GENERAL RADIO COMPANY 1608-A, Operating Instructions Manual

Page 1: ...OPERATING INSTRUCTIONS TYPE 1608 A IMPEDANCE BRIDGE 1 GENERAL RADIO COMPANY A I 0 o OJ I ...

Page 2: ...ING INSTRUCTIONS TYPE 1608 A IMPEDANCE Form 1608 0100 A February 1962 BRIDGE Copyright 1962 by General Radio Company West Concord Massachusetts USA G ENE R A L R A 0 I 0 COMPANY WEST CONCORD MASSACHUSETTS USA ...

Page 3: ... Bias to Unknown 22 3 2 Measurements on Shielded Three Terminal Components 26 3 3 Remote Measurements 26 3 4 Use of Type 1650 P1 Test Jig 27 3 5 Measurements on Grounded Components 27 3 6 Limit Testing 27 3 7 Measuring Resonant Frequency and Resonant Impedance of Tuned Circuits 27 Section 4 PRINCIPLES OF OPERATION 4 1 Bridge Circuits 4 2 Bridge Sources and Detectors 4 3 Bridge Switching 4 4 Centad...

Page 4: ...ove 1 kC f Q of R or G 0 0005 1 kc 2 GENERATOR AND DETECTOR Internal Oscillator 1 kc 1 normally supplied Plug in modules for other frequencies available on request Level control provided Internal Ac Detector Can be used either flat or selective at frequency of plug in module normally 1 kc Second harmonic rejection approximately 25 db sensitivity control pro vided Internal Dc Supplies 3 5 v 35 v 35...

Page 5: ...II 9 12 10 13 3 15 4 6 Figure 1 1 The Type 1608 A Impedance Bridge for legend see page 2 7 8 16 17 18 ...

Page 6: ...ections for the four on positions of the function switch INT AC INT DC EXT AC EXT DC are shown schematically in Figure 1 3 Cs LOW 0 o TO I SERIES CAPACITANCE RN Cx R Cr Ox IIICx Rx OICrRr Cp HIGH 0 02 2 PARALLEL CAPACITANCE C x 1 2 2 CONTROLS AND CONNECTORS Table 1 1 lists the controls and connectors on the front and rear panels of the Type 1608 A Impedance Bridge 1 3 SYMBOLS ABBREVIATIONS AND DEF...

Page 7: ...tary sWItch and R measurements 8 Continuous rotary control 9 GEN LEV Continuous rotary control Controls output level of internal generator ac and dc 10 DET SENS Continuous rotary control Controls sensitivity of internal detector ac and dc CONNECTORS Fig 1 1 Ref Name Type Function 11 EXT GEN Jack top binding post Connection to external gen pair erator ac and dc 12 DET OUT Jack top binding post Outp...

Page 8: ...ductance Gp Rs R Gs cuL for inductors or inductive resistors Q __s_ R INT DC EXT GEN EXT DC Figure 1 3 Generator and detector connections LOWEST TWO R RANGES HIGHEST 5 R RANGES HIGHEST THREE GRANGES LOWEST 4 GRANGES GEN LEV for capacitors D R power factor VR2 X2 frequency angular frequency 21Tf ohm a unit of resistance reactance or impedance kilohm 1 kD 1000 D megohm 1 MD 1 000 000 D milliohm 1 mD...

Page 9: ...ircuits lor complex impedance 1 5 ACCURACY OF MEASUREMENTS 1 5 1 CGRL ACCURACY AT 1 KC The basic bridge accuracy is 0 1 This is a function of the accuracy of the adjustment and stability of the bridge arms The in strument is initially calibrated to an accuracy of 0 05 or better and should hold the 0 1 accuracy for well beyond the two year warranty period A simple calibra tion check procedure is gi...

Page 10: ...ee Figure 1 5 kc Figure 1 6 Resistance and conduct ance errors vs frequency FREQUENCY J ff I JV 1 VI I j TOTAL ERROR a rIbOOI r OTAL ERloR Q O VI 1 0 1 1 V 1 12 1 0002 1 1 I Ike 10ke 100 o 0 0 100 10 The Q adjustment for the Rs and Gp bridges con sists of two decades of mica capacitors and a variable capacitor with infinite resolution Losses in the mica capacitors appear as an R or G error when Q ...

Page 11: ...c term in the o and Q accuracy specifications for C and L measure ments depends upon the tracking accuracy of the DQ 6 rheostats with the dial calibration The fixed term 0 0005 depends upon the phase angle of each arm of the bridge and many compensating components are re quired to achieve this accuracy refer to paragraph 4 5 This specification of O OOO holds for measurements made down to 1 20 of t...

Page 12: ...INTRODUCTION ...

Page 13: ...09 0 001 0 1 20 0 002 0 2 30 0 00 0 0 01 0 3 0 4 60 Q02 70 Q5 80 0 6 90 100 0 05 0 7 0 8 0 9 0 1 I 200 0 2 300 0 5 400 500 600 700 800 900 6 1000 7 8 9 10 Q XL LS ANY FREQ I kc ONLY m o nh 0 ph k o mh 2 m o 1 0 1 1 k o 1 10 9 8 7 6 5 200 300 400 1000 900 800 700 600 500 Figure 1 8 Nomograpb for conversion of Rs to L s and vice versa 8 ...

Page 14: ...counter an X is used in place of the number 10 To interpret a reading containing an X simply substitute 0 for the X and add 1 to the digit im mediately to the left of the X For example 102X3 10303 99X2 10002 The letter X is also used on two of the three Q OPERATING PROCEDURE dials used with the Rs and Gp bridges Here again sub stitute 0 in place of the X and add 1 to the digit to the left of the X...

Page 15: ... ac tual voltage applied to any unknown resistor when meas ured on the R bridge with a Il5 volt line voltage EIA specifications for testing different types of resistors are summarized in Tables 2 2 and 2 3 Figure 2 1 shows thar these standard voltages can be supplied from the internal power supplies over most of the resis tance range For low resistance measurements the GEN LEV control can be set f...

Page 16: ...D Rs llD 0 5 1v 10 99 D Rs 1l0D 0 5 1v 100 999 D Rs 1l00D 2 5 3 v 19 2 23v 1000 9999 D Rs II kD 8 10 v 13 4 16 7 v 1O 99kD Rs 1l0kD 24 30 v 25 6 32v 100kD 1MD Rs 1100kD 80 100v 81 101 v 1MD up Gp 1nU 80 100v 81 101 v TABLE 2 3 EIA STANDARD TEST VOLTAGES Fixed Film Resistors RS A6 Low Power Wire Wound Resistors REC 117 up to 9999 D RESISTANCE BRIDGE RANGE EIA MAX VOLTAGE MAX BRIDGE VOL TS less tha ...

Page 17: ...ce ranges set the function switch to EXT GEN but apply the voltage between the BIAS terminals and the EXT DQ terminals R bridge only When an external supply or detector is used the measurement procedure is the same as that with the in ternal supply and detector except that the GEN LEV control does not control the level of an external sup ply and the DET SENS control does not control the sen sitivi...

Page 18: ...0 2 2 4 2 l KC INDUCTANCE MEASUREMENT 2 4 2 1 Procedure a Set the GEN LEV control fully clockwise OPERATING PROCEDURE Note For some iron cored inductors the induc tance measured will depend upon the excitation level refer to paragraph 2 4 5 4 b Set the BRIDGE SELECTOR to Ls if the series inductance is desired and Q is be tween 0 5 and 5 0 Lp if the parallel inductance is desired and Q is greater t...

Page 19: ... 0 5 2 is added to the specifi cations ref er to paragraph 1 5 3 This error is neglig ible when Q is greater than 5 TABLE 2 5 CORRECTIONS FOR ERRORS CAUSED BY TERMINAL AND LEAD IMPEDANCES Add or subtract from the measured value as indicated Measured Series Resi stance Series Inductance Parallel Capacitance Ro 0 9 mD t leads Lo 0 14 J 1 h tleads Co 0 25 pf t leads C s NO ERROR u 2LoCx2 Co 1 Dx2 D u...

Page 20: ...nd high est G ranges where the accuracy is 0 2 of the reading 0 005 of full scale On the lowest R range the residual resistance of the bridge approximating 0 9 mD should be subtracted OPERATING PROCEDURE from the measured resistance Use short heavy leads to connect the unknown resistor measure the resis tance of these leads by connecting the free ends to gether and subtract this value from the mea...

Page 21: ...nting the unknown 2 4 5 3 AC Sensitivity The generator bridge detector system is sensitive enough to balance the bridge to the stated accuracy specifications However there are cases where additional sensitivity may be useful such 16 as measuring accurate D or Q when the main CGRL ad justment is at the low end of its range or when the sig nal level on the unknown must be set at some low level In th...

Page 22: ... sensitivity of resistance measurements over that possible with dc without using a higher ap plied voltage or a sensitive dc amplifier The ac re sistance of a resistor can differ from the dc value for a number of reasons However most of those are neg ligible at 1000 cps and in some cases the use of ac avoids undesirable effects thar can cause errors in dc lTIeasurement 2 4 6 2 Frequency Effects a ...

Page 23: ...e the effective measured paral lel conductance Gp will decrease with frequency The expression 1 1 Gp R u 2R2C2 gives the first error term At 1 ke 1 1 1 Gp R 1 R2 C x 106 where R is in MD and C is in 18 pf This gives a 1 error when R 100 MD and C 1 pf This effect is just noticeable if a large resistor is spaced very close to the bridge panel and causes no measurable error if the unknown is_spaced a...

Page 24: ...the internal bridge transformer when the function switch is in the EXT AC position and the low generator ter minal is connected to the bridge chassis which should be grounded refer to paragraph 2 1 2 A second ground connection to the generator should be avoided If the external generator can be overdriven when connected to a low impedance load it is generally de sirable to place a resistor in serie...

Page 25: ...adjustments for the various bridges The shaded ther limit on the voltage applied to the EXT GEN ter minals whichever is larger This transformer has a 3 to l step down ratio and an equivalent resistance referred to the primary of 20 ohms Therefore to limit the power ap plied to the bridge to 1 2 watt a series resistor of E2 20D should be placed in series with the external 2 supply ANY PANEL L CONNE...

Page 26: ...ustment should be a decade resistance box or a calibrated rheostat connected to the OPERATING PROCEDURE EXT DQ terminals of the bridge For the Cp and R s bridges a decade capacitance box should be connected from either EXT DQ terminal to chassis the two termin als should be shunted together The readings on the external adjustments can be converted to give D or Q by means of the following form ulas...

Page 27: ...tput impedance For this method of bias the bridge and the dc supply do not have a common ground and one must be left floating This problem is discussed in paragraph 3 1 5 Method 2 Cp Bridge see Figure 3 1b This method is the same as Method 1 above except that a large blocking capacitor is placed in the standard bridge arm to prevent direct current from flowing through the D adjustment rheostat Con...

Page 28: ... disconnecting the dc supply of the unknown inductor Method 1 see Figure 3 2a 30 ma max This method is preferred because both the dc sup ply and bridge are grounded and up to 30 rna may be ap plied to large inductors At the 30 ma level there is an added 0 03 error in inductance and there may be a 1 D EQ error as large as 0 001 The resistor in series with the supply should be large enough to avoid ...

Page 29: ...drop of the unknown resistor The voltage rating of capacitor Ce connected to the BIAS terminals should be greater than Idc x 7 6 k o and the capacitance should be over 50 Lt A resistor should be placed in series with the dc supply to avoid shunting the detector with a low ac im pedance A variation in this method is to short circuit the two blocking capacitors Cd and Ceo Then the current through th...

Page 30: ...1232 A Tuned Amplifier and Null Detector In some cases the induced hum may overload the internal detector causing erroneous readings in which case the external detector should be connected between the LOW UNKNOWN ter minal and the bridge panel rather than to the DET OUT terminals In extreme cases the bridge may be discon nected from the power line thus removing all internal source of hum This has ...

Page 31: ...ces are measured and the LOW UNKNOWN terminal is grounded Earphones may be helpful in de tecting the null of the fundamental in the presence of hum In extreme cases the bridge can be disconnected from the power line and a battery operated selective de tector such as the Type 1232 A Tuned Amplifier and Null Detector can be used to avoid all internal hum pickup 26 3 2 MEASUREMENTS ON SHIELDED THREE ...

Page 32: ...l hum pickup to the bridge chassis which can usually be removed by grounding of nearby equipment This hum pickup can become very large when high impedance components are measured SPECIAL MEASUREMENTS There is less hum pickup in the measurement of high impedance components if the other unlabeled UN KNOWN terminal is grounded However the internal capacitance of the bridge chassis to ground approxi m...

Page 33: ...range from 1 ohm to 1 megohm are all General Radio precision wire wound resistors The two ganged DQ adjustments are wire wound rheostats with a 40 db logarithmic range 4 2 BRIDGE SOURCES AND DETECTORS There are three dc sources of approximately 3 5 35 and 350 volts open circuit that are connected to the bridge for dc resistance and conductance measurements according to the schedule of Table 2 1 Re...

Page 34: ...s the ratio arm resistor of the bridge Two separate rotors are used so that a clockwise rotation will increase the size of the unit for all six bridges Both ends of the re sistors are switched out and the unused resistors are grounded to reduce stray capacitance The range switch also positions the decimal point on the main readout de termines which dc supply will be used for dc G or R measurements...

Page 35: ...placed across this arm by the bridge transformer and wiring C14 CIS and C16 These capacitors are used to compensate for inductance in the winding of the lower valued DQ rheostat R4 LA LB CC etc RA RB RC etc on R1 The inductors are used to compensate for the capacitance placed across the whole variable arm by the wiring and 30 switches The inductors have enough resistance to re quire resistors in p...

Page 36: ...tandards used A General Radio Type 1409 T Standard Capacitor is recommended as a capacitance standard This capacitor is calibrated to O 03 Type 500 Resistors are recommended as the resistance standards Their accuracy is 0 05 except for the I ohm unit whose accuracy is 0 15 More ac curate resistors should be used if available or Type 500 Resistors can be measured to greater accuracy if a suit able ...

Page 37: ...end upon the same compo nents for both bridges see Figure 1 2 Likewise it is easier to check the Gp bridge than the Rs bridge 32 The fixed phase shift error 0 0005 can be checked on the C bridge by measurement of capacitors with low known D values The D error on the lowest C ran e de pends somewhat on the position of the 1 M ratio arm R13 The fixed Q error on th Rs and Gp bridges can be set by adj...

Page 38: ...can be replaced ac curately The unit dial must be removed to replace the unit indicating lamps and should be replaced in the same position To replace the lamps held in place by insula ting washers it is easier to unsolder the connection on the pin coming through the washer Be careful not to let solder or rosin run down this pin and prevent its free mO lement in the washer All lamps are GE Type 327...

Page 39: ...minal to either EXT DQ terminal when the bridge is set to R s L s or L p If there is no output when the function switch is in the INT AC position and the GEN LEV con trol is on clockwise the oscillator is not operating properly Note the output will be very low with a low impedance unknown The test point voltages given in Table 5 2 and the diagram Figure 5 16 should enable anyone skilled in the art...

Page 40: ...S3 401 FR Figure 5 1 Top interior view RI F300 I 12 JI Figure 5 2 Right side interior view 35 ...

Page 41: ...R5 R4 Figure 5 3 Left side interior view R562 C530 T400 R533 JI4 JI5 L _ _ R5 JI3 LI CI C3A S1 1 1 R2 Figure 5 4 Rear interior view 36 ...

Page 42: ...Figure 5 7 Etched board layout o o o o o I I Figure 5 5 Etched board layout Figure 5 6 Etched board layout 37 ...

Page 43: ...2 RN VERNIER 0 71 212 RD Lp z RNRACT RX I QX GJLX GJCTRT G p CAP Q 0 1 21 PARALLEL CONOVCTANCE RS lND Q 0 1 2J SERIES RESISTANCE LS LOW Ii 0 5 50J SERIES INDUCTANCE DP SS IO F DET SS 20 F DET S3 204F VERNIEIi 0 71 212 20 F S2 J OIF R VT J O 1F R 81 J HF R RA SI J 1 1J RArlO ARM R7 O 982 o S J I Lx RfVR A CT Q wLx X wCrRT Rx 2F cell RI CENTADE 0 T 6KI2 RN VERNIER 0 71 2 J RA RATIO ARM BRIDGE GROUND...

Page 44: ...PACITOR C2 DECADE t AT 53 S4 S5 v R3 C5 TO CI2 AT 52 J4 310F 52 30lF OIR 52 308FR 305FR BK 412F 53 402F WH BL BR BK 504R 52 505R GY 511F 52 512F 204F 53 211F WH YE BR W H lQ JI Figure 5 9 Simplified schematic diagram showing bridge in various positions of FULL SCALE RANGE switch Gp bridge 51 516R 504R 52 504F 503F 51 511R 504R S2 BRICGE SELECTOR Gp S3 GENERATOR SELECTOR INT DC 51 502R 507R 513R R4...

Page 45: ...11F 52 50lFR S2 BRIDGE SELECTOR Rs S3 GENERATOR SELECTOR INT DC 504RWH_YE_BK 505FR 51 52 503F BK 53 505F AT 50 51 511R 516R CHASSIS GROUND AT 50 BRIDGE GROUND 504R 513R 51 502R 507R R401 R403 WH YE OR 0400 CW 0401 53 o WH JI41GY 311F 312F B I GN L _ 53 309F o JI5 C WH GY RD 153 308R I I I I I I I I I I I I I I R400 I ________ J DOTTED CONNECTIONS TO R401 a R400 ARE MADE ONLY WHEN S3 SWITCH IS HALF...

Page 46: ...EN LEVEL 53 AC DC OET 304F 306F C556 204F Figure 5 11 Simplified schematic diagram AMP OUTPUT WH AT 40 showing bridge in various positions of GN D 1Y BL AMP DET S3 function switch BK INPUT SENS AT 33 AC 211F 202FR 52 51 JI3 JI4 511F 501FR 505F 515F A B WH 0 0 WH WH WH YE OR GY 0 GY BR YT BL JI5 GN WH YE GY C 51 M400 WH YE YT 53 307R 305R DET WH UTPUT RO BL BR WH 310R 6 516R 504R 511R 30lR 53 52 BK...

Page 47: ... WH GN BR 112R I06R I04F I03F WH OR WH 52 J WH BL BK IOIR 52 GN BL _IIOF WH RD loaR _IIIF WH GN WH BL I09R I07F WH GY BR WH BL BR 1I0R Ip2 P3 PI3 J mH WH WH PI4 P4 GY VT PI5 nF V 0 PU P5 P6 P7 C 115F 114F PIO PII PI21 WH GY BI IIOOpF 51 112F WH RD BR II nF 113F WH RD BL 1I0nF 1I00nF IlpF 1I0pF 1I00pF P9 P8 Q CT CAP mv 52 Cs cp Gp Rs Ls Lp Figure 5 12 Simplified schematic diagram showing light circ...

Page 48: ...555 2N520A _TRANSFORMERS T300 345 479 T400 746 436 NOTES A Type designations for resistors and capacitors are as follows COA Capacitor air COC Capacitor ceramic CaE Capacitor electrolytic COM Capacitor mica COT Capacitor trimmer COW Capacitor wax B All resistances are in ohms except as otherwise indicated by kilohms on M megohms C Value determined in General Radio calibration laboratory ...

Page 49: ...f l 500dcwv COM IF 103A R502 15 8k l 1 4w REF 65 1581A C525 50 1 3dcwv COE 63 R503 15 8k l 1 4w REF 65 1581A C526 40 1 6dcwv COE 54 R504 7 87k l 1 4w REF 65 7871A C527 25 1f 50dcwv COE 48 C528 10 1 25dcwv COE 56 R525 3k 5 1 2w REF 20BF 302B C530 10 1f 25dcwv COE 56 R526 22k 5 1 2w REF 20BF 223B C550 25 1f 50dcwv COE 48 R527 62 5 1 2w REC 20BF 620B C551 lO 1f 25dcwv COE 56 R528 150 5 1 2w REC 20BF ...

Page 50: ...2R 55 YE 55 I1R 51 S4111R GN 5HIELO D LEADS OR AT51 RI4 IK C6 Z02F1 00475 1ji r 0 J p r J C5 I 00243 I I 154 I I I 1i 2 O R fl ___ I 0 I 10 10 I 20JR I I 0 V C2 14 270 l TO S3 40lR CI5 10 BL JIOF 52 JOIR 52 JIOR 52 52 Jf o J07R sotIF8R oIf o l I ro 53 204F _ W H TO S 412F BK Figure 5 13 Schematic diagram of bridge circuits 43 ...

Page 51: ...2 iOK I I R30I 1 2W 6 C OIB 100 R300 10 IW 6 C300B r 100 C6 C 03AB 200 Cb C302A B 20 C C301A 100 030B A T INI692 VT 10 A r It OR I I D30I I INI692 O OO r oo Af INI692 lC __ o o SHIELD 71 ANO FRAME o o I I 0302 I INI692 I I I 0303 I INI692 IlIl Ar r t A T I a rom I r 111Ic 6N 1 IMt_ _ ro OSC AMP I At 0304 R304 PWB A r 42 I INI692 390 WH RO 6N I f I I I A r I 1 BK I f j A r 22 I WH BK A r A T 1 t t ...

Page 52: ...R t I DETSENS I I AC I I I I I TO AMP INPUT r 1 WH E B RL ___J JIJ I 7 W H G BL S K r O A M P our P U T J I II J iR I A r A T U WH YE oR 60 62 C l JI 1 4 i I I R40I 1 J V b I 47K I V L R403 16 2 L 1 O 7 r H G Y G f NI r I cJ 0 5K A ToT llB I I TO 1 1 J f 0 eew 11400 61 iJ I 0 DET SENS EXT METER J J DC CONNECTIONS JO r J04F 0 0 I 6 0 J05R WH Rfl RJ IU eOJI5 jL 6F t J I I Ii WH YF qy I LJ Figure 5 1...

Page 53: ...558 10K R571 18K R569 K R570 150K 1608 272 R556 10K R557 lOOK R568 4 7K R555 4 7K Q553 C551 Q555 2 620 10 Q554 2 N520 2N445A if Xk 0551 I C562 I IV I NI692 1r 0 Y F M 7 C 1 52Jf i i t t D5 111 1 0 INI692 A r 38 R554 10K R553 IK C559 10 r R567 4 7K R551 17K R552 20K WH BR 11 C550 25 WH RO BK R550 lOOK R527 r 0525 0526 62 1N91 rIN91 C527 R526 g C526 22K 25 40 R528 R529 150 IK CW R525 3K 1 I I I I I ...

Page 54: ...W YORK WEST COAST CANADA MIDWEST RADIO WASHINGTON 8055 13th St Silver Spring Md Telephone JUniper 5 1088 NEW YORK Broad Ave at Linden Ridgefield N J Telephone N Y WOrth 4 2722 N J WHitney 3 3140 SYRACUSE Pickard Bldg East Molloy Rd Syracuse 11 N Y Telephone GLenview 4 9323 PHILADELPHIA 1150 York Rd Abington PenQa Telephone TUrner 7 8486 Philo HAncock 4 7419 FLORIDA 113 East Colonial Dri e Oflando ...