Guildline 6622T Series User manual

Operation Manual
For The
6622T Series
Automatic DCC Thermometry Bridges
www.guildline.com
NOTICE
The contents and information contained in this manual are proprietary to
Guildline Instruments Limited. They are to be used only as a guide to the
operation and maintenance of the equipment with which this manual was
issued and may not be duplicated or transmitted by any means, either in whole
or in part, without the written permission of Guildline Instruments Limited.
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TABLE OF CONTENTS
1. INTRODUCTION.......................................................................................................1-1
1.1. SCOPE................................................................................................................................................................1-1
1.2. GENERAL DESCRIPTION............................................................................................................................1-1
1.3. OVERVIEW......................................................................................................................................................1-2
1.4. PRINCIPLE OF OPERATION ......................................................................................................................1-3
1.4.1.1. Low Ohm Measurement Mode............................................................................................................1-5
1.4.1.2. Normal Ohm Measurement Mode.......................................................................................................1-5
2. INSTALLATION........................................................................................................2-1
2.1. PRELIMINARIES............................................................................................................................................2-1
2.1.1. Unpacking.......................................................................................................................................................2-1
2.1.2. Power Voltage Selection................................................................................................................................2-1
2.1.3. Fuse Replacement...........................................................................................................................................2-2
2.1.4. Setup And Power On......................................................................................................................................2-3
2.2. INCOMING INSPECTION.............................................................................................................................2-3
2.3. 6622T SERIES FRONT PANEL DISPLAY AND CONTROLS................................................................2-5
2.3.1. Standard Resistor Input Terminals (Bench Model Only)..............................................................................2-5
2.3.2. Resistor Under Test Input Terminals (Bench Model Only)..........................................................................2-6
2.3.3. Guard Terminal (Bench Model Only) ...........................................................................................................2-6
2.3.4. Circuit Common Terminal (Bench Model Only)..........................................................................................2-6
2.3.5. Power..............................................................................................................................................................2-6
2.3.6. Display............................................................................................................................................................2-7
2.3.7. Numeric Keypad.............................................................................................................................................2-7
2.3.8. Special Keys...................................................................................................................................................2-7
2.3.8.1. Cursor Movement Keys .......................................................................................................................2-7
2.3.8.2. Function Keys.......................................................................................................................................2-7
2.4. 6622T SERIES REAR PANEL CONNECTORS AND CONTROLS........................................................2-8
2.4.1. IEEE-488 Interface.........................................................................................................................................2-8
2.4.2. Line Input Connector .....................................................................................................................................2-9
2.4.3. Standard Resistor Input Terminals (Rack Model Only)................................................................................2-9
2.4.4. Resistor Under Test Input Terminals (Rack Model Only)............................................................................2-9
2.4.5. Guard Terminal (Rack Model Only) .............................................................................................................2-9
2.4.6. Circuit Common Terminal (Rack Model Only)............................................................................................2-9
2.4.7. Ground Terminal..........................................................................................................................................2-10
2.4.8. Extender Connector......................................................................................................................................2-10
3. QUICK MEASUREMENT GUIDE.............................................................................3-1
3.1. MEASUREMENT OPERATION GUIDE ....................................................................................................3-1
3.1.1. Normal Ohm Mode Resistance Measurement (All 6622T Models).............................................................3-2

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3.1.2. Low Ohm Mode Resistance Measurement (All 6622T Models)..................................................................3-5
3.1.3. Thermometry Measurement Mode..............................................................................................................3-10
3.2. BRIDGEWORKS DATA ACQUISITION SOFTWARE .........................................................................3-12
4. INSTRUMENT OPERATION....................................................................................4-1
4.1. FRONT PANEL OPERATING PROCEDURE...........................................................................................4-1
4.2. 6622T THERMOMETRY MEASUREMENT BRIDGE ............................................................................4-1
4.3. GENERAL KEY/DISPLAY OPERATIONS................................................................................................4-6
4.3.1. Base menu.......................................................................................................................................................4-6
4.4. BASIC MENU OPERATIONS.......................................................................................................................4-7
4.4.1. Menu Option-<MEASURE>.........................................................................................................................4-7
4.4.2. Menu Option - <any other menu but measure>.............................................................................................4-8
4.4.3. Base Edit/Select Menu - one column of data.................................................................................................4-9
4.4.4. Base Edit/Select Menu - two columns of data...............................................................................................4-9
4.4.5. Operation of Select/Edit Data Menus..........................................................................................................4-10
4.4.5.1. Function - <Scrn n-N> .......................................................................................................................4-10
4.4.5.2. Function - <Edit> ...............................................................................................................................4-10
4.4.5.3. Function - <Ok>.................................................................................................................................4-10
4.5. TITLE SCREEN .............................................................................................................................................4-11
4.6. MAIN MENU...................................................................................................................................................4-12
4.6.1. <Measure> MENU Fn-1 (Main)..................................................................................................................4-12
4.6.1.1. <Measure> MENU Fn-1 (MAIN) Page 1 of 3..................................................................................4-13
4.6.1.2. <Measure> MENU Fn-1 (MAIN) Page 2 of 3..................................................................................4-14
4.6.1.3. <Measure> MENU Fn-1 (MAIN) Page 3 of 3..................................................................................4-15
4.6.2. <Setup> MENU Fn-1 (Setup_MAIN).........................................................................................................4-16
4.6.3. <Profiles> MENU Fn-1 (Profiles MAIN)...................................................................................................4-16
4.6.4. View..............................................................................................................................................................4-17
4.6.4.1. Summary.............................................................................................................................................4-17
4.6.4.2. Detail Graph .......................................................................................................................................4-18
4.6.4.3. Detail...................................................................................................................................................4-19
4.6.4.4. Window ..............................................................................................................................................4-19
4.6.5. <Edit Ohms> MENU Fn-2 (Edit_Ohms MAIN)........................................................................................4-20
4.6.5.1. <Normal> MENU Fn-1 (Edit Ohms MAIN) ....................................................................................4-20
4.6.5.2. <Low Ohms> MENU Fn-3 (Edit Ohms_MAIN)..............................................................................4-21
4.6.6. <Edit> MENU (Probe) Fn-2 (Edit MAIN)..................................................................................................4-23
4.6.6.1. <IPTS 68> MENU Fn-1 (Edit MAIN)..............................................................................................4-23
4.6.6.2. <ITS 90> MENU Fn-2 (Edit MAIN) ................................................................................................4-24
4.6.6.3. <IEC 751> MENU Fn-3 (Edit MAIN)..............................................................................................4-26
4.6.6.4. <Probe Set> MENU Fn-4 (Edit MAIN)............................................................................................4-26
4.6.7. <Sofcal> MENU Fn-3 (MAIN)...................................................................................................................4-27
4.6.7.1. <GPIB>MENU Fn-1 (Sofcal_MAIN)...............................................................................................4-29
4.6.7.2. <Coef Set> MENU Fn-2 (Sofcal_MAIN).........................................................................................4-29
4.6.7.3. <Diagnostic> MENU Fn-3 (Sofcal_MAIN) .....................................................................................4-30
4.6.7.4. <P.O.S.T.> MENU Fn-1 (Sofcal_MAIN).........................................................................................4-33
4.6.7.5. <Filter> MENU Fn-2 (Sofcal_MAIN)..............................................................................................4-34
4.6.7.6. <Datum> MENU Fn-3 (Sofcal_MAIN)............................................................................................4-34

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4.6.7.7. <Sys Time>MENU Fn-2 (Sofcal MAIN)..........................................................................................4-35
4.6.7.8. <Extender>MENU Fn-3 (SofcalMENU)..........................................................................................4-35
4.6.6.9 PASSWORD> MENU Fn-1 (Sofcal_MAIN)...................................................................................4-40
5. VERIFICATION AND CALIBRATION......................................................................5-1
5.1. RESISTANCE RATIO ACCURACY VERIFICATION ............................................................................5-1
5.1.1. Purpose ...........................................................................................................................................................5-1
5.1.2. Equipment Required.......................................................................................................................................5-1
5.1.3. Set Up .............................................................................................................................................................5-2
5.1.4. Verification.....................................................................................................................................................5-2
5.2. TEMPERATURE RATIO VERIFICATION ...............................................................................................5-4
5.2.1. Purpose ...........................................................................................................................................................5-4
5.2.1. Equipment Required.......................................................................................................................................5-4
5.2.2. Set Up .............................................................................................................................................................5-5
5.2.3. Verification.....................................................................................................................................................5-5
6. TROUBLESHOOTING AND MAINTENANCE.........................................................6-1
6.1. INTRODUCTION.............................................................................................................................................6-1
6.1.1. Error Messages...............................................................................................................................................6-1
6.1.2. Model 6622T Setup Warnings.......................................................................................................................6-3
6.1.3. Bridge Coefficients.........................................................................................................................................6-3
6.2. QUICK RATIO CHECK.................................................................................................................................6-3
6.2.1. Purpose ...........................................................................................................................................................6-4
6.2.2. Equipment Required.......................................................................................................................................6-4
6.2.3. Set Up .............................................................................................................................................................6-4
6.2.4. Check Procedure.............................................................................................................................................6-5
7. REMOTE CONTROL................................................................................................7-1
7.1. INTERFACES...................................................................................................................................................7-1
7.2. IEEE-488 (GPIB) INTERFACE .....................................................................................................................7-1
7.2.1. Controller........................................................................................................................................................7-2
7.2.2. IEEE-488 Responses......................................................................................................................................7-2
7.2.3. Interconnecting Cable And IEEE-488 Connector.........................................................................................7-2
7.2.4. Typical System...............................................................................................................................................7-3
7.2.5. Address And Talk/Listen Selection...............................................................................................................7-4
7.2.6. IEEE-488 Electrical Interface........................................................................................................................7-4
7.2.7. IEEE-488 Input Buffering..............................................................................................................................7-4
7.2.8. IEEE-488 Output Buffering...........................................................................................................................7-6
7.2.9. IEEE-488 Deadlock........................................................................................................................................7-6
7.3. COMMAND LANGUAGE..............................................................................................................................7-7
7.3.1. General Syntax For Commands.....................................................................................................................7-7
7.3.2. General Syntax For Numbers.........................................................................................................................7-7
7.4. MODEL 6622T REMOTE AND LOCAL OPERATION ...........................................................................7-7

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7.5. MODEL 6622T PROGRAMMING COMMAND SUMMARY.................................................................7-8
8. APPENDICES...........................................................................................................8-1
8.1. GENERAL SPECIFICATIONS (continued) ................................................................................................8-1
8.2. RESISTANCE MEASUREMENT SPECIFICATION................................................................................8-2

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LIST OF FIGURES
FIGURE 1-1 : MODEL 6622T BLOCK DIAGRAM ......................................................................................................1-4
FIGURE 2-1 : LINE VOLTAGE SELECTOR.................................................................................................................2-2
FIGURE 2-2 : 6622T FRONT VIEW (BENCH / RACK)...............................................................................................2-5
FIGURE 2-3 : 6622T REAR VIEW (BENCH / RACK)..................................................................................................2-8
FIGURE 3-1 : RESISTANCE MEASUREMENT RESPONSE VERSUS TEST SAMPLE.........................................3-1
FIGURE 3-2 : REAR PANEL CONNECTIONS - NORMAL OHM MODE................................................................3-2
FIGURE 3-3 : REAR PANEL CONNECTIONS –LOW OHM MODE WITH 6623...................................................3-8
FIGURE 3-4 : REAR PANEL CONNECTIONS –LOW OHM MODE WITH 6623A-300.........................................3-9
FIGURE 3-5 : REAR PANEL CONNECTIONS –PRT/SPRT.....................................................................................3-11
FIGURE 4-1 : MENU TREE –MEASURE/SOFCAL ....................................................................................................4-2
FIGURE 4-2 : MENU TREE –SETUP (RESISTOR).....................................................................................................4-3
FIGURE 4-3 : MENU TREE –SETUP (PROBE) ...........................................................................................................4-4
FIGURE 4-4 : MENU TREE –MEASURE-VIEW.........................................................................................................4-5

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LIST OF TABLES
TABLE 2-1 : FUSE RATINGS.........................................................................................................................................2-2
TABLE 3-1 : RECOMMENDED NORMAL OHM MODE TEST SETUPS ................................................................3-4
TABLE 3-2 : 6623 RECOMMENDED LOW OHM MODE TEST SETUP..................................................................3-7
TABLE 3-3 : 6623A-300 RECOMMENDED LOW OHM MODE TEST SETUP........................................................3-7
TABLE 3-4 : RECOMMENDED TEMPERATURE MEASUREMENT TEST SETUP............................................3-10
TABLE 6-1 : MODEL 6622T ERROR MESSAGES ......................................................................................................6-2
TABLE 7-1 : FACTORY SETTING-GPIB......................................................................................................................7-2
TABLE 7-2 : IEEE-488 CONNECTOR PIN DESIGNATIONS.....................................................................................7-5
TABLE 7-3 : MODEL 6622T IEEE-488 DEVICE CAPABILITIES..............................................................................7-6
TABLE 8-1 : GENERAL SPECIFICATIONS (CONTINUED) .....................................................................................8-1
TABLE 8-2 : RESISTANCE MEASUREMENT SPECIFICATION (ALL 6622T MODELS) ....................................8-2

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Section 1
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1-1
1. INTRODUCTION
1.1. SCOPE
This document describes the operation and maintenance of the 6622T Series of Automatic DCC
Thermometry Bridges.
1.2. GENERAL DESCRIPTION
The 6622T series bridges can be controlled from the front panel or by a computer system through
software. The BridgeWorks Software Users Manual describes the operation of the 6622T with the
software. Once the computer system is installed and connected to the IEEE-488 Interface of the
6622T Thermometry Bridge, full software control of the bridge is possible. The front panel
controls and indicators of the 6622T Bridge, are shown in Figure 2-1. The corresponding rear
panel controls and connectors are shown in Figure 2-2. The following models are described in this
manual.
6622T-B (Base model with measurement up to 100 kΩ)
6622T-XP (eXtended Precision model with measurement up to 100 kΩ, and higher accuracy)
The 6622T series bridges is installed with additional temperature functionality.

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1-2
1.3. OVERVIEW
The 6622T is a microprocessor-based, direct-current-comparator bridge designed for the automatic
measurement and display of the ratio of two resistances to accuracies better than 0.1 ppm. The ratio
of the two resistances is determined from a direct measurement of the voltage of the bridge
imbalance while an ampere-turn balance is maintained. A microprocessor-based, 16 bit technology
is used to control the direct-current-comparator, set the bridge measurement currents and
measurement configuration, initiate the voltage measurement cycle and maintain the ampere-turn
balance. This fully automated measurement process achieves optimum resistance ratio resolution
and accuracy at the sub-ppm level.
The bridge is designed for flexibility and ease of use and is based on the manually operated direct-
current-comparator bridge manufactured by Guildline Instruments (model 9975) and also on the
original work of the National Research Council of Canada
1
. Remote access to the embedded
microprocessor-controller, through a simple control language command set and GPIB
communication interface allows the 6622T to fully exploit the capabilities of the direct-current-
comparator to suit each user requirement while still maintaining optimum resistance ratio
measurement accuracy at the sub-ppm level.
The design approach taken for the 6622T results in an effective bridge measurement accuracy of 27
bits (to a maximum of 32 bits depending on configuration), allowing the resistance ratio of
resistances in the range 0.001 to 1 Gto be automatically measured.
The balance of the zero ampere-turn flux condition is maintained automatically using an electronic
closed loop feedback network operating on the flux detector output to drive a slave power supply
for the standard resistor current. The bridge balance (null voltage condition), is maintained
automatically by adjusting the number of turns in series with the unknown resistor.
1
MacMartin, M.P. and Kusters, N.L., "A direct -current-comparator for four terminal
resistance measurements", IEEE Trans. Instrumentation and Measurement, vol IM-15,
pp.212-220, December 1966.

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1.4. PRINCIPLE OF OPERATION
A simplified diagram of the automatic direct-current-comparator is shown in Figure 1-1.
Two sets of four terminal connections hardware are provided, one set for the standard
resistor and one set for the unknown resistance. A current (Ix), set under control of the
microprocessor, is passed through the variable turns of winding (Nx) of the comparator and
through the unknown resistance (Rx). The isolated slave current (Is) is generated under
microprocessor control, as a linear function of the number of turns (Nx) and is forced
through the fixed slave windings (Ns) and the reference resistor (Rs). The currents (Is) and
(Ix) flowing in the windings (Ns) and (Nx) respectively generate a net magnetic flux
imbalance in the flux detector windings (Nd). This flux imbalance is proportional to the net
ampere-turn error between the two windings [(Is) x (Ns)] and [(Ix) x (Nx)]. By sensing this
imbalance with the sensitive flux detector winding and an electronic peak detector, a voltage
signal is generated proportional to the sign and magnitude of the ampere-turn error. This
voltage is used in a simple closed loop control configuration to adjust the slave current (Is)
to bring the (ampere-turn) error signal to zero. At balance, the ratio of the two currents (Ix
and Is) flowing in the two windings is the same as the ratio of the turns set for each winding
(Nx and Ns).
Complete electrical isolation between circuit currents is maintained throughout the 6622T
by making full use of fiber optic technology. A fiber optic serial data communication link is
used to transfer data between each functional component and the embedded microcontroller.
A link joining the two potential leads of the unknown resistance (Rx) and the reference
resistance (Rs) and the nanovoltmeter detector provides the only connection between the
two halves of the bridge. Power supply isolation techniques as recommended by Kibble
2
are used throughout to further isolate the bridge halves. The nanovolt detector is a high
input impedance (>1 G) amplifier arrangement capable of resolving voltages at the
nanovolt level with a typical linearity accuracy of 14 bits (to a maximum of 22 bits). In the
automatic direct-current-comparator bridge arrangement this amplifier is used to measure
the potential across the reference and unknown resistances.
Knowledge of the reference resistance value (Rs), the effective resistance potential
imbalance and confirmation that ampere-turn balance is maintained, with the turns (Nx, Ns)
and current (Ix, Is) settings, allows the unknown resistance value (Rx) to be calculated.
2
Kibble, B.P. and Robinson, I.A., "An Isolated Mains Driven Power Supply", NPL
Memorandum DES 54, September 1985.

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Figure 1-1 : Model 6622T Block Diagram
DETECTOR
AND FLUX
MODULATOR
MAGNETIC
X
6622T
DISPLAY
KEYPAD
GPIB
6622T
CONTROLLER/
COMMUNICATION
CLK
CLK
Do
Di
FIBRE OPTIC
INTERFACE
Do
Di
Do
Di
C
1
1
P
Is
Is
PWR
Ix
FIBRE OPTIC
INTERFACE
Ix
PWR
Nx=0 to 8747
REAL TURNS ONLY
2
C
P
2
Rx
Tx
Rx
Tx
Rx
C
2
P
2
P
1
C
1
S
Rs
Ns=648
TURNS
-AUTORANGING
-HIGH INPUT
IMPEDANCE
-22 BITS RESOLUTION
Hi
nV
ASYNCHRNOUS
SERIAL
FIBRE OPTIC
ISOLATION
5 Mb/s SYNCHRONOUS
SERIAL INTERFACE
EACH MESSAGE IS 22 BYTES
Low
CLK
CLK

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1.4.1.1. Low Ohm Measurement Mode
This mode can be used to make 4 terminal resistance measurements down to 0.1 
against a 1 . In Low Ohm mode a high current range extender such as the model
6623A is used to improve the accuracy and allow for measurements below the
normal Ohm range.
1.4.1.2. Normal Ohm Measurement Mode
This mode allows a 4-terminal resistance measurement to be made from 1 mRx
100 k. No external devices (except the two resistors) are required with the 6622T
to make this measurement.

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Section 2
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2. INSTALLATION
2.1. PRELIMINARIES
2.1.1. Unpacking
a. Remove the 6622T Automatic DCC Thermometry Bridge and the other items
from its shipping container in a suitable location.
b. The following items are included with each new bridge
i. Operators Manual (OM6622T)
ii. Software Users Manual (SUM66XX)
iii. Spare Fuse 1 A Slo Blo (GPN# 099-21000)
iv. Spare Fuse 2 A Slo Blo (GPN# 099-22000)
v. Two 4-Wire Measurement Cables (GPN# 19591.01.02)
vi. AC Line Cord (GPN# 250-04030)
vii. Socket Screwkey, 5/64 (GPN# 950-61905)
2.1.2. Power Voltage Selection
The 6622T Automatic DCC Thermometry Bridges are shipped with the line input
voltage set to 240 V and the line frequency requested at time of order. The line
input selector must be set to the correct line voltage and the correct fuse must be
installed before power is applied to the instrument. The 6622T has a voltage
selection which must be set correctly. The settings available are 100 V, 120 V, 220
V, and 240 V. Figure 2-1 details the line input voltage selector setting.
The line frequency setting can be confirmed through front panel operation as
outlined in Section 4.6.6.2. If the line input voltage is changed from that requested
at time of order, 6622T may not be compatible with the new line input voltage and
frequency. The ADC Beta value must agree with the value provided in the Bridge
Coefficient Report supplied with the bridge.
Where the molded plug on the line cord supplied with the instrument does not
match the local power outlet socket, the plug can be removed and replaced with one
that does fit the local service. The plug should be re-wired as follows:
Brown wire - Line input
Blue wire - Neutral input
Green/Yellow - Ground (safety)

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2.1.3. Fuse Replacement
Only fuses with specified current rating type should be used for replacement if
necessary. See Table 2-1.
FUSES (TIME DELAY TYPE)
100 V
120 V
220 V
240 V
2 A, 250 V, (T)
2 A, 250 V, (T)
1 A, 250 V, (T)
1 A, 250 V, (T)
Table 2-1 : Fuse Ratings
100V
120V
220V
240V
100V
120V
220V
240V
EXPOSE LINE SELECTOR SLIDER
REMOVE SELECTOR (120V SHOWN)
PRY HERE TO REMOVE COVER
ROTATE SELECTOR AND REPOSITION
SLIDER TO DESIRED LINE INPUT
(240V SHOWN) AND REINSERT
REPLACE COVER
DISCONNECT POWER
Figure 2-1 : Line Voltage Selector

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2.1.4. Setup And Power On
a. Verify that the power switch is off.
b. Remove any excess packing material from around the front panel that is
provided for shipping purposes only.
c. Connect the computer system as applicable in accordance with the
documentation provided. Connect a GPIB cable to the GPIB connector of the
bridge and to the GPIB connector of the computer system.
d. Set the line input selector to the correct line voltage and install the correct fuse
before power is applied to the instrument as shown in Sections 2.1.2 and 2.2.
e. Connect the input power cord from the 6622T bridge to a local AC power
outlet.
f. Turn on the power switch. You should see the opening banner indicating which
model and options you have. Verify that no errors are displayed.
g. Confirm the line frequency setting, as per section 2.1.2.
h. If you are using software control open the BridgeWorks Data Acquisition
Software in the computer. Refer to the BridgeWorks Software User’s Manual.
i. If BridgeWorks indicates that the 6622T bridge has not been found, then run the
Rescan For Bridge utility in the File menu, to locate it. Note that you will also
need to run the Rescan For Bridge utility, if the bridge was turned on after
BridgeWorks was opened, has been replaced or the GPIB cables have been
disconnected.
2.2. INCOMING INSPECTION
If no errors are displayed during power up, (see section 2.1.4 above) then proceed to measure two
10 kΩ standard resistors. Use the measurement set up procedure below. Note that any two
resistance standards of equal nominal value may be used but the setup parameters will be different.
Refer to Section 3.
Step 1) Connect the resistors to the 6622T Rx & Rs terminals as illustrated in figure
3-2
From the front panel of the model 6622T select 'Setup' from the main menu
functions.
From the Setup menu, configure the measurement setup as follows:
- Select 'Normal' mode function key.
- Select 'Edit' function key.
- Enter 10000 on highlighted 'Resistance RS:' line on display by using the
numeric key pad.
- Select the down arrow key to highlight the next line on the display.
- Leave standard resistor serial number under 'serial No. RS:' line blank.
- Select the down arrow key to highlight the next line on the display.
- Enter 10000 on highlighted 'Resistance RX:' line on display by using
the numeric key pad.

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- Select the down arrow key to highlight the next line on the display.
- Enter in 15 for the reversal rate for the measurement.
- Select the down arrow key to highlight the next line on the display.
- Enter 1 mA test current value for the test
- Select the down arrow key to highlight the next line on the display.
- Enter the maximum current value of 10 mA.
- Verify that all entered data is correct, and then press 'OK'.
Step 2) Press the 'Previous' function key twice to come back to the main menu.
Step 3) Press the 'Measure' function key and then the 'Meas Off ' sub-menu function
key to start the measurement. The 6622T bridge will begin by showing the
nominal value of the resistor to be measured, and then continue to go
through a number of rough measurement cycles until a full resolution
measurement value is displayed. The measurement may be stopped at any
time by pressing the 'Meas On' menu key.
Step 4) The value displayed after about 15 minutes of measuring should read with in
100 ppm of the known ratio of the resistors.
Step 5) After completing of the test the 10 kΩresistors should be removed.
Note: The test should execute with no measurement errors indicated and should indicate a
ratio within 100 ppm of the known ratio. This is not the 6622T’s full rated accuracy but
serves a functional test for the purposes of determining the instrument has been received in
proper working order.