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Guildline 6675A Technical Manual

Automatic direct-current-comparator resistance bridge
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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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Summary of Contents for Guildline 6675A

  • Page 1 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.
  • Page 2 TABLE OF CONTENTS 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.
  • Page 3 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.
  • Page 4 Normal-Ω Measurement Mode......................4-14 4.2.3.3. High-Ω Measurement Mode ......................4-14 4.2.4. 6675A Signal Acquisition ........................4-17 4.2.5. 6675A Measurement Cycle - 4-Terminal "Normal-Ω"................. 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.
  • Page 5 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.
  • Page 6 7.2.4.3. Primary Current Drive Adjustments (Board 19108) ................. 7-13 PARTS LISTS - MODEL 6675A ................8-1 DRAWINGS - MODEL 6675A................... 9-1...
  • Page 7 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...
  • Page 8 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 ..................
  • Page 9 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.
  • Page 10 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.
  • Page 11 6. These terminals can be used when low values of resistance are to be measured using an external current range extender. 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 range extender.
  • Page 12 0 to +5 Vdc when a test current reversal occurs. 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 external device monitoring current reversals.
  • Page 13 Section 1 1.3.7. Power Switch. The power ON/OFF switch for the 6675A is an integral part of the line input power assembly. Figure 1-2 : Rear Panel Controls...
  • Page 14 Section 2 PERFORMANCE SPECIFICATIONS 2.1. GENERAL SPECIFICATIONS 6675A AUTOMATIC DCC RESISTANCE BRIDGE General Specifications Operating Temperature to +23 ± 5 °C Full Specification +73 ± 9 °F Operating Temperature (+10 to +18) (+28 to +40) °C Maximum Range <50% RH (+50 to +64) (+82 to +104) °F...
  • Page 15 Section 2 2.2. GENERAL SPECIFICATIONS (continued) 6675A AUTOMATIC DCC RESISTANCE BRIDGE General Specifications Ω Measurement Resistance Range 1 m to 1 G Resistance Ratio (Rx/Rs) Range 0.078 to 13.4 Linearity ±0.01 ppm of full scale Temperature Coefficient ±0.01 ppm/°C (+10 to +18)°C (+28 to +40)°C...
  • Page 16 0.35+0.04 0.35 10kΩ - 100kΩ 0.001 0.5+0.1 100kΩ - 1MΩ 0.001 0.75+0.3 0.75 1MΩ - 10MΩ 0.001 2.5+1.0 10MΩ - 100MΩ 0.001 8.0+3.0 100MΩ - 1GΩ * Guildline Model 6623 High Current Range Extender Table 2-3 : Resistance Measurement Specifications...
  • Page 17 Section 2 2.4. TEMPERATURE MEASUREMENT SPECIFICATION The uncertainty of temperature measurement is primarily determined by the uncertainty of the temperature probe. The 6675A contributions to resolution and uncertainty are listed below. Nominal PRT Recommended Resolution Uncertainty Resistance Excitation Current (equivalent °C) (mA) (Ω)
  • Page 18 3.1. PRELIMINARIES The 6675A has been shipped with the line input voltage selector set to 120 V. The line input selector must be set to the correct line voltage before power is applied to the instrument. The settings available are 100 V, 120 V, 220 V, and 240 V. Figure 3-1 details the line input voltage selector setting.
  • Page 19 6675A when in the rack. The 6675A will fit a standard 5U opening in the 19 inch rack, it will protrude beyond the front of the rack and will extend slightly into the front panel space of the rack opening below.
  • Page 20 Section 3 Figure 3-1 : Line Voltage Selector...
  • Page 21 3.3. OPERATING PROCEDURE The front panel of the 6675A consists of a keypad and display area with binding posts for termination of the resistors to be measured. The keypad consists of : one set of numeric keys <0,1,2,3,4,5,6,7,8,9> for numeric data entry;...
  • Page 22 Section 3 Figure 3-2: Menu Tree - SETUP/MEASURE...
  • Page 23 Section 3 Figure 3-3: Menu Tree - SOFCAL/VOLTMETER...
  • Page 24 Section 3 3.4. GENERAL KEY/DISPLAY OPERATIONS 3.4.1. Base Menu. Typically consists of four function key (or less) description areas, and a status line. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Status Line ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒══════════╤══════════╤═════════╤══════════▒ ▒Function 1│Function 2│Function3│Function 4▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒...
  • Page 25 Section 3 3.5. BASIC MENU OPERATIONS 3.5.1. Menu Option - <MEASURE> In the menu option <MEASURE>, several function keys are defined where each key can cause one of several actions. If the function key <Fn> has multiple states, pressing the key beneath the displayed function will cause it to toggle between the valid states.
  • Page 26 Section 3 3.5.2. Menu Option - <any other menu but measure> In all other menu options if a function key has a defined set of alternate values, pressing that function key will cause one of the alternate values to be selected and displayed in the associated active area of the display screen.
  • Page 27 Section 3 3.5.3. Base Edit/Select Menu - one column of data An optional header line can appear at the top of a screen display to prompt or inform the user with "details" of the present menu level. If a header line is displayed the number of selections are restricted to 6 or less.
  • Page 28 Section 3 3.5.5.2. Function - <Select> Pressing the <Select> key will cause one of the currently selected items or the first item in a list to be highlighted. The cursor arrow keys can then be used to move the highlight from selection to selection on the screen. If the screen type is a selection screen, for example the <Resistor select menu function>, the highlighted item will be selected active, only when the soft function key <Ok>...
  • Page 29 Section 3 3.6. TITLE SCREEN At power ON the 6675A will start it’s internal self-test programming and display its opening banner: ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄▄ ▒ ▒ █ █ █ █ █ █ ▒ ▒ █▄▄ █▄▄...
  • Page 30 The main menu, on power up will display a null measurement configuration where all parameters have been initialized to zero. On power up the 6675A will default to a standby condition with the measurement cycle of operations OFF i.e. <Measure off>.
  • Page 31 Ratio Ohms The <STATUS LINE> will only appear if the 6675A is currently measuring a set of resistors. The information displayed in the <STATUS LINE> depends on the options selected. if <PPM>, <PPM SP>, <DELTA>, or <DELTA SP> is the current selection then the <STATUS LINE>...
  • Page 32 6675A is in. This block will appear on all menus and is one way to tell if the 6675A is making a measurement. Function key <Fn-3> selects the screen measurement update rate as a function of the test current reversal rate.
  • Page 33 Section 3 3.7.1.2. <Measure> MENU Fn-1 (MAIN) Page 2 of 3. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒STATUS LINE ▒ ▒ ▒ ▒CURRENT READING OR ▒ ▒Measurement configuration ▒ ▒ ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Power x1 │No Filter │Normal │MORE 2-3 ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Power x2 Decimation PPM N Average Delta...
  • Page 34 Section 3 3.7.1.3. <Measure> MENU Fn-1 (MAIN) Page 3 of 3. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒STATUS LINE ▒ ▒ ▒ ▒CURRENT READING OR ▒ ▒Measurement configuration ▒ ▒ ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Cal_Step │Chart Meas│Quick OFF│MORE 3-3 ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Cal_ch +FS Chart Cal Quick ON Cal_ch 0 Cal_ch -FS...
  • Page 35 Section 3 are invoked for the four cycle precision measurements and are used in the calculation of resistance ratio. Disabling the software filter function decreases the time required to calculate and report the measured ratio. However, the data are now noisier, and so two least significant digits are removed from the display when quick measure is turned on.
  • Page 36 Section 3 3.7.2.1.1. <Load> MENU Fn-1 (Resistors_Setup_MAIN) Screen 1 of 2 available screens. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Resistors File : ?? ▒ ▒00 SN of Resistor___ 05 _________________ ▒ ▒01 ▒ ▒02 ▒ ▒03 ▒ ▒04 ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Select │Ok │ │Screen 2 ▒...
  • Page 37 Update 2 Update 4 Function key <Fn-1> ,<Mode>, allows selection of the mode of operation of the 6675A from the <Mode> sub-menu. Function Key <Fn-2> ,<Display>, allows selection of the units displayed on the screen either Ohms or Ratio (no units).
  • Page 38 Section 3 Function Key <Fn-3> ,<Update>, allows selection of the number of times that the display should be updated for each measurement cycle; 1, 2, or 4 times per measurement cycle. <Edit> Resistors MENU Fn-2 (Resistors_Setup_MAIN) Edit resistors menu page 2 of 2. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒...
  • Page 39 Section 3 3.7.2.2.1.1. <Mode> MENU Fn-1 (Edit_Resistors_Setup_MAIN) ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Mode: <Fn-??> Ω ▒ ▒Display: RS SN: ▒ Ω ▒Update: ▒ ▒Filter: RRate: ▒ ▒Power: Ratio: ▒ ▒ ▒ ▒══════════╤══════════╤═════════┬──────────▒ ▒4 Terminal│2 Terminal│I Extend │ ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Function key <Fn-1>, <4 Terminal>, will select the 4-terminal measurement mode of operation.
  • Page 40 Section 3 If the condition : (I(test) X (Rx/Rs)) ≥ Max Current is satisfied, then the test is terminated. Max current is the maximum current that can be carried by the REFERENCE RESISTOR (Rs). The reported ratio is (Rx/Rs). 3.7.2.2.1.1.2.<2 Terminal> MENU Fn-2 (Mode_Edit_Resistors_Setup_MAIN) Enter configuration for 2-terminal high resistance mode measurements.
  • Page 41 Section 3 3.7.2.2.1.1.3.<I Extend> MENU Fn-3 (Mode_Edit_Resistors_Setup_MAIN) Enter range extender configuration data. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Resistance RS: 0000000000 ▒ ▒Serial No. RS: 1111111111 ▒ ▒Resistance RX: 2222222222 ▒ ▒Reversal Rate: 3333333333 ▒ ▒Extender Ratio: 444444444 ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Edit │Ok │ │...
  • Page 42 Section 3 Function Key <Fn-1> ,<Mode>, allows entry to the <Mode> menu level where the temperature mode of operation of the 6675A can be set from one of : IPTS-68 Set the IPTS-68 coefficients for the temperature probe under test.
  • Page 43 Section 3 3.7.2.2.2.1.1.<IPTS 68> MENU Fn-1 (Mode_Edit_Probes_Setup_MAIN) ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒A: ▒ ▒B: ▒ ▒b4: ▒ ▒e4: ▒ ▒ ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Edit │Ok │ │ ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Press <Edit> and use arrow keys to move the highlight to the data line to be changed. Modify data and press <Ok>.
  • Page 44 Section 3 3.7.2.2.2.1.2. <ITS 90> MENU Fn-2 (Mode_Edit_Probes_Setup_MAIN) ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒-Coeff: <Range 1> +Coeff: <Range 6> ▒ ▒a1: ▒ ▒b1: ▒ ▒c1: ▒ ▒c2: ▒ ▒ ▒ ▒──────────┬══════════┬─────────┬══════════▒ ▒-Coeff │Edit Neg │+Coeff │Edit Pos ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Function Key <Fn-1> ,<-Coeff>, selects from the ITS90 set of temperature ranges: <Range 1>...
  • Page 45 Section 3 When either the <Edit Neg> or <Edit Pos> key is pressed the PASSWORD CHECK display menu is activated. Before the selected set of coefficients can be changed the correct password must be entered. If an incorrect password is entered, the error message "Invalid Password" will be displayed and the edit session will be terminated.
  • Page 46 Section 3 3.7.2.2.2.1.2.1.2.<Edit Neg> MENU Fn-2 (ITS90_Mode_Edit_Probes_Setup_MAIN) ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Neg Coeff Range : <-259C to 0C> ▒ ▒c4: ▒ ▒c5: ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Edit │Ok │ │Screen 2 ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Press <Edit> and use arrow keys to move the highlight to the data line to be changed. Modify data and press <Ok>.
  • Page 47 Section 3 3.7.2.2.2.1.3.<Probe Set> MENU Fn-3 (Mode_Edit_Probes_Setup_MAIN) Probe set menu screen 1 of 2. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Resistance RS: ▒ ▒Serial No. RS: ▒ ▒R0 Probe (or R(tpw)): ▒ ▒Ser. No. Probe: ▒ ▒RRate: ▒ ▒Test Current (mA): ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Edit │Ok │...
  • Page 48 Section 3 3.7.2.2.2.1.4.Password Check Menu. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒PASSWORD CHECK ▒ ▒PASSWORD: ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Edit │Ok │ │ ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Press <Edit> and enter the numeric password from the keypad. If the password entered is incorrect the edit function that initiated the password check will terminate without any action being taken.
  • Page 49 Section 3 Function Key <Fn-1> ,<Filter>, allows selection of the filter that will be used on the displayed readings, where: No Filter display most recent reading Decimation display (100-N) percent previous reading. Where N is the percentage value <Sofcal><Filter> menu Decimation.
  • Page 50 Section 3 <Save> MENU Fn-3 (Resistors_Setup_MAIN) Screen 2 of 2. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Resistors ▒ ▒10 _________________ ▒ ▒11 ▒ ▒12 ▒ ▒13 ▒ ▒14 ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Select │Ok │ │Screen 2 ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ 3.7.2.3.1.<Save> MENU Fn-3 (Probes_Setup_MAIN) This menu allows saving to memory of the temperature probe parameter information.
  • Page 51 Section 3 3.7.3. <Voltmeter> MENU Fn-1 (MAIN) The function keys behave the same as in the <Measure> menu and toggle through the available options in the function key window. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒STATUS LINE ▒ ▒ ▒ ▒ ▒ ▒Voltmeter Reading ▒ ▒...
  • Page 52 Section 3 Voltmeter function menu selection screen 2 of 2 ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒STATUS LINE ▒ ▒ ▒ ▒ ▒ ▒Voltmeter Reading ▒ ▒ ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒Cal_Ch Off│Chart Off │ │MORE 2-2 ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ Cal_Ch +FS Chart On Cal_Ch 0 Cal_Ch -FS Function Key <Fn-1>...
  • Page 53 3.7.4. <Sofcal> MENU Fn-4 (MAIN) The menu options available through this function allow configuration setup and general modes of operation of the 6675A. Three pages of menu options are available for this Sofcal selection. Sofcal menu page 1 of 3.
  • Page 54 Section 3 Function Key <Fn-2> ,<Selftest>, displays the result of the power on self test and the revision level of the installed software. Function Key <Fn-3> ,<Chart>, allows setting of the chart recorder/analog output range value. Sofcal menu selection menu page 3 of 3. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒...
  • Page 55 If RS232 is in the Talk/Listen mode then the <Mode> key will never display the Talk/Listen mode option since only one remote controller can be active with the 6675A at a time. 3.7.4.2. <RS232> MENU Fn-2 (Sofcal_MAIN) RS232 Sofcal menu selection page 1 of 3.
  • Page 56 NOTE: If GPIB is in the Talk/Listen mode then the <Mode> key will never display the Talk/Listen mode option since only one remote controller can be active with the 6675A at a time. 3-39...
  • Page 57 Section 3 3.7.4.3. <Voltmeter> MENU Fn-3 (Sofcal_MAIN) ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Zero Volts: ▒ ▒High Volts: ▒ ▒Ref Volts: ▒ ▒ADC Beta: ▒ ▒ ▒ ▒ ▒ ▒──────────┬══════════╤═════════┬──────────▒ ▒20V Range │Volts Set │Coeff Set│ ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ 2V Range 200mV Range 20mV Range 2mV Range Function Key <Fn-1>, <Range>...
  • Page 58 Section 3 Function Key <Fn-2>, <High Volts> takes a 5 second average of the reading on the nanovolt meter in counts and displays it on the screen. Make sure that the applied voltage is set between the P terminals and that a voltage level is entered for <Ref Volts>.
  • Page 59 Section 3 3.7.4.4. <Diagnostic> MENU Fn-1 (Sofcal_MAIN) Diagnostic menu selection page 1 of 4. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Set Internal Values ▒ ▒Reading: Range: ▒ ▒Turns: <Fn-3> Mode: ▒ ▒Sign: Speed: ▒ ▒milliAmps: Cur Ramp: ▒ ▒Volts: Volt Ramp: ▒ ▒══════════╤══════════┬─────────┬──────────▒ ▒Monitor │Dacs │Turns │MORE 1-4 ▒...
  • Page 60 Section 3 3.7.4.4.2.<Dacs> MENU Fn-2 (Diagnostic_Sofcal_MAIN) ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒Dac Settings ▒ ▒DAC A(▒ 10V): ▒ ▒DAC B(▒ 10V): ▒ ▒DAC C(10V): ▒ ▒DAC D(10V): ▒ ▒ ▒ ▒──────────┬──────────┬─────────┬──────────▒ ▒DAC A │Set DAC │Ramp Off │ ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ DAC B Ramp On DAC C DAC D Function key <Fn-1>, <DAC A>...
  • Page 61 Section 3 Function key <Fn-2>, <milliamps> sets the magnitude of the current output. For the current to flow to the front panel <Mode> must be set to <4 Wire>. The current range is from 0 to 150 mA. Function key <Fn-3>, <Volts> sets the magnitude of the voltage output. For the voltage to be set onto the front panel <Mode>...
  • Page 62 Voltage. For the Voltage to be set onto the front panel, the <Mode> must be set to 2-terminal. 3.7.4.5. <Selftest> MENU Fn-2 (Sofcal_MAIN) This Sofcal menu selection displays the results of the internal self test performed by the 6675A. ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ▒ERROR_STATUS: ▒...
  • Page 63 Section 3 ERROR STATUS displays the error bits in hexadecimal notation. ╔═══════════════════════════════════════════════════════════════╗ ║ 0000_0000_0000_0000_0000_0000_0000 ║ ║ │XXX XXXX XXXX XXX│ XXX│ ││││ X│││ ║ ║ │ │ │ ││││ ││└ ROM 1 CHECKSUM ║ ║ │ │ │ ││││ │└─ ROM 2 CHECKSUM ║...
  • Page 64 │ ▒ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ The values displayed in this menu are used as datum values when the 6675A is measuring ratio, resistance, temperature, or voltage. The datum function is applied only to two menu functions from the <MAIN> menu, they are the <Measure> menu and the <Voltmeter> menu.
  • Page 65 Function key <Ok> will accept the new password as entered. NOTE: The factory default password is : 6675A If the password has been changed and subsequently misplaced see section 3.7.4.5 <SOFCAL_Selftest>, to allow recovery of the factory default password setting.
  • Page 66 3.8.2. Resistance Measurement Normal Ohms - 1 mΩ ≤ Rs ≤ 10 kΩ The Model 6675A bridge in its normal ohms mode enables measurement of resistance of values up to 10 kΩ : 100 kΩ (Rx:Rs). Several types of resistance thermometers, each involving a different resistance range, reference resistor and thermometer current can also be measured in this mode.
  • Page 67 Section 3 Figure 3-4 : Front Panel Connections - Normal Ohms 3-50...
  • Page 68 Section 3 Figure 3-5 : Recommended Guarding for Normal Ohms 3-51...
  • Page 69 1:1 and 13.4:1 (Rx:Rs). This ensures the best available precision. Step 3) From the <Main Menu> on the 6675A, select the <Setup Menu> and make sure the softkey on the extreme right indicates <Resistors> (and not <Probes> ).
  • Page 70 Section 3 Resistor Setup: Rs - The value in ohms of the Rs resistor. A positive number has to be entered for a valid measurement configuration. The value given for Rs determines what nanovoltmeter range the measurement is done on as follows: Rs ≥...
  • Page 71 Section 3 Test current may be determined using the following relationship: × I = Testcurrent ( Max Current (mA) - a number greater than 0 needs to be entered here for a valid measurement configuration. This current is the maximum current allowed in the Rs resistor and the check : (Max current) >...
  • Page 72 Section 3 c) <Update 1/2/4> - the display is updated every 2 × Reversal rate for update 1. 1 × Reversal rate for update 2. ½ × Reversal rate for update 4. d) <Power ×1/×2> - ×1 : the I current (voltage for 2 wire) is as set ×2 : the I ×√2)
  • Page 73 3-7 for Internal HV power supply connections. Figure 3-8 details a suggested guarding interconnection for the high resistance measurement mode. The Model 6675A bridge in its High Ohms mode enables measurement of resistance values up to 1 GΩ:100 MΩ (Rx:Rs). This is a 2-terminal measurement. In this measurement mode there is a ±90 mA current source with a 30 volt compliance available on the Program Out...
  • Page 74 Section 3 Figure 3-6 : Front Panel Connections High Ohms - External HV Supply 3-57...
  • Page 75 Section 3 Notes: 1. For 4 terminal measurement; adjust Rc2 lead compensation for null across P1’s and then short P1’s together. 2. For 2 terminal measurement; C and P terminals are combined as 1 terminal, and lead compensation is optional. Figure 3-7 : Front Panel Connections High Ohms - Internal HV Supply 3-58...
  • Page 76 Section 3 Figure 3-8 : Recommended Guarding for High Resistance Mode 3-59...
  • Page 77 Section 3 Step 4) From the Main Menu on the 6675A, select the <Setup Menu> (making sure the softkey on the extreme right displays <resistors> and not <probes>) and either a) Select a stored measurement configuration by entering the menu <Main_Setup_load_select>...
  • Page 78 Guildline model 6623 Range Extender. A typical "Low Ohms" measurement configuration, using the model 6623 Range Extender is shown in Figure 3-9. Ratio measurements made with the Guildline Range Extender should be made such that the condition : Rs = (Rx) x (EXTENDER RATIO) is maintained.
  • Page 79 Rx, to the high current supply, and to the model 6623 Range Extender as shown in Figure 3-9. Step 2) From the Main Menu on the 6675A select the <Setup Menu> (making sure the Softkey on the extreme right displays <resistors> and not <probes> )
  • Page 80 In this measurement mode there is a ±5 mA current source signal with 30 V compliance available at the PROGRAM OUT terminals, which is sufficient to drive a Guildline model 9606 High Current Reversing Switch or the “Program Input” terminals of the model 6623. It is also possible to use the "pseudo" open collector output of the SYNC terminals on the rear panel to drive the Model 9606 switch.
  • Page 81 Section 3 Figure 3-9 : Front Panel Connections Low Ohms, 6623 Range Extender 3-64...
  • Page 82 Rs terminals and connect the temperature probe to the Rx terminals. Step 2) From the Main Menu on the 6675A select <Setup> (making sure that the right most softkey displays <probes> and not <resistors>). Step 3)
  • Page 83 Section 3 NOTE: When a temperature measurement is in progress the last coefficient set selected is used to calculate temperature. Probe Setup: Rs - the value of the standard resistor used in this temperature measurement. A positive non-zero number has to be entered for a valid configuration.
  • Page 84 Section 3 At all times the inequality: Max Current > Test Current × ratio is tested and if it fails, the measurement is stopped. When editing is complete, press the <OK> key to accept all changed data and press the <PREVIOUS> key until the display returns to the Main Menu. Step 4) Now that you are in the Main Menu you can go into the <Measure>...
  • Page 85 Section 3 High Ohm mode, 2-terminal measurements (10 milliwatt on Rs), 90 second reversal rate. Vtest Vmax Comment (Ω) (Ω) 100 k 100 k 31.6 100 k 31.6 10 M 10 M 10 M 1000 10 M 100 M 1000 100 M 100 M 1000...
  • Page 86 3.9. 6675A DATA ACQUISITION SOFTWARE A computer program that can assist with the remote control and operation of the model 6675A is included with Volume II of the 6675A Technical Manual. The Guildline 6675A Data Acquisition software, ResCal™, requires the following hardware and software for proper execution.
  • Page 87 The design approach taken for the 6675A 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 Ω...
  • Page 88 Section 4 4.1.1. The automatic direct-current-comparator resistance bridge. 4.1.1.1. The manual bridge - background. The direct-current-comparator bridge is a resistance bridge particularly suited for the comparison of "low value" resistors and the scaling of low resistances under conditions in which each resistor functions at its own power level. In this bridge network, the ratio of the resistances is determined from a knowledge of the ratio of the currents flowing in the bridge resistors.
  • Page 89 Section 4 Manual Adjustment Flux Detector Demodulator Master PSU and Slave Modulator Magnetic TOROID ASSEMBLY Current Comparator Null Detector Figure 4-1 : Direct-Current-Comparator Bridge Also, by semi-automating the balance of the zero ampere-turn flux condition, using an electronic closed loop feedback network operating on the flux detector output to drive a slave power supply for Is, the operator need only make manual adjustments for one effective bridge balance (null voltage condition), by adjusting the windings in the turns Nx.
  • Page 90 (Nx and Ns). Complete electrical isolation between circuit currents is maintained throughout the 6675A by making full use of fibre optic technology. A fibre optic serial data communication link is used to transfer data between each functional component and the embedded microcontroller.
  • Page 91 Section 4 SERVO LO O P Demodulator Microprocessor Controlled Flux Detector & Slave PSU Master PSU Magnetic Modulator Microprocessor Controlled TO RO ID W indings Nx ASSEM BLY Current Comparator B(1) NANO- VOLTM E TE R nVd=a.Vd -B(2) Figure 4-2 : Automatic DCC Bridge Balance 4.1.3.
  • Page 92 Section 4 β(1) and nanovoltmeter offset β(2) • Ic + (Ix) x (Nx) (Is) x (N) • (Ix) x (Nx / N)+Ic / N • (Is) x (Rs) - (Ix) x (Rx) + Vos Then we can state the generalized formula: ⎡...
  • Page 93 Section 4 Subtracting (9) from (8): ⎡ ⎤ nV(-t)(-) - nV(+t)(-) = Rs. .Ixx ⎣ ⎢ ⎦ ⎥ (10) Adding expressions (7) and (10): ⎡ ⎤ . Ix + Ixx .Rs = nVexpr ⎣ ⎢ ⎦ ⎥ (11) where: nVexpr = nV(+t)(+) - nV(-t)(+) + nV(-t)(-) - nV(+t)(-) (12) Then: ⎡...
  • Page 94 0.001 Ω , a high current range extender option is available for use with the 6675A. A stable, microprocessor controlled, adjustable power supply capable of sourcing up to 990 V DC is provided by the 6675A to allow higher resistance values (100 k Ω to 1 G Ω ) to be measured in a two terminal configuration.
  • Page 95 The core of the 6675A is a 13 bit current dac based on 0 to 8747 real turns which is done in a base 3 switching arrangement to minimize the number of relays used.
  • Page 96 DC loading of the nanovolt detector is negligible. (Note that in the 6675A we have no fractional or subfractional turns to deal with and the attendant calibration problems associated with fractional turns, however the nanovoltmeter has to be linear to 14 bits on all 5 ranges).
  • Page 97 Section 4 Figure 4-3 : Block Diagram 9975, 4-Wire Measurement 4-11...
  • Page 98 Section 4 Figure 4-4 : Block Diagram 6675A 4-12...
  • Page 99 Current, I-controller (6675A). This was done to increase the noise immunity of the servo and to increase the open loop gain. The "smart" feature of the 6675A servo is the 8 channel 12-bit A/D converter, the Tracking dac and the variable speed of the I-controller. During all phases of the measurement cycle (see Figure 4-7) the servo value is looked at and its value is added to the tracking dac the next time through that phase.
  • Page 100 4.2.3.2. Normal- Ω Measurement Mode This mode allows a 4-terminal resistance measurement to be made from 1 m Ω ≤ Rs ≤ 10 k Ω . No external devices (except the two resistors ) are required with the 6675A to make this measurement.
  • Page 101 Section 4 Figure 4-5 : 6675A Servo "Is" 4-15...
  • Page 102 Section 4 40 mA/V CONVERTER TO RELAY CARD Figure 4-6 : 6675A Primary Current "Ix" 4-16...
  • Page 103 Section 4 4.2.4. 6675A Signal Acquisition This section details the three stage signal acquisition process consisting of a Rough Null Phase, a Fine Null Phase and a Measurement Phase, and also the derivation of the formula used to determine the null turn (T...
  • Page 104 Section 4 Fine = Int[ 648 x (Rx/Rs)] ⎡ ⎤ ⎢ ⎥ Rough − ⎤ ⎤ ⎢ ⎥ Fine Int 648 ⎦ ⎥ ⎦ ⎥ ⎢ ⎥ ⎡ ⎤ nV t +I) - nV(t -I) ⎢ ⎥ ⎢ ⎥ − − −...
  • Page 105 The net result is that the flux detector sees two small glitches on a turns switch instead of one rather large transient. The 6675A uses the algorithm described in section 4.2 and the reasons for doing so was that the algorithm described in section 4.1 and the next section (the original 6675A measurement algorithm) was based on the original 9975 measurement principle which didn't correctly account for the Primary Current offsets.
  • Page 106 Section 4 ▒ ▒ Figure 4-7 : 6675A Measurement Cycle 4-20...
  • Page 107 Section 4 The alternative approach was to use the original algorithm and go to the expense of actually nulling the Primary Current and core offsets. However, we have a linear detector, and so we are actually measuring their effects and can account for them in the present algorithm. The final thing to notice is that in the expression for resistance ratio, the nanovolt detector readings only appear in the form: nV(+t)(+) - nV +t)(-)
  • Page 108 = (T_*) / 648 ; and (Rx / Rs) ⏐ (Rx / Rs)⏐ = (T+*) /648 Ix<0 Ix>0 Then (Rx /Rs) = (1 / 2) [ (Rx / Rs) ⏐ + (Rx / Rs) ⏐ Ix<0 Ix>0 Figure 4-8 : 6675A Turn Switching and nV Reading Graphical Representation 4-22...
  • Page 109 Section 4 4.3. NANOVOLT DETECTOR CPU OPTIONS 4.3.1. Dip Switches. The nanovolt detector has an 8 position piano style switch located as shown in Figure 4-9 on the nanovolt detector CPU PCB. Each of the 8 switches enable or disable an option. Figure 4-9 : Nanovolt Detector CPU Option Switch Location 4.3.1.1.
  • Page 110 4.3.2. Nanovolt Detector Principles of Operation. 4.3.2.1. Introduction. The nanovolt detector consists of the following functional blocks: Power Supply (Guildline drawing number 19103.01.02) - generates +5 volts, ±15 volts, and ±30 volts. Nanovolt Detector CPU PCB (Guildline drawing number 19855.01.02) -...
  • Page 111 Section 4 4.3.2.4. Analog Interface Address decoder U27 and PAL U28 provide the address decoding and read/write controls for the I/O latches. U23, U24, and U25 form a 24-bit Input Latch, which receives the serial data from the 12-bit ADC on the A/D Converter PCB. The serial data and clock from the ADC are coupled through the optocoupler U11.
  • Page 112 4.3.2.7. Serial Fibre-Optic Communication Interface. The serial fibre-optic communication interface section contains an interface to the main 6675A controller cpu assembly. 4.3.2.8. Gpib Interface. The GPIB interface is built up from a 68488 controller IC (U6) and two buffers (U3 and U4).
  • Page 113 Section 4 block of data comes from the digitized output of the integrator, after the integrator has been halted at the end of the conversion cycle. The pause between conversions is 3.5 mS, which allows ample time for the processor to compute the result before the next cycle begins. SERIAL CLOCK 12-BIT SERIAL DATA...
  • Page 114 Section 4 4.3.3.1. Voltage To Current (V/I) Converter. The input signal is converted into a current by an op amp U11, resistors R10-R13, R16, and R17. The op amp is configured as a bilateral current source with an offset current added in (via a -1.5 V reference source) so that bipolar input signals can be accommodated.
  • Page 115 Section 4 4.3.3.7. The Integrator. This consists of an ultrastable Teflon capacitor C18, and a FET buffer amplifier U15. 4.3.3.8. Charge Balance Sampler. This consists of U16, a limit comparator, and U4, a very fast flip-flop. On the rising edge of the master clock the output of the limit detector is sampled. If the integrator has gone over the preset limit, then on the next falling edge of the master clock, a charge packet is taken out of the integrator capacitor to bring it back below the preset limit.
  • Page 116 Section 4 4.3.3.12.A/D Trigger. This consists of 1/2 of U5, a one shot, which generates a 1 µs trigger pulse to start the 12-bit A/D converter. This trigger pulse occurs about 30 µs after the integrator has been halted, so that the output of U15, the integrator buffer, has settled to better than 0.01% of its final value.
  • Page 117 Section 4 4.3.4.2. Input And Range Selection. Control data from the CPU (SD) for Input and Range Selection is clocked into the shift register U200 by a clock signal (SCLK) provided by the CPU PCB. SCLK is also monitored by the monostable U201, which provides U200 a signal used to latch the data after all the data has arrived.
  • Page 118 The major hardware interfaces to the nanovolt detector microprocessor are the fibre-optic interface (and ultimately the 6675A user) to the 6675A cpu, and the analog to digital (also analog input amplifier) converter.
  • Page 119 6675A in an automated system. It is also possible to connect a printer to the remote interface of the 6675A and have the 6675A output some or all of the measurements taken to the printer for a permanent record.
  • Page 120 The cable should be double shielded and should have both a shielded plug and a receptacle connector type at each end of the cable. Guildline Part Number 996-23006 is a suitable IEEE-488 cable assembly of length 2 metres. Each connector assembly is fitted with a pair of captive locking screws.
  • Page 121 The IEEE-488 Address and Talk/Listen status can be set using the front panel controls as directed by the operator menuing system. If there is no controller and the 6675A is hooked up to a printer for hard copy then Talk Only mode should be selected as the preferred mode of operation.
  • Page 122 Section 5 ┌────────┬────────┬────────────────────────────────────────────┐ │ │ NAME │ DESCRIPTION │ ╞════════╪════════╪════════════════════════════════════════════╡ │ │ DIO1 │ Data Input Output Line 1 │ ├────────┼────────┼────────────────────────────────────────────┤ │ │ DIO2 │ Data Input Output Line 2 │ ├────────┼────────┼────────────────────────────────────────────┤ │ │ DIO3 │ Data Input Output Line 3 │...
  • Page 123 (MAV) bit will be set in the status register. 5.2.9. IEEE-488 Deadlock. If the controller demands a byte of data from the 6675A and the buffer is empty, the 6675A will set the Query Error flag in the Event Status Register.
  • Page 124 5.3. RS232C INTERFACE The 6675A has an RS232C interface which can be connected to a controller or to a simple printer. The controller (which can be almost any computer with an RS232C interface) can control the 6675A through a variety of commands which allow setting the instruments operating parameters, and analyzing the measurements made by the 6675A.
  • Page 125 Section 5 5.3.1. RS232C - Pin Designations. The 6675A Automatic direct-current-comparator is a data communication equipment (DCE) so TxD is an input (the data which the modem is to transmit). ┌──────┬───────┬─────────────────────────────────┐ │ Pin │ │ Function Direction │ ╞══════╪═══════╪═════════════════════════════════╡ │...
  • Page 126 The 6675A can be operated using the front panel keys or it can be operated remotely using a remote controller. In addition the 6675A can be placed in a local lockout condition at any time by a command from the controller. When combined, the local, remote, and lockout conditions yield four...
  • Page 127 Remote with lockout is similar to the remote state but restricted: The Remote softkey will not return to the local state. To return the 6675A to the local with lockout state the controller must send a GTL interface command. To return the 6675A to...
  • Page 128 Resistance Bridge. All tests are to run for a minimum of 1 hour. If the unit under test fails any test outlined in this section refer to the 6675A Technical Manual to assist in the repair and alignment of the unit. The procedure for testing low resistance ratios using the Model 6623 Range Extender is covered in the 6623 Technical Manual.
  • Page 129 6.4.1. Model 9330 /10 k Ω to Model 9350 /(100 k Ω Configuration) Step 1. Set up the 6675A in Normal Ohms measurement mode with the two resistors in a temperature controlled oil bath. Attach the 10 kΩ Standard Resistor to Rs and the Resistance Transfer Standard configured as 100 kΩ...
  • Page 130 6.5.1. Model 9330 /100 M Ω to Model 9330 /100 M Ω Step 1. Set up the 6675A in High Ohms measurement mode. Do not emerse the two resistors in oil. Attach the 100 MΩ Standard Resistor to Rs and the Resistance Transfer Standard configured as 100 MΩ...
  • Page 131 Section 7 MAINTENANCE 7.1. INTRODUCTION This section covers troubleshooting and repair and alignment of the 6675A. 7.1.1. Error Messages. Error Number Error Corrective Measures nV Detector -None, fatal hardware error (try Communication Failure power switch) Invalid Test Setup -Resistors not wired to front panel...
  • Page 132 Test Value is below minimum Voltage output (15.8V)!!! Setting DAC C or DAC D may magnetize the core!!!! Set Internal Values. This menu allows full control of 6675A. Great care should be taken when using these functions. Self test not completed Operation cancelled.
  • Page 133 The 6675A does not require or have calibration coefficients for resistance ratio measurements. The accuracy of the resistance ratio measurement reported by the 6675A depends on the turns setting of the current comparator and on the linearity of the nanovoltmeter (not the absolute nanovolt detector reading).
  • Page 134 Section 7 The procedure to calibrate a voltage range on the 6675A is as follows: Go into the menu <Main_SoftCal_Voltmeter_(select range)_Volts Set> and connect a precision voltage source to the Rs-P (High) and Rx-P (Low) terminals. Set the voltage source to 0 volts (and enable its output) and select the <zero volts>...
  • Page 135 7.1.4. Disassembly Procedure. This section describes the general procedure to be followed to gain access to modules located in the 6675A main assembly. 7.1.4.1. Cover Removal Procedure. Remove the rear handles (remove the 10-32 x 3/4" polished oval head (oh) screws (3 for each) that secure the handles).
  • Page 136 Section 7 Carefully disconnect BLU wire #15 or #16 that runs between the Primary Current Drive and PDCC Comparator modules. Carefully disconnect YEL wire #3 that runs between the Primary Current Drive module and the Rx C1 terminal on the front panel. Carefully disconnect BLU wire #5 that runs between the Primary Current Drive module and positive PROGRAM OUT terminal on the front panel.
  • Page 137 Section 7 Carefully disconnect RED wire #1 or #2 and GRN wires #17 and #18 that run between the Servo-loop and PDCC Comparator modules. Carefully disconnect WHT wire #4 that runs between the Servo-loop module and the Rs C1 terminal on the front panel. Carefully disconnect YEL wire #7 and RED wire #11 that run between the Servo-loop and Primary Current Drive modules.
  • Page 138 Section 7 Disconnect the BLU guard wire that runs between the PDCC Comparator module and GUARD Rx terminal on the front panel from the PDCC Comparator module. Carefully disconnect RED wires #1 and #2, BLU wires #15 and #16 and GRN wires #17 and #18 that run between the PDCC Comparator module and the rest of the system.
  • Page 139 Section 7 7.2.3. Power Supply Check 7.2.3.1. Primary Current Drive Power Supply PCB Test Procedure Using a DMM, measure the DC voltages at the Primary Current Drive Power Supply PCB test points. The voltages should be as shown in Table 7-3.
  • Page 140 Section 7 7.2.3.2. Servo Loop Power Supply PCB Test Procedure Using a DMM, measure the DC voltages at the Servo Loop PCB test points. The voltages should be as shown in Table 7-4. Using an oscilloscope, measure the noise voltage levels at the Servo Loop Power Supply PCB test points.
  • Page 141 Section 7 7.2.3.3. Nanovolt Dual Power Supply PCB Assy 19334 Test Procedure Using a DMM, measure the DC voltages at the Nanovolt Dual Power Supply PCB test points. The voltages should be as shown in Table 7-5. NOTE : Ensure that a jumper is installed at E2. Using an oscilloscope, measure the noise voltage levels at the Nanovolt Dual Power Supply PCB test points.
  • Page 142 Section 7 7.2.3.4. 6675A CPU and Display Power Supply PCB Test Procedure Using a DMM, measure the DC voltages at the 6675A CPU and Display Power Supply PCB test points. The voltages should be as shown in Table 7- Using an oscilloscope, measure the noise voltage levels at the 6675A CPU and Display Power Supply PCB test points.
  • Page 143 Ensure that there is NO loud hum from any of the transformers and that the ventilation fan at the rear of the unit is exhausting air OUT of the 6675A. Verify that the front panel display illuminates and no error message is displayed after initialisation is complete (after approximately 15 seconds) Turn the 6675A power OFF.
  • Page 144 Section 7 Select the "Sofcal" function by pressing the corresponding menu key. NOTE: The software responds slowly to a key press. Quick key presses may not be acknowledged. The "Gpib/RS232/Voltmeter/More 1-3" menu should appear on the display. Press the menu key under "More 1-3" until the "Diagnostic/Self Test/Chart/More 2-3"...
  • Page 145 Section 7 If necessary, adjust potentiometer R101 on the Primary Current Drive PCB until the voltage for POSITIVE polarity is greater than the voltage for NEGATIVE polarity. If necessary, further adjust R101 on the Primary Current Drive PCB until the voltage closest to 0 V is of opposite polarity to the voltage furthest from 0 V and within 20 µ...
  • Page 146 Section 7 Set the current to 0 mA. Repeat Steps 16 to 25. 7.2.4.3.2.Output Impedance Calibration Remove the 10 Ω resistors and the links from the Rs and Rx front panel terminals. Short Rs C to Rs C Connect a 1 kΩ, 0.1% resistor across Rx C and Rx C Using a 10 MΩ...
  • Page 147 Repeat the Primary Current Calibration. Record the voltages. 7.2.4.3.3.High Voltage Check Turn the 6675A Power ON. Enter the Sofcal Diagnostic menu. Using a DMM, monitor the DC voltage at the HIGH VOLTAGE OUT terminal with respect to. the Rx Ground terminal.
  • Page 148 Section 7 Record the voltage. Set the voltage to 0 V. Using a DMM, monitor the ac voltage (noise level) at the Rx Ground terminal. Set the voltage to 990 V. Ensure that the noise level is ≤ 40 mV rms.
  • Page 149 TP305 and TP302 on the Servo-loop PCB (connect the positive terminal of the standard to TP305). Leave the standard's output disabled. Turn the 6675A Power ON and enter the Sofcal Diagnostic menu. Select the "Monitor" function by pressing the corresponding menu key.
  • Page 150 Section 7 If necessary, adjust potentiometer R311 on the Servo-loop PCB until the "Calibration" reading is between +2046 and +2047. Adjust R311 until both numbers appear 50% of the time. Disable the voltage standard's output, set the standard for -9.9976 V and re-enable the standard's output.
  • Page 151 A male-to-male interface wire will be required. Connect the RED wire from TP102 on the Servo-loop PCB to the RED wire from the Rs C terminal on the 6675A front panel (i.e. bypass the Comparator Toroid's Ns winding.) NOTE: A female-to-female interface wire will be required.
  • Page 152 Section 7 Turn the 6675A Power ON. Enter into the Sofcal Diagnostic menu. Set the Speed to "Slowest" (reset) and the number of turns to 648. Using a 10 MΩ input impedance DMM, monitor the voltage at Rs with respect to Rs C (use the 2 V range on the DMM).
  • Page 153 Allow time for the reading to stabilize and readjust potentiometer R42 on the Magnetic Modulator PCB if necessary. Temporarily place the top cover on the 6675A and allow time for the unit to warm up with the cover on. 7-23...
  • Page 154 Set the Precision DC Calibrator for 0 V. Ensure that the Precision DC Calibrator is NOT in STANDBY mode. Turn the 6675A Power ON. NOTE: When turning the 6675A Power ON, wait ≈ 15 seconds for initialization. After initialization, the "Measure/Setup/Voltmeter/Sofcal" menu should be displayed.
  • Page 155 Section 7 The “GPIB/RS232/Voltmeter/More 1-3" menu should appear on the 6675A display. Select the "Voltmeter" function by pressing the corresponding menu key. The “20V Range/Volts Set/Coef Set/" screen should appear on the display. Select the "Volts Set" function by pressing the corresponding menu key.
  • Page 156 Select the "Voltmeter" function by pressing the corresponding menu key. Ensure that the voltage displayed on the 6675A display is between +14.9997 V and +15.0003 V (±15 V ± 20 ppm). Set the Precision DC Calibrator for -15 V (-75% of full scale).
  • Page 157 Section 7 Turn the 6675A Power ON. NOTE: When turning the 6675A Power ON, wait ≈ 15 seconds for initialization. After initialization, the "Measure/Setup/Voltmeter/Sofcal" menu should be displayed. Select the "Voltmeter" function by pressing the corresponding menu key. NOTE: The software responds slowly to a key press. Quick key presses may not be acknowledged.
  • Page 158 Section 7 Put the lid on the 6675A Nanovoltmeter module and allow approximately 15 minutes for the module to warm up. Press <PREVIOUS> until "Measure/Setup/Voltmeter/Sofcal" menu is displayed. Select the "Sofcal" function by pressing the corresponding menu key. The "GPIB/RS232/Voltmeter/ More 1-3" menu should appear on the 6675A display.
  • Page 159 Press the menu key under "20V Range" until the desired range appears. Ensure that the voltage displayed on the 6675A display is within the voltage range indicated in Table 7-7. Set the Precision DC Calibrator for -75% of full scale of the range selected.
  • Page 160 Section 7 Repeat Steps 16 to 44 for the remaining ranges indicated in Table 7- Turn the 6675A Power OFF. Reassemble 6675A. Reference Range of Voltage Range of Voltage Range Volts for 75% FS for 50% FS 20 V 15 V 14.9997 V to 15.0003 V...
  • Page 161 Nanovolt Amplifier CPU PCB Assembly PL19334.01.02 Nanovolt Dual Power Supply PCB Assembly PL19464.02.02 6675A CPU PCB Assembly PL19473.01.02 6675A CPU & Display Power Supply PCB Assembly PL19331.01.02 Transformer Module Assembly PL19485.02.01 Front Panel Mechanical Assembly PL19472.01.02 Keypad Switch PCB Assembly PL19111.01.02...
  • Page 162 Nanovolt Dual Power Supply PCB Assembly 19464.02.04 6675A CPU PCB Schematic 19464.02.02 6675A CPU PCB Assembly 19473.01.04 6675A CPU & Display Power Supply PCB Schematic 19473.01.02 6675A CPU & Display Power Supply PCB Assembly 19331.01.02 Transformer Module Assembly 19485.02.01 Front Panel Mechanical Assembly 19472.01.04...