Isotech milliK Operating Manual

User Maintenance Manual/Handbook

Issue 2.01

Software version 3.0.0+

Firmware version 3.0.0+

Isothermal Technology Limited, Pine Grove, Southport, PR9 9AG, England

Isothermal Technology Limited, Pine Grove, Southport, PR9 9AG, EnglandIsothermal Technology Limited, Pine Grove, Southport, PR9 9AG, England

Tel: +44 (0)1704 543830 Fax: +44 (0)1704 544799 Internet:

Tel: +44 (0)1704 543830 Fax: +44 (0)1704 544799 Internet: www.isotech.co.uk

Tel: +44 (0)1704 543830 Fax: +44 (0)1704 544799 Internet: Tel: +44 (0)1704 543830 Fax: +44 (0)1704 544799 Internet:

EEEE----mail:

mail: info@isotech.co.uk

info@isotech.co.uk

mail: mail:

info@isotech.co.ukinfo@isotech.co.uk

www.isotech.co.uk

www.isotech.co.ukwww.isotech.co.uk

The company is always willing to give technical advice and assistance where appropriate. Equally,

because of the programme of continual development and improvement we reserve the right to amend

or alter characteristics and design without prior notice. This publication is for information only.

Contents

1 Introduction ........................................................................................................................ 6

1.1 Unpacking ................................................................................................................... 6

1.2 Safety ........................................................................................................................... 6

2 Getting Started ................................................................................................................... 9

2.1 A Quick Tour of Your milliK ................................................................................... 10

2.2 Driving your milliK ................................................................................................... 12

2.2.1 The ‘Graph’ Window ......................................................................................... 13

2.2.2 The ‘Numeric’ Window ..................................................................................... 13

2.2.3 The ‘Settings’ Window ...................................................................................... 14

2.2.4 The ‘Instrument’ Window.................................................................................. 16

2.3 Battery Operation ...................................................................................................... 17

3 Detailed Description by Function .................................................................................... 18

3.1 Using a PRT/SPRT with milliK ................................................................................ 18

3.1.1 Configuring milliK to measure a PRT/SPRT .................................................... 19

3.1.2 Determining Self-Heating of a PRT/SPRT ........................................................ 21

3.1.3 Using 3 or 4 Wire Measurement ........................................................................ 21

3.2 Using a Thermistor with milliK ................................................................................ 23

3.2.1 Configuring milliK to Measure Temperature with a Thermistor....................... 24

3.3 Using a Thermocouple with milliK ........................................................................... 25

3.3.1 Using Internal Reference Junction Compensation ............................................. 26

3.3.2 Using External Reference Junction Compensation............................................ 26

3.3.3 Using an Ice-Point for the Reference Junction .................................................. 27

3.3.4 Configuring milliK to Measure a Thermocouple............................................... 28

3.4 Using a 4-20mA Transmitter with milliK ................................................................. 30

3.4.1 Configuring milliK to Measure a 4-20mA Transmitter ..................................... 31

3.5 Measuring the Difference Between Two Channels................................................... 32

3.6 Changing Graph Scales ............................................................................................. 32

3.7 Using Rolling Statistics ............................................................................................. 33

3.8 Logging Results to a File .......................................................................................... 34

3.8.1 Transferring Logged Data to a PC ..................................................................... 36

3.8.2 File Format for Logged Data ............................................................................. 36

3.8.3 Clearing Logged Data from Internal Memory ................................................... 37

3.9 Using the Thermometer Database ............................................................................. 38

3.9.1 Creating a New Thermometer Entry .................................................................. 38

3.9.2 Using a PRT with IEC60751 (2008) Conversion .............................................. 40

3.9.3 Using a PRT with Callendar Van Dusen Conversion ........................................ 41

3.9.4 Using a PRT with ITS90 Conversion ................................................................ 42

3.9.5 Using a Thermocouple with Calibration Coefficients / Data Pairs.................... 43

3.9.6 Using a Thermistor with the Steinhart-Hart Polynomial ................................... 44

3.9.7 Using a Thermistor with Polynomial Temperature Conversion ........................ 45

3.9.8 Using a 4-20mA Transmitter with Linear Conversion ...................................... 46

3.10

Updating the Software ........................................................................................... 47

3.11

Using and Changing Passwords ............................................................................ 47

3.11.1 Recovering a Lost Password .............................................................................. 48

3.12

Controlling Temperature Sources with milliK ...................................................... 49

3.12.1 Creating a Temperature Profile .......................................................................... 51

4 Connecting Thermometers to milliK ............................................................................... 53

4.1 Connecting PRTs/SPRTs to milliK ........................................................................... 53

4.2 Connecting Thermistors to milliK............................................................................. 54

4.3 Connecting Thermocouples to milliK ....................................................................... 55

4.4 Connecting 4-20mA Transmitters to milliK ............................................................. 56

5 Calibration........................................................................................................................ 57

5.1 Standards Required for Calibration ........................................................................... 58

5.1.1 Making a 4-Terminal Short-Circuit ................................................................... 58

5.1.2 Making a 0mV Source in a Thermocouple Connector ...................................... 59

5.2 Checking the Calibration ........................................................................................... 59

5.2.1 PRT/SPRT Resistance Range ............................................................................ 60

5.2.2 Thermistor Resistance Range (500kΩ) – Span Check ...................................... 61

5.2.3 Thermocouple Voltage Range – Zero Check ..................................................... 62

5.2.4 Thermocouple Voltage Range – Span Check .................................................... 63

5.2.5 4-20mA Transmitter Range – Zero and Span Check ......................................... 63

5.2.6 Reference Junction Compensation Accuracy .................................................... 64

5.3 Adjusting the Calibration .......................................................................................... 66

5.3.1 Starting the Calibration Adjustment Feature ..................................................... 66

5.3.2 Adjusting SPRT (115) Resistance Range ....................................................... 67

5.3.3 Adjusting PRT (460) Resistance Range ......................................................... 68

5.3.4 Adjusting Thermistor (500k) Resistance Range ............................................. 68

5.3.5 Adjusting Zero Voltage Offsets ......................................................................... 69

5.3.6 Adjusting Voltage Gain ..................................................................................... 69

5.3.7 Adjusting 4-20mA Transmitter Range............................................................... 70

5.3.8 Adjusting the RJC Sensor Calibration ............................................................... 71

5.4 Exporting Calibration information ............................................................................ 72

6 Maintenance and Cleaning ............................................................................................... 73

7 Interfacing to milliK ........................................................................................................ 74

7.1 Isotech Software ........................................................................................................ 74

7.2 RS232 Interface ......................................................................................................... 74

7.2.1 Establishing an RS232 Connection .................................................................... 75

7.3 Ethernet Interface ...................................................................................................... 78

7.3.1 Establishing an Ethernet Connection ................................................................. 78

7.3.1 Using SCPI Commands with the Ethernet Connection ..................................... 80

7.3.2 Using Remote Desktop Access .......................................................................... 81

8 SCPI Command Set ......................................................................................................... 83

8.1 Command Terminators .............................................................................................. 83

8.2 SCPI Command Structure ......................................................................................... 83

8.3 SCPI Numeric Suffices ............................................................................................. 84

8.4 Parameters ................................................................................................................. 84

8.5 Units .......................................................................................................................... 85

8.6 Making Measurements Using SCPI Commands ....................................................... 85

8.6.1 Measuring Resistance using SCPI Commands .................................................. 86

8.6.2 Measuring Voltage (with optional RJC) using SCPI Commands ...................... 86

8.6.3 Measuring Current using SCPI Commands ....................................................... 88

8.6.4 Measuring Temperature using SCPI Commands ............................................... 88

8.6.5 SCPI Commands ................................................................................................ 94

8.6.6 Command: *IDN? .............................................................................................. 96

8.6.7 Command [MILLik:]REMote ............................................................................ 96

8.6.8 Command [MILLik:]LOCal .............................................................................. 97

8.6.9 Command SENSe:FUNCtion[:ON] ................................................................... 98

8.6.10 Command SENSe:FUNCtion[:ON]? ................................................................. 98

8.6.11 Command SENSe:CHANnel ............................................................................. 98

8.6.12 Command SENSe:CHANnel? ........................................................................... 98

8.6.13 Command SENSe[:RESistance]:RANGe[:UPPer] ............................................ 99

8.6.14 Command SENSe[:RESistance:]RANGe[:UPPer]? .......................................... 99

8.6.15 Command SENSe:RESistance:WIRes............................................................... 99

8.6.16 Command SENSe:RESistance:WIRes? ........................................................... 100

8.6.17 Command SENSe:CURRent ........................................................................... 100

8.6.18 Command SENSe:CURRent? .......................................................................... 100

8.6.19 Command SENSe:PROBe ............................................................................... 101

8.6.20 Command SENSe:PROBe? ............................................................................. 101

8.6.21 Command SENSe:INITs .................................................................................. 101

8.6.22 Command SENSe:UNITs? .............................................................................. 102

8.6.23 Command SENSe:RJC .................................................................................... 102

8.6.24 Command SENSe:RJC?................................................................................... 102

8.6.25 Command INITiate[:IMMediate][:ALL] ......................................................... 102

8.6.26 Command FETCh[:SCALar]? ......................................................................... 103

8.6.27 Command READ[:SCALar]? .......................................................................... 103

8.6.28 Command MEASure[:SCALar]:TEMPerature<channel#>? ........................... 103

8.6.29 Command MEASure[:SCALar]:VOLTage[:DC]<channel#>? ....................... 104

8.6.30 Command MEASure[:SCALar]:RESistance<channel#> ................................ 105

8.6.31 Command MEASure[:SCALar]:CURRent? .................................................... 105

8.6.32 Command MEASure[:SCALar]:RJC? ............................................................. 106

8.6.33 Command PROBe:UNLock............................................................................. 106

8.6.34 Command PROBe:LOCK ................................................................................ 106

8.6.35 Command PROBe:COUNt? ............................................................................ 106

8.6.36 Command PROBe:NAMe<probe#> ................................................................ 106

8.6.37 Command PROBe:NAMe<probe#>? .............................................................. 107

8.6.38 Command PROBe:TYPe<probe#> .................................................................. 107

8.6.39 Command PROBe:TYPe<probe#>? ................................................................ 107

8.6.40 Command PROBe:MANufacturer<probe#> ................................................... 107

8.6.41 Command PROBe:MANufacturer<probe#>? ................................................. 108

8.6.42 Command PROBe:MODel<probe#> ............................................................... 108

8.6.43 Command PROBe:MODel<probe#>? ............................................................. 108

8.6.44 Command PROBe:SERial<probe#> ................................................................ 108

8.6.45 Command PROBe:SERial<probe#>? .............................................................. 108

8.6.46 Command PROBe:DATe<probe#> ................................................................. 109

8.6.47 Command PROBe:DATe<probe#>? ............................................................... 109

8.6.48 Command PROBe:MINimum<probe#> .......................................................... 109

8.6.49 Command PROBe:MINimum<probe#>? ........................................................ 109

8.6.50 Command PROBe:MAXimum<probe#> ........................................................ 110

8.6.51 Command PROBe:MAXimum<probe#>? ...................................................... 110

8.6.52 Command PROBe:WIRes<probe#> ................................................................ 110

8.6.53 Command PROBe:WIRes<probe#>? .............................................................. 111

8.6.54 Command PROBe:CONVersion<probe#> ...................................................... 111

8.6.55 Command PROBe:CONVersion<probe#>? .................................................... 112

8.6.56 Command PROBe:COEFficient<probe#> ...................................................... 112

8.6.57 Command PROBe:COEFficient<probe#>? ..................................................... 113

8.6.58 Command PROBe:CVD:FORM ...................................................................... 113

8.6.59 Command PROBe:CVD:FORM? .................................................................... 114

8.6.60 Command PROBe:ITS90:FORM<probe#> .................................................... 114

8.6.61 Command PROBe:ITS90:FORM<probe#>? ................................................... 114

8.6.62 Command PROBe:CREate .............................................................................. 114

8.6.63 Command PROBe:DELete<probe#> .............................................................. 115

8.6.64 Command PROBe:FIND? ............................................................................... 115

8.6.65 Command CALibrate:UNLock ........................................................................ 115

8.6.66 Command CALibrate:LOCK ........................................................................... 115

8.6.67 Command CALibrate:RESistance:GAIN ........................................................ 116

8.6.68 Command CALibrate:RESistance:GAIN? ...................................................... 116

8.6.69 Command CALibrate:VOLTage:OFFSet<channel#> ..................................... 116

8.6.70 Command CALibrate:VOLTage:OFFset<channel>? ...................................... 117

8.6.71 Command CALibrate:VOLTage:GAIN .......................................................... 117

8.6.72 Command CALibrate:VOLTage:GAIN? ......................................................... 117

8.6.73 Command CALibrate:CURRent:GAIN ........................................................... 118

8.6.74 Command CALibrate:CURRent:GAIN? ......................................................... 118

8.6.75 Command CALibrate:RJC:OFFSet ................................................................. 118

8.6.76 Command CALibrate:RJC:OFFSet? ............................................................... 119

8.6.77 Command CALibrate:IDENtification .............................................................. 119

8.6.78 Command CALibrate:IDENtification? ............................................................ 119

8.6.79 Command CALibrate:IDENtification:LAST? ................................................. 119

8.6.80 Command CALibrate:PASSword .................................................................... 120

8.6.81 Command CALibrate:VALid? ......................................................................... 120

9 Specification .................................................................................................................. 121

10 Approvals ....................................................................................................................... 124

10.1

CE Declaration .................................................................................................... 124

10.2

FCC Statement ..................................................................................................... 124

10.3

Standards Applied................................................................................................ 125

11 Revision History ............................................................................................................ 125

1 Introduction

The milliK precision thermometer provides a complete measurement and control interface for

users wishing to make high accuracy temperature measurements or calibrate thermometers. It

supports a wide range of thermometer types including 25 SPRTs, 100 PRTs, thermistors,

thermocouples and 4-20mA transmitters (self-powered and loop-powered) and can control

Isotech temperature sources, sequencing through a programmable list of temperature set

points whilst logging data to internal memory or a USB drive.

The milliK sets new measurement standards in its class (<±5ppm for SPRTs/PRTs, <±2µV

for thermocouples, <±50ppm for thermistors and <±0.01% for current transmitters). The

Windows™ CE operating system provides a simple and intuitive user interface and with a

wide range of interfaces (USB, RS232, ethernet) allows the user to access the comprehensive

features of the milliK. A USB keyboard and mouse can be plugged into the milliK to make

control and data entry with the milliK as simple as using a laptop PC.

1.1 Unpacking

Your product should comprise the following items:

 milliK Precision Thermometer  power supply with interchangeable plug heads  two Lemo 6-pin connectors  null modem RS232 cable  this user manual

If any item is missing or damaged, please report this immediately to your supplier. If

possible, we recommend that you retain the packaging material in case you need to return the

instrument for calibration or service.

1.2 Safety

The milliK is a precision instrument, designed for use in a laboratory or light industrial

environment. It complies with the requirements of safety standard EN61010-1 (2001) and is

therefore safe to use in laboratory or light industrial environments. It is not intended for use

outdoors or in extreme environments (refer to specification in Section 9).

The milliK is likely to be connected to thermometer sensors in use and the user should take

care to ensure that the complete system is safe. For example, metal sheathed thermometers

may be connected to the milliK and then placed in a furnace powered from a 230V electrical

supply. Single fault conditions in such a furnace could lead to the thermometer wires and the

front terminals of the milliK, to which they are connected, becoming electrically live and

therefore a hazard to the user. Suitable precautions should be taken, such as using an isolating

transformer in the supply to such a furnace. If you require further advice on safety issues,

please contact Isothermal Technology or one of our appointed distributors - we have

extensive experience of thermometry and can provide advice and equipment to help you.

Retain these instructions. Use only as specified in these operating instructions or the intrinsic

protection may be impaired.

Please observe the following safety precautions:

 Do not use your milliK if it is damaged  Only connect the power supply to an electrical supply that conforms to the

specification given on its rating plate

 This equipment is for indoor use within an ambient temperature range of 0°C to 40°C

with maximum relative humidity of 95%

 This equipment is for use in moderate climates only. NEVER use the equipment in

damp or wet conditions

 Avoid excessive heat, humidity, dust & vibration  Do not place liquid filled containers on the equipment  Do not use where the equipment (or any associated accessories) may be subjected to

dripping or splashing liquids

 Ensure all cables and wires are routed safely to avoid tripping: also, to avoid sharp

bends and pinches

 Clean only with a damp cloth. Do not wet or allow moisture to penetrate the

equipment. Do not use solvents; see section 6 for details of cleaning procedure

 The product should be subjected to regular in-service inspections as required by local

regulations; a yearly interval is suggested

 Do not apply earth test currents to any terminals nor to the shrouds of the USB,

RS232, or ethernet connectors

 The product is designed to comply with EN 61010-1 and can be flash tested. It is

fitted with radio frequency interference suppressors. Therefore, it is recommended that only a D.C. test be performed. Performing flash tests repeatedly can damage insulation

 This equipment contains no user-serviceable parts. Refer all repairs to qualified

service personnel. Contact Isothermal Technology or one of our appointed distributors for details of approved service outlets

 The power supply has been approved to the following safety standards:

UL60950-1, 2 CSA C22.2 No. 60950-1-07, 2nd Edition: 2007-03

Edition: 2007-03-27

EN 60950-1: 2006 including A11 BS EN60950-1: 2006 AS/NZS60950-1: 2003 including amendments 1, 2 and 3

2 Getting Started

The power supply operates from any standard AC electrical supply (90-264V RMS at 47-

63Hz), so unless your supply is unusual you can simply connect the power supply to a

suitable electrical outlet.

The power supply is fitted with a standard BS 1363 plug head but is provided with alternative

heads that cover the majority of electrical sockets used worldwide. If you need to connect to

an outlet socket that is not supported by the plug heads provided, you should source a suitable

adaptor to suit one of these connector heads. The plug head can easily be changed by pressing

the head release button on the connector head and sliding it off of the power supply body:

Do NOT insert plug head alone into socket

Head Release Button

Enter keys

Connector

Plug the DC connector from the power supply into the “DC Power” socket on the rear of the

milliK. Press the on/off button on the front panel to turn on your milliK. The milliK will load

the operating system and software (25s) and then restore itself to the settings used when it

was de-powered. This manual provides comprehensive details on using your milliK. In

addition video tutorials are available on the Isotech website (see video tab at

www.isotech.co.uk/precision-thermometers/instruments/instruments/millik-precision-

thermometer).

2.1 A Quick Tour of Your milliK

On the front of your milliK you will find two sets of connectors (Lemo 6-pin circular

connectors for SPRTs/PRTs/thermistors and miniature thermocouple connectors) for

channels 1 and 2. On the rear of your milliK you will find the 4mm sockets for channel 3

(used exclusively for 4-20mA transmitters).

Colour

LCD

Up/Down/

Left/Right/

On/Off

Button

Tilt

Feet

Context

Sensitive

Function

Keys

Channel 1

Lemo

Channel 1

Miniature

Thermocouple

Connector

Channel 2 Lemo

Channel 2 Miniature Thermocouple Connector

Input

Connector

(COM1)

(COM2)

Sockets for

Channel3

(4-20mA)

4mm

Compartment

RJ45

Ethernet

Battery

Power

RS232 Connector

USB Host

The milliK is controlled using the ←←←← →→→→ ↑↑↑↑ ↓↓↓↓ ↵↵↵↵ (left/right/up/down/enter) key cluster and the

4 function keys located below the display. The ←←←← →→→→ ↑↑↑↑ ↓↓↓↓ keys are used to navigate between

items on the screen and the ↵↵↵↵ key is used to select or toggle the highlighted item. The

function keys select the context sensitive function displayed above each key. The milliK will

display soft keyboards when required so that all features of the milliK can be accessed using

these keys. You can also connect a keyboard and/or mouse to the USB port (rear panel) and

use these to control the milliK. The function keys below the display are mapped to keys F1-

F4 on the keyboard so that you can control the milliK completely using a USB keyboard.

The milliK is also equipped with two RS232 ports (these are completely interchangeable), a

USB 2.0 host port and ethernet port (10/100MBit), which are available on the rear panel. The

milliK is primarily for use as a bench-top laboratory standard but can also be powered from 4

x AA cells (Ni-MH, Alkaline or Lithium) if a suitable electrical supply is not available

(typical rechargeable Ni-MH cells provide > 4 hours operating life). The battery compartment

is located on the rear panel.

2.2 Driving your milliK

When the milliK is turned on, the opening window appears showing the configuration:

Press the right-hand function key below Start to proceed (or connect a USB keyboard or

mouse and press F4 or click Start). The milliK software will then start and you will see the

main Windows:

There are four main windows, which can be selected using the function keys below the

display. The software always starts with the Graph window selected as shown above.

We will now provide a description of each window. If you wish to perform a particular

function (for example changing the time/date) then you can find help on this by locating it in

the table of contents at the start of this manual and going straight to the relevant section.

2.2.1 The ‘Graph’ Window

In the Graph window you can view a single channel (or the difference between any

channel and Channel 1) in graphical and numerical form. Functions available from within this

window are:

 Select which channel (or the difference between which channel and channel 1) to

view

 Clear the graph  Set the scales for the graph (automatic scaling available for vertical axis)  Start/stop logging of data to internal or external (USB drive) memory

Use the ←←←←→→→→ keys to select from the buttons displayed at the top of the screen and press the ↵↵↵↵

key to activate that function (for example, to clear the statistics). To change which channel is displayed (or to select a difference) use the ←←←←→→→→ keys to select the right-hand button and

either use the ↑↑↑↑↓↓↓↓ keys to sequence through the channels or press the ↵↵↵↵ key to open a window

containing a list of all the available channels. Only channels that are enabled (in the ‘Settings’

window) appear, so if only one channel is enabled this button has no effect.

2.2.2 The ‘Numeric’ Window

In the Numeric window you can view enabled channels in numeric form, together with

their mean and standard deviations. Channels that are not enabled in the Settings window

do not appear. You can choose whether to view a single channel with a large font or all the

channels with a smaller font using the Single Channel / All Channels button. If you choose

to view a single channel then the base units for the thermometer will be displayed at the same

time:

Functions available from within this window are:

 Select which channel (or the difference between which channel and channel 1) to

view

 Select whether to display a single channel or all channels  Clear the rolling statistics and reset the statistics counter  Start/stop logging of data to internal or external (USB drive) memory

Use the ←←←← →→→→ keys to select from the buttons displayed at the top of the screen and press the

↵↵↵↵ key to activate that function (for example, to clear the statistics).

2.2.3 The ‘Settings’ Window

In the ‘Settings’ window you can change the settings for each measurement channel.

Use the ↑↑↑↑ ↓↓↓↓ keys to select the setting you wish to change and then use the ←←←← →→→→ keys to

change it to the required value. If a channel is not being used, it is best to change its ‘Status’

to “Disabled” as this will then make the measurement time available to other enabled

channels, which will speed up these measurements. The ‘Type’ field is for information

purposes only and cannot be changed. Pressing the ↵↵↵↵ key when the ‘Thermometer’ setting is

selected opens a window with a list of all thermometers in the milliK’s database:

Use the ↑↑↑↑ ↓↓↓↓ keys to highlight the required thermometer and press the OK (F4) key to select

it. The Page Up/Page Down (F2/F3) keys below the display provide easy navigation if a

large number of thermometers has been created.

Press the ↵↵↵↵ key when the ‘Samples/Reading’ or ‘Readings in Stats’ settings are selected to

open a numeric entry window and specify a value. This may be quicker than using the ←←←← →→→→

keys to change the value:

Use the ←←←← →→→→ ↑↑↑↑ ↓↓↓↓ keys to move to a number button and select it using the ↵↵↵↵ key. As soon as

you start entering a new number, the original value is deleted. Press the OK (F4) key to apply

the new value.

The ‘Samples/Reading’ setting is initially set to 1 but can be increased to a maximum of 100.

This will cause the milliK to take the specified number of samples for each reading and will

reduce the noise at the expense of slower measurement speed.

2.2.4 The ‘Instrument’ Window

In the ‘Instrument’ window you can access the milliK’s database of thermometers, perform

maintenance tasks (such as backing up, clearing or restoring information stored to internal

memory, updating software, calibrating your milliK), change the IP

address/passwords/date/time settings and define temperature profiles you wish to use when

calibrating thermometers with your Isotech temperature source:

Use the ↑↑↑↑ ↓↓↓↓ keys to select the required function and then press the ↵↵↵↵ key to open a new

window to access that function. Some functions are password protected, in which case a soft

keyboard will appear and you will be asked to enter the password before proceeding:

Use the ←←←← →→→→ ↑↑↑↑ ↓↓↓↓ keys to move to a button and select it using the ↵↵↵↵ key. Press OK to enter

the password. A separate password is provided to protect the calibration of the milliK. Both

passwords are initially set to “1234” but should be changed prior to use in order to ensure the

security of measurements made using your milliK (see section 3.11). A password recovery

process is available if you forget your password, please contact Isothermal Technology or its

approved distributor for assistance if required (see section 3.11.1).

2.3 Battery Operation

The milliK is primarily intended for use as an AC powered, bench-top instrument and is

supplied with a universal power supply for this purpose. However, it may also be powered

from batteries (not supplied) so that it can be used where an AC electrical supply is not

available.

The battery compartment is located on the rear panel. To gain access, squeeze the tabs on the

sides of the battery drawer and slide it out. The battery compartment accepts four AA size

cells.

The milliK can use primary (alkaline or lithium) cells or rechargeable (NiMH) cells. Lithium

cells provide the longest battery life (>6 hours), but are expensive and are not rechargeable.

Rechargeable NiMH cells provide good battery life (> 4 hours) and being rechargeable offer

low running costs, they are therefore the recommended solution for users wishing to use the

battery powered option. Alkaline cells can be used, but they provide limited operating life;

tests have shown that alkaline cells offer half the operating life of NiMH cells with the same

quoted capacity (mAh) because they have a higher output impedance during discharge

(leading to a lower output voltage).

3 Detailed Description by Function

This section describes all the features available on the milliK by function. If you wish to learn

how to do something with your milliK use the table of contents on page 2 onwards to look up

the appropriate section.

3.1 Using a PRT/SPRT with milliK

The milliK can measure the resistance of PRTs and SPRTs. It can convert measurements

from resistance to temperature units (K, °C or °F) so that you can make precise temperature

measurements or calibrate other thermometers from a reference standard.

The milliK provides two resistance measurement ranges which are optimised for PRTs and

SPRTs:

• 0-115: optimised for 25.5 SPRTs

• 0-460: optimised for 100 PRTS

The milliK will measure 25.5 SPRTs on the 460 range, but better measurement

uncertainty is achieved by using the 115 range. The sense current for both ranges is 1mA

(or 1.428mA).

Connect your PRTs/SPRTs to either of the Lemo 6-pin circular connectors on the front panel

(see section 4.1 for pin-out and connection details). Ensure that the miniature thermocouple

connector for the same channel is unused (since it is connected in parallel with the Lemo

connector). Isotech can (optionally) supply thermometers fitted with a suitable Lemo

connector. Your milliK is supplied with two Lemo connectors for you to use with your own

PRT/SPRT (or thermistor). The part number for this connector is:

Lemo part number: FGG.1B.306.CLAD62Z

Additional connectors are readily available internationally from Farnell Electronics and can

be ordered via their website www.farnell.com (Farnell stock code 3817325).

Channels 1 and 2 are not isolated from each other, but are isolated from Channel 3 and from

the digital interfaces in order to optimise immunity to external noise sources.

3.1.1 Configuring milliK to measure a PRT/SPRT

Press the Settings (F3) key to access the Settings window, which opens with the

‘Channel’ parameter selected. Use the ←←←← →→→→ keys to select the channel that you want to

configure. Then use the ↑↑↑↑ ↓↓↓↓ keys to select each parameter in turn and set it to the required

value either by using the ←←←← →→→→ keys to sequence through the options or pressing the ↵↵↵↵ key to

open a new window with all the options listed. A typical configuration for an uncalibrated

PRT would be:

‘Range’ would normally be set to 460 for a 100 PRT and to 115  for a 25.5  SPRT

(see section 3.1). Most PRT/SPRT measurements are made with a 1mA sense current, but

this can be increased to 1.428mA in order to determine the self-heating effect (see section

3.1.2). The ‘Samples/Reading’ setting is the number of samples averaged together to form a

single reading. Increasing this value will reduce the noise on the measurements (standard

deviation will reduce as the square root of the number of samples) but also slows down the

update rate.

Higher accuracy measurements can be made using calibrated PRTs/SPRTs whose resistance-

temperature characteristics have been determined. Before being used, the thermometer and its

calibration details must be entered into the milliK’s thermometer database (see section 3.9.1). The thermometer will then appear in the ‘Thermometer’ list. Use the ←←←← →→→→ keys to sequence

through the thermometers or press the ↵↵↵↵ key to open a new window with all thermometers

listed:

Select the thermometer and set the remaining parameters in the Settings window. A

typical configuration for a calibrated SPRT would be:

Once you have configured the milliK to work with your PRT/SPRT, press either the Graph

(F1) or Numeric (F2) keys to view the measurements:

Use the ←←←← →→→→ ↑↑↑↑ ↓↓↓↓ ↵↵↵↵ keys to navigate between and select the on-screen buttons, which select

the channel, clear the graph (‘Graph’ window), clear the statistics (‘Numeric’ window), set

the scales or start/stop logging of data to a file.

3.1.2 Determining Self-Heating of a PRT/SPRT

The normal sense current used by the milliK for PRTs/SPRTs is 1mA. This current causes a

small amount of self-heating in the thermometer (typically 1 to 3mK). Provided that the

thermometer is calibrated and used at the same current, this leads to negligible uncertainty in

the measurement.

In some special applications the self-heating effect is a significant source of measurement

uncertainty and it may be necessary to determine the amount of self-heating in the

thermometer. This is easily achieved by varying the sense current and observing the change

in indicated temperature. The milliK provides a feature that allows the sense current to be

increased by a factor of 1.428 ( mA), which increases the power dissipated by a factor

of two (since power is proportional to current squared). The change in indicated reading

caused by this change is then a direct measure of the self-heating effect at the normal 1mA

sense current (if the self-heating effect at 1mA is δT, then the self-heating at mA is 2δT

and the difference between the two readings is 2δT - δT i.e. δT). Subtracting the change (δT)

from the value at 1mA gives the resistance without any self-heating.

3.1.3 Using 3 or 4 Wire Measurement

The milliK uses a 4-wire connection technique to eliminate the effect of the cable resistance

from the measurement. This involves supplying the sense current through one pair of wires

and monitoring the voltage developed across the PRT element with a separate pair of wires:

Since the current along the voltage sense wires is effectively zero, the milliK is able to

measure the resistance of the PRT element without being affected by the resistance of the

wires.

In some industrial applications a 3-wire connection technique is used in order to reduce the

cost of cabling (important when a large number of PRTs and long cable runs are involved,

such as in a petrochemical plant). In this arrangement, there is a separate current and voltage

sense connection to one side of the PRT element, but the other side has a common

connection:

The milliK measures the voltage developed across the I- wire by measuring the voltage

between pins 4 and 6. Provided the wires are all the same gauge and length (same resistance)

the voltage drop down the I+ wire will be the same, so the milliK can subtract this correction

from the voltage measured between V+ and V- (pins 1 and 6) to determine the voltage across

the PRT element. In this way, the milliK can perform a 3-wire measurement that is

substantially immune to the resistance of the wires. The common and current leads should be

cut to the same length and connected directly to pins 2 and 3 and link wires (carrying no

current) should be used to link pins 1 to 2 and pins 3 to 4 in order to minimise uncertainty due

to the limitations of 3-wire measurement (inequalities in the wire resistance).

If you wish to make temporary connections to a 3-wire PRT using intermediate connectors

(typically required for calibrating 3-wire PRTs), then you must ensure that the resistance in

the extension connections to the I+ and I- wires is the same:

This can be achieved by using the same gauge and length of wire for the I+ and I- leads. Use

the lowest resistance wire (that is mechanically suitable) so as to minimise the resistance of

the extension connections and therefore minimise any error from the imbalance in their

resistance.

3.2 Using a Thermistor with milliK

The milliK can be used with resistance thermometers based on thermistors. These are

typically NTC (negative temperature coefficient) devices that have well defined

characteristics and can offer accuracies down to 25mK or less. Compared with PRTs/SPRTs,

thermistors have a much higher resistance (typically measured in tens of k), operate over a

more limited temperature range (typically < 150°C), are highly non-linear but are lower cost

and can be more robust. The non-linear resistance-temperature characteristics make

thermistor sensors very sensitive over a limited temperature range. Their relatively high

resistance means that 4-wire measurement is not as important as with PRTs/SPRTs (although

the milliK still uses 4-wire measurement). However, their high resistance makes them more

prone to electrical interference, so greater care is required when connecting them to the

milliK, in particular the use of screened cables is highly recommended (see section 4.2).

Unlike PRTs/SPRTs, the resistance-temperature characteristics vary considerably between

different types of thermistor. There are, therefore, no nominal or generic conversion

algorithms. The milliK can be used to monitor the resistance of a thermometer declared to be

a Default Thermistor, but in order to measure temperature, the thermistor and its calibration

details must be entered into the milliK’s thermometer database.

Connect your thermistor to either of the Lemo 6-pin circular connectors on the front panel

using a 2-wire or 4-wire connection arrangement (see section 4.2 for pin-out and connection

details). Ensure that the miniature thermocouple connector for the same channel is unused

(since it is connected in parallel with the Lemo connector). Your milliK is supplied with two

Lemo connectors for you to use with thermistors. The part number for this connector is:

Lemo part number: FGG.1B.306.CLAD62Z

Additional connectors are readily available internationally from Farnell Electronics and can

be ordered via their website www.farnell.com (Farnell stock code 3817325).

Channels 1 and 2 are not isolated from each other, but are isolated from Channel 3 and from

the digital interfaces in order to optimise immunity to external noise sources.

3.2.1 Configuring milliK to Measure Temperature with a Thermistor

Firstly, the thermistor and its calibration details must be entered into the milliK’s

thermometer database (see section 3.9.1), the thermistor will then appear in the

‘Thermometer’ list. Press the Settings (F3) key to access the Settings window, which

opens with the ‘Channel’ parameter selected. Use the ←←←← →→→→ keys to select the channel that

you want to configure. Then use the ↑↑↑↑ ↓↓↓↓ keys to select each parameter in turn and set it to the

required value either by using the ←←←← →→→→ keys to sequence through the options or pressing the

↵↵↵↵ key to open a new window with all the options listed. A typical configuration for a

thermistor would be:

The Samples/Reading parameter is the number of samples averaged together to form a single

reading. Increasing this value will reduce the noise on the measurements (standard deviation

will reduce as the square root of the number of samples) but also slow down the update rate.

The resistance of a thermistor can be measured without entering any calibration information

by declaring the ‘Thermometer’ as a “Default Thermistor”. This can be useful when

calibrating thermistors against other thermometers:

Once you have configured the milliK to work with your thermistor, press either the Graph

(F1) or Numeric (F2) keys to view the measurements:

Use the ←←←← →→→→ ↑↑↑↑ ↓↓↓↓ ↵↵↵↵ keys to select and activate the on-screen buttons to clear the

graph/statistics, set the scales and start/stop logging of data to a file.

3.3 Using a Thermocouple with milliK

The milliK can be used with any thermocouple (calibrated or uncalibrated) fitted with a

standard miniature thermocouple connector. Connect your thermocouple to either of the

miniature thermocouple connectors on the front panel. Ensure that the Lemo circular

connector for the same channel is unused (since it is connected in parallel with the

thermocouple connector). Isotech supply thermocouples fitted with standard miniature

thermocouple connectors for direct connection to your milliK.

3.3.1 Using Internal Reference Junction Compensation

The EMF developed by a thermocouple depends on the temperature difference between the

measurement and reference junctions. It is therefore necessary to know the temperature of the

reference junction (the point at which the electrical circuit changes to copper) in order to

calculate the temperature at the measurement junction. The milliK measures the temperature

of the contacts in the miniature thermocouple connectors on the front panel so that these can

be used as the reference junction in the thermocouple system. In this arrangement there is no

externally accessible reference junction and wires that make up the thermocouple are

connected to the milliK using a connector made of the same material as the wire itself. It is

essential that the correct “typed” connector is used with the thermocouple:

Reference Junction

Measurement

M+

Junction

M-

When using a thermocouple with internal reference junction compensation, the ‘Reference’

parameter in the Settings window should be set to “Internal” (see section 3.3.4).

For greater accuracy, you can use an external reference junction whose temperature is

measured with a calibrated thermometer (see section 3.3.2) or that is immersed in an ice-point

at 0°C (see section 3.3.3).

3.3.2 Using External Reference Junction Compensation

The milliK allows you to measure the temperature of an external reference junction using a

thermometer connected to another channel. This technique can provide better measurement

uncertainty than using internal reference junction compensation (see section 3.3.1), provided

that the reference junction and sensing thermometer are adequately isothermal and that the

reference junction thermometer is sufficiently accurate:

Channel A Channel B

I-

V+V-

I+

Reference

Junction Junction

M+

M-

Isothermal Environment

+tc

When using a thermocouple with external reference junction compensation, the ‘Reference’

parameter in the Settings window should be set to the channel used to measure the

reference junction (see section 3.3.4). Also, you MUST use a copper miniature thermocouple

connector in order to avoid introducing unwanted additional thermal EMFs. Only channels

configured to measure temperature (i.e. having a Conversion defined) appear in the

‘Reference’ parameter list. Thermocouple channels do not appear in the ‘Reference’

parameter list in order to avoid circular dependencies.

For greater accuracy, you can immerse the reference junction in an ice-point at 0°C (see

section 3.3.3).

3.3.3 Using an Ice-Point for the Reference Junction

The best measurement uncertainty is generally achieved by immersing the reference junction

in an ice-point and measuring the EMF it generates (Isotech can provide ice-point reference

systems for this application):

Reference Measurement

Junction Junction

M+

M-

Ice Point

When using a thermocouple with the reference junction in an ice point, the ‘Reference’

parameter in the

Settings window should be set to 0°C (see section 3.3.4). Also, you

MUST use a copper miniature thermocouple connector in order to avoid introducing

unwanted additional thermal EMFs.

3.3.4 Configuring milliK to Measure a Thermocouple

The milliK can be used with both calibrated and uncalibrated thermocouples. Press the

Settings (F3) key to access the Settings window, which opens with the ‘Channel’ parameter

selected. Use the ←←←← →→→→ keys to select the channel that you want to use. Then use the ↑↑↑↑ ↓↓↓↓ keys

to select each parameter in turn and set it to the required value either by using the ←←←← →→→→ keys

to sequence through the options or pressing the ↵↵↵↵ key to open a new window with all the

options listed. For an uncalibrated thermocouple or one that is not supplied with calibration

data, set ‘Thermometer’ to “Default Thermocouple”. If you want to use temperature units,

select one of the standard conversions for thermocouples. If your thermocouple is supplied

with calibration data (data pairs of polynomial coefficients), you can create a thermometer

entry in the database (see section 3.9.5) that uses this data to provide more accurate

conversion of the measured EMF to temperature.

A typical configuration for an uncalibrated (type K) thermocouple (using internal reference

junction compensation) would be:

In order to use external reference junction compensation (see section 3.3.2) you must enable

and configure one of the other channels to measure temperature using a PRT/SPRT or

thermistor. This channel will then appear as one of the options in the ‘Reference Junction’

parameter. A typical configuration for a type K thermocouple (using external reference

junction compensation by a PRT connected to channel 2) would be:

The lowest uncertainty can be achieved with a thermocouple by using an ice-point as the

reference junction (see section 3.3.3). A typical configuration for a calibrated gold-platinum

thermocouple entered into the database as “AuPt thermocpl” and using an ice-point reference

would be:

Once you have configured the milliK to work with your thermocouple, press either the

Graph (F1) or Numeric (F2) keys to view the measurements:

Use the ←←←← →→→→ ↑↑↑↑ ↓↓↓↓ ↵↵↵↵ keys to select and activate the on-screen buttons, which select the

channel, clear the graph (‘Graph’ window), clear the statistics (‘Numeric’ window), set the

scales and start/stop logging of data to a file.

3.4 Using a 4-20mA Transmitter with milliK

The milliK can be used with 4-20mA temperature transmitters by using the 4mm sockets on

the rear of the milliK (designated Channel 3). The centre 4mm socket is the current sense

input to the milliK, the other 4mm sockets are 0V and a +24V supply. Connect the

transmitter between the appropriate 4mm sockets depending on whether it is self-powered or

loop-powered (suitable for a 24V loop supply):

4-20mA 4-20mA

Self-Powered Transmitter Loop-Powered Transmitter

The 4-20mA system and 24V supply are isolated from both the measurement system of

Channels 1 and 2 and from the digital interfaces in order to optimise immunity to external

(common-mode) noise sources.

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Isotech milliK Operating Manual

Specifications and Main Features

Frequently Asked Questions

User Manual