Guildline 6675A User manual

VOLUME I
TECHNICAL MANUAL
FOR
MODEL 6675A
AUTOMATIC DIRECT-CURRENT-COMPARATOR
RESISTANCE BRIDGE
NOTICE
The contents and information contained in this manual are proprietary to
Guildline Instruments. 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.
VOL I TM6675A-C-00
January 30, 2001

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TABLE OF CONTENTS
1. INTRODUCTION.......................................................................................................1-1
1.1. MODEL 6675A AUTOMATIC DIRECT-CURRENT-COMPARATOR RESISTANCE BRIDGE
GENERAL DESCRIPTION...........................................................................................................................................1-1
1.2. PANEL FRONT TERMINALS/CONTROLS..............................................................................................1-1
1.2.1. Reference Resistor Input Terminals..........................................................................................................1-1
1.2.2. Resistor Under Test Input Terminals........................................................................................................1-1
1.2.3. Numeric Keypad........................................................................................................................................1-1
1.2.4. Special Keys..............................................................................................................................................1-2
1.2.4.1. Cursor Movement Keys. ......................................................................................................................1-2
1.2.4.2. Function Keys.......................................................................................................................................1-2
1.2.5. Display.......................................................................................................................................................1-2
1.2.6. High Voltage Out Terminals.....................................................................................................................1-2
1.2.7. Program Out Terminals.............................................................................................................................1-2
1.2.8. Extender In Terminals...............................................................................................................................1-3
1.2.9. Ground Terminals......................................................................................................................................1-3
1.2.10. Guard Terminals........................................................................................................................................1-3
1.3. REAR PANEL CONNECTORS/CONTROLS.............................................................................................1-4
1.3.1. Chart Recorder Output..............................................................................................................................1-4
1.3.2. IEEE-488 Interface....................................................................................................................................1-4
1.3.3. RS232 Interface.........................................................................................................................................1-4
1.3.4. Sync Output...............................................................................................................................................1-4
1.3.5. Line Input Voltage Selector. .....................................................................................................................1-4
1.3.6. Line Input Connector. ...............................................................................................................................1-4
1.3.7. Power Switch.............................................................................................................................................1-5
2. PERFORMANCE SPECIFICATIONS.......................................................................2-1
2.1. GENERAL SPECIFICATIONS .....................................................................................................................2-1
2.2. GENERAL SPECIFICATIONS (continued) ................................................................................................2-2
2.3. RESISTANCE MEASUREMENT SPECIFICATIONS..............................................................................2-3
2.4. TEMPERATURE MEASUREMENT SPECIFICATION..........................................................................2-4
3. OPERATING INSTRUCTIONS.................................................................................3-1
3.1. PRELIMINARIES............................................................................................................................................3-1
3.1.1. Rackmount Bracket...................................................................................................................................3-1
3.2. WARNING.........................................................................................................................................................3-2
3.3. OPERATING PROCEDURE..........................................................................................................................3-4
3.4. GENERAL KEY/DISPLAY OPERATIONS................................................................................................3-7
3.4.1. Base Menu.................................................................................................................................................3-7
3.4.1.1. Base Menu Display. .............................................................................................................................3-7

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3.5. BASIC MENU OPERATIONS.......................................................................................................................3-8
3.5.1. Menu Option - <MEASURE>..................................................................................................................3-8
3.5.2. Menu Option - <any other menu but measure>........................................................................................3-9
3.5.3. Base Edit/Select Menu - one column of data..........................................................................................3-10
3.5.4. Base Edit/Select Menu - two columns of data........................................................................................3-10
3.5.5. Operation of Select/Edit Data Menus .....................................................................................................3-10
3.5.5.1. Function - <Screen ?>........................................................................................................................3-10
3.5.5.2. Function - <Select>............................................................................................................................3-11
3.5.5.3. Function - <Ok>.................................................................................................................................3-11
3.6. TITLE SCREEN .............................................................................................................................................3-12
3.7. MAIN MENU...................................................................................................................................................3-13
3.7.1.1. <Measure> MENU Fn-1 (MAIN) Page 1 of 3..................................................................................3-14
3.7.1.2. <Measure> MENU Fn-1 (MAIN) Page 2 of 3..................................................................................3-16
3.7.1.3. <Measure> MENU Fn-1 (MAIN) Page 3 of 3..................................................................................3-17
3.7.2. <Setup> MENU Fn-2 (MAIN)..............................................................................................................3-18
3.7.2.1. <Load> MENU Fn-1 (Setup_MAIN)................................................................................................3-18
3.7.2.2. <Edit> Resistors MENU Fn-2 ...........................................................................................................3-20
3.7.2.3. <Save> MENU Fn-3 (Resistors_Setup_MAIN)...............................................................................3-32
3.7.3. <Voltmeter> MENU Fn-1 (MAIN)........................................................................................................3-34
3.7.4. <Sofcal> MENU Fn-4 (MAIN)..............................................................................................................3-36
3.7.4.1. <GPIB> MENU Fn-1 (Sofcal_MAIN)..............................................................................................3-37
3.7.4.2. <RS232> MENU Fn-2 (Sofcal_MAIN)............................................................................................3-38
3.7.4.3. <Voltmeter> MENU Fn-3 (Sofcal_MAIN).......................................................................................3-40
3.7.4.4. <Diagnostic> MENU Fn-1 (Sofcal_MAIN) .....................................................................................3-42
3.7.4.5. <Selftest> MENU Fn-2 (Sofcal_MAIN)...........................................................................................3-45
3.7.4.6. <Chart> MENU Fn-3 (Sofcal_MAIN)..............................................................................................3-46
3.7.4.7. <Filter> MENU Fn-1 (Sofcal_MAIN) ..............................................................................................3-47
3.7.4.8. <Datum> MENU Fn-2 (Sofcal_MAIN)............................................................................................3-47
3.7.4.9. <PASSWORD> MENU Fn-3 (Sofcal_MAIN).................................................................................3-48
3.8. MEASUREMENT OPERATION GUIDE ..................................................................................................3-49
3.8.1. Introduction .............................................................................................................................................3-49
3.8.2. Resistance Measurement Normal Ohms - 1 mRs10 k............................................................3-49
3.8.2.1. General Procedures.............................................................................................................................3-52
3.8.3. Resistance Measurement - High Ohms - 100 kRs100 M; Rx 1 G....................................3-56
3.8.3.1. High Ohms Measurements - General Procedures..............................................................................3-56
3.8.4. Resistance Measurement - Low Ohms. ..................................................................................................3-61
3.8.4.1. General Procedures Using Guildline High Current Range Extenders..............................................3-62
3.8.5. Thermometry Measurements. .................................................................................................................3-65
3.8.6. Summary of Recommended Test Setups................................................................................................3-67
3.9. 6675A DATA ACQUISITION SOFTWARE..............................................................................................3-69
4. THEORY OF OPERATION.......................................................................................4-1
4.1. THEORY I INTRODUCTION.......................................................................................................................4-1
4.1.1. The automatic direct-current-comparator resistance bridge.....................................................................4-2
4.1.1.1. The manual bridge - background.........................................................................................................4-2
4.1.2. The automatic bridge.................................................................................................................................4-3
4.1.3. Automatic direct-current-comparator bridge balance...............................................................................4-5
4.2. THEORY II RESISTANCE MEASUREMENT - 9975 BACKGROUND................................................4-8
4.2.1. Theory II 6675A........................................................................................................................................4-9
4.2.2. 6675A Servo Circuit................................................................................................................................4-13

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4.2.3. 6675A Primary Current Ix.......................................................................................................................4-13
4.2.3.1. Low-Measurement Mode...............................................................................................................4-13
4.2.3.2. Normal-Measurement Mode..........................................................................................................4-14
4.2.3.3. High-Measurement Mode..............................................................................................................4-14
4.2.4. 6675A Signal Acquisition.......................................................................................................................4-17
4.2.5. 6675A Measurement Cycle - 4-Terminal "Normal-".........................................................................4-19
4.2.6. Graphical Representation of Turns Switching and nV readings............................................................4-21
4.3. NANOVOLT DETECTOR CPU OPTIONS...............................................................................................4-23
4.3.1. Dip Switches............................................................................................................................................4-23
4.3.1.1. Option Switch 1 - 50/60 Hz Select.....................................................................................................4-23
4.3.1.2. Option Switches 2 to 8 - ADC Beta...................................................................................................4-23
4.3.2. Nanovolt Detector Principles of Operation. ...........................................................................................4-24
4.3.2.1. Introduction. .......................................................................................................................................4-24
4.3.2.2. Nanovolt Detector Power Supply (19103.01.02)..............................................................................4-24
4.3.2.3. Nanovolt Detector CPU PCB (19855.01.02).....................................................................................4-24
4.3.2.4. Analog Interface.................................................................................................................................4-25
4.3.2.5. Central Processing Unit......................................................................................................................4-25
4.3.2.6. Memory ..............................................................................................................................................4-26
4.3.2.7. Serial Fibre-Optic Communication Interface.....................................................................................4-26
4.3.2.8. Gpib Interface.....................................................................................................................................4-26
4.3.3. Analog To Digital (A/D) Converter (19502.01.02)................................................................................4-26
4.3.3.1. Voltage To Current (V/I) Converter. .................................................................................................4-28
4.3.3.2. High Speed Low Noise Current Buffer. ............................................................................................4-28
4.3.3.3. Precision References. .........................................................................................................................4-28
4.3.3.4. Precision Current Sink........................................................................................................................4-28
4.3.3.5. Current Mode Switch.........................................................................................................................4-28
4.3.3.6. Start/Stop Integrator Switch...............................................................................................................4-28
4.3.3.7. The Integrator.....................................................................................................................................4-29
4.3.3.8. Charge Balance Sampler....................................................................................................................4-29
4.3.3.9. Master Clock.......................................................................................................................................4-29
4.3.3.10. Conversion Timer..........................................................................................................................4-29
4.3.3.11. Interconversion Pause. ..................................................................................................................4-29
4.3.3.12. A/D Trigger...................................................................................................................................4-30
4.3.3.13. 12 BIT A/D Converter...................................................................................................................4-30
4.3.4. Nanovolt Detector Input Amplifier PCB (19503.01.02)........................................................................4-30
4.3.4.1. High Input Impedance Low Noise Amplifier....................................................................................4-30
4.3.4.2. Input And Range Selection. ...............................................................................................................4-31
4.3.4.3. Charge Pump......................................................................................................................................4-31
4.3.4.4. Attenuator...........................................................................................................................................4-31
4.3.4.5. Power Supplies...................................................................................................................................4-31
4.3.4.6. Overload Protection............................................................................................................................4-31
4.3.5. Nanovolt Detector Software....................................................................................................................4-32
5. REMOTE CONTROL................................................................................................5-1
5.1. INTERFACES...................................................................................................................................................5-1
5.2. IEEE-488 (GPIB) INTERFACE .....................................................................................................................5-1
5.2.1. Controller...................................................................................................................................................5-2
5.2.2. IEEE-488 Responses.................................................................................................................................5-2
5.2.3. Interconnecting Cable And IEEE-488 Connector....................................................................................5-2
5.2.4. Typical System..........................................................................................................................................5-2
5.2.5. Address And Talk/Listen Selection. .........................................................................................................5-3
5.2.6. IEEE-488 Electrical Interface. ..................................................................................................................5-3
5.2.7. IEEE-488 Input Buffering.........................................................................................................................5-3

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5.2.8. IEEE-488 Output Buffering......................................................................................................................5-5
5.2.9. IEEE-488 Deadlock...................................................................................................................................5-5
5.3. RS232C INTERFACE......................................................................................................................................5-6
5.3.1. RS232C - Pin Designations.......................................................................................................................5-7
5.3.2. RS232C Responses. ..................................................................................................................................5-7
5.4. COMMAND LANGUAGE..............................................................................................................................5-8
5.4.1. General Syntax For Commands................................................................................................................5-8
5.4.2. General Syntax For Numbers....................................................................................................................5-8
5.5. REMOTE AND LOCAL OPERATION........................................................................................................5-8
6. CALIBRATION..........................................................................................................6-1
6.1. TEST EQUIPMENT.........................................................................................................................................6-1
6.2. RATIO 1:1 Using Model 9330 / 1 to Model 9330 / 1 ............................................................................6-1
6.3. RATIO 1:1 Using Model 9330 / 10 kto Model 9350 / (10 kConfiguration).....................................6-1
6.4. RATIO 10:1........................................................................................................................................................6-2
1.1.1. Model 9330 /10 kto Model 9350 /(100 kConfiguration) .................................................................6-2
6.4.2. Model 9350 /(1K Configuration) to Model 9330 /10 k....................................................................6-2
6.5. RATIO 1:1..........................................................................................................................................................6-1
6.5.1. Model 9330 /100 Mto Model 9330 /100 M.......................................................................................6-1
7. MAINTENANCE........................................................................................................7-1
7.1. INTRODUCTION.............................................................................................................................................7-1
7.1.1. Error Messages..........................................................................................................................................7-1
7.1.2. 6675A Warnings. ......................................................................................................................................7-2
7.1.3. Nanovolt Detector Calibration..................................................................................................................7-3
7.1.3.1. Introduction. .........................................................................................................................................7-3
7.1.3.2. Nanovoltmeter Calibration...................................................................................................................7-3
7.1.3.3. ADC Beta. ............................................................................................................................................7-4
7.1.4. Disassembly Procedure.............................................................................................................................7-5
7.1.4.1. Cover Removal Procedure. ..................................................................................................................7-5
7.1.4.2. Primary Current Drive Module (19327) Removal Procedure.............................................................7-5
7.1.4.3. Servo-loop Module (19328) Removal Procedure................................................................................7-6
7.1.4.4. PDCC Comparator Module (19121) Removal Procedure...................................................................7-7
7.1.5. Reassembly Procedure ..............................................................................................................................7-8
7.2. TROUBLESHOOTING...................................................................................................................................7-8
7.2.1. Introduction ...............................................................................................................................................7-8
7.2.2. Power Up...................................................................................................................................................7-8
7.2.3. Power Supply Check.................................................................................................................................7-9
7.2.3.1. Primary Current Drive Power Supply PCB Test Procedure................................................................7-9
7.2.3.2. Servo Loop Power Supply PCB Test Procedure...............................................................................7-10
7.2.3.3. Nanovolt Dual Power Supply PCB Assy 19334 Test Procedure......................................................7-11
7.2.3.4. 6675A CPU and Display Power Supply PCB Test Procedure..........................................................7-12
7.2.4. Alignment Procedure..............................................................................................................................7-12
7.2.4.1. Alignment Test Equipment Required ................................................................................................7-12
7.2.4.2. Initial Checks......................................................................................................................................7-13

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7.2.4.3. Primary Current Drive Adjustments (Board 19108) .........................................................................7-13
8. PARTS LISTS - MODEL 6675A...............................................................................8-1
9. DRAWINGS - MODEL 6675A...................................................................................9-1

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LIST OF FIGURES
FIGURE 1-1 : FRONT PANEL CONTROLS..................................................................................................................1-3
FIGURE 1-2 : REAR PANEL CONTROLS ....................................................................................................................1-5
FIGURE 3-1 : LINE VOLTAGE SELECTOR.................................................................................................................3-3
FIGURE 3-2: MENU TREE - SETUP/MEASURE.........................................................................................................3-5
FIGURE 3-3: MENU TREE - SOFCAL/VOLTMETER.................................................................................................3-6
FIGURE 3-4 : FRONT PANEL CONNECTIONS - NORMAL OHMS.......................................................................3-50
FIGURE 3-5 : RECOMMENDED GUARDING FOR NORMAL OHMS ..................................................................3-51
FIGURE 3-6 : FRONT PANEL CONNECTIONS HIGH OHMS - EXTERNAL HV SUPPLY................................3-57
FIGURE 3-7 : FRONT PANEL CONNECTIONS HIGH OHMS - INTERNAL HV SUPPLY .................................3-58
FIGURE 3-8 : RECOMMENDED GUARDING FOR HIGH RESISTANCE MODE................................................3-59
FIGURE 3-9 : FRONT PANEL CONNECTIONS LOW OHMS, 6623 RANGE EXTENDER.................................3-64
FIGURE 4-1 : DIRECT-CURRENT-COMPARATOR BRIDGE...................................................................................4-3
FIGURE 4-2 : AUTOMATIC DCC BRIDGE BALANCE .............................................................................................4-5
FIGURE 4-3 : BLOCK DIAGRAM 9975, 4-WIRE MEASUREMENT ......................................................................4-11
FIGURE 4-4 : BLOCK DIAGRAM 6675A ...................................................................................................................4-12
FIGURE 4-5 : 6675A SERVO "IS".................................................................................................................................4-15
FIGURE 4-6 : 6675A PRIMARY CURRENT "IX".......................................................................................................4-16
FIGURE 4-7 : 6675A MEASUREMENT CYCLE ........................................................................................................4-20
FIGURE 4-8 : 6675A TURN SWITCHING AND NV READING GRAPHICAL REPRESENTATION.................4-22
FIGURE 4-9 : NANOVOLT DETECTOR CPU OPTION SWITCH LOCATION....................................................4-23
FIGURE 4-10 : CHARGE BALANCE A/D CONVERTER........................................................................................4-27

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LIST OF TABLES
TABLE 2-1 : GENERAL SPECIFICATIONS.................................................................................................................2-1
TABLE 2-2 : GENERAL SPECIFICATIONS (CONTINUED) .....................................................................................2-2
TABLE 2-3 : RESISTANCE MEASUREMENT SPECIFICATIONS...........................................................................2-3
TABLE 2-4 : TEMPERATURE MEASUREMENT SPECIFICATIONS......................................................................2-4
TABLE 3-1 : 4-TERMINAL MODE TEST SETUP.....................................................................................................3-67
TABLE 3-2 : 2-TERMINAL MODE TEST SETUP......................................................................................................3-68
TABLE 3-3 : LOW OHM MODE TEST SETUP ..........................................................................................................3-68
TABLE 4-1 : NANOVOLT DETECTOR CPU OPTION SWITCHES........................................................................4-23
TABLE 5-1 : IEEE488 CONNECTOR PIN DESIGNATIONS......................................................................................5-4
TABLE 5-2 : IEEE488 DEVICE CAPABILITIES..........................................................................................................5-5
TABLE 5-1 : RS232 CONNECTOR PIN DESIGNATIONS..........................................................................................5-7
TABLE 7-1 : 6675A ERROR MESSAGES......................................................................................................................7-1
TABLE 7-1 : 6675A WARNINGS ...................................................................................................................................7-2
TABLE 7-1 : TEST POINT VOLTAGES ASSEMBLY 19108......................................................................................7-9
TABLE 7-1 : TEST POINT VOLTAGES ASSEMBLY 19107....................................................................................7-10
TABLE 7-1 : TEST POINT VOLTAGES ASSEMBLY 19334....................................................................................7-11
TABLE 7-1 : TEST POINT VOLTAGES POWER SUPPLY ASSEMBLY 19473 ....................................................7-12
TABLE 7-1 : REFERENCE VOLTAGES......................................................................................................................7-30

Section 1
1-1
1. INTRODUCTION
1.1. MODEL 6675A AUTOMATIC DIRECT-CURRENT-COMPARATOR
RESISTANCE BRIDGE GENERAL DESCRIPTION
This document describes the preliminaries to setup and use the Guildline Model 6675A Automatic
Direct-Current-Comparator Resistance Ratio Bridge.
1.2. PANEL FRONT TERMINALS/CONTROLS
The 6675A front panel controls are shown in Figure 1-1.
1.2.1. Reference Resistor Input Terminals
The reference resistor input terminals consist of 4 low thermal copper binding posts. The
binding posts have the ‘Rs’ label inside the group of four posts. The posts are labeled from
left to right, ‘C1’, ‘P1’, ‘P2’, and ‘C2’. A 2 meter, 4 conductor cable set with guard wire, is
provided in the 6675A Spare Parts Kit, Guildline part number 19543.01.02, for connection
to these terminals.
1.2.2. Resistor Under Test Input Terminals.
The resistor under test input terminals consist of 4 low thermal copper binding posts. The
binding posts have the ‘Rx’ label inside the group of four posts. The posts are labeled from
left to right, ‘C1’, ‘P1’, ‘P2’ and ‘C2’. A 2 meter, 4 conductor cable set with guard wire, is
provided in the 6675A Spare Parts Kit, Guildline part number 19543.01.02, for connection
to these terminals.
1.2.3. Numeric Keypad.
The numeric keypad consists of 15 keys. The key list contains the following; <0>, <1>,
<2>, <3>, <4>, <5>, <6>, <7>, <8>, <9>, <->, <.>, <CLEAR>, <E>, <LOAD>.

Section 1
1-2
1.2.4. Special Keys.
1.2.4.1.Cursor Movement Keys.
The cursor movement keys consist of 4 keys, <LEFT ARROW>,<UP
ARROW>,<DOWN ARROW> and <RIGHT ARROW>
1.2.4.2.Function Keys.
The function keys consist of four unlabelled keys located below the display. The
function of these four keys are variable and can take on any of the "soft" functions
described in section 3.4 of this manual. In addition to the "soft" function keys are
two keys fixed function keys <PREVIOUS> and <CANCEL>. Pressing the
<PREVIOUS> key returns control to the previous menu level, above the currently
selected menu. Pressing the <CANCEL> key will undo any keypad entry changes
that have been made.
1.2.5. Display.
The green vacuum fluorescent graphic display is a combined 256 x 64 pixel graphic display
and an 8 line by 42 column character display.
1.2.6. High Voltage Out Terminals.
The High Voltage Output Terminal is a blue four way binding post located on the sloped
part of the front panel, on the far left side. The output from this terminal can be used to
provide the test current when measuring two terminal high value resistances. A 1 meter
single conductor, high voltage cable is provided in the 6675A Spare Parts Kit, Guildline
part number 19543.01.02. for connection to this terminal.
1.2.7. Program Out Terminals.
The Program Out Terminals consist of 2 four way binding posts, one black and one red.
These terminals can be used when a reversing switch external to the 6675A is to be used to
control the test voltage for a two terminal high value resistance measurement. The signal
low terminal is referenced to the Rx input. An optional 1.5 meter, double banana plug,
cable set is offered as Guildline part number 996-00122, for connection between these
terminals and the reversing switch.