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Guildline 6634A Resistance Standard Operator's Manual

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OPERATORS MANUAL
FOR
MODEL 6634A
RESISTANCE STANDARD
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.
OM6634A-B-02
4 January 2019

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Summary of Contents for Guildline 6634A Resistance Standard

  • Page 1 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.

  • Page 3: Table Of Contents

    TABLE OF CONTENTS INTRODUCTION ....................1-1 1.1. SCOPE ..............................1-1 1.2. GENERAL DESCRIPTION ........................ 1-1 1.2.1. Resistance Ranges ..........................1-1 1.2.2. Standard Model Configurations ......................1-1 1.3. FRONT PANEL INDICATORS AND CONTROLS ................. 1-2 1.3.1. Power ..............................1-2 1.3.2. Heater ..............................1-2 1.3.3. Over Temperature ..........................1-2 1.3.4.
  • Page 4 PRINCIPLES OF OPERATION ................5-1 5.1. INTRODUCTION ..........................5-1 5.2. TEMPERATURE SENSITIVE OSCILLATOR ................5-2 5.3. AMPLIFIER AND DETECTOR......................5-2 5.4. HEATER DRIVER ..........................5-3 5.5. OVERTEMPERATURE CIRCUIT ....................5-3 5.6. POWER SUPPLY ..........................5-4 OM6634A-B-02 4 January 2019...
  • Page 5 TABLE OF FIGURES FIGURE 1-1: FRONT VIEW ............................1-2 FIGURE 1-2: REAR VIEW ............................1-3 FIGURE 5-1: HEATER CONTROL UNIT ......................5-1 FIGURE 5-2: TEMPERATURE SENSITIVE OSCILLATOR .................5-2 FIGURE 5-3: AMPLIFIER AND DETECTOR ......................5-2 FIGURE 5-4: HEATER DRIVER ..........................5-3 FIGURE 5-5: POWER SUPPLY ..........................5-4 OM6634A-B-02 4 January 2019...
  • Page 6 LIST OF TABLES TABLE 2-1: GENERAL SPECIFICATIONS ......................2-1 TABLE 2-2: RESISTANCE SPECIFICATION ......................2-2 TABLE 4-1: CONTROL CIRCUIT BOARD TESTING ..................4-2 TABLE 4-2: TRANSISTOR VOLTAGES........................4-4 OM6634A-B-02 4 January 2019...

  • Page 7: Introduction

    1.2. GENERAL DESCRIPTION The model 6634A Resistance Standard is a rack mountable or bench top instrument which provides a set of precision resistance standards enclosed in a multi-walled constant temperature chamber. The internal temperature is maintained by a solid-state control system at 30 C  0.01 C.

  • Page 8: Front Panel Indicators And Controls

    Section 1 Note that if 0.001 and/or 0.01 values are ordered they physically take more space so are delivered with fewer elements. Figure 1-1: Front View 1.3. FRONT PANEL INDICATORS AND CONTROLS The front panel indicators and controls are illustrated in Figure 1-1. They are provided to indicate power status, heater operation and temperature status.

  • Page 9: Rear Panel Connectors And Controls

    Section 1 Figure 1-2: Rear View 1.4. REAR PANEL CONNECTORS AND CONTROLS The rear panel connectors and controls are illustrated in Figure 1-2. They include power entry, resistor terminals and guard/ground terminals. The terminals are not installed for resistance element values that are not provided in specific models. 1.4.1.

  • Page 10: Chassis Ground Terminal

    Section 1 1.4.4. Chassis Ground Terminal The CHASSIS GND terminal consists of a four-way green binding post. The CHASSIS GND terminal is bonded to the chassis of the model 6634A and to the power ground of the line input connector. OM6634A-B-02 4 January 2019...

  • Page 11: Specifications

    Section 2 SPECIFICATIONS 2.1. GENERAL SPECIFICATIONS MODEL 6634A RESISTANCE STANDARD General Specifications Operating Temperature +23  5 °C +73  9 °F Storage Temperature -20 to +60 °C -4 to +140 °F Operating Humidity (non-condensing) < 70 % RH Storage Humidity (non-condensing) <...

  • Page 12: Resistance Specification

    Section 2 2.2. RESISTANCE SPECIFICATION Nominal Nominal Stability Stability Temperature Maximum Resistance Initial over any 24 12 months Coefficient Voltage (Ω) Tolerance hour period (volts) (ppm) (ppm/°C) (ppm) (ppm) (Note 1) 0.001 0.04 0.01 0.01 0.02 0.03 0.01 0.01 0.005 0.32 0.01 0.005...

  • Page 13: Operating Instructions

    Connection to the resistor terminals should be made with solid copper wire having low thermal EMF characteristics. The wires to each C-P pair of standard resistor terminals should be twisted and preferably shielded to avoid spurious pick-up. Use Guildline Type SCW Wire or equivalent. The certified resistance of each resistance element installed and the date of calibration are indicated in the Report of Calibration.
  • Page 14 Section 3 and P2. Set the ohmmeter to the best range for measuring 112  with an excitation current of 1 mA or less. Measure the resistance of the PRT (R ). The change in internal chamber temperature from the previously measured resistance value: −...

  • Page 15: Maintenance

    Section 4 MAINTENANCE 4.1. PREVENTIVE MAINTENANCE 4.1.1. Cleaning The instrument requires very little maintenance other than periodic dusting of the outside of the enclosure. Use alcohol to clean around the standard resistor terminals to avoid formation of leakage paths. 4.1.2. Temperature Check the internal temperature with the imbedded PRT before using the resistors as references and also periodically.

  • Page 16: Temperature Control

    Section 4 control circuit. Proceed to paragraph 4.3.3. Check the internal temperature with the imbedded PRT to compare the calculated temperature with the value given in the Report of Calibration. 4.3.2. Temperature Control If the temperature is low and the HEATER indicator is lit, check the continuity and resistance of the heater circuit.
  • Page 17 Section 4 Check the operation of the temperature sensitive oscillator. If the resistance of RT1/RT2 is greater than the resistance of Rl, then the oscillator should be running. Check with an oscilloscope between TP1 (collector of Q102) and Pl-7. The waveform should be as shown.

  • Page 18: Table 4-2: Transistor Voltages

    Section 4 DEVICE VOLTAGE READINGS (Pl-7 Common) HEATER ON HEATER OFF Q101 -3.05 -3.2 -5.2 -3.05 -3.2 -5.2 Q102 -5.4 -5.2 -3.05 -5.4 -5.2 -3.05 Q103 -2.95 -3.05 -5.3 -2.95 -3.05 -5.3 Q104 -1.4 -2.0 -1.45 -----------Variable-------- Q105 -0.75 -1.42 -1.45 -----------Variable-------- -0.25...

  • Page 19: Principles Of Operation

    Section 5 PRINCIPLES OF OPERATION 5.1. INTRODUCTION The heater control unit in the model 6634A enclosure consists of the following functional blocks. a) Temperature Control - consisting of a sensor, oscillator, amplifier, detector and heater. b) Over temperature Circuit c) Power Supply CONTROL AMPLIFIER/ HEATER...

  • Page 20: Temperature Sensitive Oscillator

    Section 5 5.2. TEMPERATURE SENSITIVE OSCILLATOR P1-12 P2-D T101 Q102 Q101 P1-10 P2-C RT1/RT2 C104 P2-A P1-9 R110 Figure 5-2: TEMPERATURE SENSITIVE OSCILLATOR Temperature changes are sensed by the thermistor RT1/RT2 connected with Rl across the 1:2 ratio autotransformer T101. As the temperature decreases, the thermistor resistance increases and the voltage divider output to the base of Q101 increases.

  • Page 21: Heater Driver

    Section 5 5.4. HEATER DRIVER P1-16 -12V OVER TEMP R114 P2-F Q104 HEATER Q105 HEATER P1-14 P2-E R119 R121 R122 P1-7 P2-J Figure 5-4: HEATER DRIVER The voltage across C107 causes base current in the emitter follower Q104, which in turn drives another emitter follower Q105.

  • Page 22: Power Supply

    Section 5 5.6. POWER SUPPLY -12V POWER P1-20 CR106 CR102 P1-16 R107 -8.2V P1-21 CR107 CR101 C101 Figure 5-5: POWER SUPPLY A universal power transformer T2 allows for operation of circuit is fed from a regulator consisting of R107, CR101 and C1 the instrument from 100/120 VAC or 220/240 VAC, 50 or 60 Hz, and feeds a full-wave rectifier.

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