Isotech TTI-7-R Operator's Handbook Manual

Model TTI-7-R

Precision Digital Thermometer

Operators Handbook

Isotech North America

158 Brentwood Drive, Unit 4

Colchester, VT 05446

Phone: [phone]
Fax: [phone]

www.isotechna.com

[e-mail]

ENGLISH

IMPORTANT SAFETY INFORMATION

22/1/97

GENERAL

This instrument has been designed and tested to comply with the Electromagnetic Compatibility Directive 89/336/EEC
and Low Voltage Directive 93/68EEC in accordance with EN 61010 -1 :1995 relating to the safety requirements for
electrical equipment for measurement, control and laboratory use.

Before connecting the instrument to the main supply please ensure the following safety precautions have been read and
understood.

SAFETY SYMBOLS

The following symbols are used to describe important safety aspects of th is instrument, these symbols appear on the
instrument and in the operation instructions.

Attention Symbol:

Indicates a potentially hazardous condition exists and that it is
necessary for the operator to refer to the instruction manual to ensure the safe operation
of thi s instrument.

Hot Surface Warning:

Indicates a hot surface that may be at a temperature capable of

causing burns, refer to the instruction manual for further safety information.

Caution Risk of Electric Shock:

Indicates hazardous voltages may be present,

refer to the instruction manual for further safety information.

Protective Conductor Terminal:

For protection against electrical shock during a fault
condition. This symbol is used to indicate terminals that must be connected to electrical
ground before operating equipment.

SUMMARY OF SAFETY PRECAUTIONS

The following general safety precautions must be observed while operating or servicing thi s instrument. Failure to
comply with these precautions may result in personnel i njur y or death.

INSTRUMENT ELECTRICAL EARTH

This instrument is designed as a Class 1 electrical safety ins ulat ion device. To ensure continued protection from
electric shock the instrument chassis must be connected to an electrical ground. The instrument is supplied with an AC
power cable with an earth connection.

LIVE CIRCUITS DANGER

Do not connect the power supply to or operate thi s instrument with the protective covers removed. Component
replacement and internal adjustments must be made by qua li fied service personnel. Do not replace components with the
power cable connected. Under certain conditions, dangerous voltages may exist with the power cable removed. To avoid
inj ur ie s always disconnect power and discharge circuits before touching them.

DO NOT MODIFY THIS INSTRUMENT OR SUBSTITUTE PARTS

Because of the danger of introducing additional hazards; do not perform any unauthorized modification or i nst a l l
substitute parts to the instrument. Only fuses with the rated current, voltage and specified type should be used,
fai lu re to do so may cause an electric shock or f ir e hazard. Return the instrument to Automatic Systems Laboratories
for service and repair to ensure the safety features are maintained.

DO NOT OPERATE IN EITHER DAMP OR EXPLOSIVE ENVIRONMENTS

This instrument is not designed to operate w h ile wet, in an environment of condensing humidity or in the presence of
flammable gases or vapors. The operation of thi s instrument in such an environment constitutes a safety hazard.

HOT SURFACES DANGER

Equipment marked with a Hot Surface warning symbol should be regarded as operating at temperatures capable of
causing burns. Do not touch, handle or transport hot components or l iqu id s un t il they are at safe temperatures. Care
should be taken not to spill or splash water or volatile fluids on or into hot surfaces or liquids.

CERTIFICATION

Automatic Systems Laboratories certifies that th is product met it s published specifications at the time of shipment
from our factory. A ll calibration measurements performed in the manufacture of t his instrument are traceable to the
National Physical Laboratory (London).

ASSISTANCE

For after sales support and product service assistance please contact Automatic Systems Laboratories Customer
Support Group. Contact information is provided in the operation instruction manual.

Contents

Table of Contents

1. INTRODUCTION.................................................................................................................1-1

1.1 Overview ...................................................................................................................1-1

1.2 Definitions and Terminology.......................................................................................1-3

1.3 Principles of measurement........................................................................................1-4

1.3.1 PRT measurement...........................................................................................1-4

1.3.2 Thermocouple measurement............................................................................1-5

1.3.3 Thermocouple reference junction compensation...............................................1-6

2. SETTING UP THE TTI-7-R ............................................................................................... 2-1

2.1 Safety information......................................................................................................2-1

2.2 Unpacking the instrument..........................................................................................2-1

2.3 Voltage selection and fuse rating...............................................................................2-2

2.3.1 Setting the Voltage and Fuse Rating.................................................................2-2

3. ABOUT THE TTI-7-R ........................................................................................................ 3-1

3.1 The Front Panel ........................................................................................................3-1

3.2 On/Off switch and internal battery.............................................................................. 3-1

3.3 The Function Keypad ................................................................................................3-2

3.4 About the TTI-7-R Display ......................................................................................... 3-4

3.5 Thermometer inputs..................................................................................................3-8

3.6 Rear panel .................................................................................................................3-9

3.6.1 AC Power Input Socket..................................................................................3-10

3.6.2 Rating plate ....................................................................................................3-10

3.6.3 Input channel expansion card .........................................................................3-10

3.6.4 RS232/IEEE 488.2 Communication interface card ..........................................3-10

3.6.5 Analogue output .............................................................................................3-10

3.6.6 Name plate.....................................................................................................3-10

4. MEASURING TEMPERATURE...........................................................................................4-1

4.1 Measurement uncertainty and traceability .................................................................4-1

4.2 International temperature scale .................................................................................4-1

4.3 Thermocouple measurement introduction ..................................................................4-3

4.3.1 Connecting thermocouples ................................................................................4-4

4.4 PRT measurement .................................................................................................... 4-4

4.4.1 PRT linearization functions ...............................................................................4-6

5. OPERATING THE TTI-7-R ................................................................................................. 5-1

5.1 About the display screen ...........................................................................................5-1

5.2 About function keys ..................................................................................................5-3

5.3 Power-up sequence .................................................................................................. 5-4

5.3.1 Self-Test ..........................................................................................................5-4

5.3.2 System Configuration....................................................................................... 5-5

5.4 Setting up Measurement Options ..............................................................................5-6

Contents - 1

Contents

5.4.1 Selecting thermometer input channel. .............................................................. 5-6

5.4.2 Selecting differential input measurement .......................................................... 5-6

5.4.3 Setting up a PRT measurement....................................................................... 5-7

5.4.4 Setting up a PRT measurement with user defined probe memories.................. 5-9

5.4.5 Setting up a PRT measurement: checking/editing probe memory co-eff. values..

...................................................................................................................... 5-10

5.4.6 Selecting thermocouple type.......................................................................... 5-11

5.4.7 Selecting the reference junction compensation method.................................. 5-12

5.4.8 Selecting ext. ref. junction PRT linearization whose temperature is measured by

a PRT connected to the same channel. ........................................................................... 5-13

5.5 Selecting Screen Display Options........................................................................... 5-14

5.5.1 Selecting measurement units ........................................................................ 5-14

5.5.2 Selecting display resolution modes................................................................ 5-14

5.5.3 Selecting relative temperature measurement .................................................5-14

5.5.4 Using the measurement trigger function [Run/Hold] .......................................5-15

5.5.5 Selecting PRT measurement sense current................................................... 5-15

5.6 Data Logger ............................................................................................................ 5-17

5.6.1 Data logger functions ..................................................................................... 5-17

5.6.2 Setting up the data logger ..............................................................................5-17

5.6.3 Configuring the Scanner ................................................................................ 5-18

5.6.4 Configuring the Timer. .................................................................................... 5-19

5.6.5 Configuring the data log memory ................................................................... 5-21

5.6.6 Starting the data log.......................................................................................5-22

5.6.7 Reviewing log results ..................................................................................... 5-23

5.6.8 Reviewing log statistics .................................................................................. 5-24

5.7 Setting up the basic controls .................................................................................. 5-25

5.7.1 Review system configuration.......................................................................... 5-25

5.7.2 Setting up the TTI-7-R ................................................................................... 5-26

5.7.3 Configuring the communications interface. ..................................................... 5-28

5.7.4 Setting up Trigger Mode................................................................................. 5-30

5.7.5 Displaying the firmware version ...................................................................... 5-31

5.7.6 Adjusting the display contrast........................................................................ 5-31

6. CALIBRATING THE TTI-7-R .............................................................................................6-1

6.1 TTI-7-R Instrument calibration ................................................................................... 6-1

7. COMMUNICATIONS INTERFACE .....................................................................................7-1

7.1 Introduction............................................................................................................... 7-1

7.2 Fitting the Interface................................................................................................... 7-2

7.3 Overview of the RS-232 Serial Interface .................................................................... 7-3

7.3.1 The RS-232 Connector. .................................................................................... 7-4

7.3.2 Pin Connections............................................................................................... 7-4

7.3.3 RS-232 Settings............................................................................................... 7-5

7.3.4 RS-232 Operating Modes ................................................................................. 7-5

7.3.5 RS-232 Interface Commands ........................................................................... 7-6

Contents - 2

Contents

7.4 Programming the Interface ........................................................................................7-6

7.4.1 Introduction ......................................................................................................7-6

7.4.2 Command Tree.................................................................................................7-7

7.4.3 Command Directives ........................................................................................7-7

7.4.4 Command Syntax .............................................................................................7-8

7.5 IEEE-488.2 Common Command Group ....................................................................7-10

7.5.1 IEEE-488.2 Common Command Summary.....................................................7-10

7.5.2 IEEE-488.2 Common Commands ..................................................................7-10

7.6 Measurement Command Group ..............................................................................7-14

7.6.1 Measurement command summary...................................................................7-14

7.6.2 CONFigure Commands...................................................................................7-14

7.6.3 MEASure Command .......................................................................................7-18

7.7 SENSe Command Group........................................................................................7-20

7.7.1 Sense command summary.............................................................................7-20

7.7.2 Sense Commands .........................................................................................7-20

7.8 Mathematical Operation Commands........................................................................7-22

7.8.1 CALCulate:AVERage command summary ......................................................7-22

7.8.2 CALCulate:AVERage commands ....................................................................7-22

7.9 Route Command Group ...........................................................................................7-23

7.9.1 Route command summary. .............................................................................7-23

7.9.2 Route commands ...........................................................................................7-23

7.10 Trigger Command Group.....................................................................................7-25

7.10.1 Trigger command summary ............................................................................7-25

7.10.2 Trigger commands..........................................................................................7-25

7.11 System Related Commands ...............................................................................7-29

7.11.1 System command summary...........................................................................7-29

7.11.2 System commands .........................................................................................7-29

7.12 DATAIogger Command Group..............................................................................7-31

7.12.1 Datalogger command summary.......................................................................7-31

7.12.2 Datalogger commands ...................................................................................7-31

7.13 Status Reporting Structure AND Commands ......................................................7-34

7.13.1 The Status Reporting System is summarised in the following diagram.............7-35

7.14 Command Summary...........................................................................................7-39

7.15 Analogue Output.................................................................................................7-42

7.15.1 Specification...................................................................................................7-42

7.75.1 Default Settings..............................................................................................7-42

7.15.1 Analogue Output Connection..........................................................................7-42

8. OPTIONS AND ACCESSORIES ........................................................................................8-1

8.1 Accessories ..............................................................................................................8-1

8.2 High = PRTs ..............................................................................................................8-1

8.3 Low = PRTs .............................................................................................................. 8-2

9. SPECIFICATIONS .............................................................................................................9-1

9.1 Pt100 resistance thermometer measurement............................................................ 9-1

Contents - 3

Contents

9.2 Thermocouple measurement............................................................................................ 9-1

9.3 Internal battery operation ................................................................................................. 9-2

9.4 Supply ...................................................................................................................... 9-2

9.5 Environmental........................................................................................................... 9-2

9.6 Data communication interface options ...................................................................... 9-2

9.7 Analogue output option............................................................................................. 9-3

9.8 Display...................................................................................................................... 9-3

9.9 Physical....................................................................................................................9-3

9.10 Pt100 System accuracy ....................................................................................... 9-3

10. CLEANING AND MAINTENANCE................................................................................... 10-1

10.1 Cleaning............................................................................................................. 10-1

10.2 Preventive Maintenance...................................................................................... 10-1

10.3 General Safety Warning .....................................................................................10-1

11. SERVICE AND WARRANTY........................................................................................... 11-1

11.1 Technical Support .............................................................................................. 11-1

11.2 Returned Instruments ......................................................................................... 11-1

Contents - 4

1.1 Overview

The TTI-7-R Precision Thermometer is a high accuracy instrument

designed for laboratory and industrial temperature measurement and

calibration applications.

Features include:

• unique dual capability for both thermocouple and resistance

thermometer measurements;

• number of input channel can be expanded from two to ten

channels;

• large graphic LCD display for temperature measurement values

as well as configuration settings and statistical results;

• advanced functions include differential measurement, four

programmable scanning routines, programmable timer, data

logging to none volatile memory, statistical reporting;

• analogue output, IEEE 488 and RS232 communication

interfaces available for automated monitoring and calibration

applications;

• internal battery provides up to 20 hours mains free operation for

remote measurement and data logging applications.

The TTI-7-R will operate with any Pt25 (25 Ohm) and all 2, 3 and 4-wire

Pt100 (100 Ohm) platinum resistance thermometers as well as most

standard international thermocouple types. Temperature measurement

units are selectable by single front panel key operation; °C, °F,K Base
measurement units mV,  are also displayed.

Resistance accuracy is better than ±4m for Pt100 400 Ohm range
and ±1.5m for Pt25 100 Ohm range (over full range of –200 to 100°C

at +20°C ±2°C). This is equivalent to temperature measurement

precision of ±15mK for Pt25 thermometers and ±10mK for Pt100

thermometers. Total system measurement uncertainties as low as

±20mK are possible when the TTI-7-R is used with a calibrated

reference thermometer.

1. Introduction

Page 1-1

Introduction

Overall system accuracy depends on the PRT quality and calibration. See Section

9 for details of the system measurement accuracy specification.

Standard miniature and 4mm instrument sockets allow convenient connection for

thermocouple inputs. Connection sockets incorporate integral temperature

compensation sensors making high accuracy thermocouple measurement

possible without the use of an external reference junction.

Standard features of the TTI-7-R Precision Thermometer include:

• direct temperature measurement display in °C, °F,K;

• 2 x Pt 25 or Pt100 channel inputs on front panel using 4mm gold plated

spade lug connectors or wire/banana plugs;

• 2, 3 and 4 wire PRT probe measurement;

• Thermocouples B,C,D,E,J,K,N,R,S,T,U,W

• 1 to 20 probe coefficients for ITS90 or CVD entered and stored from

programming PRT calibrations;

• High Accuracy to 0.01 deg.C over –200 to 660 deg.C

• High Resolution 0.001 deg.C for 25/100 Ohm PRT’s and 0.01 deg.C for TC’s;

• Measuring Range –200 to 1100 deg.C for PRT’s and 0 to 2315 deg.C TC’s;

• PRT self-heating and measurement current polarity selection;

• illuminated display;

• compact rugged case;

• 2 to 10 channel expansion with rear panel SPRT, RTD, and TC modules;

• Automatic Cold Junction compensation for TC’s;

• Switched DC (current reversal) option to eliminate thermal e.m.f.s on PRT’s;

• Internal data logging and storage of 4000 measurements;

• Statistical data internally (Min, Max, Peak/Peak, Average, Std. Deviation) ;

• Differential (Difference between any 2 channels connected) ;

• PC interface (RS232) included;

• Portable 20 hour use using internal battery + charger fitted or mains supply;

Page 1-2

Introduction

1.2 Definitions and Terminology

i. 0°C = 273.15K

ii. 1 mK (milli-Kelvin) = 0.001 °C (one milli-degree Celsius)

iii. 1 milli-degree C = 0.001 °C = 1m°C = 1mK= 1.8m°F

iv. 1 milli-degree F = 0.001 °F = 1 m°F = 0.56mK = 0.56m°C

v. Alpha, or , is the temperature coefficient, or temperature

sensitivity, of the platinum wire used in PRTs. In general, the

greater the alpha value, the better the PRT thermometer

measurement reproducibility, stability and performance.

vi. Abbreviations for platinum resistance thermometers include: PRT

(Platinum Resistance Thermometer)

Pt100 (PRT with nominally 100 resistance at 0°C) RTD (Resistance

Temperature Device) vii. Thermocouples are referred to as a TC

element or TC sensor.

viii. The TTI-7-R 's thermocouple connection sockets are often referred

to as a temperature compensated reference junction. See Section

1.3 for more details.

ix. System accuracy refers to the overall, combined accuracy of the

TTI-7-R and thermometer.

Key functions and menu options are described as [Function] in the

text or the actual keytop is shown.

General warning symbol. This indicates that a

hazardous condition or general danger may exist.

You must read the relevant sections in the

Operator's Handbook before operating the

instrument.

Page 1-3

Introduction

1.3 Principles of measurement

1.3.1 PRT measurement

The TTI-7-R measures the voltage (Vt) developed across the unknown

sensor resistance (Rt) and the voltage (Vs) across a stable internal

reference resistance (Rs) connected in series and passing the same

current. The voltages are in proportion to the resistances so the

thermometer resistance is derived from: Rt = Rs x Vt / V

s

This technique achieves immunity from slow moving time and

temperature drift in the electronics as it is not affected by voltage

measurement gain variations or current source fluctuations.

In the same way that AC resistance measurement eliminates thermal

EMFs, switched DC achieves a similar advantage. Switched DC

works by reversing the current flow on alternate measurement cycles

and taking the average value, thereby cancelling any thermal EMF

offsets from the measurement.

For PRTs, the relationship between resistance and temperature varies

slightly from one PRT to another. Therefore, no matter how accurately

the TTI-7-R measures the PRT resistance, if the relationship between

resistance and temperature for a particular PRT is not known,

accurate temperature measurement is not possible.

The TTI-7-R uses PRT calibration data to overcome this problem and

calculates temperature from temperature conversion functions stored

in internal memory. This method enables the TTI-7-R accurately to

convert resistance to temperature, uniquely for each PRT used. It is

very important therefore that a PRT is used on the correct and

properly configured input channel.

The system accuracy is a combination of the TTI-7-R accuracy in

measuring PRT resistance and the calibration uncertainty placed on

the PRTs by the calibrating laboratory. Using the TTI-7-R with PRT

type 935-14-61, this is ±0.020°C for temperatures from -80°C to

+350°C. See section 9.1 for PRT measurement performance details.

Page 1-4

Introduction

1.3.2 Thermocouple measurement

As well as the PRT resistance measurement facility the TTI-7-R also

functions as a precision milli-voltmeter. Designed for high accuracy

measurement over the EMF voltage range of all standard base and

precious metal thermocouples, the TTI-7-R achieves a basic voltage

accuracy of better than 3µV

(at +20 °C ±2 °C) over the full measurement range and significantly

better over smaller ranges. See Section 9.2 for thermocouple

measurement performance details. Thermocouple EMFs are

converted to temperature using the NIST monograph 175

linearization functions. Special types C and D use the linearizations

specified by ASTM E988.

The voltage input connection is specially designed to minimise the

thermal gradient between the terminals. This is particularly important

when the internal reference junction compensation is used, as any

temperature difference at the connection junction will influence the

measurement result. The connection junction is introduced in

Section 1.3.3 below.

Page 1-5

Introduction

1.3.3 Thermocouple reference junction compensation

The electrical connection between the thermocouple element and the

TTI-7-R input connector is often referred to as the internal reference

junction. All standard thermocouple reference functions are defined

relative to 0°C. To eliminate the physical need to reproduce this

temperature inside the TTI-7-R , the actual connection temperature

is accurately measured with an internal PRT. This temperature is

converted to an equivalent EMF and added to the actual

thermocouple voltage measurement, thereby correcting for the

connection temperature.

For high precision thermocouple measurement applications, i.e.

calibration, an external reference junction may be used. Using an

external reference junction eliminates the uncertainties associated

with reference junction compensation.

Page 1-6

2.1 Safety information

Please read and follow these important safety instructions:

• Read the safety information sheet at the beginning of this

handbook before operating the TTI-7-R ;

• Make the necessary electrical safety and connection checks. In

particular, select the correct line voltage and make sure that the

correct AC power fuse is installed. Incorrect voltage or fuse

selection present both an electrical safety and a fire hazard.

2.2 Unpacking the instrument

When you unpack the TTI-7-R thermometer, check that the following

items are present before starting to use the unit:

• 1x TTI-7-R thermometer

• 1 x AC power cord

• 1x Operator's handbook

• 1x Calibration certificate

Please contact the ISOTECH NA Technical Services Group

immediately if any of these items are missing or damaged.

2. Setting up the TTI-7-R

Page 2-1

Setting up the TTI-7-R

2.3 Voltage selection and fuse rating

The AC Power Input Unit incorporates a voltage selector and fuse

holder, to enable the TTI-7-R operating voltage and fuse rating to be

selected for the local AC electricity supply. The table below describes

the correct voltage selection range and fuse to use.

Voltage Selection

Voltage Range

Fuse Type

100V 90-110V T630mA (250V AC)

120V 108- 132V T630mA (250V AC)

220V 198-244V T315mA (250V AC)

240V 216-264V T315mA (250V AC)

WARNING: DO NOT CONNECT THE POWER

CABLE UNTIL THE VOLTAGE AND FUSE RATING

OF THE INSTRUMENT HAVE BEEN CHECKED

AND CHANGED IF NECESSARY.

2.3.1 Setting the Voltage and Fuse Rating

Lever open the Power Input Unit from the top with a flat bladed

screwdriver. Inside is a plastic cam: remove this and replace it so that

the voltage to be set is displayed through the window as detailed in

Figure 2.1.

Where fused plugs are connected to the AC power cord, the correct

fuse rating is 3 Amps. The AC power cord provided with the TTI-7-R is

colour coded in accordance with national standards to match the plug

type fitted, as follows:

Page 2-2

Setting up the TTI-7-R

Earth (protective conductor) Green Green/Yellow

Live Black Brown

Neutral White Blue

Figure 2.1 - Fused Power Input Unit and Voltage Selector

INSERT SCREWDRIVER
TO LEVER DOOR OPEN

VOLTAGE SELECT
PLASTIC CAM

FUSE
HOLDER

Page 2-3

Setting up the TTI-7-R

This page has been left blank intentionally

Page 2-4

3. About the TTI-7-R

This section introduces you to the features and functions of the TTI-7-

R Precision Thermometer.

3.1 The Front Panel

Figure 3.1- Front Panel

On/Off
switches

Function keys

Display

Thermometer
inputs

3.2 On/Off switch and internal battery

The ON / OFF keys switch the TTI-7-R on and off. During power

on all TTI-7-R measurement functions are reset to their default state.

It is important to note that THE POWER OFF FUNCTION DOES

NOT DISCONNECT THE TTI-7-R FROM THE ELECTRICITY

SUPPLY. The power supply remains connected to the mains supply.

Page 3-1

About the TTI-7-R

Battery charging operation is unaffected by the ON / OFF

key operation.

The TTI-7-R 0 may be operated from the AC electricity supply or the

internal battery. Fully charged batteries provide approximately 8 hours

continuous operation. The internal battery charger operates

whenever the electricity supply is connected. Front panel LEDs

indicate connection to the AC electricity supply and when the battery

is charging.

The batteries are a sealed lead acid type and require no routine

maintenance. Continuous charging causes no harm to the batteries.

Operate the TTI-7-R from the mains when possible to ensure the

batteries are always fully charged.

<LOW BATTERY> indication is displayed when the batteries have

approximately 10% charge or 50 minutes operating time remaining.

To extend the battery operation time, switch the display backlight off.

See Section 5.6.1.

If the batteries are left discharged for a long time, they become

difficult to charge on the first re-charging cycle. During this first re-

charge, it may not be possible to turn on the TTI-7-R . Leave the TTI-

7-R connected to the AC electricity supply for at least 12 hours to

allow the batteries to fully re-charge before using the TTI-7-R again.

3.3 The Function Keypad

All TTI-7-R measurement and programming facilities are accessed

through the function keypad. A brief description of key functions is

given in the table below. For a detailed description of how to use the

keys to configure and operate the TTI-7-R , refer to Section 5.

Page 3-2

About the TTI-7-R

Table 3.1 Summary of basic key functions

Page 3-3

Key symbol Description Function

Direct
function
or Menu

Setting up Input Channels

A

Select input
channel A0 to A4

Selects and displays
measurement channel A0 to A4

Direct
from
keypad

B

Select input
channel BO to B4

Selects and displays
measurement channel BO to B4

Direct
from
keypad

Diff

Select differential
measurement Ch1 ­Ch2

Relative measurement function
which displays the difference
between the Ch1 and Ch2 inputs

Direct
from
keypad

Setting up Measurement Options

SENS

Temperature
sensor type

Selects sensor type and
measurement configuration for the
selected channel

Menu

UNIT

Measurement
units

Selects measurement display
units: °C, °F, K

Direct
from
keypad

RES

Measurement

display resolution

Selects measurement display
resolution: Thermocouple: 0.1,

0.01 PRT:0.01, 0.001

Direct
from
keypad

ZERO

Measurement
display zero
function

Nulls the display at the current
reading and displays measured
values relative to the nulled value.

Direct
from
keypad

TRIG

Measurement run/
hold/single step

Display hold function, triggers
single or continuous
measurement.

Direct
from
keypad

Logging Data and Statistical Displays

MATH

Math display
functions

Selects the math menu statistical
display and function

Menu

CAL

Calibration menu
functions

Selects the instrument calibration
menu functions

Menu

Options and configuration

OPT

Setup options and
functions

Selects the instrument
configuration options menu and
communication interface
functions

Menu

About the TTI-7-R

(Table 3.1 continued:)

SCAN

Scanner, timer
and data logger
functions

Scanner, timer and data logger
menu.

Menu

PRT measurement current

+ l

PRT
measurement
positive current
mode

Positive PRT measurement
current polarity selection

Direct
from
keypad

-I

PRT
measurement
negative current
mode

Negative PRT measurement
current polarity selection

Direct
from
keypad

AVE

PRT
measurement
current reversal
mode

Measures average sensor
resistance with successive
positive and negative current
polarity Default PRT
measurement state

Direct
from
keypad

2

PRT
measurement 2
current selection

2 measurement current division,
reduces measurement current to
allow PRT self heating effect to be
calculated

Direct
from
keypad

Scroll and contrast control

Up command
key; Display
contrast, page
scroll

Controls the display contrast and
page scroll functions

Direct
from
keypad

Down command
key; Display
contrast, page
scroll

Controls the display contrast and
page scroll functions

Direct
from
keypad

3.4 About the TTI-7-R Display

The liquid crystal graphic display clearly indicates the measured

temperature and measurement status as well as displaying available

menu options and measurement analysis when selected. Whilst in

Temperature Mode (see Section 5.1), there are three possible

display layouts:

Page 3-4

About the TTI-7-R

Figure 3.2 - Main display layout (PRT measurement)

A1 Pt100 IEC751 / R0 = 100.000 a=3850 4-wre

+ 18.90 °C

Input = +106.591 Ohm Ave

XXXX/YYYY

Figure 3.3 - Main display layout (Thermocouple measurement)

A1 TC Type
N

RJ Mode= Internal

+ 18.90 °C

Input = -0.170 mV RJ = +24.62 deg C

Mem Adr Rem

Page 3-5

Busy

LOBAT

Run Mem Adr

Zero

Rem

SLX

Busy
LOBA

T

Run

X

XXX/YYYY

Zero SL

X

About the TTI-7-R

Figure 3.4 -Main display layout (Relative A1-B1 measurement)

A1-B1

- 0 . 1

°C

Busy

LOBAT

Adr

XXXX/YYYY

The table below describes the location of information as it appears in the

various display layouts:

Page 3-6

Run

Re

Mem

Zero SL

X

About the TTI-7-R

Table 3.2 - Measurement mode display features

PRT measurement Thermocouple Relative Ch1 - Ch2

1

Selected channel
temperature

Selected channel
temperature

Temperature
difference between
CM and Ch2

2

Input channel
selected

Input channel selected CM - Ch2

3

Pt100 TC Not used

4

PRT linearization
standard

Thermocouple type
selected, letter
designation

Not used

5

PRT alpha value

Reference junction
mode

Not used

6

3, 4 wire
measurement
configuration

Not used Not used

7

Temperature display
units

Temperature display
units

Temperature display
units

8

Measured input value
in Ohms

Measured input value

in mV

Not used

9

Measurement current
polarity

Reference Junction
temperature if selected

Not used

10

Measurement status Measurement status Measurement status

11

Trigger run/ hold,
single condition

Trigger run/ hold,
single condition

Trigger run/ hold,
single condition

12

Measurement zeroed
indication

Measurement zeroed

indication

Measurement zeroed

indication

13

Low Battery indication Low Battery indication Low Battery indication

14

Re mote/Addressed
remote operation

Remote/Addressed
remote operation

Re mote/Addressed
remote operation

15

R0 value in ohms Not used Not used

16

X samples taken of Y
number of samples

X samples taken of Y
number of samples

X samples taken of Y
number of samples

17

Logging data to none
volatile memory

Logging data to none
volatile memory

Logging data to none
volatile memory

18

Scanning mode ON
SLx scan list

Scanning mode ON
SLx scan list

Scanning mode ON
SLx scan list

Page 3-7

About the TTI-7-R

3.5 Thermometer inputs

The TTI-7-R has two main thermometer input channels, the input

sockets are located on the instruments front panel.

The two input channels can be independently configured for

measurement of PRT sensors or thermocouples.

Separate connection is provided for PRTs and thermocouples,

enabling easy direct connection of most thermometer types.

PRTs are connected via the 5 pin DIN sockets. You may connect 2, 3,

or 4 wire PRTs as shown in Figure 3.5. See Section 5.3.3 on PRT

selection. Un-terminated platinum resistance thermometers may be

connected through an optional adapter box which is available as an

accessory, (Part Number FA-ADAP-250). Refer to the Accessory

section at the end of this handbook.

Figure 3.5 - PRT input connection configuration

PRT CONNECTION - 2 WlRE PRT CONNECTION - 3 WIRE PRT CONNECTION - 4 WIRE

(5-pin DIN connector) (5-pin DIN connector) (5-pin DIN connector)

Pt100

R100

R100

View towards front panel connector

Thermocouples may be directly connected to the TTI-7-R either at the

standard miniature sockets or the two 4mm instrument sockets as

shown in Figure 3.6. Special adapter connectors are available for

connecting bare wire thermocouples to the TTI-7-R . These sockets

are within a temperature compensated isothermal block which

eliminates the need for an external ice point reference junction.

However, the TTI-7-R may also be used with an external ice point

reference for high precision measurement and calibration work.

Page 3-8

About the TTI-7-R

Figure 3.6 - Thermocouple input connection

THERMOCOUPLE

CONNECTION

LOW THERMAL EMF
COPPER BANANA (4mm)
PLUGS

3.6 Rear panel

Figure 3.7 - Rear Panel layout, showing all options

PRT expansion
module ( op t ional)

Thermocouple
expansion module
(optional)

RS232or I EE E

Communications
Interface (optional)

Analogue output
(optional)

Voltage selector
and fuse cover

Name plate

IE C power

connector

Rating plate

Page 3-9

About the TTI-7-R

3.6.1 AC Power Input Socket

Accepts an IEC type power connector.

The AC power input unit incorporates a voltage selection tumbler, to

enable the user to match the TTI-7-R to the local AC voltage

supply, and a power line fuse holder.

3.6.2 Rating plate

Instrument rating plate, contains the AC voltage selection and line

fuse rating, operating supply frequency range, the instrument

maximum power consumption and instrument serial number.

3.6.3 Input channel expansion card

Optional input channel expansion card slots. Blanking plates are

fitted if there is no input channel expansion cards.

3.6.4 RS232/IEEE 488.2 Communication interface card

Optional RS232/IEEE 488.2 communication interface card slot. A

blanking plate is fitted if there is no communication interface card.

3.6.5 Analogue output

Optional analogue output BNC socket. A blanking plug is fitted if

there is no analogue output.

3.6.6 Name plate

Instrument name plate, contains the manufacture name and

address details.

Page 3-10

4.1 Measurement uncertainty and traceability

Measurement is usually made on the assumption that there is a true

value. Whenever a measurement is performed it is unlikely that the

measured value will equal the true value. The difference between the

two values is the measurement error which will lie within the specified

limits of uncertainty. Uncertainty is defined as an estimate

characterising the range of values within which the true value lies.

By taking a statistically significant number of measurement samples, a

distribution of results will emerge. Confidence in the distribution

increases as more measurements are made. Using statistical

methods, the distribution may be described in terms of mean, variance

and standard deviation. The uncertainty or precision limit of a particular

measurement is characterised by this distribution.

Traceability is defined as the property of a measurement that may be

related to appropriate reference standards through an unbroken chain

of comparisons. Through traceability it is possible to demonstrate the

accuracy of a measurement in terms of SI units.

4.2 International temperature scale

The purpose of the International Temperature Scale is to define

procedures by which certain specified practical thermometers

including PRTs and thermocouples of the required quality can be

calibrated. The values of temperature obtained from them can be

precise and reproducible, matching at the same time the

corresponding thermodynamic values as closely as current technology

permits.

4. Measuring Temperature

Page 4-1

Since 1968 when the International Practical Temperature Scale of

1968 (IPTS68) was adopted, there have been significant advances in

the techniques employed in establishing temperature standards and

in the measurement of thermodynamic temperature. The

International Temperature Scale of 1990 (ITS-90) gives practical

effect to these improvements. Particular features are:

• ITS-90 specifies the use of the PRT up to the freezing point of

silver, 961.78 °C. The platinum 10% rhodium/platinum

thermocouple is no longer specified for use in the scale, though

it and other noble metal thermocouples will continue to be used

as secondary standards.

• New, more precise, fixed points have been introduced and

mathematical procedures for calculating resistance temperature

equivalents have been revised so as to reduce the 'non-

uniqueness' of the scale: that is, to reduce the differences which

occur between different, identically calibrated PRTs. In particular,

the calibration of a PRT can no longer be extrapolated beyond

the freezing point of zinc, 419.527 °C, but requires a

measurement at the freezing point of aluminium, 660.323 °C.

• Alternative definitions are permitted in certain sub-ranges, the

calibration of a PRT can be terminated at almost any fixed point.

This allows primary calibrations to be carried out with suitable

PRTs over reduced ranges, and will be of special importance to

metrology standards departments which need to make precise

measurements at ambient temperatures.

• The part of the ITS-90 scale which may be measured by PRTs

extends from 83.8058 K (-189.3442 °C) to 961.78 °C. The TTI-7-

R

is specified to measure temperature over the range

-200 °C to +962 °C. The actual range of temperatures which may

be measured depends on the type and range of the PRT.

Measuring Temperature

Page 4-2

Measuring Temperature

The ITS-90 scale has much improved continuity, precision and

reproducibility compared with IPTS68. The implementation of the

ITS-90 scale according to its definition calls for changes in

equipment and procedure compared with IPTS68, but lower

uncertainties of calibration are achievable in all parts of the range.

However, the instruments and equipment needed to implement the

ITS-90 scale in calibration laboratories will be substantially the

same.

4.3 Thermocouple measurement introduction

Very broadly the thermoelectric effect occurs when an electrical

circuit consisting of dissimilar metal conductors is subjected to a

temperature gradient. An electric potential or voltage is developed

along the conductors. This voltage potential varies proportionally with

temperature and provides a means by which to measure

temperature.

There are two categories of thermocouple:

• Rare metal, Platinum based types

• Base metal, Nickel based

Rare metal, platinum types are mostly used for high temperature

precision thermometry. Maximum temperatures of 1700 °C and

measurement uncertainties of up to 0.3 °C are possible. The

sensitivity of platinum based thermocouples is usually in the region of

10µV/ °C, which means that high accuracy, high resolution

measurements require sensitive instruments such as the TTI-7-R .

Base metal thermocouples easily account for the bulk of temperature

sensors used today, and offer the advantages of being easy to

package into a variety of sensor configurations and relatively low

cost. Base metal thermocouples operate over a wide temperature

range with high temperature types designed for use up to 1600 °C.

Temperatures above 2300°C are possible with new high temperature

tungsten rhenium types. Typical sensitivity figures of

Page 4-3

Measuring Temperature

>30µV/ °C characterise most of the base metal thermocouple

family.

Base metal thermocouples are easily affected by contamination

effects which results in decalibration and drift. This is especially

pronounced at high temperatures where drift figures of the order of

10 °C are possible. It is important to be aware of the particular

contamination effects and to select the correct thermocouple for the

measurement environment. The N type thermocouple offers the best

performance in terms of reproducibility and measurement

uncertainty, operating up to 1250 °C. It is the best choice for most

general measurement applications, calling for accuracy with low

time and temperature drift.

4.3.1 Connecting thermocouples

Thermocouples measure temperature difference. As all practical

thermocouples consist of at least 2 junctions, it is important when

performing absolute temperature measurement that one of the

junctions is referenced to a known temperature.

The reference junction and voltage measurement precision

significantly influence the overall temperature measurement

accuracy. Intermediate connection junctions such as connectors and

extension cables between the measurement thermocouple and the

TTI-7-R also influence the measurement result.

4.4 PRT measurement

The TTI-7-R will operate with either 25 Ohm SPRT’s/PRT’s or a

range of 2, 3 and 4-wire 100 Ohm PRTs. The best performance will

be achieved only where good quality PRTs are used from reputable,

proven sources. As with any measured parameter, the performance

of a measurement system depends upon its stability and

repeatability. Low quality PRTs are likely to reduce system

performance.

The relationship between temperature and resistance depends on

several factors, including the alpha value and the PRT calibration.

Page 4-4