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OM6634A-B-02
4 January 2019

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

Содержание 6634A Resistance Standard

Страница 1: ...ry 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 ...

Страница 2: ......

Страница 3: ...nals 1 3 1 4 3 Guard Terminal 1 3 1 4 4 Chassis Ground Terminal 1 4 2 SPECIFICATIONS 2 1 2 1 GENERAL SPECIFICATIONS 2 1 2 2 RESISTANCE SPECIFICATION 2 2 3 OPERATING INSTRUCTIONS 3 1 3 1 INSTALLATION 3 1 3 2 OPERATING NOTES 3 1 3 2 1 Connection to Standard Resistors 3 1 3 2 2 Monitoring of the Internal Temperature 3 1 4 MAINTENANCE 4 1 4 1 PREVENTIVE MAINTENANCE 4 1 4 1 1 Cleaning 4 1 4 1 2 Tempera...

Страница 4: ...4 January 2019 ii 5 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 ...

Страница 5: ...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 ...

Страница 6: ...OM6634A B 02 4 January 2019 iv 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 ...

Страница 7: ...will disable the heating system if the temperature exceeds 34 C 3 C The model 6634A is intended to be used as a Working Standard Resistance Reference for an automated resistance measurement system 1 2 1 Resistance Ranges The ten resistor elements within the model 6634A 10 cover the range of 0 001 Ω to 100 MΩ in decade steps Each resistor element is isolated and has a 4 terminal connection at the b...

Страница 8: ...occur when the unit is operated in an ambient temperature in excess of the operating temperature or in the event of control failure 1 3 4 PRT The platinum resistance thermometer imbedded within the temperature controlled chamber is configured as a four terminal resistor The four terminals terminate in four low thermal binding posts labelled PRT The set of terminals consists of two black binding po...

Страница 9: ... amp time delay fuse is provided for 220 240 VAC operation 1 4 2 Resistor Terminals There are a set of four terminal input outputs for each installed resistance element Each set consists of four low thermal binding posts labelled with the nominal value of each of the standard resistors Each set of terminals consists of two black binding posts for the P1 and C1 terminals and two red binding posts f...

Страница 10: ...ary 2019 1 4 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 ...

Страница 11: ...he resistors 30 0 003 C 86 0 005 F Temperature Stability 1 year exclusive of the self heating effects of the resistors 30 0 01 C 86 0 02 F Cold Power on Stabilization Time to Specified Accuracy 36 hours Power Requirements 15 VA Voltage Requirements 100 120 220 or 240 10 VAC Line Frequency 50 or 60 5 Hz Dimensions Nominal 1 D 503 W 440 H 132 mm D 19 8 W 17 4 H 5 2 in Weight Bench Top 11 kg 24 lb Ra...

Страница 12: ...nce is defined as the maximum variation of resistance mean values as initially adjusted at the point of sale 2 Calibrated in ambient conditions of 23 C referred to the unit of resistance as maintained by the National Research Council of Canada or the National Institute of Standards and Technology and expressed as a total uncertainty with a coverage factor of k 2 3 Stability is exclusive of the eff...

Страница 13: ...nstall it in an equipment rack as required Connect the line cord to the appropriate line power outlet and switch the instrument on using the power switch at the back of the instrument at the line input connect The red POWER lamp should light together with the green HEATER lamp When the inner chamber containing the standard resistors reaches its operating temperature the HEATER lamp will indicate p...

Страница 14: ... R t o t 392 0 Where Ro is the previously measured resistance value Figure 3 1 Opening the Power Receptacle Check to see that the fuses inserted in the receptacle correspond to the correct type specified in Section 1 4 1 Line Input Connector 100V 120V 220V 240V 100V 120V 220V 240V EXPOSE LINE SELECTOR SLIDER REMOVE SELECTOR 120V SHOWN PRY HERE TO REMOVE COVER ROTATE SELECTOR AND REPOSITION SLIDER ...

Страница 15: ...ed enclosure has been allowed to cool the resistors should be allowed to stabilize at the operating temperature for at least 36 hours before measurement or before use 4 3 CORRECTIVE MAINTENANCE Symptoms appear at the beginning of each of the following paragraphs as a guide to detailed fault location Refer to Section 5 of this manual for the PRINCIPLES OF OPERATION 4 3 1 Preliminary Checks Check PO...

Страница 16: ...esistance of Rl and the thermistor pair RT1 RT2 Rl should be 3k ohm to 5k ohm RT1 RT2 is equal to Rl at 30 C and is larger than R1 if the temperature is less than 30 C It has a temperature coefficient of approximately 4 C If necessary replace Rl and RT1 RT2 as a matched pair Control circuit board testing Measure the voltage at the pins of connector P1 as indicated in Table 4 1 Between PIN And PIN ...

Страница 17: ... R110 TP1 If oscillation is observed then check between TP2 collector Q103 and Pl 7 The waveform should be as shown If not then check the following components Q103 C106 R117 R112 R106 TP2 If this waveform is observed then measure the D C voltage between TP3 CR104 anode and Pl 7 It should read 2 5 volts If not then check C105 C107 CR103 and CR104 If it is correct then check Q104 Q105 R121 R122 and ...

Страница 18: ...emperature sensitive switch S2 is open If these conditions are satisfied then replace fuse F1 and check that the HEATER indicator is lit Monitor the increase in temperature with the PRT If the lamp does not indicate heater cycling when the temperature approaches normal then check the operation of the control circuit as follows Locate pins A and C of P2 Short pin A to pin C The HEATER indicator sho...

Страница 19: ...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 Figure 5 1 HEATER CONTROL UNIT OSCILLATOR AMPLIFIER DETECTOR HEATER DRIVER POWER SUPPLY AC IN HTR CONTROL O T SWITCH ...

Страница 20: ... the voltage divider output to the base of Q101 increases As soon as this voltage exceeds half the transformer output the circuit gain becomes greater than one and oscillation occurs 5 3 AMPLIFIER AND DETECTOR Figure 5 3 AMPLIFIER AND DETECTOR The output of the oscillator is amplified by Q103 and rectified by a voltage doubler consisting of C105 CR103 CR104 and C107 The resistor R115 gives current...

Страница 21: ...nsistor Q1 which controls the heater current The resistors R119 R121 and R122 ensure that Q1 is not conducting when there is no output from the oscillator 5 5 OVERTEMPERATURE CIRCUIT If the temperature in the enclosure exceeds 34 C 3 C switch S2 closes The load provided by R2 is sufficient to blow the fuse Fl and disconnect all power to the heater R119 R121 R122 Q104 Q105 R114 T R2 HEATER S2 P1 14...

Страница 22: ...2 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 The heater is fed from the unregulated output and the control 01 T2 12V CR106 CR107 CR102 P1 20 P1 21 P1 16 8 2V C101 R107 CR101 POWER ...

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