. Level: the alarm sounds whenever the input exceeds the values set with the Min and Max

controls. The alarm also sounds whenever the input is disconnected or the sensor value exceeds the range of the input.

Rate /s: the alarm sounds whenever the rate of change of the input (in degrees per second) exceeds the Min or Max values. The alarm also sounds whenever the input is disconnected or the sensor value exceeds the range of the input.

Latch

I e control. If set to No, the alarm turns itself off once the input is again within the alarm limits.

Mute

Temporarily silences the alarm sound but does not otherwise affect the alarm. Once this button is touched, the alarm stays muted until the alarm condition goes away or until the button is touched again.

Sound

Controls which sound plays when the alarm goes off.

Output

T zero and temporarily disabling that chann the output returns to its previous value and the feedback is re-enabled. This feature can be used to guard against runaway feedback loops or to otherwise protect equipment from damage due to excessive temperatures. For example, one or more backup temperature sensors can be programmed to shut off a PID output to prevent damage in case the primary sensor fails.

he channel to be shut off. If a channel is already selected, touching it again de-selects the channel and no channel will be shut off when the alarm triggers.

Relay

If a digital I/O card is installed in slot 6, the alarm can switch one of its four relays o possible to assign more than one alarm to a given relay, in which case the relay will turn on if any one of the alarms is triggered.

Operation 71

PTC10 Programmable Temperature Controller

Min

The lowest permissible value of the input. The alarm is triggered if the input (or the rate of

change of the input) becomes lower than this value.

Max

The highest permissible value of the input. The alarm is triggered if the input (or the rate of

change of the input) exceeds this value.

Lag

Prevents noise or glitches from inadvertently triggering the alarm. The alarm will not be triggered until the input has continuously exceeded the min or max setting for this number of seconds. The lag applies when the alarm is being switched and when it is being switched off.

Channel screen: Cal column

This menu is only available for input channels.

Type

The Calibration Type control affects how raw sensor readings are converted to temperature measurements. This control does not affect how the sensor is read.

or which custom calibration tables have been loaded. It does not, by default, appear on the four analog I/O channels, the digital I/O channel, the relay channel, and virtual channels.

If the I/O card only supports a single calibration curve, the calibration type is grayed out and

cannot be changed, unless a custom calibration is loaded.

If the selected channel uses a custom calibration table, its calibration type reads

then reverts to the normal list of calibration types supported by the I/O card.

The available calibration types depend on the sensor type. RTDs: Choose ITS-90 for RTDs with an alpha of 0.00385; US for RTDs with an alpha of

0.00392; or Custom to enter your own Callendar van Dusen calibration coefficients.

Thermocouples: Indicates the thermocouple type (E, J, K, N, or T). Cannot be changed, since

the thermocouple type is determined by the back-panel connector.

Thermistors: The available calibration types are named according to the resistance of the thermistor at 25°C. Thermistors from Omega, Measurement Specialties, Inc. (formerly YSI), and others that conform to the same calibration curve are supported. Note that unlike RTDs and thermocouples, there are no international standards for thermistors. Therefore, thermistors from

-in

calibrations even though they have the correct resistance at 25°C.

Diodes: Choose from the list of commercial cryogenic diodes. See the description of the PTC320 I/O card on page 2 for more information on standard diode calibrations.

A (RTD, thermistor, and diode calibrations only) B (RTD, thermistor, and diode calibrations only) C (RTD, thermistor, and diode calibrations only) R0 (RTD calibrations only)

Custom calibration coefficients. These settings let you define custom calibration curves for some sensor types without making a custom calibration table. The values can only be changed if the

Operation 72

PTC10 Programmable Temperature Controller

RTDs: If the sensor is an RTD, A, B, C, and R0 are the constants for the Callendar van Dusen

equation:

Rt = R0(1 + At + Bt² + (t 100)Ct³) below 0°C

Rt = R0 (1 + At + Bt²) above 0°C

where Rt is the measured resistance of the RTD in ohms, R0 is the resistance of the RTD at 0°C, also in ohms, and t is the temperature in °C.

If a standard RTD calibration is selected (i.e. IEC751 or US), preset values of A, B, and C are

used. The value of R0, however, is not preset and can be modified.

The Callendaris accurate to about 50 mK in the range -200 400°C. In contrast, class A commercial RTDs that have not been individually calibrated are accurate to 150 mK at 0°C and 950 mK at 400°C.

re calibrating your own sensor and the calibration points are separated by less than 50°C,

easier and more accurate to load the calibration in the form of a calibration table instead

of calculating the Callendar-van Dusen coefficients.

Thermistors: If the sensor is a thermistor and the calibration type is s , the A, B, and C settings are the Steinhart-Hart coefficients. The temperature T (expressed in K) is calculated from the thermistor resistance R (in ohms) using the following equation:

T = (A + B·ln(R) + C·ln³(R))-1

If a standard thermistor calibration is selected, the A, B, and C controls show best-fit coefficients for whichever curve is selected. These figures are approximations only and are not actually used to calculate the temperature unless the calibration type is changed to

Diodes: If the sensor is a diode and the calibration settings are a polynomial fit to the diode calibration curve:

T = A BV CV²

where T is the temperature in Kelvins and V is the voltage across the diode in volts. Note that polynomial fits are only accurate within a limited temperature range.

If a standard diode calibration is selected, the A, B, and C controls show best-fit coefficients for whichever curve is selected. These figures are approximations only and may not produce the same results as the standard calibration curve.

A standard diode or bipolar junction transistor can be connected to the PTC320 input card and used as a low-cost temperature sensor. In this case a custom calibration must be used. If the voltage across the diode is measured at two known temperatures, the calibration coefficients can be calculated as follows:

B = (T1 T2) / (V1 V2)

A = T1 + (V1 · B) + 273.15

C = 0

where V1 is the voltage (expressed in volts) at temperature T1 (expressed in °C), and V2 is the voltage at temperature T2. The resulting calibration is a linear approximation. For greater accuracy, a custom calibration table should be used instead of the A, B, C coefficients; see page 36.

Operation 73

PTC10 Programmable Temperature Controller

Offset Gain

The offset/gain filter modifies the value of an input channel as follows:

output = (input · gain) + offset

where input is the input to the offset/gain filter, and output is the output of the filter. This filter can be used as a simple way to adjust sensor calibrations.

The offset/gain filter is appl

before the other input filters (difference, lowpass, and derivative).

Channel screen: PID column

This menu is only available for output channels. In addition, if no Input channel is selected, all of

the other PID buttons are grayed out.

Input

one temperature sensor as the input for more than one PID loop.

Mode

Three options are available:

f: PID feedback is inactive. In this mode, t

control.

: PID feedback is enabled and actively controls the heater output, ideally maintaining the

input channel at the setpoint.

: In this mode, the output continuously tracks the input, with a gain and offset (zero point) applied. Follow mode can be used if, for example, two identical heater outputs are needed; one heater channel can follow another that has PID feedback turned on. Follow mode can also be used (typically on the ±10V aux output channels) to provide an analog representation of a temperature to other electronic hardware.

Setpoint

The temperature at which the PID feedback loop tries to keep the input.

Zero pt (Follow mode only)

In Follow mode, this value is subtracted from the input. Thus, when the input is equal to this

value, the output is zero. In follow mode, the output is determined by the equation:

Output = (Input Zero pt)Gain

Ram p

This button is used to set the ramp rate in degrees per second, controlling how quickly the

PTC10 heats or cools your system.

Whenever the feedback setpoint is changed, the PTC10 gradually adjusts the ramp temperature

ontrol, below), increasing or decreasing it at the ramp rate until it reaches the new setpoint. The PID feedback loop, in turn, attempts to control the sensor temperature such that it tracks the ramp temperature. Assuming the feedback is properly tuned and

Operation 74

PTC10 Programmable Temperature Controller

that your heater can respond quickly enough, the sensor temperature should rise or fall at the ramp rate until it reaches the new setpoint.

If Ramp is set to zero, ramping is disabled and the PTC10 heats or cools your system at the

maximum possible rate.

Ram p T

Shows the temperature that the PID feedback is currently trying to maintain. Ramp T is equal to

the setpoint unless 1) the feedback is disabled or 2) a temperature ramp is currently in progress.

If the feedback is disabled, Ramp T follows the sensor temperature. When the feedback is enabled, Ramp T increases or decreases at the ramp rate until it reaches the setpoint. This ensures that the temperature of your sample ramps smoothly to the setpoint at the rate specified by the

. To reach the setpoint more quickly, touch the Ramp T button and enter the

setpoint value.

Once it reaches the setpoint, Ramp T will remain exactly equal to the setpoint until the setpoint is changed. When the setpoint is changed, Ramp T increases or decreases at the ramp rate until it reaches the new setpoint.

If the feedback is disabled, Ramp T immediately starts to follow the sensor temperature again. It

ramp to the sensor temperature because the feedback is now off.

The Ramp T button can be used to monitor the progress of temperature ramps. The sensor temperature could also be used for this purpose, but is subject to noise, external disturbances, and other artifacts that in some cases could make it difficult to determine the intended temperature.

Sets the proportional gain factor. The PID equation is:

Outputt = Pet + 0.5IT( (e0 + e1) + (e1 + e

2 t 2

+ e

t 1

) + (e

t 1

+ et) ) + (D/T)(et e

t 1

)

where P, I, and D are the derivative gains, et is the error (the difference between the setpoint and the PID input signal) at time t, and T is the ADC sampling time. Thus, larger values of P, I, or D produce a faster feedback response. Increasing P or I tends to create oscillations, while increasing D reduces oscillations but adds noise. Negative values of P, I, and D should be used if the output drives a fan or other device that cools the sample.

Gain (Follow mode only)

In follow mode, the input is multiplied by this value before being sent to the output. See Zero pt.

Sets the integral gain factor. Integral gain should normally be about one-tenth of proportional gain.

Sets the derivative gain factor.

Zone

This control stores up to eight sets of feedback parameters. Each set can be associated with a temperature range (or zone) and automatically recalled when the setpoint enters that range. The zone can also be manually selected, ignoring the temperature.

and the P, I, and D feedback gains. By default, zone 1 is selected and contains the current values of

Operation 75

PTC10 Programmable Temperature Controller

these parameters; the rest of the table is empty. Touch one of the parameter cells to modify its value. If a particular set of parameters is no longer needed, touch its z column to clear the entries for that location.

The PID zone editor

To manually se 8. The feedback parameters immediately change to the values stored in the corresponding row of the Zone table. If the selected zone contains empty cells, the feedback parameters don copied into the empty cells.

Whenever the feedback parameters change (for example, if the feedback is tuned), the selected zone is automatically updated with the new values.

To have the PTC10 automatically select zones based on the temperature, assign each zone a in any order; they do not have to be monotonically ascending or descending. Next, set the zone to

PTC10 automatically selects the zone with the largest Min value that is less than the

mode.

Status

r, if the PID feedback loop

is not functioning, a message explaining why. The information is updated once every second.

Operation 76

PTC10 Programmable Temperature Controller

PID status display

Casc

Cascade control. A cascade control system consists of two (or more) PID loops. As in a normal PID system, a primary PID loop monitors a temperature that needs to be regulated (the primary temperature). However, instead of driving the physical output (heater, valve, etc.), the output of the primary loop becomes the setpoint for a secondary PID loop. The secondary loop monitors a secondary temperature reading and controls the physical output. The secondary temperature reading is typically a temperature that is not in and of itself critical to the application, but responds more quickly to the control output than the primary reading.

For example, the temperature of an incubator might need to be kept constant using a forced-air heater. In this case, the primary temperature is the air temperature inside the incubator, while the secondary temperature might be the temperature of the hot air entering the incubator (the vent temperature). The primary loop controls the air temperature in the incubator by telling the secondary loop how hot the vent air should be. The secondary loop regulates the temperature of the vent air by controlling the power to a heater coil. The advantage of cascade control is that variations in the vent temperature can be accounted for much more quickly than would be possible with a single PID loop.

To use cascade feedback, select one of the PTC10

A list of output channels appears. Touch one of the channels to

make its PID setpoint track the value of the virtual channel.

To disable cascade control, touch t select it.

Channel screen: Tune column

This menu, which is only available for output channels, configures the PID autotuner. See the

Mode

Use this button to start the autotuning process. The button is greyed out if a PID input channel

start the relay

46 for more information.

Operation 77

PTC10 Programmable Temperature Controller

Step Y

The size of the disturbance that the autotuner applies to the output. It should be large enough to increase the temperature by several degrees, or significantly more than any noise or other temperature variations that would normally occur over several minutes. If Step Y is too small, the autotuner will produce inaccurate PID feedback parameters. If Step Y is too large, the tuning process will increase the temperature of your experiment to unacceptably high levels.

time autotuning is started.

Lag

Controls how long the autotuner waits before it first checks the response of the system to the output disturbance. This time should be long enough for the temperature to rise noticeably after the output is increased by Step Y. If Lag is too small, the autotuner will mistake small noise spikes

autotuner will produce inaccurate results.

If the Lag setting is changed while autotuning is in progress, ve any effect until the next time autotuning is started.

Status

Touch this button to display a text box with information on the progress of the autotuner.

Type

Controls which PID tuning rules are used by the autoresults in minimal overshoot (ideally, zero overshoot) but very slow response. Conversely, the

f these three tuning types, the

relay tuner uses more aggressive tuning rules than the step response tuner. tuner uses aggressive tuning if the derivative gain is nonzero and conservative tuning if D is zero

before tuning. This setting works well if the step response tuner is used for an initial rough tuning at room temperature and the relay tuner is used for a final tuning once the system has reached its target temperature.

Operation 78

PTC10 Programmable Temperature Controller

The System screen includes controls for all settings that affect the entire instrument. Time and

date, Ethernet and GPIB parameters, and data logging are set up through this screen.

Nothing happens if the System button is pressed when the System screen is already showing.

System screen: Macro column

Buttons with the names of up to six currently-defined macros appear in this menu. Pressing one of these macro buttons runs the corresponding macro, and the button remains selected (i.e., highlighted,

A macro button appears to be selected whenever a macro with the name shown on the button is running. Touching a selected macro button stops all currently-running macros with that name. See the Macro Names topic in the Remote Programming section for more information on macro names.

System screen: Log column

Interval

Sets the default time between log points. Each channel also has its own log interval setting that can override this default. If the interval is set, for example, to 1 s, the PTC saves a data point once per second, and each point represents the average reading over one second period.

when the log interval is changed, meaning that accumulated

data will disappear from the plot. Data logged to a USB memory stick is not erased.

Clear

Erases logged data. There are three options:

RAM deletes all memory.

USB deletes all log files (not just the current file) from the log folder on the external USB

memory stick. Specifically, all files \<folder>\XX\LogYY.csv are deleted, where <folder> is the folder name specified by the Folder button, and XX and YY are two-digit numbers.

All is the same as selecting RAM and USB.

Operation 79

PTC10 Programmable Temperature Controller

Folder

Sets the USB device folder into which the PTC10 writes log files. If the folder does not exist, it is created. If the folder does exist and contains PTC10 log files, the PTC10 appends data to the highest-numbered log file.

Log to

Enables or disables logging to a USB memory device. I to the USB device and also stores the data in its internal memory the PTC10 stores data in its internal memory but not on the USB device. store data at all, and the plots on the Plot screen are always empty.

USB logging can also be enabled or disabled by touching the red USB Logging indicator in the top-right corner of the screen.

If the USB device is unplugged, the System.Log.Log To to indicate that data is no longer being written to USB.

USB

I o , the PTC immediately starts logging data plugged into the instrument. The System.Log.

SB a USB flash key or hard drive with available memory plugged into the PTC, data will be logged to it.

If set to , when a USB device is plugged in, the user must touch the red USB logging

indicator to start logging data to the device. The System.Log.Log To button automatically switches

n a USB device is plugged in. If you unplug a device and plug it back in, the PTC stops logging data to the device and newly-acquired data is not permanently saved.

Status

Shows the name and size of the current log file. The information is updated every 5 seconds.

When the size reaches 100%, a new log file is created.

System screen: COM column

RS -232

Sets the RS-232 baud rate. The RS-232 interface always has 8 bits, 1 stop bit, and no parity.

GPIB

Sets the primary GPIB address. The address must be a value between 0 and 31, inclusive, but in

most GPIB systems 0 is reserved for the controller-in-charge and should not be used.

Verbose

Determines how the PTC10 responds to RS-

PTC10 only sends messages in response to queries. This mode should be selected for IEEE488.2

s a message in response to each instruction that sets or gets a parameter, and the message includes the parameter name. Example responses are shown in the table below.

Response to

Operation 80

PTC10 Programmable Temperature Controller

Verbose

level

2A?

xyz

2A = 37.47

Low

37.4722

(no response)

Medium

37.4722

(no response)

High

2A.Value = 37.4722

2A.Value = 37.47

History

This button brings up a window that that shows the contents of the last twelve messages sent or

received over the COM ports. The window is helpful for debugging communications issues.

Errors

This button produces a window that shows the last six errors caused by COM port

communications.

Closes the Ethernet port. The PTC10 only accepts

possible to switch between Telnet and UDP without closing the port.

The Close button is greyed out when the Ethernet port is not in use. Once a Telnet connection is made or a UDP packet is received, the Close button is un-greyed, indicating that the PTC10 is bound to a client computer and will not accept macros from any other computer until the Close button is pressed, the PTC10 is rebooted, or the client closes the telnet connection.

System screen: IP column

DHCP

DHCP server is present on the network, the other IP settings are automatically configured and are grayed out.

Address

Sets the IP address. The button is greyed out if DHCP is enabled.

Port

Sets the telnet port for Ethernet communications. Remote commands can be sent to the PTC through a telnet connection or a raw UDP stream addressed to the selected port. The port must be a value between 0 and 65535, inclusive, and should normally be either 23 (the default) or a value greater than 1024.

Status

Shows the status of the Ethernet interface.

up/down at 10/100/1000 Mbps: if the link is up, that means the PTC10 is physically connected to a network. hardware problem.

Max frames received: the PTC10 has a queue of unprocessed Ethernet packets, and this value

is the longest that the queue has gotten in last 5 seconds. If this number reaches 40, that means Ethernet data is being received faster than the PTC10 can process it.

Operation 81

PTC10 Programmable Temperature Controller

Remote IP: shows the IP address of the remote system that the PTC10 is accepting

commands from. If this is n , press the

have the PC send a command.

Indicates which protocol the PTC10 is using to communicate with the PC. se, touch the Close button and then have the PC send a command using a different protocol.

The status of the TCP connection. Normally the state is either listen , which means the PTC10 is waiting for a connection, or established , which mean active connection.

me sort of network incompatibility.

The state of the process that automatically assigns an IP address to the PTC10. The state is n s turned off or another state for more than a few s communicate with the DHCP server.

The PTC10 only accepts messages from a single computer and only in a single protocol (Telnet

or raw UDP stream). To change the computer or the protocol, press the Close button.

The Close button is greyed out if Telnet

received any UDP packets addressed to the active port .

is being used and the computer

closes it.

System screen: Display column

Units

Sets the temperature units for the entire instrument. Temperature measurements are both displayed and logged in the specified units. If the units are changed in the middle of an experiment, there will appear to be a large jump in all of the temperature records. PID setpoint values are not adjusted to compensate for the new units.

Five units options are available: °C, K, mK, °F, and Sensor. If the Sensor option is selected, sensor measurements are not converted to temperature and instead appear in the native units of the sensor, i.e. millivolts for thermocouples, volts for diode sensors, and ohms for resistive sensors.

Bright

S turned on again for 2 seconds by touching the screen.

Monitors

Most els that can show additional information about the card or the status of its I/O channels. For example, most cards have an onboard sensor that measures the temperature of the card itself. Cards that are intended to drive resistive heaters have a channel that shows the resistance of the heater, and may also have channels that show the heater voltage and current. While not typically needed for normal day-to-day use, these monitor channels can be very useful when debugging performance issues.

To save memory and processor time, the monitor channels are disabled by default. They can be enabled by touching the button and then selecting from the pop-up menu. The monitor channels will then appear on the Select screen like any other ll be logged to

Operation 82

PTC10 Programmable Temperature Controller

internal memory and to a USB stick (if USB ll appear in the response to the

t appear on the Select screen

still logged internally and to the

mmands. In

particular, the monitor channels are removed from the response to the getOutput command, while

nnels.

X labels

more concise, easy-to-read labels that indicate the amount of time between grid lines. The elapsed time is reset to zero once per minute, hour, or day, depending on the X range of the graph.

Absolute X labels

Elapsed X labels

Operation 83

PTC10 Programmable Temperature Controller

Figures

Sets the maximum number of figures that are shown after the decimal point for all channel values. Fewer digits may be shown if the fit into the available space. This setting does not affect logged data, PID feedback, or plots.

Each channel also has its own Figures setting that can override this global setting.

Cal

Calibrates the touchscreen. When this button is pressed, two crosses are displayed. Touch both crosses to calibrate the location wh calibration is cancelled after 15 seconds.

In this case, send the command -232, Ethernet, or GPIB port to activate the calibration feature.

System screen: Other column

Fan

Controls the speed of the front-panel fan. If a PTC430 DC output card or PTC440 TEC driver is being used, the fan should generally be set to Max or Auto, otherwise the card may overheat and be permanently damaged. The accuracy of temperature measurements may be reduced if the fan is disabled.

Volume

Sets the speaker volume. The volume affects all sounds played, including alarms.

Tim e

The system time. Changing the time does not affect time stamps on previously-acquired data points. Therefore, if the time is advanced by one hour, a one-hour gap appears in the plot. Conversely, if the time is set back by one hour, any data taken over the last hour is no longer plotted, and newly-acquired data appears in its place. The data is not actually erased from the USB

Date

The system date. Changing the date can affect the display of previously-acquired data; see the

About

Displays a text box with information about the firmware version and installed I/O cards.

Reset

Resets one of the following:

Running macros: stops all running macros. Has no effect on saved macros. Saved macros: deletes all saved macros from local memory. Does not delete macros from

USB memory devices. Has no effect on running macros.

Display

Returns the front panel to the Select menu, de-selects all channels in all groups, and erases locally-stored log data (data on USB drives is not affected). Returns all plots to autoscaled X and Y with a 1 minute X range and changes the plot location of all channels to 1. If a *TRG

Operation 84

PTC10 Programmable Temperature Controller

remote command was previously received, re-enables automatic A/D conversions. Hides internal monitor channels.

Ports: Closes all I/O ports and re-opens them. USB and Telnet connections are lost. The port

settings (baud rate, IP address, etc.) remain unchanged.

Port settings: Resets all I/O port settings to their factory defaults. Channels: Resets the settings on the Channel menu for all channels to their factory defaults.

Also sets the A/D rate to 100 ms.

Log: Resets the default log rate to 1 second, sets the log rate for each channel to the default,

and enables automatic logging to USB. If a USB storage device is attached, erases log files in the root directory and begins logging to USB.

All: resets all of the above items.

SRS Labs PTC10 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Safety and Preparation for Use v

Specifications vii

Introduction

PTC320 thermistor/diode/RTD card

PTC321 RTD reader

PTC323 2-channel thermistor/diode/RTD card

PTC330 thermocouple reader

PTC420 AC output card

PTC430 50 W DC output card

PTC431 100W DC output card

PTC440 TEC driver

PTC510 analog I/O card

PTC520 digital I/O card

Operation

Turn the instrument on

The Select screen

Configure the sensor inputs

If the sensor reading does not appear

Plot data

Test the outputs

Set the data logging rate

Save data to and retrieve data from a USB memory device

Interface with a computer

Control a temperature

Input filters

Custom calibration tables

Virtual channels

Logging data to internal memory

Logging data to USB

ADC sampling and logged data

Format of PTC10 log files

Basic PID feedback concepts

Manual tuning

Automatic tuning algorithms

Using the automatic tuner

USB logging indicator