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Fluke 720A User's Manual

1. H rn S ae TT ET it E o ath eB 25 bu ABS OLUTE LINEARITY 0 1 105 1 3 HEHEHOE SH rrr IRE Som toos QONO nom mm 10 5 10 6 G 1077 wo 1074 DIAL SETTING 5 Figure 1 1 POWER COEFFICIENT OF LINEARITY 0 2 ppm of input watt maximum at dial settings of 1 1 to 0 1 0 2 108 2 ppm of input watt maximum at dial settings S of 0 1 to 0 See Figure 1 4 MAXIMUM END ERRORS Zero error at output low Zero error at input low Full scale error 0 004 ppm of input 0 05 ppm of input 0 05 ppm of input THERMAL VOLTAGES 0 5 uv maximum MAXIMUM INPUT POWER 10 watts on 1 0 INPUT terminal 11 watts on 1 1 INPUT terminal Absolute linearity is defined as the linearity between maximum and minimum output voltages MAXIMUM INPUT VOLTAGE 1000 volts on 1 0 INPUT terminal 1100 volts on 1 1 INPUT terminal 1 2 ABSOLUTE LINEARITY BREAKDOWN VOLTAGE 2000 volts to case at 10 000 feet 2500 volts to case at sea level INPUT RESISTANCE 100 kilohms 0 005 at 1 0 INPUT terminal at 25 C 110 kilohms 0 005 at 1 1 INPUT terminal at 25 C TEMPERATURE COEFFICIENT OF INPUT RESISTANCE 1 ppm C maximum
2. u iriri MA ZE T M B d ji MM MRO 2 Haast ERLE LEN TE Lb deu Eq BIHIMET 2 3 SUR HH HERE FEE I tHe AH Pn EE i mauu O O EAE A LB dup RID HME EEEE i Em HH H S T M om AGrene N 1074 E 1075 F 1076 G 107 m onmi 10000 Hi 2600011 Figure 1 2 STABILITY 28 10 BH 5 M CRINES E Ze 5 FEE a HSE Up TEE 1073 z a m 5 AU kht RIZ tei AHI HUMERIS lr prada 3 Figure 1 3 Y C 1 0 A 1072 C 10 3 DIAL SETTING 5 TEMPERATURE COEFFICIENT tila HH i E CHOLET j CI E PEE Ge MS NAGS hs TBAB DONNE ea 00 38 HT A ot 3 O i HSER T UT ET LE ite UM NIHR a lilii pali R
3. Gea etree T etus ut OS LAIA s 9 AR Te 5 pp SORT een e Senne os em z e E A AAA e A E Meets xo m ve See T err as gt O PAR RS EPP OSOS s ert x gt Pe RRA OO n bois AS e NODE RR AS ss ass Q Sasa minis lt Ass gt WA Asas a asao at aaa aaa ena E SO RR RO 2295 iim sae 099 at te 2 AN A hata PARAR o ORG eee i oe ERA e rf zi O RRA gt Doc rose E P o e tenete s t RAR is OOO eterne terere Mie Sx ii od e 2 A Raia lt gt Ss SES gt 0099s t x e 5 799 ES S em NS
4. 2 1 2 7 Ratio Errors Caused by Loading or Leakage 2 1 2 18 Temperature Control ior ue Sp M RI 2 3 2 00 Power Coefficient on 2 4 2 22 End Errors Sd cet a 2 4 2 24 Saelf Calibration wu 2 4 2 26 Check Positions of the Function Switch ee SA 2 7 2 28 Applications of the Model 720A 2 7 3 THEORY OF OPERATION o m 3 1 3 Introduction onm t 3 1 3 3 The Basic Circuit 3 1 3 6 Circuit Refinements 3 1 3 8 The Model 720A ont 3 1 Rev 1 i 720A TABLE OF CONTENTS continued SECTION TITLE 4 MAINTENANCE 4 1 Introduction nee m gt 4 4 Test Equipment Required for Maintenance 4 6 Preventive Maintenance 4 19 Calibration 4 28 Troubleshooting 4 38 Repair 4 41 Service Information 5 LIST OF REPLACEABLE PARTS 5 1 Introduction 5 3 Columnar Information 5 4 How to Obtain Parts 5 8 Serial Number Effectivity 6 OPTIONS NOT APPLICABLE 7 GENERALINFORMATION 8 SCHEMATIC DIAGRAMS PAGE 4 1 4 1 4 1 4 1 4 13 4 18 4 19 4 19 5 1 5 1 5 1 5 2 5 2 Rev 1 Rev 1 FIGURE Frontispiece 1 1 1 2 1 3 2 1 22 2 3 2
5. RENE RR MANENTE OR RN E SR n Bue E Eeee OO 2x OS DA Sasa RS AREA SS ene oe nn isin atte RN OS as RRR AE See Figure 2 7 EQUIPMENT CONNECTIONS FOR CALIBRATING A VOLTAGE DIVIDER 81055 PERE BAM RAR over veri 2222222 i 44528 RIZK kuu 2144125 xS zu TEST DIVIDER intet ue COR us 255 RD DIVIDER 4 34 ee O ici tet STANDA SALANCE ku 77 es 720A 9 ES ES 2 8 the only applications of the instrument they are the most common applications of a high accuracy Kelvin Varley divider such as the Model 720A 2 30 Calibrating a Voltage Divider 2 31 The Model 720A in company with a dc voltage source a null detector and a lead compensator can be used to calibrate voltage dividers to an accuracy of 0 1 parts per million of input Typical associated equipment for this application is listed in Figure 2 6 With this equipment the full electrical capabilities of the Model 720A Kelvin Varley Voltage Divider may be realized 2 32
6. Er Ry EUM Ru Ro R o but BL therefore 1 p Rr T and Es Bo 1 Ro Rr 2 2 Converting to errors expressed as a fraction of the input voltage the expression becomes 6 Rr If the 1 1 INPUT terminal is used then E E i IN d TUER ana O 1 1 5 1 EIN Eo EIN Using the 1 0 INPUT terminal Figure 2 2 THEVININ EQUIVALENT CIRCUIT 2 12 The following list of definitions are given for the terms used in the preceding paragraphs a Eo Nominal output voltage b Em Input voltage Error in output voltage as fraction of output 4 Divider linearity error as a fraction of output e Loading error as a fraction of output Error in output voltage fraction of input g Divider linearity error as a fraction of input Loading error as a fraction of input i 8 Divider dial setting R Divider output resistance k Ry Load resistance including leakage re sistance from the tap terminal to the di vider input terminal 720A 2 13 Output Resistance Versus Loading 2 14 The graph in Figure 2 3 illustrates the approx imate variation of output resistance with the dial setting for both the 1 0 and 1 1 INPUT terminals This resist ance is measured by shorting the input high and input low terminals and measuring the res
7. peor FOR SELF CALIBRATION Ae lt lt SSS en x ER RU Ms m ee E e SLI AS n igure MERO F en x T prevent problems from current loops connect trument to a common Ins 2 SS PS the power source On the shielded cables connect one tos s en e ea gt s gt states gt eee grounding point preverably end of the shield to ground and leave the other end open NOTE each Rev 2 720A NOTE The BRIDGE BALANCE control and R203 are now ready for the self cal procedures for A and B decades in paragraph 2 24 assuming R312 and its associated trim resistors have not shifted excessively in value If insufficient trim range remains at 1 A 2 etc the 720A should be returned to the factory for repair Perform the C decade and S3 shunt check in paragraph 4 21 prior to performing the self cal at A and B decades 4 27 4KILOHM BRIDGE STANDARD This proce dure is used to adjust the total resistance of the bridge arm used for calibration of the third decade so the bridge can be balanced to measure a nominal 4007 6 ohms Cali bration of the dec
8. MAXIMUM OUTPUT RESISTANCE 66 kilohms 1 6 MECHANICAL AND ENVIRONMENTAL SPECIFICATIONS OPERATING TEMPERATURE RANGE 0 to 50 C 32 F to 122 NOTE When the Model 720A is used at temperatures below 15 C 59 F or above 35 C 95 F the range of the calibration adjustments may be 4 5 67891 ae EBEA E s E P 1 0 1 a i i i E HH EE HE A 4567891 PPM OF INPUT E SUEDE EB DIES S 10 4 5 67891 o NODE ea oe Be EIAS ES 2290 IH PIU d EXE 104 RITA E FTH w Watu mami RH AMLO i SSE p 010 RE dB LL EH ri E e PAN i eH SSES D DIAL SETTING 5 720A met EH CUAL 1130117 HE H SEIN Hi ll deis nu BN HN 8 MALUM NEIN ODS 2 si AA CU MESAS Fr HES fe PUBS Ree Bo tre Ht Si FE SUD MA SS HEI Tui 235 MM RU
9. 4702 215269 3800P 502 4705 192500 Res met flm 4 75k 41 1 2w Type CEC TO R1090 Res ww 1002 0 5 1 2w 4707 155846 4707 155846 R1091 Res ww factory selected o R1092 Res var ww 5k 10 1w 4702 215269 3800P 502 R1093 met flm 4 75k 1 1 2w 4705 192500 Type CEC TO R1094 ww 1009 0 5 1 2w 4707 155846 4707 155846 R1095 Res ww factory selected R1096 Res var ww 10 1w 4102 215269 3800P 502 R1097 Res met flm 4 75k 1 1 2w 4705 192500 Type CEC TO ww 4009 0 25 1 2w 4707 131698 4707 131698 5 10 STOCK TOT REC ie ww factory selected var WW met flm met flm var ww met flm met flm var WW met flm met flm var ww met flm met flm var WW met flm met var WW met flm met flm var WW met flm met flm var WW met flm met flm var WW met flm met flm var WW met flm met flm var ww met flm met flm var ww 1502 20 1 1 4w 252 10 1 23 20 41 1 102 19 2582 10 1 1 4w 23 22 1 1 2w 102 1 1 2w 259 10 1 1 4w 23 20 1 1 2w 102 1 1 2w 252 10 1 1 4w 23 22 1 1 2w 102 1 1 2w 252 10 1 1 4w 23 20 1 1 2w 109 1 1 2w 259 10 1 1 4w 23 22 1 1 2w 102 1 1 2w 259 10 1 1 4w 23 22 1 1 2w 102 1 1 2w 252 10 1 1 4w 23 22 1 1 2w 102 1 1 2w 252 10 1 1 4w 23 22 1
10. Brooklyn NY 77900 Shakeproof Lock Washer Co Now 78189 77969 Rubbercraft Corp of CA Ltd Torrance CA 78189 IL Tool Works Inc Shakeproof Div Elgin IL 78277 Sigma Instruments Inc South Braintree MA 78290 Struthers Dunn Inc Pitman NJ 78553 Eaton Corp Engineered Fastener Div Cleveland OH 7 9 78592 Stoeger Industries South Hackensack NJ 79497 Western Rubber Co Goshen IN 79727 C W Industries Southampton PA 79963 Zierick Mfg Corp Mount Kisco NY 8C798 Ken Tronics Inc Milan IL 8D528 Baum gartens Atlanta GA 8F330 Eaton Corp Cutler Hammer Product Sales Office Mountain View CA 8T100 Tellabs Inc Naperville IL 80009 Tektronix Beaverton OR 80031 Mepco Electra Inc Morristown NJ 80032 Ford Aerospace amp Communications Corp Western Development Laboratories Div Palo Alto CA 80145 LFE Corp Process Control Div Clinton OH 80183 Sprague Products Now 56289 80294 Boums Instruments Inc Riverside CA 80583 Hammerlund Mfg Co Inc Paramus NJ 80640 Computer Products Inc Stevens Amold Div South Boston MA 81073 Grayhill Inc La Grange IL 81312 Litton Systems Inc Winchester Electronics Div Watertown CT 7 10 Federal Supply Codes for Manufacturers cont 81439 Therm O Disc Inc Mansfield OH 81483 International Rectifier Corp Los Angeles CA 81590 Korry Electronics Inc Seattle WA 8174
11. 1 2w 102 41 1 2w 252 10 1 1 4w 23 22 1 1 2w 102 41 1 2w 259 410 1 1 4w 23 22 1 1 2w 108 1 1 2w nd 161703 4705 200790 4705 151043 4702 161703 4705 200790 4705 151043 4702 161703 4705 200790 4705 151043 4702 161703 4705 200790 4705 151043 4702 161703 4705 200790 4705 151043 4705 200790 4705 151043 4702 161703 4705 200790 4705 151043 4702 161703 4705 200790 4705 151043 4702 161703 4705 200790 4705 151043 4102 161703 4705 200790 4105 151043 4702 163642 Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 Type CEC TO Type CEC TO Type 110 720A These resistors factory selected Replace with exact value When ordering include model serial number reference designation and all information stamped on the resistor 5 11 720A MER TOT REC USE BRIDGE P C ASSEMBLY Figure 5 4 1702 200295 1702 200295 720A 4002 R201 Res ww 39 536k matched set 2 gt R202 Res ww 39 536k matched set R203 Res var ww 1002 20 1 1 4w 4702 112797 Type 110 R204 Res ww 15 814k 0 02 1w 4707 200550 4707 200550 R205 Res var ww 1009 20
12. 720A Kelvin Varley Voltage Divider Instruction Manual P N 294058 C March 1969 Rev 2 9 74 WARRANTY Notwithstanding any provision of any agreement the following warranty is exclusive The JOHN FLUKE MFG INC warrants each instrument it manufactures to be free from defects inmaterial and workmanship under normal use and service for the period of 1 year from date of purchase This warrant y extends only to the original purchaser This warranty shall not apply to fuses disposable batteries rechargeable type batteries are warranted for 90 days or any product or parts which have been subject to misuse neglect accident or abnormal conditions of operations d In the event of failure of a product covered by this warranty John Fluke Mfg Co Inc will repair and calibrate an instrument returned to an authorized Service Facility within 1 year of the original purchase provided the warrantor s examination discloses to its satisfaction that the product was defective The warrantor may at its option replace the product in lieu of repair With regard to any instrument returned within 1 year of the original purchase said repairs or replacement will be made without charge If the failure has been caused by m suse neglect accident or abnormal conditions of operations repairs will be billed at nominal cost In such case an estimate will be submitted before work is started if requested THE FOREGOING WARRANTY IS I
13. e teeny i gt ee pm QT i x i qe 2 E ESL i m Ve E ind _ Cem rar Em m lt m 25 23 2 vO 7 23 23 2 TN 7 e R405 pioc7 acak RIOGS EM 475K 7O 4 oo lt 5 SECTA y Rioza EN RIO29 RIO3O SK 8 45K R1031 OO D 61026 5 8 45 027 co OIL TANK ad x 72 RIO73 R1074 Ris 5 2308 I 2 ARS 407 RIOTS 5 555 Kk G DIAL DIAL DIAL DIAL RIS 25 232 RWJ DIAL 4 RIO7G RIOTT RIO78 OO r S7A X SGA we SSA s lt meo T p di 4 RIN8 RUNS 2s RIZO iQ RACE nese 3 2 3 RAOS Rioss SK 475 082 100 EN pm SK R1039 CH 8 2 z203 R204 2905 loi 1 9 t v lt RUZ 7 03 ROOS reos V lt R1122 2 232 RU23 RIO84 RIOS5 40 RIOBS 2 ao I G ese RAO RIo8T S Sex A R200 r
14. x E E one s S na ea Ne 3158 217323 11 11 217315 1702 200295 Mi 3158 217307 3158 places 7 1 51 Sea 59 720 Figure 5 1 720A KELVIN VARLEY VOLTAGE DIVIDER Sheet 1 of 2 720A 14 13 3158 217612 A oe Front Panel Assembly 702 210716 Figure 5 1 7204 KELVIN VARLEY VOLTAGE DIVIDER Sheet 2 of 2 5 5 720A J10 J11 J12 J13 R1 16 17 18 19 20 21 DESCRIPTION FRONT PANEL ASSEMBLY Figure 5 2 Binding post Binding post Binding post Binding post Binding post red 1 1 INPUT red 1 0 INPUT black LOW INPUT GROUND INPUT red HIGH OUTPUT Binding post black LOW OUTPUT Binding post GROUND OUTPUT Binding post black BRIDGE DETECTOR Binding post GROUND BRIDGE DETECTOR Binding post red BRIDGE POWER Binding post black BRIDGE POWER Binding post GROUND BRIDGE POWER Res var ww 5k 3 3w BRIDGE BALANCE not illustrated Cover calibration access Handle chrome plated brass Knob A through G Knob BRIDGE BALANCE Knob FUNCTION Panel front 20 19 18 7 places Binding post red BRIDGE DETECTOR STOCK MER TOT REC NO 2811 149856 2811 149856 2811 149864 2811 155911 2811 149856 58474 BHB 10208 G22 BH
15. 2 40 The 720 may used in setup including a null detector a power supply and a standard resistor to measure an unknown resistance with a high degree of accuracy Typical associated equipment for this ap plication is listed in Figure 2 13 The unknown re sistance and the standard resistance should be in the Same order of magnitude for the best accuracy 2 41 To measure an unknown resistance connect the equipment as shown in Figure 2 14 using shielded leads Apply the positive lead from the dc voltage source to the 1 0 INPUT terminal of the Model 720A Proceed as follows and decimal ratio set on readout dials of the Model 720A at points and respectively If Rx R std is greater than 100 ohms the use of a lead compensator is desirable lead compensator is used can be made equal to 1 0000000 and can be made equal to 0000000 TYPICAL EQUIPMENT DC Voltage Source John Fluke Mfg Co Model 332B or equivalent DC Null Detector John Fluke Mfg Co Model 845AB or equivalent R std P3 If lead resistance between the resistors is made insig nificant in addition to using a lead compensator then Po P3 and the equation may be further simplified to Rx 1 R std P 1 a Set the dc voltage source to the desired test voltage CAUTION Do not exceed the current rating of the stan dard resistor
16. 8 45k 1 1 2w ww 1002 0 5 1 2w ww factory selected var ww 10 1w met flm 8 45k 1 1 2w ww 1002 0 5 1 2w ww factory selected var ww 5k 10 lw met flm 8 45k 195 1 2w ww 1009 0 5 1 2w ww factory selected var ww 5k 10 1w met flm 8 45k 105 1 2w ww 1002 0 5 1 2w ww factory selected var ww 5k 10 1w met flm 8 45k 1 1 2w ww 1002 0 5 1 2w ww factory selected var ww 10 lw met flm 8 45k 1 1 2w ww 1002 0 5 1 2w ww factory selected var ww 410 1w met flm 8 45k 1 1 2w ww 1002 0 5 1 2w ww factory selected var ww 5k 10 1w met flm 8 45k 105 1 2w ww 1000 40 5 1 2w Www factory selected var ww 5k 10 1w met flm 8 45k 1 1 2w ww 1000 0 5 1 2w ww factory selected var ww 5k 10 1w met flm 8 45k 1 1 2w ww 1009 0 5 1 2w ww factory selected ww 1009 0 5 1 2w ww factory selected ww factory selected var ww 5k 10 1w 1702 210716 720A 4001 4702 215269 4705 159475 4707 155846 V 4102 215269 4705 159475 4707 155846 V 4702 215269 4702 159475 4707 155846 V 4702 215269 4705 159475 4707 155846 V 4702 215269 4705 159475 4707 155846 L 4702 215269 4705 159475 4707 155846 e 4702 269 21 4705 159475 4707 155846 V 4702 215269 4705 159475 4707 155846 V 4702 215269 4705 159475 4707
17. Burlingame CA 24347 Penn Engineering Co S El Monte CA 24355 Analog Devices Inc Norwood MA 24444 General Semiconductor Industries Inc Tempe AZ 24546 Bradford Electronics Bradford PA 24618 Transcon Mfg Now D J Associates Inc 24655 Genrad Inc Replaced General Radio 05173 Concord MA 24759 Lenox Fugle Electronics Inc South Plainfield NJ 24796 AMF Inc Potter amp Brumfield Div San Juan Capistrano CA 24931 Specialty Connector Co Greenwood IN 24995 ECS Grants Pass OR 25088 Siemen Corp Isilen NJ 25099 Cascade Gasket Kent WA 25403 Amperex Electronic Corp Semiconductor amp Micro Circuit Div Slatersville RI 25435 Moldtronics Inc Downers Grove IL 25706 Dabum Electronic amp Cable Corp Norwood NJ 26402 Lumex Inc Bayshore NY 26629 Frequency Sources Inc Sources Div Chelmsford MA 26806 American Zettler Inc Irvine CA 27014 National Semiconductor Corp Santa Clara CA 27167 Coming Glass Works Corning Electronics Wilmington NC 21264 Molex Inc Lisle IL 27440 Industrial Screw Products Los Angeles CA 27494 Staffall Inc Providence RI 27745 Associated Spring Bames Group Inc Syracuse NY 27918 Component Parts Corp Bellmore NY 27956 Relcom Now 14482 28175 Alpha Metals Chicago IL 28198 Positronic Industries Springfield MO 28213 MN Mining amp Mfg Co Consumer Products Div 3M C
18. Co Boonton NJ 91462 Alpha Industries Inc Logansport IN 91502 Associated Machine Santa Clara CA 91506 Augat Alcoswitch N Andover MA 91507 Froeliger Machine Tool Co Stockton CA 91637 Dale Electronics Inc Columbus NE 91662 Elco Corp A Gulf Western Mfg Co Connector Div Huntingdon PA 91737 ITT Cannon Gremar Now 08718 91802 Industrial Devices Inc Edgewater NJ 91833 Keystone Electronics Corp NY NY 91836 King s Electronics Co Inc Tuckahoe NY 91929 Honeywell Inc Micro Switch Div Freeport IL Federal Supply Codes for Manufacturers cont 91934 Miller Electric Co Woonsocket RI 91967 National Tel Tronics Div of electro Audio Dynamics Inc Meadville PA 91984 Maida Development Co Hampton VA 91985 Norwalk Valve Co S Norwalk CT 92218 Wakefield Corp The Wakefield ME 92527 VTC Inc Bloomington MN 92607 Tensolite Co Div of Carlisle Corp Buchanan NY 92914 Alpha Wire Corp Elizabeth NJ 93332 Sylvania Electric Products Semiconductor Products Div Wobum MA 94144 Raytheon Co Microwave amp Power Tube Div Quincy MA 94222 Southco Inc Concordville PA 94988 Wagner Electric Corp Sub of Mcgraw Edison Co Whippany NJ 95146 Alco Electronic Products Inc Switch Div North Andover MA 95263 Leecraft Mfg Co Long Island City NY 95275 Vitramon Inc Bridgeport CT 95303 RCA Corp Receiving Tube D
19. H T HIT TT J m HH HH HH HH HH HH s E NIE ae DER BS 1 O88 I ll b 2 HTr r NS r TT rc HH HILL HH SICH 7 T T T O I HEHHE NP o 10 ES Ht tt ttt EA ooo ae LI UT Ne T ERP ID PE FE OCs s 3 P EIL Nt AH Ht L Et Hts II Ht 4 ss tt PH R T le eee fei wu x O 5 sett t t pc Pi TEER reese Gam SS IEEE FP SE P E O ee AAA 2 TIT THI TT T P Il ee AA Il I j ES rr s ME Ry sewa E N 2 e Q 10 lt si mum mes EE E cose CIEN EL EI ooo cee ae aa 1 1 O 1 1 BE GSE ee SEE 000 OS O ee L elllllll m E Ill pee T Ba ER Ku Pr IT T 18 Es EE j y HHH III I T I Jj I sm ttt t ER HH ERR B TERRE mH s 1 1 F H ES HE IE
20. Thus all steps are kept equal Each step of the second decade is two kilohms The four kilohms spanned by the switch contacts is shunted by the four kilohms effective resistance of the third decade Similarly 800 ohms of the third decade is shunt ed by the 800 ohms total resistance of the fourth decade 3 6 CIRCUIT REFINEMENTS 3 7 Although the simplified Kelvin Varley divider shown in Figure 3 1 shows all of the essential details of the basic circuit a number of common design refine ments should be mentioned The latter decades may employ step resistors which are all of the same value and a shunt across the entire decade to reduce the effec tive decade resistance to the proper value In Figure 3 1 this could be accomplished by using 400 ohm re sistors in the fourth decade with a 1000 ohm shunt across the decade to reduce the effective resistance of 720A Section 3 Theory of Operation the decade to 800 ohms This avoids the necessity of using resistors of very small value in the latter decades Usually each step of at least the first decade will con sist of two equal resistors matched for equal but op posite temperature coefficients This matching tends to produce a zero temperature coefficient for each step and for the entire decade which reduces the nonlin earity caused by uneven temperature when power is applied Some Kelvin Varley dividers have adjustable trimmer resistors in the first or even the second and third
21. 2N3565 Q107 108 for 845AR s n 168 If you must order structural parts not listed in the parts list describe the part as completely as possible A sketch of the part showing its location to other parts of the instrument is usually most helpful 5 8 SERIAL NUMBER EFFECTIVITY 5 9 A Use Code column is provided to identify cer tain parts that have been added deleted or modified during production of the Model 720A Each part for which a use code has been assigned may be identified with a particular instrument serial number by consulting the Use Code Effectivity List below All parts with no code are used on all instruments with serial numbers above 123 New codes will be added as required by instrument changes USE CODE EFFECTIVITY No Code Model 720A serial number 123 and on A Model 720A serial number 536 and on 5 2 Rev 2 720A STOCK MFR TOT REC USE IPTI KELVIN VARLEY VOLTAGE DIVIDER Figure 5 1 Front Panel Assembly See Figure 5 2 Trimmer P C Assembly See Figure 5 3 Bridge P C Assembly See Figure 5 4 Resistor Can Assembly If a resistor in this assembly requires replacement the entire instrument must be returned to the factory for 1702 210716 120 4001 1702 200295 720A 4002 3158 217612 720A 4018 1702 210716 1702 200295 3158 217612 1 1 2 3 4 5 6 7 Rev 2 repair and recalibration Switch A DECADE rotary 3p 12 pos 3 sect Decade Switch
22. 55943 D J Associates Inc Replaced Transcon Mfg 24618 Fort Smith AZ 56282 Utek Systems Inc Olathe KS 56289 Sprague Electric Co North Adams MA 56365 Square D Co Corporate Offices Palatine IL 56375 WESCORP Div Dal Industries Inc Mountain View CA 56481 Shugart Associates Sub of Xerox Corp Sunnyvale CA 56637 RCD Components Inc Manchester NH 56708 Zilog Inc Campbell CA 56856 Vamistor Corp of TN Sevierville TN 56880 Magnetics Inc Baltimore MD 57026 Endicott Coil Co Inc Binghamton NY 57053 Gates Energy Products Denver CO 57170 Cambridge Thermionic Cambridge MA Replaced by 71279 Interconnection Products Inc 57668 R ohm Corp Irvine CA 57962 SGS Thomson Microelectronics Inc Montgomeryville PA 58014 Hitachi Magnalock Corp Now 12581 58104 Simco Atlanta GA 58364 BYCAP Inc Chicago IL 58451 Precision Lamp Cotat CA 58474 Superior Electric Co Bristol CT 58614 Communications Instruments Inc Fairview NC 59124 KOA Speer Electronics Inc Bradford PA 59422 Holmberg Electronics Irvine CA 7 8 Federal Supply Codes for Manufacturers cont 59610 Souriau Inc Valencia CA 59635 HV Component Associates Howell NJ 59640 Supertex Inc Sunnyvale CA 59660 Tusonix Inc Tucson AZ 59730 Thomas and Betts Corp IA City IA 59831 Semtronics Corp Watchung NJ 611053 American Components Inc an I
23. Assembly See Figure 5 5 Decade Switch Assembly See Figure 5 6 and Decades Switch Assy See Figure 5 7 Switch FUNCTION 5p 11 pos 5 sect Switch INTERNAL FUNCTION 4p 3 pos 2 sect Bushing dial Bushing dial Coupler switch not illustrated Cover bottom not illustrated Cover internal function switch Cover top not illustrated Detent switch Detent internal function switch not illustrated Dial 0 0 1 0 Cal Dial 0 Cal Dial 0 Dial 0 9 Foot rubber not illustrated Heat sink resistor Knob INTERNAL FUNCTION Panel rear 5105 220012 5110 217307 720A 4004 5110 217315 720A 4005 5110 217323 720A 4006 5105 220020 5107 218560 2502 130435 3153 130252 2402 200592 3156 217117 3156 217521 3156 217125 5108 218578 5108 218552 2403 208611 2403 208595 2403 208603 2403 208587 2819 103309 3156 217463 2405 170050 3156 217075 5105 220012 5110 217307 5110 217315 5110 217323 5105 220020 5107 218560 2502 130435 3153 130252 2402 200592 3156 217117 3156 217521 3156 217125 5108 218578 5108 218552 2403 208611 2403 208595 2403 208603 2403 208587 9102 W 3156 217463 2405 170050 3156 217075 m N y pb 65 e 5 3 places 0 1 11 TU Mee RESINA ta reat pe MIRA RU SR
24. At this point the ratio will be high As the switch is advanced so the contacts no longer span the open resistor the measured output will be the source voltage If a decade shunt is open all steps of the decade will be equal but resistance of the decade will be high This will cause nonlinearity in the pre ceding decade which may be observed by dialing it up ward from zero Below the midpoint the output will be high above the midpoint the output will be low 4 34 An over value resistor in any decade will reduce the proportion of all other steps and increase the pro portion of the step containing the over value resistor In all decades except the seventh this increase will be seen at two adjacent switch positions because the switch contacts span two resistance steps In the seventh dec ade there will be only one over value step If a decade shunt is over value all steps of the decade will be equal but the resistance of the decade will be high This will cause nonlinearity in the preceding decade which may be observed by dialing it upward from zero Below the midpoint the output will be high above the midpoint the output will be low 4 35 An under value resistor in any decade will in crease the proportion of all other steps and decrease the proportion of the step containing the under value resistor In all decades except the seventh this de crease will be seen at two adjacent switch positions In the seventh decade there will b
25. Co Model 332B or Model 412B DC Null Detector John Fluke Mfg Co Model 845AB Lead Compensator John Fluke Mfg Co Model 721A Standard Divider John Fluke Mfg Co Model 720A Standard Divider 11 Steps Decade Resistance Standard Electro Scientific Industries Model RS925A SPECIFICATIONS REQUIRED Source of 0 to 1100 vdc Accuracy at least 0 25 Stability at least 0 005 per hour Sensitivity at least 10 microvolts full scale 10 Megohm input Resistance Resolution of 0 1 milliohm Ratio capability of 110 1 Ratio accuracy of 0 1 ppm of input Ratio accuracy of 0 05 ppm of input 4007 6 ohms 10 000 ohms Accuracy of 20 ppm Figure 4 1 TEST EQUIPMENT REQUIRED FOR MAINTENANCE the simple leakage resistance test described in this para graph This test should also be performed after cleaning to assure that all contamination has been removed To measure leakage resistance proceed as follows a Place the Model 720A on a sheet of dielectric b Use teflon insulated wire to connect the Model 720A a 1000 volt source Model 332B and a null detector Model 845AB as shown in Figure 4 2 Connect shunt resistor across the input of the null detector to bring its input resistance to one megohm on the one millivolt range The value required for theModel 845AB is 1 1 megohms d Turn on the 1000 volt supply and read the null detector An indication of 1 millivolt corresponds to leakage resistance of
26. Concord MA 05236 Jonathan Mfg Co Fullerton CA 05245 Corcom Inc Libertyville IL 05276 ITT Pomona Electronics Div Pomona CA 05277 Westinghouse Elec Corp Semiconductor Div Youngwood PA 05347 Ultronix Inc Grand Junction CO 05397 Union Carbide Corp Materials Systems Div Cleveland OH 05571 Sprague Electric Co Now 56289 05574 Viking Connectors Inc Sub of Criton Corp Chatsworth CA 05791 LYN TRON Burbank CA 05820 EG amp G Wakefield Engineering Wakefield MA 05839 Advance Electrical Chicago IL 05972 Loctite Corp Newington CT 06001 General Electric Co Electric Capacitor Product Section Columbia SC 06141 Fairchild Weston Systems Inc Data Systems Div Sarasota FL 06192 La Deau Mfg Co Glendale CA 06229 Electrovert Inc Elmsford NY 06383 Panduit Corp Tinley Park IL 06473 Bunker Ramo Corp Amphenol NA Div SAMS Operation Chatsworth CA 06540 Mite Corp Amatom Electrical Div 06555 Beede Electrical Instrument Penacook NH 06665 Precision Monolithics Sub of Boums Inc Santa Clara CA 06666 General Devices Co Inc INpolis IN 06739 Electron Corp Littleton CO 06743 Gould Inc Foil Div Eastlake OH 06751 Components Inc Semcor Div Phoenix AZ 06776 Robinson Nugent Inc New Albany IN 06915 Richco Plastic Co Chicago IL 06961 Vernitron Corp Piezo Electric Div Bedford OH 06980 EIMAC
27. Corp Westbury Long Island N Y 32559 Bivar Santa Ana CA 32719 Siltronics Santa Ana CA 32767 Griffith Plastics Corp Burlingame CA 32879 Advanced Mechanical Components Northridge CA 32897 Murata Erie North America Inc Carlisle Operations Carlisle Pennsylvania 32997 Bourns Inc Tnmpot Div Riverside CA 33025 M A ComOmni Spectra Inc Replacing Omni Spectra Microwave Subsystems Div Tempe AZ 33096 CO Crystal Corp Loveland CO 33173 General Electric Co Owensboro KY Federal Supply Codes for Manufacturers cont 33246 Epoxy Technology Inc Billerica MA 33292 Pioneer Sterilized Wiping Cloth Co Portland OR 33297 NEC Electronics USA Inc Electronic Arrays Inc Div Mountain View CA 33919 Nortek Inc Cranston RI 34114 Oak Industries Rancho Bemardo CA 34263 CTS Electronics Corp Brownsville TX 34333 Silicon General Inc Garden Grove CA 34335 Advanced Micro Devices AMD Sunnyvale CA 34359 MN Mining amp Mfg Co Commercial Office Supply Div Saint Paul MN 34371 Harris Corp Harris Semiconductor Products Group Melbourne FL 34576 Rockwell International Corp Newport Beach CA 34641 Instrument Specialties Euless TX 34649 Inte Corp Santa Clara CA 34802 Electromotive Inc Kenilworth NJ 34848 Hartwell Special Products Placentia CA 35009 Renfrew Electric Co Ltd IRC Div Toronto Ontario Canada 35986 Am
28. DEVICES USE A HIGH RESIS 1 MINIMIZE HANDLING TANCE GROUNDING WRIST STRAP 2 KEEP PARTS IN ORIGINAL CONTAINERS UNTIL READY FOR USE 4 HANDLE S S DEVICES BY THE BODY Page 1 of 2 5 USE STATIC SHIELDING CONTAINERS FOR HANDLING AND TRANSPORT 6 DO NOT SLIDE S S DEVICES OVER ANY SURFACE 7 AVOID PLASTIC VINYL AND STYROFOAM IN WORK AREA PORTIONS REPRINTED WITH PERMISSION FROM TEKTRONIX INC AND GENERAL DYNAMICS POMONA DIV Dow Chemical Page 2 of 2 10 11 WHEN REMOVING PLUG IN ASSEMBLIES HANDLE ONLY BY NON CONDUCTIVE EDGES AND NEVER TOUCH OPEN EDGE CONNECTOR EXCEPT AT STATIC FREE WORK STATION PLACING SHORTING STRIPS ON EDGE CONNECTOR HELPS TO PROTECT INSTALLED SS DEVICES HANDLE S S DEVICES ONLY AT A STATIC FREE WORK STATION ONLY ANTI STATIC TYPE SOLDER SUCKERS SHOULD BE USED ONLY GROUNDED TIP SOLDERING IRONS SHOULD BE USED A complete line of static shielding bags and acces sories is available from Fluke Parts Department Telephone 800 526 4731 or write to JOHN FLUKE MFG INC PARTS DEPT M S 86 9028 EVERGREEN WAY EVERETT WA 98204 J0089D 07U8604 SE EN Litho in U S A Rev 1 MAR 86 720A Section 2 Operating Instructions 2 1 INTRODUCTION 2 2 Although the Model 720A is a primary ratio standard it has the versatility necessary for use ina wide variety of measurement and control applications In most applications the divider is used as an
29. For example if the readout dials are set at 7500055 and the input is 11 volts the unknown voltage is 7 500055 volts Rev 1 720A D id mre Baa oe s BB SOB LE 39523 HER WPLSRHLE SRL Ripe MG 01141098 STANDARD CELL ENCLOSURE BARE 1083888 CH ma PONES 38 Chie GATER ELL eem m 572 SG FEAT Wes 14910 5 Qui CETL EIOR 84 U UNKNOWN DC VOLTAGE 3594 o ERGE BRAKE 332 o 3 SSS s G 5 6 33583583 ESSE ist i em 2 5 uem S ee ee ee o S o 5 ee S E gt rer er Ee Era at 8 5 E S w A Y E o Y vw F YE yg CASES S Susy 22356583588 2 11 Figure 2 10 EQUIPMENT CONNECTIONS FOR VOLTAGE MEASUREMENTS Sheet 1 of 2 Rev 2 720A NULL D dal 7 LEAD A 845 STD ELE LEAD B UNKNOWN 720A 750A 3328 DC K V VOLTAGE REFERENCE VOLTAGE VOLTAGE DIVIDER DIVIDER STANDARD Figure 2 10 EQUIPMENT CONNECTIONS FOR VOLTAGE MEASUREMENTS Sheet 2 of 2 2 39 Measuring Unknown Resistance
30. Return the A decade to zero upon completion of the CAL position adjustment i Set the power supply output to 10 volts j Adjust the BRIDGE BALANCE to obtain a null 720A k Set the FUNCTION switch to CAL B and adjust the associated variable resistor BO to produce a null 1 microvolt NOTE As the procedure is continued occasionally re turn the FUNCTION switch to CAL A and re check bridge balance 1 In turn advance B decade one position B1 through B CAL and adjust the associated variable resistor m Return decade to zero upon completion of the CAL position adjustment n Set the FUNCTION switch to CAL 51 and adjust variable resistor 51 for a null 1 microvolt Set the power supply to 20 volts p Set the decade to 0 and set the FUNCTION switch to CAL A q Adjust the BRIDGE BALANCE control for a null Set the FUNCTION switch to CAL 52 and adjust variable resistor S2 for a null x0 5 microvolt s Set the FUNCTION switch to OPR and disconnect the test units The self calibration is complete 2 26 CHECK POSITIONS OF THE FUNCTION SWITCH 2 27 Check positions CK B etc are provided on the FUNCTION switch to permit checking the linearity of each decade from the front panel This linearity check is a maintenance procedure It should not be undertaken as a part of operation 2 28 APPLICATIONS OF THE MODEL 720A 2 29 The following paragraphs give general instru
31. SETTINGS STANDARD 120 DIVIDER 1 0 900000 0 910000 O 920000 930000 940000 950000 960000 970000 8 980000 9 990000 999999X 99999X 98999X 9 8 97999x 96999X 95999X 94999X 93999X 92999X 91999X 90999X gt la la lo ls lo lo ls lo la ls lo ls 15 15 ls 15 Figure 4 8 Turn the FUNCTION switch to CK E Set the standard divider to zero Set the divider under test to 1 0 999000 Place the null detector in the zero mode adjust it for zero deflection and return it to operating mode Adjust the LOW BALANCE controls of the lead compensator to obtain a zero indication on the null detector at au av aw PERMISSIBLE DEVIATION PPM of INPUT to DECADE MAX TEST VOLTAGE 0 100V C DECADE LINEARITY TEST Turn the HIGH BALANCE COARSE control to the same setting as the LOW BALANCE COARSE control Set the standard divider to full scale Set the divider under test to 1 0 99999X Adjust the HIGH BALANCE FINE control to obtain a zero indication on the null detector Set the divider under test back to 1 0 999000 and set the standard divider back to zero 720A SETTINGS PERMISSIBLE STANDARD DEVIATION MAX DIVIDER PPM of INPUT to TEST VOLTAGE DECADE 8 9 999999X 9 8 Figure 4 9 DECADE LINEARITY TEST ay Re adjust the LOW BALANCE FINE control if bd Place the null detector in the zero mod
32. See Varian San Carlos CA Federal Supply Codes for 07047 Ross Milton Co The Southampton PA 07138 Westinghouse Electric Corp Industrial amp Govemment Tube Div Horseheads NY 07233 Benchmark Technology Inc City of Industry CA 07239 Biddle Instruments Blue Bell PA 07256 Silicon Transistor Corp Sub of BBF Inc Chelmsford MA 07261 Avnet Corp Culver City CA 07263 Fairchild Semiconductor North American Sales Ridgeview CT 07344 Bircher Co Inc The Rochester NY 07374 Optron Corp Woodbridge CT 07557 Campion Co Inc Philadelphia PA 07597 Bumdy Corp Tape Cable Div Rochester NY 07716 TRW Inc Can use 11502 IRC Fixed Resistors Burlington Burlington VT 07792 Lerma Engineering Corp Northampton MA 07810 Bock Corp Madison WI 07910 Teledyne Semiconductor Min View CA 07933 Raytheon Co Semiconductor Div Mountain View CA 08FG6 Calmos Systems Inc Kanata Ont Canada 080A9 Dallas Semiconductor Dallas TX Manufacturers cont 08111 MF Electronics New Rochelle NY 08235 Industro Transistor Corp Long Island City NY 08261 Spectra Strip An Eltra Co Garden Grove CA 08445 Electri Cord Mfg Inc Westfield PA 08530 Reliance Mica Corp Brooklyn NY 08718 ITT Cannon Electric Phoenix Div Phoenix AZ 08806 General Electric Co Minature Lamp Products Cleveland OH 08863 Nylomatic Fallsington PA 08988 Skotti
33. Support Scientific amp Industrial 25 27 Paul St North North Ryde N S W 2113 Tel 61 02 888 8222 Austria Oesterreichische Philips Industrie Unternehmensbereich Prof Systeme Triesterstrasse 66 Postfach 217 A 1101 Wein Tel 43 222 60101 x1388 Belgium Philips amp MBLE Associated S A Scientific amp Industrial Equip Div Service Department 80 Rue des deux Gares B 1070 Brussels Tel 32 2 525 6111 Brazil Hi Tek Electronica Ltda Al Amazonas 422 Alphaville CEP 06400 Barueri Sao Paulo Tel 55 11 421 5477 Canada Fluke Electronics Canada Inc 400 Britannia Rd East Unit 1 Mississauga Ontario L4Z 1X9 Tel 416 890 7600 Chile Intronica Chile Ltda Casilla 16228 Santiago 9 Tel 56 2 2321886 2324308 China Fluke International Corp P O Box 9085 Beijing Tel 86 01 512 3436 Colombia Sistemas E Instrumentacion Ltda Carrera 13 No 37 43 Of 401 Ap Aereo 29583 Bogota DE Tel 57 232 4532 Denmark Philips A S Technical Service amp E Strandlodsveij 1A PO Box 1919 DK 2300 Copenhagen S Tel 45 1 572222 Ecuador Proteco Coasin Cia Ltda P O Box 228 A Ave 12 de Octubre 2285 y Orellana Quito Tel 593 2 529684 Egypt Philips Egypt 10 Abdel Rahman el Rafei st el Mohandessin P O Box 242 Dokki Cairo Tel 20 2 490922 England Philips Scientific Test amp Measuring Division Colonial Way Watford Hertforshire WD2 4TT Tel 44 923 40511 Fin
34. Textool Co Houston TX 53184 Xciton Corp Lathan NY 53217 Technical Wire Products Inc Santa Barbara CA 53342 Opt Industries Inc Phillipsburg NJ 53673 Thompson CSF Components Corp Semiconductor Div Conaga Park CA 53718 Airmold W R Grese amp Co Roanoke Rapids NC 53848 Standard Microsystems Hauppauge NY 53894 AHAM Inc RanchoCA CA 53944 Glow Lite Pauls Valley OK 54178 Plasmetex Industries Inc San Marcos CA 54294 Shallcross Inc Smithfield NC 54453 Sullins Electronic Corp San Marcos CA 54473 Matsushita Electric Corp Panasonic Secaucus NJ 54492 Cinch Clamp Co Inc Santa Rosa CA 54583 TDK Garden City NY 54590 RCA Corp Distribution amp Special Products Cherry Hill NY 54869 Piher Intemational Corp Arlington Heights IL 54937 DeYoung Mfg Bellevue WA 54590 RCA Corp Electronic Components Div Cherry Hill NJ 55026 American Gage amp Machine Co Simpson Electric Co Div Elgin IL 55112 Plessey Capacitors Inc Now 60935 55261 LSI Computer Systems Inc Melville NY 55285 Bercquist Co Minneapolis MN 55322 Samtech Inc New Albany IN 55408 STI CO Industries Co Buffalo NY 55464 Central Semiconductor Corp Hauppauge NY 55557 Microwave Diode Corp W Stewarstown NH 55566 RA F Electronic Hardware Inc Seymour CT 55576 Synertek Santa Clara CA 55680 Nichicon America Corp Schaumburg IL
35. To calibrate a voltage divider connect the equip ment as shown in Figure 2 7 and proceed as follows NOTE Figure 2 8 is a schematic diagram of the test setup obtained by interconnecting the equip ment as shown in Figure 2 7 a Set both dividers to zero b Turn all equipment on and allow it to warm up until it reaches temperature equilibrium c Place the null detector in zero mode adjust it for zero deflection and return it to operating mode d Adjust the LOW BALANCE controls of the lead compensator to obtain a zero indication on the null detector e Turn HIGH BALANCE COARSE control to the same setting as the LOW BALANCE COARSE con trol HIGH BALANCE PART 721A LEAD COMPENSATOR R LEAD NULL DETECTOR TEST DIVIDER RLEAD LOW BALANCE PART 721 LEAD COMPENSATOR 720A NOTE If the dividers are set from one calibration point to the next while the test setup is energized the null detector meter will require several seconds to recover between readings Measurement may be performed more rapidly if the VOLTAGE switch of the lead compensator is turned to OFF before switching Measurement may be speeded further by turning the ZERO OPR switch of the null detector to ZERO during switching This prevents the transient caused by turning the voltage on from saturating the null detector amplifier Set both dividers to full scale and adjust the HIGH BALANCE FINE control to obtain
36. Yit 38 8 eem ve VENE 1885 EA STANDARD DIVIDER SIGUR 1758 FEE t preferably connect one on the power source On the shielded cables end of the sh ield to ground To prevent problems from current loops connect ME Rate E each instrument to a common and leave the other end open grounding poin NOTE k a OS ots oo SOOKE ws ME SOR OS REN 2 z 2 teta lt ee gt s te us Css tas s 55 Sree SSS m 220 ue Sum 555 22222 x es 2 Q i s maaa 25000 e 500 5 es rs ete 7 5 295 00 ESPERO 28588 538 5 RARAS SR ee 9888895559 k PROCES o ig Figure 4 3 EQUIPMENT CONNECTIONS FOR LINEARITY COMPARISON TEST 4 CAUTION Great care should be used to avoid excessive use of contact lubricant on the switches of the Model 720A The contacts should not be lub ricated unless there is evidence of irregular operation Before applying the lubricant clean the switch
37. a zero indication on the null detector Set both dividers to zero and re adjust the LOW BALANCE FINE control if necessary to obtain a zero indication on the null detector Set both dividers to the first calibration point Observe the null detector and adjust the Model 720A to obtain a zero indication on the null detector The difference between the setting of the Model 720A and the nominal value of the calibration point is the error of the divider being calibrated expressed as a decimal fraction of the input Find the error at each calibration point until the calibration is complete R LEAD STANDARD DIVIDER 720A RLEAD Figure 2 8 SIMPLIFIED SCHEMATIC DIAGRAM OF VOLTAGE DIVIDER CALIBRATION 720A TYPICAL EQUIPMENT DC Voltage Source John Fluke Mfg Co Model 332Bor equivalent DC Null Detector 2 required John Fluke Mfg Co Model 845AB or equivalent Standard Cell Guildline Instruments Model 9152 or equivalent DC Reference Voltage Divider John Fluke Mfg Co Model 750A or equivalent J REQUIRED SPECIFICATIONS Output voltage from 0 to 1100 volts Stability of 0 0015 per hour Output ripple less than 40 uv rms 1 uv full scale sensitivity 10 megohms input resistance At least three saturated cells Accuracy of 0 0005 Output accuracy of 10 ppm Input and output voltage Rating of 1100V dc Figure 2 9 TYPICAL ASSOCIATED EQUIPMENT FOR MEASURING UNKNOWN VOLTAGES 2 33 Measuring
38. divider calibration make the linearity measurements given in Figure 4 12 The null detector indications must be within 4 21 Divider Calibration the limits listed in the permissible deviation umn coium 4 22 This procedure is used to adjust the linearity by Disconnect the test equipment and return the FUNC of the A B and C decades of the Model 720A so Rev 2 4 13 720A STANDARD DIVIDER 999999X SETTINGS PERMISSIBLE DEVIATION MAX PPM of INPUT to TEST VOLTAGE DECADE Figure 4 12 DECADE LINEARITY TEST that any readout setting is accurate within 0 1 ppm of input This procedure consists of two parts calibration of the C decade and 53 shunt and calibration of the and decades and their shunts The latter is the self calibration procedure which is performed from the front panel 4 23 calibrate decade and 83 shunt pro Turn the B decade switch to the blank position and apply 10 volts from the voltage source Adjust the BRIDGE BALANCE control to obtain a null indication 10 microvolts NOTE If the null meter cannot be nulled using the Bridge Balance Control perform the Bridge NOTE Calibration Procedure paragraph 4 25 ceed as follows Insure the system has the correct connections and ground as shown in Figure 4 14 a Turn the FUNCTION switch to OPR turn the internal FUNCTION switch
39. ei MESE 107 Ht ttt HA HH HN O S H P PPEP 1 E S HH CR FO a T EEES 0 I IT 1px n oo HH 444 HI BENE sss 10 ED EROS 5 6 559 GO SN ND UL 5 T Ht Ep P E S WFE SE SEED sHrrT L 1 H r T TT L L T rC L 4H 94499 HH GC T LL HH es E a HEI H I iN UNES Set ET Hh ce O MS TT ha A AE EA 0 7 5 I 1 eres Sas LE j m tt EHI RUNG ER E HH HIT TL E II HAM M HH HH AHHH Gn Ht tt HH r T Ili j T l l1 S TL 03 IIT T L See Apr Lc HH S u umo Tu o3 i 107 e DIAL SETTING 5 1 0 INPUT OR 1 1 INPUT Figure 2 4 APPROXIMATE VARIATION OF MINIMUM LOAD RESISTANCE FOR 0 03 PPM OF INPUT LOADING ERROR 2 5 720A L 3 2184 KABA VOLTAGE Hi 1000V 2 Cy 2284 KEL FUNCTION ki see oh i Gi Si i 14 4 5 2 9 s 9 Figure 2 5 CONNECTIONS FOR DETERM
40. nii ui M DEP T ita 5 s 4 67 PPM OF INPUT E POWER d pc 0 0 2 10S 2 WATT uu UWE RH 1 gb in M 103 i HM CINE uin H i ain He He a I n o n bi THI IEEE 1 35 1074 HERE Hee ota LE Essl Enni 1079 tit i ae m N n Y n N 5 9 og m N ze 1 0 10 1 B 10 2 107 D 10 E 10 5 10 G 10 7 DIAL SETTING S Figure 1 4 POWER COEFFICIENT 1 4 static awareness A Message From John Fluke Mfg Co Inc Some semiconductors and custom IC s can be damaged by electrostatic discharge during handling This notice explains how you can minimize the chances of destroying such devices by 1 Knowing that there is a problem 2 Learning the guidelines for handling them 3 Using the procedures and packaging and bench techniques that are recommended The Static Sensitive S S devices are identified in the Fluketechnical manual parts list with the symbol The following practices should be followed to minimize damage to S S devices lt 3 DISCHARGE PERSONAL STATIC BEFORE HANDLING
41. positions of the FUNC TION switch are provided to permit access to the individual decades of the Model 720A under test so that each may be checked against the first decade of the standard divider test the linearity of each decade individually proceed as follows 4 6 Change the test setup to that shown in Figure 4 5 NOTE Figure 4 6 is a schematic diagram of the test set up obtained by interconnecting the equipment as shown in Figure 4 5 Turn the FUNCTION switch to CK B Set the standard divider to zero Set the divider under test to 1 0 000000 Set the voltage source to the desired test voltage CAUTION Do not exceed the maximum test voltages listed in Figures 4 7 through 4 12 Place the null detector in the zero mode adjust it for zero deflection and return it to operating mode Adjust the LOW BALANCE controls of the lead compensator to obtain a zero indication on the null detector Turn the HIGH BALANCE COARSE control to the same setting as the LOW BALANCE COARSE control NOTE If the dividers are set from one calibration point to the next while the test setup is energized the null detector meter will require several seconds to recover between readings Measurement may be performed more rapidly if the VOLTAGE switch of the lead compensator is turned to OFF before switching Measurement may be speeded further by turning the ZERO OPR switch of the null detector to ZERO during switching This pre
42. problems shielded cables i ground each instrument to a common end of the shield to ground and leave the other end open from current loops NOTE 2 15 2 16 Figure 2 14 EQUIPMENT CONNECTIONS FOR DETERMINING AN UNKNOWN RESISTANCE VALUE Sheet 2 of 2 Rev 2 INTRODUCTION 3 2 The Kelvin Varley divider is a resistive circuit used primarily as a ratio standard It is capable of dividing the input voltage with high resolution usually to six or seven decimal places and with high accuracy usually a few parts per million 3 3 THE BASIC CIRCUIT 3 4 Figure 3 1 is a simplified schematic diagram of a basic Kelvin Varley divider This simplified divider is capable of dividing the input voltage into 10 000 parts It consists of four decades or resistive dividers each of which divides its input voltage into 10 equal parts 104 10 000 3 1 3 5 For a decade to divide the voltage across it into 10 equal parts it must consist of 10 equal resistances Placing the resistance of succeeding decade in parallel with a portion of the resistance of a decade reduces the effective resistance of that portion Referring to Figure 3 1 notice that the shunted resistance in the first dec ade is 20 kilohms and that each of the other steps is 10 kilohms The 20 kilohms in the first decade is shunted by the 20 kilohms total effective resistance of the sec ond decade resulting in a total effective resistance of 10 kilohms for that step
43. standards The linearity has a small power derating coefficient of 0 2 ppm per watt which is a chieved by matching the resistors temperature coef ficients close to zero This permits operation at up to 1100 volts and 11 watts 1 3 The Model 720A has two high input terminals The terminal labeled INPUT 1 0 is for general use in all Kelvin Varley applications for which direct reading in ratio is desired The terminal labeled INPUT 1 1 is used for voltage measurement applications when both direct reading in voltage and over ranging are desired An example of this application is the measurement of standard cell voltages Use of the 1 1 INPUT at a level of 1 1 volts in this application results in divider reso lution of 0 1 microvolt and allows comparison of stand ard cells to within 1 microvolt 1 4 Only thoroughly aged resistors of the highest quality are used in the Model 720A Kelvin Varley Di vider result linearity change per year will not exceed one part per million unless the instrument is subjected to abuse To assure that the divider remains within its specifications throughout its useful life ad justments are provided for the resistors of the first three decades The third decade adjustments nor mally will be used only during annual calibration Per forming the self calibration procedure sets the adjust ments of the first two decades With reasonable care these adjustments will provide instrument accuracy of 0 1 par
44. stop If the indication does not change smoothly sweep R203 from stop to stop several times Adjust R203 to obtain an indication of 0 100 microvolts Select the one millivolt range on the null detector Vary the Bridge Balance control while observing the null detector When the electrical center is ob tained leave the BRIDGE BALANCE control at that position Re adjust R203 to obtain an indication of 0 100 microvolts Calibration of the 10 kilohm bridge standard is complete Rev 2 720A f 4 16 Figure 4 13 INTERNAL FUNCTION SWITCH Adjust the Bridge Balance control to the center of its travel range NOTE BRIDGE BALANCE is a concentric control with both a Fine and Coarse range on the same control knob Observe the null detector and sweep R203 the bridge circuit board slowly from stop to stop If the indication does not change smoothly sweep R203 from stop to stop several times Adjust R203 to obtain an indication of 0 100 microvolts Select the one millivolt range on the null detector Vary the Bridge Balance control while observing the null detector When the electrical center is ob tained leave the BRIDGE BALANCE control at that position Re adjust R203 to obtain an indication of 0 100 microvolts Calibration of the 10 kilohm bridge standard is complete Rev 2 E A 7 332B BE e 2222 s fe gt teens 1 s
45. to CAL C exercise the C decade switch by turning it twice through all positions and set the readout to 0000000 b Connect the voltage source to the red and the black BRIDGE POWER binding posts Connect null detector to the BRIDGE DETEC TOR binding posts The guard terminal of the null detector must be connected to the common terminal 4 14 Locate the C O trimmer R1130 on the circuit board and sweep it slowly from stop to stop while observing the null detector If the indica tion does not change smoothly sweep it from stop to stop several times Set the null detector to the 30 microvolt range and adjust the C O trimmer to obtain an indica tion of 0 10 microvolts Observe the null detector and tap the trimmer the indication should remain within 10 of zero Rev 2 i Use the following procedure to calibrate the C deck switch positions 1 through CAL 1 Turn C deck switch clockwise to the next position to be calibrated 2 Observe the null detector and slowly sweep the trimmer corresponding to the switch position C 1 through C CAL from stop to stop If the indication does not change smoothly sweep the trimmer from stop to stop several times 3 Observe the null detector and adjust the trimmer to obtain an indication of 0 10 microvolts 4 Observe the null detector and tap the trim mer the indication should stay within 10 microvolts of the zero 5 Turn th
46. 0 National Semiconductor Corp Danbury CT 7 3 12060 Diodes Inc Northridge CA 12136 PHC Industries Inc Formerly Philadelphia Handle Co Camden NJ 12300 Canada Ltd Potter Brumfield Guelph Ontario Canada 12323 Practical Automation Inc Shelton CT 12327 Freeway Corp Cleveland OH 12406 Elpac Electronics Inc Santa Ana CA 12443 Budd Co The Plastics Products Div Phoenixville PA 12581 Hitachi Metals Inernational Ltd Hitachi Magna Lock Div Big Rapids MO 12615 US Terminals Inc Cincinnati OH 12617 Hamlin Inc LaKe Mills WI 12673 Wesco Electrical Greenfield MA 12697 Clarostat Mfg Co Inc Dover NH 12749 James Electronic Inc Chicago IL 12856 MicroMetals Inc Anaheim CA 12881 Metex Corp Edison NJ 12895 Cleveland Electric Motor Co Cleveland OH 12954 Microsemi Corp Components Group Scottsdale AZ 12969 Unitrode Corp Lexington MA Federal Supply Codes for 13050 Potter Co Wesson MS 13103 Thermalloy Co Inc Dallas TX 13327 Solitron Devices Inc Tappan NY 13511 Bunker Ramo Corp Amphenol Cadre Div Los Gatos CA 13606 Sprague Electric Co Use 56239 13689 SPS Technologies Inc Hatfield NJ 13764 Micro Plastics Flippin AZ 13919 Burr Brown Research Corp Tucson AZ 14099 Semtech Corp Newbury Park CA 14140 McGray Edison Co Commercial Development Div Manchester NH 14189 Ortronic
47. 02 215269 3800P 502 R1061 Res met flm 4 75k 1 1 2w 4705 192500 Type CEC TO Res ww 1002 0 5 1 2w 4707 155846 4707 155846 ww factory selected var ww 5k 10 1 4102 215269 3800P 502 R1065 Res met flm 4 75k 1 1 2w 4705 192500 Type CEC TO R1066 Res ww 1008 0 5 1 2w 4707 155846 4707 155846 R1067 Res ww factory selected R1068 var ww 5k 10 1w 4702 215269 3800P 502 4705 192500 4707 155846 Res met flm 4 75k 11 1 2w Res ww 1002 0 5 1 2w Res ww factory selected Res var ww 5k 10 1w Type CEC TO 4707 155846 4702 215269 3800P 502 R1073 met flm 4 75k 1 1 2w 4705 192500 Type CEC TO R1074 ww 1009 0 5 1 2w 4707 155846 4707 15584 R1075 Res ww factory selected 3800P 502 Type CEC TO 4707 155846 4702 215269 4705 192500 4707 155846 Res var ww 10 1 Res met flm 4 75k 1 1 2w ww 1009 0 5 1 2w ww factory selected Res var ww 10 1w Res met flm 4 75k 1 1 2w Res ww 1009 0 5 1 2w ww factory selected 3800P 502 Type CEC TO 4707 155846 4702 215269 4705 192500 4707 155846 3800P 502 Type CEC TO 4707 155846 4702 215269 4705 192500 4707 155846 var ww 10 1 Res met flm 4 75k 41 1 2w Res ww 1009 0 5 1 2w Res ww factory selected var ww 10 lw
48. 1 Chicago Lock Co Chicago IL 82227 Airpax Corp Cheshire Div Cheshire CT 82240 Simmons Fastner Corp Albany NY 82305 Palmer Electronics Corp South Gate CA 82389 Switchcraft Inc Sub of Raytheon Co Chicago IL 82415 Airpax Corp Frederick Div Frederick MD 82872 Roanwell Corp New York NY 82877 Rotron Inc Custom Div Woodstock NY 82879 ITT Royal Electric Div Pawtucket RI 83003 Varo Inc Garland TX 83014 Hartwell Corp Placenua CA 83055 Signalite Fuse Co Now 71744 83058 TRW Assemblies amp Fasteners Group Fasteners Div Cambridge MA 83259 Parker Hannifin Corp O Seal Div Culver City CA 83298 Bendix Corp Electric amp Fluid Power Div Eatonville INJ 83315 Hubbell Corp Mundelein IL 83330 Kulka Smith Inc A North American Philips Co Manasquan NJ 83478 Rubbercraft Corp of America West Haven CT 83553 Associated Spring Barnes Group Gardena CA 83740 Union Carbide Corp Battery Products Div Danbury CT 84171 Arco Electronics Commack NY 84411 American Shizuki TRW Capacitors Div Ogallala NE 84613 FIC Corp Rockville MD 84682 Essex Group Inc Peabody MA 84830 Lee Spring Co Inc Brooklyn NY 85367 Bearing Distributing Co San Fransisco CA 85372 Bearing Sales Co Los Angeles CA 85480 W H Brady Co Industrial Product Milwaukee WI 85840 Brady WH Co Industrial Products Div Milwauk
49. 1 1 4w 4702 112797 Type 110 R206 Res ww 4 873k matched set gt R207 Res ww 4 873k matched set R208 Res met flm 15k 1 1 2w 4705 151498 Type CEC TO R209 Res ww 2502 0 5 1 2w 4707 199893 4707 199893 These resistors are factory matched If replacement is required an entire set part number 4710 217679 must be ordered These resistors are factory matched If replacement is required an entire set part number 4710 217687 must be ordered V V 5 12 720A 0 07 03 Figure 5 4 BRIDGE P C ASSEMBLY 5 13 720A MFR TOT REC USE PARTNO QTY QTY CODE DESCRIPTION B DECADE SWITCH ASSEMBLY Figure 5 5 5110 217307 89536 5110 217307 720A 4004 4707 199810 89536 4707 199810 Res ww 9 898k matched set Res ww 39 536k 0 01 1w Switch rotary 3p 11 pos 5 sect 5107 218602 89536 5107 218602 These resistors are a factory matched set part number 4710 217646 If replace ment of one or more resistors in the set is required include all information stamped on the resistor along with the information described in paragraph 5 6 Should the information on the resistor not be discernible include all of the above information about the adjacent resistors R410 R406 R404 R410 R408 R404 R402 R411 S2 R409 R403 R403 R409 R407 R405 R401 R412 RIEN BOTTOM VIEW Figure 5 5
50. 1012ohms If the indica tion is more than 1 millivolt the leakage resistance is too low and corrective measures must be taken If repeated cleaning fails to correct the problem troubleshooting must be undertaken 4 10 CLEANING 4 11 When the Model 720A is properly cared for and 4 2 kept in a controlled atmosphere cleaning will seldom be re quired However any contamination particularly oil in the instrument can contribute to reduced leakage resistance which will impair accuracy Special care has been taken in the design and manufacture of the instrument to prevent leakage The voltage dial switches are supported by Lexan spacers and the circuit board is coated with a moisture sealant and isolated from the chassis by polyethelene grom mets These insulators and the switches can be contaminated easily by handling or by airborne contaminants Dust may be removed with dry oil free air at a pressure of 15 pounds per square inch or less To remove oil place the instrument on its side place paper towels under it and spray with de natured anhydrous ethyl alcohol Crown SPRA TOOL No 8011 or equivalent When dry perform switch contact lub fication paragraph 4 12 After cleaning and drying the leakage resistance test should be performed to assure that the excessive leakage has been corrected 4 12 Switch Contact Lubrication 4 13 Corrosion of switch contacts can cause high con tact resistance in one or more positions resulting i
51. 155846 V 4102 215269 4705 159475 4707 155846 V 4702 215269 4705 159475 4707 155846 4707 155846 d bo I bo ran bo eo 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 02660 12400 89536 89536 02660 1702 210716 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800P 502 Type CEC TO 4707 155846 3800 502 4707 155846 4707 155846 3800P 502 24 12 23 REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF REF 720A STOCK TOT REC USE DESCRIPTI 5 7 720A 5 8 R1133 R1100 R1051 R1103 R1099 R1055 R1059 R1063 R1067 R1071 R1075 R1079 R1083 R1087 R1091 R1095 R1115 R1118 R1004 R1008 R1012 R1016 R1020 R1024 R1028 R1032 R1036 R1040 R1044 R1046 Figure 5 3 TRIMMER P C A
52. 218594 5107 218594 56 Switch rotary 2p 10 pos 4 sect 5107 218594 9107 218594 REF 97 Switch rotary lp 11 3 sect 5107 218586 5107 218586 1 gt gt These resistors are a factory matched set part number 4710 217661 If replace ment of one or more resistors in the set is required include all information stamped on the resistor along with the information described in paragraph 5 6 Should the information on the resistor not be discernible include all of the above information about the adjacent resistors 5 16 720A S7 S S5 4 A et Ee eee R906 R804 R806 R808 R704 R706 R708 604 R606 910 R908 18802 R811 R810 R702 R711f R710 R602 R611 R902 R904 R903 R905 R909 R801 R812 R809 R701 R712 R709 R601 612 R609 R901 R907 R803 R805 R807 R703 R705 R707 R603 R605 R607 BOTTOM VIEW Figure 5 7 G DECADES SWITCH ASSEMBLY Rev 2 5 17 5 18 Section 7 General Information 7 1 This section of the manual contains generalized user information as well as supplemental information to the List of Replaceable Parts contained in Section 5 REV 5 7 89 7 1 D9816 Westermann Wilhelm Augusta Anlage Mannheim Nackarau Germany S0482 Sony Corp Tokyo Japan S3774 Oshino Electric Lamp Works Tokoyo Japan 086 IN General El Paso TX 0AE39 Autosplice Inc Woodside NY 0BW21 Noritake Co Inc Burlington MA OANFO Topaz Semiconduct
53. 34 Bliley Electric Co Erie PA 71183 Westinghouse Electric Corp Bryant Div Bridgeport CT 71279 Interconnection Products Inc Formerly Midland Ross Cambion Div Santa Ana CA 71400 Bussman Manufacturing Div McGraw Edison Co St Louis MO 71450 CTS Corp Elkhart IN Federal Supply Codes for Manufacturers cont 71468 ITT Cannon Div of ITT Fountain Valley CA 71482 General Instrument Corp Clare Div Chicago IL 71590 Mepco Centralab A North American Philips Co Fort Dodge IA 71707 Coto Corp Providence RI 71744 General Instrument Corp Lamp Div Worldwide Chicago IL 71785 TRW Inc Cinch Connector Div Elk Grove Village IL 71984 Dow Coming Corp Midland MI 72005 AMAX Specialty Metals Corp Newark NJ 72136 Electro Motive Mfg Corp Florence NC 72228 AMCA International Corp Continental Screw Div New Bedford MA 72259 Nytronics Inc New York NY 72619 Amperex Electronic Corp Dialight Div Brooklyn NY 72653 G C Electronics Co Div of Hydrometals Inc Rockford IL 72794 Dzus Fastner Co Inc West Islip NY 72928 Gulton Industries Inc Gudeman Div Chicago IL 72962 Elastic Stop Nut Div of Harrard Industries Union NJ 72982 Erie Specialty Products Inc Formerly Murata Erie Erie PA 73138 Beckman Industrial corp Helipot Div Fullerton CA 73168 Fenwal Inc Ashland MA 73293 Hughes Aircraft Co Electr
54. 4 2 5 2 6 2 7 2 8 2 9 2 10 2 11 2 12 2 13 2 14 720A List of Illustrations TITLE Model 720A Kelvin Varley Voltage Divider Absolute Linearity Stability Temperature Coefficient Power Coefficient Functions of Controls and Terminals Thevinin Equivalent Circuit Approximate Variation of Output Resistance With Dial Setting Approximate Variation of Minimum Load Resistance for 0 03 PPM of Input Loading Error Connections for Determining End Errors Typical Associated Equipment for Voltage Divider Calibration Equipment Connections for Calibrating a Voltage Divider Simplified Schematic Diagram of Voltage Divider Calibration Typical Associated Equipment for Measuring Voltages Equipment Connections for Voltage Measurements Typical Associated Equipment for Measuring Unknown Voltages Equipment Connections for Simplified Method of Voltage Measurement Typical Associated Equipment for Measuring Unknown Resistance Ratios Equipment Connections for Determining an Unknown Resistance Value PAGE 2 5 2 6 2 7 2 8 2 9 2 10 2 11 2 12 2 12 2 13 2 14 2 14 2 15 720A LIST OF ILLUSTRATIONS continued FIGURE 3 1 4 2 4 3 4 4 4 5 4 6 4 7 4 9 4 10 4 11 4 12 4 13 4 14 5 1 5 2 5 3 5 4 5 5 5 6 5 7 TITLE Simplified Schematic Diagram of Basic Kelvin Varley Divider Circuit Test Equipment Required for Maintenance Equipment Connections for Leakage Resistance Tes
55. 8 Electronic Concepts Inc Eatontown NJ 50579 Litronix Inc Cupertino CA 50891 Semiconductor Technology Stuart FL 50934 Tran Tec Corp Columbus NE 51167 Aries Electronics Inc Frenchtown NJ 51284 Mos Technology Norristown PA 51249 Heyman Mfg Co Cleveland OH 51372 Verbatim Corp Sunnyvale CA 51398 MUPAC Corp Brockton MA 51406 Murata Erie No America Inc Also see 72982 Marietta GA Federal Supply Codes for Manufacturers cont 51499 Amtron Corp Boston MA 51506 Accurate Screw Machine Co ASMCO Nutley NJ 51605 CODI Semiconductor Inc Kenilworth NJ 51642 Centre Engineering Inc State College PA 51705 ICO Rally Palo alto CA 51791 Statek Corp Orange CA 51984 NEC America Inc Falls Church VA 52063 Exar Integrated Systems Sunnyvale CA 52072 Circuit Assembly Corp Irvine CA 52152 MN Mining amp Mfg Saint Paul MN 52333 API Electronics Haugpauge Long Island NY 52361 Communication Systems Piscataway NJ 52500 Amphenol RF Operations Burlington MA 52525 Space Lok Inc Lerco Div Burbank CA 52531 Hitachi Magnetics Edmore MO 52745 Timco Los Angeles CA 52763 Stettner Electronics Inc Chattanooga TN 52769 Sprague Goodman Electronics Inc Garden City Park NY 52771 Moniterm Corp Amatrom Div Santa Clara CA 52840 Western Digital Corp Costa Mesa CA 53021 Sangamo Weston Inc See 06141 53036
56. A Section 5 List of Replaceable Parts 5 1 INTRODUCTION 5 2 This section contains complete descriptions of those parts one might normally expect to replace during the life of the instrument The first listing is a break down of all of the major assemblies in the instrument Subsequent listings itemize the components in each as sembly Every listing is accompanied by an illustration identifying each component in the listing Assemblies and subassemblies are identified by name in the parts list and by a ten digit stock number in the illustrations Components are identified by the schematic diagram reference designation e g R1 C107 DS1 Parts not appearing on the schematic diagram are numbered con secutively throughout the parts list with a whole number Flagnotes are used throughout the parts list and refer to ordering explanations The flagnote explanations appear at the end of the parts list in which they ar listed 5 3 COLUMNAR INFORMATION a The REF DESIG column indexes the item description to the associated illustration In general the refer ence designations are listed under each assembly in alpha numeric order Subassemblies of minor proportions are sometimes listed with the assembly of which they are apart In this case the refer ence designations for the components of the sub assembly may appear out of order b The DESCRIPTION column describes the salient characteristics of the component Indention of the
57. ALS30 7 2 Py MES gt BRIDGE POWER SBA E gt i ua CAL 3 3 3 j ef P k TO s2A 8 a E D IUIS raoa 2405 s IE QU JO 3 228 0 21063 9 2 1071 eec 1 f t RIOGB RIOGS DC 7 RIOGO 4 65 X m d cree lt ET 4 kg CKGO R1066 RIG 7O RIOS4 RIOS8 RIOG2 TO SBA 56 106 3 SHUNT i m o N n Ps s x 2 574 OSE R314 RI048 KIC49 S 12 314 X SK 5 S8C 585 85 I CAL BO aZ olx CALA CALS2 QW TANK 250 S8A NJ o 2 65 CAL A OPR O x O O o lt Z x z 4505 9995 Y E Y Y M A 2 0009 E ee o T Y I R304 R305 PU RIOZ 303 gt 10 8900 au Lis M Ser 9 Rioo4 lt pioost la CE 5 55 020 AS RIO24 e Li 81001 RICO Q4 ROOS RICO T Y 2009 RIOIO 69 9 RIOI3 RIO 91021 81022 3 5 SASK Ek _ 8 45x lt 8 45K lt 8 45 S lt 8 45 SK T RIO23 Om R1003 1007 oe RIOIS S M CR LOW m OIL TANK OIL TANK pos GND pOr wats K S A 2 a A d _
58. Alexandria VA 19613 MN Mining amp Mfg Co Textool Products Dept Electronic Product Div Irving TX 19647 Caddock Electronics Inc Riverside CA 19701 Mepco Centralab Inc A N American Philips Co Mineral Wells TX 2B178 Wire Products Cleveland OH 2K262 Boyd Corporation Portland OR Federal Supply Codes for Manufacturers cont 2Y 384 North American Philips Lighting Corp Van Wert OH 20584 Enochs Mfg Inc INpolis IN 20891 Cosar Corp Dallas TX 21317 Electronics Applications Co El Monte CA 21604 Buckeye Stamping Co Columbus OH 21845 Solitron Devices Inc Semiconductor Group Rivera Beach FL 21847 Aertech Now TRW Microwave Inc Sunnyvale CA 21962 Vectron Corp Replaced by S W Electronics 22526 DuPont EI DeNemours amp Co Inc DuPont Connector Systems Advanced Products Div New Cumberland PA 22626 Micro Semiconductor Now 14552 22670 GM Nameplate Seattle WA 22767 ITT Semiconductors Palo Alto CA 22784 Palmer Inc Cleveland OH 23050 Product Comp Corp Mount Vernon NY 23223 CTS Microelectronics Lafayette NY 23237 1 R C Inc Microcircuits Divison Philadelphia PA 23302 S W Electronics amp Mfg Corp Cherry Hill NJ 23730 Mark Eyelet and Stamping Inc Wolcott CT 23732 Tracor Applied Sciences Inc Rockville MD 23880 Stanford Applied Engineering Santa Clara CA 23936 William J Purdy Co Pamotor Div
59. B DECADE SWITCH ASSEMBLY 5 14 720A STOCK MFR TOT REC USE DESCRIPTION DECADE SWITCH ASSEMBLY 5110 217315 89536 5110 217315 Figure 5 6 Res Ww 4k matched set 4707 199836 89536 4707 199836 Res ww 40 31k 0 02 1w Switch rotary 3p 11 pos 5 sect 5107 218602 89536 5107 218602 B These resistors are a factory matched set part number 4710 217653 If replace ment of one or more resistors in the set is required include all information stamped on the resistor along with the information described in paragraph 5 6 Should the information on the resistor not be discernible include all of the above information about the adjacent resistors 8506 R510 R504 R510 R504 R508 R502 R511 S3 R503 R503 R509 R507 R505 R501 R512 TOP VIEW BOTTOM VIEW Figure 5 6 C DECADE SWITCH ASSEMBLY 5 15 720A STOCK TOT REC D E F AND DECADES SWITCH 5110 217323 89536 5110 217323 ASSEMBLY Figure 5 7 720A 4006 R601 thru Res ww 1k matched set R611 R612 Res ww 2 5k matched set R701 thru Res ww 1k matched set R711 R712 Res ww 2 5k matched set R801 thru Res ww 1k matched set R811 R812 Res ww 2 5k matched set R901 thru Res ww 1k matched set R910 54 Switch D rotary 2p 10 pos 4 sect 5107 218594 5107 218594 3 55 Switch E rotary 2p 10 pos 4 sect 5107
60. B 10208 G22 BHB 10208 G21 GP30NC BHB 10208 G22 2811 149864 2811 155911 2811 149864 BHB 10208 G21 GP30NC BHB 10208 G21 2811 149856 BHB 10208 G22 2811 155911 GP30NC BHB 10208 G22 BHB 10208 G21 GP30NC 2811 149856 2811 149864 2811 155911 4702 215319 4702 215319 3156 217083 2404 101683 2405 158949 3156 217083 1010 13 2405 158949 2405 158956 2405 190249 1406 217042 2405 158956 2405 190249 1406 217042 21 16 17 J2 J3 Jl J9 J8 010 411 J12 J13 45 6 J7 Figure 5 2 PANEL ASSEMBLY R1001 R1002 R1003 R1004 R1005 R1006 R1007 R1008 R1009 R1010 R1011 R1012 R1013 R1014 R1015 R1016 R1017 R1018 R1019 R1020 R1021 R1022 R1023 R1024 R1025 R1026 R1027 R1028 R1029 R1030 R1031 R1032 R1033 R1034 R1035 R1036 R1037 R1038 R1039 R1040 R1041 R1042 R1043 R1044 R1045 R1046 R1047 R1048 TRIMMER P C ASSEMBLY Figure 5 3 Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res var ww 10 1w met flm 8 45k 1 1 2w ww 1009 0 5 1 2w ww factory selected var ww 5k 10 1w met flm
61. BAL ANCE Control 4 26 10 KILOHM BRIDGE STANDARD This proce dure is used to adjust the total resistance of the bridge arm used for calibration of the A and B decades self calibration of the instrument so the bridge can be balanced to measure a nominal 10 000 ohms If the bridge can be balanced near the center of travel for the BRIDGE BALANCE during self cal at CAL A Zero positions the procedure following does not need to be performed However if during self cal in the CAL A Zero position See paragraph 2 24 the bridge cannot be balanced using the BRIDGE BALANCE Control perform the procedure below NOTE Insure the system has the correct connections and ground as shown in Figure 4 14 a Turn the FUNCTION switch to CAL A turn the internal FUNCTION switch to OPR Fig 4 13 and set the readout to 0000000 b Connect a 20 volt DC source to the red and the black BRIDGE POWER binding posts Connect null detector to the BRIDGE DETEC TOR binding posts The guard terminal of the null detector must be connected to the Common terminal 4 15 720A d f 4 16 INTERNAL FUNCTION SWITCH Figure 4 13 INTERNAL FUNCTION SWITCH Adjust the Bridge Balance control to the center of its travel range NOTE BRIDGE BALANCE is a concentric control with both a Fine and Coarse range on the same control knob Observe the null detector and sweep R203 on the bridge circuit board slowly from stop to
62. ET lI TEMPERATURE yard EEE Ete 040 1 105 i Ja lt 8 T v S SH Serna E HAHI t E Hubo AA H zu H fine LLL ELEM peu HHH j HER HHEH EH EAE THAT LS ELE bn SINI PSS sane i o Reeth it be 5 j f Du H E CL Sees PE ee eee N v m N v m HDN OM D 1074 E 1073 F 10 6 G 1077 1 3 720A exceeded and linearity must be derated 0 1 STORAGE TEMPERATURE RANGE from the calibration temperature 34 C to 70 C 29 F to 158 P SHOCK OPERATING HUMIDITY RANGE Meets requirements of MIL T 945A and MIL S 901B Up to 70 relative humidity at 35 C 95 F No derating rigidly mounted with slides is required Up to 80 relative humidity at 35 C 95 F Linearity VIBRATION derating is 0 1 ppm of input for any relative humidity Meets requirements of MIL T 945A rigidly mounted between 70 and 80 or rack mounted with slides E Lu WI Tal Ha ESS 2 Edo 12221 3 4 5 6 7891 pi ME MACETAS 107 3 45678917 apie ite wr
63. H FUNCTIONAL SCHEMATIC SIA AM Bl P an 3 lt E MODEL 720A jw KELVIN VARLEY 1 c a ete VOLTS GE ou uad 9 ste fo m on ASI re m Eco E FLUKE mMFG inc i PO 7428 Seuttle 1 4 3 n gt i a be i a Qr AME D E E E ies Sete Bd fox
64. HI INPUT 721A LEAD COMPENSATOR HI OUTPUT 845AB NULL DETECTOR LOW BALANCE PART OF STANDARD 332 721A LEAD COMPENSATOR DIVIDER VOLTAGE Lo OUTPUT CBRIDGE POWER d TEST DIVIDER 720 R LEAD R LEAD Figure 4 6 SIMPLIFIED SCHEMATIC DIAGRAM OF DECADE LINEARITY TEST within the limits listed in the Permissible Deviation u Turn the HIGH BALANCE COARSE control to the column same setting as the LOW BALANCE COARSE control NOTE EOS v Set the standard divider to full scale An indication beyond these limits is a symptom of trouble within the instrument Refer to the w Set the divider under test to 1 0 99999X troubleshooting instructions to determine the nature of the fault x Adjust the HIGH BALANCE FINE control to obtain a zero indication on the null detector o Set the voltage source to the desired voltage for y Set the divider under test back to 1 0 900000 and testing decade set the standard divider back to zero p Turnthe FUNCTION switch to C 7 Re adjust the LOW BALANCE FINE control if necessary to obtain a zero indication on the null q Set the standard divider to zero detector r Set the divider under test to 1 0 900000 aa Set the null detector for the desired sensitivity and s Place the null detector in the zero mode adjust make the linearity measurements listed in Figure it for zero deflection and return it to operating 4 8 mode ab Set the volta
65. INING END ERRORS first two decades to compensate for any resistance changes caused by temperature changes or aging Thus the absolute linearity of the instrument is adjusted to 0 1 ppm of input The only external test units required are a stable source of 10 volts and 20 volts such as the Fluke Model 412B and a sensitive null detector such as the Fluke Model 845AB The procedure may be adapted easily to use batteries as the voltage source if a suit able dc power supply is not available The procedure is as follows a Connect the null detector 845AB to the BRIDGE DETECTOR binding posts using low thermal leads b the Model 720A set the FUNCTION switch to CAL A and the decade readout to 0000000 c On the Model 845AB set the range switch to 10 microvolts set the OPR ZERO switch to ZERO and adjust for zero meter deflection Return the OPR ZERO switch to OPR position d Set the power supply 412B for 20 volts output and connect it to the BRIDGE POWER binding posts e Adjust the BRIDGE BALANCE control for a null indication on the Model 845AB f Advance the decade to 0 1 and adjust the associated variable resistor A 1 to produce null 0 5 microvolts _ NOTE As the procedure is continued occasionally re turn the decade switch to zero and recheck bridge balance g In turn advance decade one position A 2 through A CAL and adjust the associated variable resistor h
66. N LIEU OF ALL OTHER WARRANTIES EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY FITNESS OR ADEQUACY FOR ANY PARTICULAR PURPOSE OR USE JOHN FLUKE MFG CO INC SHALL NOT BE LIABLE FOR ANY SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES WHETHER IN CONTRACT TORT OR OTHERWISE If failure occurs the following steps should taken 1 Notify the JOHN FLUKE MFG or nearest service facility giving full details of the difficulty and include the model number type number and serial number On receipt of this information service data or shipping instructions will be forwarded to you Z 2 On receipt of the shipping instructions forward the instrument transportation prepaid Repairs will be made at the Service Facility and the instrument returned transportation prepaid SHIPPING TO MANUFACTURER FOR REPAIR OR ADJUSTMENT All shipments of JOHN FLUKE MFG CO INC instruments should be made via United Parcel Service or Best Way prepaid The instrument should be shipped in the original packing carton or if it is not available use any suitable container that is rigid and of adequate size If asubstitute container is used the instrument should be wrapped in paper and surrounded with at least four inches of excelsior or similar shock absorbing material CLAIM FOR DAMAGE IN SHIPMENT TO ORIGINAL PURCHASER The instrument should be thoroughly inspected immediately upon original
67. SSEMBLY Sheet 1 of 2 R1102 R1101 R1105 R1104 R1108 R1107 R1106 R1111 R1110 R1109 R1114 R1113 R1112 R1117 R1116 R1120 R1119 R1123 R1122 R1121 R1126 R1125 R1124 R1129 R1128 R1127 R1132 R1131 R1130 R1047 R1050 R1098 R1054 R1058 R1062 R1066 R1070 R1074 R1078 R1082 R1086 R1090 R1094 R1003 R1007 R1011 R1015 R1019 R1023 R1027 R1031 R1035 R1039 R1043 R1045 720A R1002 R1001 R1006 R1010 R1014 R1018 R1022 x a NE an 1034 R1033 1 R E 1041 Figure 5 3 TRIMMER ASSEMBLY Sheet 2 of 2 720A STOCK MFR TOT REC USE 4705 159475 4707 199893 Res met flm 8 45k 195 1 2w Res ww 2502 0 5 1 2w Type CEC TO 4707 199893 gt R1051 Res ww factory selected R1052 Res var ww 10 1w 4702 215269 3800 502 1053 met flm 4 75k 1 1 2w 4705 192500 Type CEC TO R1054 ww 1002 0 5 1 2w 4707 155846 4707 155846 R1055 Res ww factory selected R1056 Res var ww 5k 10 lw 4702 215269 3800P 502 R1057 Res met flm 4 75k 1 1 2w 4705 192500 Type CEC TO ww 1002 0 5 1 2w 4707 155846 4707 155846 R1059 ww factory selected R1060 Res var ww 5k 10 1w 47
68. Unknown Voltages 2 34 The Model 720A in company with a stable dc voltage source two null detectors a standard cell and a reference voltage divider may be used to measure an unknown voltage with high accuracy Typical equip ment for this application is listed in Figure 2 9 With this equipment the full electrical capabilities of the Model 720A may be realized 2 35 To measure an unknown voltage first connect the equipment as shown in Figure 2 10 The size of wire for leads A and B should be no smaller than No 24 and the total length should be less than 3 feet Then measure the approximate voltage by dialing the Model 720A to 0000000 and reading the null detector on the appropriate voltage range Proceed as follows a Open standard cell voltage switch on the refer ence divider and set the standard cell voltage dials to the correct standard cell voltage b Set the reference divider input switch to the first position higher than the voltage to be measured Set the output switch to the same position c Turn on all equipment and allow it to warm up until it reaches temperature equilibrium d Set the standard cell switch of the reference divider to momentary position and adjust the output of the de source to obtain a null indication on null detector number 1 e Adjust the readout dials of the Model 720A to obtain a null indication on null detector number 2 f Calculate the unknown voltage by multiplying the input vol
69. ade consists of setting each step the decade to a nominal 4007 6 ohms If the bridge can be balanced with the BRIDGE BALANCE control on the front panel during self cal in the CAL C Zero position described in paragraph 4 21 this procedure does not need to be performed To reset the range of the BRIDGE BALANCE control for balance of the bridge perform the following procedure a Turn the FUNCTION switch to OPR and turn the internal FUNCTION switch to CAL C and set the readout to 0000000 NOTE The internal FUNCTION switch which is shown in Figure 4 13 is used only for calibration of the C decade and the S 3 shunt It should not be confused with the FUNCTION switch located on the front panel b Connect the voltage source to the red and the black BRIDGE POWER binding posts Connect null detector to the BRIDGE DETEC TOR binding posts The guard terminal of the null detector must be connected to the common ter minal d Turn the C decade switch to the blank position and apply 10 volts from the voltage source e Adjust BRIDGE BALANCE to the mid position and adjust R1130 Decade C 9 to mid position 4 18 f Observing the Null Detector sweep R205 Bridge Circuit Board thru its range Ifthe null detector does not show a smooth change sweep R205 through its range several times g Adjust R205 for 0 50 microvolts on the Null Detector h Place the Null Detector on the 300 microvolt range Obse
70. ar Technology Milpitas CA 64537 KDI Electronics Whippany NJ 64782 Precision Control Mfg Inc Bellevue WA 64834 West M G San Francisco CA 64961 Electronic Hardware LTD North Hollywood CA 65092 Sangamo Weston Inc Weston Instruments Div Newark NJ 65786 Cypress Semi San Jose CA 65940 Rohm Corp amp Whatney Irvine CA 65964 Evox Inc Bannockbum IL 66150 Entron Inc Winslow Teltronics Div Glendale NY 66302 VLSI Technology Inc San Jose CA 66419 Exel San Jose CA 66450 Dyna Tech Electronics Inc Walled Lake MI 66608 Bering Industries Freemont CA 66891 BKC Intemational Electronics Lawrence MA 66958 SGS Semiconductor Corp Phoenix AZ 66967 Powerex Inc Aubum NY 67183 Altera Santa Clara CA 68919 WIMA Harry Levinson Co Seattle WA 7F361 Richmond Division of Dixico Zellerbach Paper Co Seattle WA TF844 Moore Business Forms Inc Seattle WA 7G902 Textron Inc Camcar Div Rockford IL 73395 Universal Plastics Welshpool WA 71696 AMD Plastics East Lake OH 7 354 Omni Spectra Inc Los Altos CA 7Z884 ALPS Seattle WA 7X634 Duracell USA Div of Dart amp Kraft Inc Valdese NC 70290 Almetal Universal Joint Co Cleveland OH 70485 Atlantic India Rubber Works Inc Chicago IL 70563 Amperite Company Union City NJ 70903 Cooper Belden Corp Geneva IL 71002 Bimbach Co Inc Farmingdale NY 710
71. at least one of every part in the instrument be stocked The USE CODE column identifies certain parts which have been added deleted or modified during the production of the instrument Each part for which a Use Code has been assigned may be iden tified with a particular instrument serial number by consulting the Serial Number Effectivity List As Use Codes are added to the list the TOT QTY column listings are changed to reflect the most current infor mation Sometimes when a part is changed the new part can and should be used as a replacement for the original part In this event a parenthetical note is add ed in the DESCRIPTION column 5 1 720A 5 4 HOWTO OBTAIN PARTS 5 5 Standard components have been used wherever possible Standard components may be ordered directly from the manufacturer by using the manufacturer s part number or parts may be ordered from the John Fluke Mfg Co factory or authorized representative by using the Fluke part number In the event the part you order has been replaced by a new or improved part the re placement will be accompanied by an explanatory note and installation instructions if necessary 5 6 You can insure prompt and efficient handling of your order to the John Fluke Mfg Co if you include the following information a Quantity b FLUKE Stock Number c Description d Reference Designation e Instrument model and serial number Example 2 each 4805 177105 Transistors
72. b Setthe readout dials of the Model 720A to zero c Connect the null detector lead to point P and adjust the readout dials of the Model 720A to obtain a null indication Record the dial reading REQUIRED SPECIFICATIONS Output voltage from 0 to 1100 volts Stability of 0 0015 per hour Output ripple less than 40 uv rms uv full scale sensitivity 10 megohms input resistance pum 2 11 TYPICAL ASSOCIATED EQUI PMENT FOR MEASURING UNKNOWN VOLTAGES 2 12 Rev 1 NOTE To prevent problems from current loops connect each instrument to a common grounding point preverably on the power source On the shielded cables connect one end of the shield to ground and leave the other end open Rev 2 720A 3328 D 1 PARLEY VOLTAGE BIBER o PE T3 AE YORE i24 E id 34 AB im MOR BALE RETOS roars qas 5 isl vefte 2 UNKNOWN DC VOLTAGE Ss NULL DETECTOR UNKNOWN 720A 3328 DC K V VOLTAGE VOLTAGE VOLTAGE DIVIDER STANDARD Figure 2 12 EQUIPMENT CONNECTIONS FOR SIMPLIFIED METHOD OF VOLTAGE MEASUREMENT 2 13 720A TYPICAL EQUIPMENT REQUIRED SPECIFICATIONS DC Voltage Source John Fluke Mfg Co Model 332B or equivalent DC Null Detector John Fluke Mfg Co Model 845AB or equivalent Output voltage from 0 to 1100 volts Sta
73. bility of 0 0015 per hour Output ripple less than 40 uv rms 1 uv full scale sensitivity 10 megohms input resistance Figure 2 13 TYPICAL ASSOCIATED EQUIPMENT FOR MEASURING UNKNOWN RESISTANCE RATIOS d Move the null detector lead to point adjust the readout dials to obtain a null and record the dial reading e Move the null detector lead to point Pz adjust the readout dials to obtain a null and record the reading f Move the null detector lead to point P adjust the dials to obtain a null and record the dial reading i UNKNOWN NULL DETECTOR P2 P3 R STANDARD P4 720A g Calculate the unknown resistance from the following equation Rx Po 54 Ps P4 where Rx unknown resistance R std standard resistance 3328 VOLTAGE STANDARD K V VOLTAGE DIVIDER Figure 2 14 EQUIPMENT CONNECTIONS FOR DETERMINING AN UNKNOWN RESISTANCE VALUE Sheet 1 of 2 2 14 720A 332B OPI i RESISTOR t STANDARD 90114581 BARES PURER ik P PERE Re ESSERE LORE 2 E 935 395 BRIBES e ES RESISTANCE UNKNOWN 1283 REGLA 3664615 2128 95 Vit BALANCE connect On the connect one preferably 2 5 nt ng poi on the power sourc To prevent
74. c tions and equipment connections for calibrating a voltage divider measuring unknown voltages and measuring unknown resistances Although these are by no means TYPICAL EQUIPMENT REQUIRED SPECIFICATIONS DC Voltage source John Fluke Mfg Co Model 332B or equivalent DC Null Detector John Fluke Mfg Co Model 845AB or equivalent Lead compensator John Fluke Mfg Co Model 721A Output voltage from 0 to 1100 volts Stability of 0 0015 per hour Output ripple less than 40 uv rms 1 uv full scale sensitivity 10 megohms input resistance Resolution of 0 1 milliohm Figure 2 6 TYPICAL ASSOCIATED EQUIPMENT FOR VOLTAGE DIVIDER CALIBRATION 2 332B 720A To prevent problems from current loops connect each instrument to a common NOTE grounding point preferably on the power source On the shielded cables connect one REO NOE REOR RENE RO RR n RT RS RON SS E RT IRSA O ROTO RRA NR ae gt EA esf ve VEN ERIASCE ESSE Hat gati x 1598 H de the shield ground and leave the other end open Rev 2 meme lt lt
75. d self heat ing will cause the linearity of the instrument to drift This drift may continue for as long as four hours after application of the high voltage Low voltage high accuracy measurements 0 1 ppm should not be at tempted immediately after high voltage use Each time the setting of the A decade is changed the power distribution in it is changed because the current through the instrument is divided between the two shunted re sistors of the decade and the resistance of the other decades which shunts them Because of this current division the two shunted resistors do not be come as hot as the other resistors in decade The change in current distribution brought about by changing the setting of the decade causes linearity to drift for a few minutes if high voltage is applied 2 22 END ERRORS 2 23 When the Model 720A is compared to another divider and a lead compensator such as the Fluke Model 721A is used absolute linearity may be used directly without correction for end errors In other applications the use of a lead compensator is not prac tical and end error corrections must be applied Use the following procedure to determine the end error corrections for the Model 720A 2 4 a Connect the equipment as shown in Figure 2 5 A b Adjust the input voltage to 1000 volts c With all dials set to zero measure the voltage between the OUTPUT HIGH terminal and the INPUT LOW terminal This is t
76. decades to permit compensation for drift and changes of ambient temperature Overranging capability is provided in some circuits by adding an additional step of resistance and a 1 1 input terminal at the upper end of the first decade In some dividers a small series resistance is added between the lower end of the divider string and the low input terminal to compensate for contact and wiring resistance bringing the low output voltage at zero setting to the same value as the low input voltage Although these refinements improve the bility of the circuit it operates in same manner with them as without them 3 8 THE MODEL 720A 3 9 The Model 720A is a seven dial Kelvin Varley divider with overranging and adjustable trimmers in the first three decades The low output is compensated by a small resistance in series with the low input ter minal The input resistance total effective resistance of the first decade is 110 kilohms at the 1 1 input ter minal or 100 kilohms at the 1 0 input terminal Resis tors of equal value and fixed decade shunts are used in the last four decades to avoid using very small resis tance values 3 10 Design characteristics of the Model 720A which are not commonly found in Kelvin Varley dividers in clude adjustable shunts in the first three decades a built in Wheatstone bridge and switching to permit linearity adjustment self calibration from the front panel In addition internal switching provi
77. delivery to purchaser All material in the container should be checked against the enclosed packing list The manufacturer will not be responsible for shortages against the packing sheet unless notified immediately If the instrument is damaged in any way aclaim should be filed with the carrier immediately To obtain a quotation to repair shipment damage contact the nearest Fluke Technical Center Final claim and negotiations with the carrier must be completed by the customer The JOHN FLUKE MFG CO INC will be happy to answer all applications or use questions which will enhance your use of this instrument Please address your requests or correspondence to JOHN FLUKE MFG CO INC P O BOX 09090 EVERETT WASHINGTON 98206 ATTN Sales Dept For European Customers Fluke Holland B V P O Box 5053 5004 EB Tilburg The Netherlands For European customers Air Freight prepaid John Fluke Mfg Co Inc Box C9090 Everett Washington 98206 Rev 6 81 720A sre Sn Table of Contents SECTION TITLE PAGE 1 INTRODUCTION AND SPECIFICATIONS IPC 1 1 1 1 Introduction EPA 1 1 1 5 Electrical Specifications 1 1 6 Mechanical and Environmental Suecifications Bk tk 1 2 2 OPERATING INSTRUCTIONS 2 1 2 1 Introduction R4 te ele ee eS 2 1 2 3 Power Limitations zu xu Ue a QQ 2 1 2 5 Functions of Controls and
78. des access to the second through the seventh decades so the linear ity of any decade may be checked against a 10 step di vider from the front panel 3 1 720A N 0 10K 10K 10K 10K 10K 10K 10K 10K 10K 10K 10K HIGH INPUT LOW INPUT Rev 1 Figure 3 1 SIMPLIFIED SCHEMATIC DIAGRAM OF BASIC KELVIN VARLEY DIVIDER CIRCUIT 3 2 41 INTRODUCTION 4 2 This section contains the instructions and infor mation required for maintenance of the Model 720A Kelvin Varley Divider Instructions are included for pre ventive maintenance testing and repair of the instrument If repair is beyond the capability of the user it is recommended that the instrument be returned to the manufacturer All maintenance procedures except the replacement of factory selected resistors and resistors housed in the oil tank are within the capability of a skilled technician if the listed test equipment is available 4 3 The ratio accuracy of 0 1 ppm of the Model 720A is guaranteed for one year after shipment from the factory provided the instrument is regularly self calibrated in accordance with paragraph 2 24 and is operated in the same environment in which it is self calibrated The instru ment also must meet the requirements of the Leakage Resistance Test paragraph 4 8 In the self calibration procedure all resistors on the A and B decades are adjusted to be equal to each other by substituting each in turn into th
79. description indicates the relationship to other as semblies components etc In many cases it is necessary to abbreviate in this column For abbre viations and symbols used see the following page c The ten digit part number by which the item is identified at the John Fluke Mfg Co is listed in the STOCK NO column Use this number when ordering parts from the factory or authorized rep resentatives Rev 1 The Federal Supply Code for the item manufacturer is listed in the MFR column An abbreviated list of Federal Supply Codes is included in the Appendix The part number which uniquely identifies the item to the original manufacturer is listed in the MFR PART NO column a component must be ordered by description the type number is listed The TOT QTY column lists the total quantity of the item used in the instrument Second and subsequent listing of the same item are referenced to the first listing with the abbreviation REF In the case of optiona subassemblies plug ins etc that are not always par of the instrument the TOT QTY column 11515 the total quantity of the item in that particular assembly Entries the REC QTY column indicate recom mended number of spare parts necessary to support one to five instruments for a period of two years This list presumes an availability of common elec tronic parts at the maintenance site For mainte nance for one year or more at an isolated site it is recommended that
80. e C deck switch away from the position being calibrated return it and ob serve the meter The indication should be within 10 microvolts of zero NOTE If the indication is not within 10 microvolts of zero exercise the switch and repeat the proce dure If this fails lubricate the switch as in structed in paragraph 4 12 6 Proceed to the next position to be calibrated j Return the deck switch to the 0 position k Turn the internal FUNCTION switch to the CAL S3 position 1 Observe the null detector and slowly sweep the CAL S3 trimmer from stop to stop If the indica tion does not change smoothly sweep it from stop to stop several times m Adjust the CAL S3 trimmer to obtain an indica tion of 0 10 microvolts n Observe the null detector and tap the trimmer The indication should stay within 10 microvolts of zero Rev 2 720A O Turn the C decade switch away from the 0 positions and return it to zero The null detector indication should be within 10 microvolts of zero p Return the internal FUNCTION switch to OPR Calibration of decade and S3 shunt is complete 4 24 To calibrate the A and B decades perform the self calibration procedure using the instructions given in paragraphs 2 24 and 2 25 4 25 Bridge Calibration NOTE The Bridge Calibration procedure is required only if a null could not be obtained during Divider Calibration with the BRIDGE
81. e adjust it necessary to obtain a zero indication on the null for zero deflection and return it to operating mode detector be Adjust the LOW BALANCE controls of the lead az Set the null detector for the desired sensitivity compensator to obtain a zero indication on the and make the linearity measurement given in null detector Figure 4 10 The null detector indications must be within the limits listed in the permissible bf Turn the HIGH BALANCE COARSE control to the deviation column same setting as the LOW BALANCE COARSE control bg Set the standard divider to full scale ba Turn the FUNCTION switch to CK F bh Set the divider under test to 1 0 99999X bb Set the standard divider to zero bi Adjust the HIGH BALANCE FINE control to obtain bc Set the divider under test 1 0 999900 a zero indication on the null detector 4 11 720A PERMISSIBLE DEVIATION PPM of INPUT to DECADE MAX TEST VOLTAGE STANDARD DIVIDER 8 9 999999X 9 8 Figure 4 10 E DECADE LINEARITY TEST bj Set the divider under test back to 1 0 999900 and set bo Set the divider under test to 1 0 999990 the standard divider back to zero bp Place the null detector in the zero mode adjust it bk Re adjust the LOW BALANCE FINE control if for zero deflection and return it to operating mode necessary to obtain zero indication on the null detector bq Adjust the LOW BALANCE controls of the
82. e Electronics Inc Archbald PA 09021 Airco Inc Airco Electronics Bradford PA 09023 Cornell Dublier Electronics Fuquay Varina NC 09214 General Electric Co Semiconductor Products Dept Aubum NY 09353 C and K Components Inc Newton MA 09423 Scientific Components Inc Santa Barbara CA 09922 Bumdy Corp Norwalk CT 09969 Dale Electronics Inc Yankton SD 09975 Burroughs Corp Electronics Components Detroit MI 1A791 LFE Electronics Danvers MA 1B715 United Shoe amp Nylock Corp Nylock Fastener Corp Paramus NJ 10059 Barker Engineering Corp Kenilworth NJ 10389 IL Tool Works Inc Licon Div Chicago IL 11236 CTS Corp Resistor Products Div Beme IN 11237 CTS Corp of CA Electro Mechanical Div Paso Robles CA 11295 ECM Motor Co Schaumburg IL 11358 Columbia Broadcasting System CBS Electronic Div Newburyport MA 11403 Vacuum Can Co Best Coffee Maker Div Chicago IL 11502 can also use 35009 TRW Inc TRW Resistive Products Div Boone NC 11503 Keystone Columbia Inc Freemont IN 11532 Teledyne Relays Teledyne Industries Inc Hawthome CA 11711 General Instrument Corp Rectifier Div Hicksville NY 11726 Qualidyne Corp Santa Clara CA 12014 Chicago Rivet amp Machine Co Naperville IL 12020 Ovenaire Div of Electronic Technologies Charlottesville VA 12038 Simco Div of Ransburg Corp Hatfield PA 1204
83. e measurement divider 2 18 TEMPERATURE CONTROL 2 19 Because of slight differences in temperature coefficients of the resistors used in the Model 720A the linearity of the divider will vary with ambient tem perature This change in linearity will never exceed 0 1 ppm of input per degree centigrade for dial settings above 0 1 and typically will be 0 05 ppm C For measurement applications which require the best pos sible accuracy temperature and temperature variations must be considered The operating temperature should be within 1 C of the self calibration temperature if at all possible If the desired operating temperature is 2 3 720A L EEES amm d E OUTPUT RESISTANCE R OHMS mm oN lt n wv lt m 1 0 10 1 10 2 10 3 P uS m 1074 107 E m DIAL SETTING S Figure 2 3 APPROXIMATE VARIATION OF OUTPUT RESISTANCE WITH DIAL SETTING appreciably different from the last calibration tempera ture the instrument should be allowed to stabilize at the operating temperature and then the self calibration procedure should be performed to adjust linearity to 0 1 ppm of input The Model 720A is factory tested at a temperature of 23 1 2 20 POWER COEFFICIENT 2 21 The power coefficient will not exceed 0 2 ppm per watt of input power and typically will be 0 1 ppm per watt or less With high voltage applie
84. e only one under value step H a decade shunt is under value all steps of the decade will be equal but the resistance of the decade will below This will cause nonlinearity in the preceding decade which may be observed by dialing it upward from zero Below the midpoint the output will be low above the midpoint the output will be high 4 36 A defective switch usually will cause erratic or irregular operation of the decade A broken contact may cause one step to be missing although all others are of the correct value or it may completely open the divider circuit When a switch defect is suspected the switch should be checked for continuity at each position Rev 2 A shorted resistor will decrease the overall 720A 4 37 Defective wiring usually will cause one step of a decade to be missing or will completely open the divider circuit Wiring continuity should be checked to isolate the fault 4 38 REPAIR 4 39 Any parts of the Model 720A except factory se lected resistors and resistors housed in the oil tank may be replaced without difficulty by an experienced elec tronic maintenance technician When a switch is re placed all leads should be tagged as they are discon nected to assure that they are correctly connected to the new switch Care should be exercised in any sol dering operation to assure that good electrical contact is made parts except precision wirewound resis tors may be ordered from the factory by g
85. e self contained resistance bridge The Linearity Test given in paragraph 4 14 should be performed once each year to verify instrument performance If testing and calibration are beyond the capability of the user these services may be obtained from a commercial calibration laboratory or from the manufacturer Rev 2 720A Section 4 Maintenance 44 TEST EQUIPMENT REQUIRED FOR MAINTENANCE 4 5 The test equipment required for maintenance is listed in Figure 4 1 Equivalent or similar units may be substituted for those listed providing they have the re quired specifications listed in the figure 4 6 PREVENTIVE MAINTENANCE 4 7 Preventive maintenance of the Model 720A con sists of leakage resistance testing cleaning switch contact lubrication and linearity testing The frequency with which preventive maintenance procedures should be scheduled depends upon the user s requirements and the environment of the instrument In an air conditioned standards labora tory there will be little contamination of surfaces within this instrument and therefore testing and cleaning will sel dom be required In a contaminated atmosphere frequent testing and cleaning may be required to maintain the accuracy of the instrument 4 8 Leakage Resistance Tests 4 9 The need for cleaning can be determined without removing the cover from the Model 720A by performing 4 1 720A RECOMMENDED EQUIPMENT DC Voltage Source John Fluke M g
86. ee WI 85932 Electro Film Inc Valencia CA 86577 Precision Metal Products Co Peabody MA 86684 Radio Corp of America Now 54590 86928 Seastrom Mfg Co Inc Glendale CA 87034 Illuminated Products Inc Now 76854 87516 Standard Crystal KS City KS 88044 Aeronautical Standards Group Dept of Navy amp Air Force 88219 GNB Inc Industrial Battery Div Langhorne PA 88245 Winchester Electronics Litton Systems Useco Div Van Nuys CA 88486 Triangle PWC Inc Jewitt City CT 88690 Essex Group Inc Wire Assembly Div Dearbom MI 88786 Atlantic India Rubber Co Goshen IN 88978 Philips Now Fluke Mahwah NJ 89020 Amerace Corp Buchanan Crimptool Products Div Union NJ 89265 Potter Brumfield See 77342 89462 Waldes Truarc Inc Long Island NY 89536 John Fluke Mfg Co Inc Everett WA 89597 Fredericks Co Huntingdon Valley PA 89709 Bunker Ramo Eltra Corp Amphenol Div Broadview IL 89730 General Electric Lamp Div Newark NJ 9R216 Data Composition Sve Inc Laurel MD 98171 Port Plastics Tukwila WA 9W423 Amatom El Mont CA 90201 Mallory Capacitor Co Sub of Emhart Industries Inc Indianapolis IN 90215 Best Stamp amp Mfg Co KS City MO 90303 Duracell Inc Technical Sales amp Marketing Bethel CT 91094 Essex Group Inc Suflex IWP Div Newmarket NH 91247 IL Transformer Co Chicago IL 91293 Johanson Mfg
87. element of a system for measuring ratios voltages or resist ances 2 3 POWER LIMITATIONS 2 4 is possible to damage the Model 720A by apply ing voltages incorrectly to the input terminals or by drawing more than 11 milliamperes from the output tap The instrument will be damaged if a potential greater than 200 volts is applied between the 1 0 INPUT terminal and the 1 1 INPUT terminal To prevent damage caused by drawing excessive current from the output tap either the input or the output can be fused for 11 milliamperes Another method of protecting the instrument is through the use of a power supply with current limiting capa bility The current limit should be set for 11 milliam peres or less 2 5 FUNCTIONS OF CONTROLS AND TERMINALS 2 6 Figure 2 1 shows the controls and terminals of the Model 720A and describes their functions 2 7 RATIO ERRORS CAUSED BY LOADING OR LEAKAGE 2 8 Measurements of any kind require a knowledge of the errors associated with the equipment used to perform the measurement Measurement made with the Model 720A are not different 2 9 very important source of error in measure ments employing the Model 720A is the effect that exter nal load and leakage resistances have on overall accuracy If excessive current is drawn from the di vider output tap because of loading or leakage linearity errors which far exceed the linearity specifications can result For this reason Kelvin Var
88. enter Saint Paul MN 28309 Kaiser Minette AL 28425 Serv O Link Euless TX 28478 Deltrol Corporation Deltrol Controls Div Milwaukee WI 28480 Hewlett Packard Co Corporate HQ Palo Alto CA 7 5 28484 Emerson Electric Co Gearmaster Div McHenry IL 28520 Heyco Molded Products Kenilworth NJ 28932 Lumax Industrials Inc Altoona PA 29083 Monsanto Co Santa Clara CA 29604 Stackpole Components Co Raleith NC 29907 Omega Engineering Inc Stamford CT 3D536 Aimsco Inc Seattle WA 30035 Jolo Industries Inc Garden Grove CA 30045 Solid Power Corp Farmingdale NY 30146 Symbex Corp Painesville OH 30148 AB Enterprise Inc Ahoskie NC 30161 Aavid Engineering Inc Laconia NH 30315 Itron Corp San Diego CA 30323 IL Tool Works Inc Chicago IL 30800 General Instrument Corp Capacitor Div Hicksville NY 30838 Fastec Chicago ILL 31019 Solid State Scientific Inc Willow Grove PA 31091 Alpha Industries Inc Microelectronics Div Hatfield PA 31323 Metro Supply Company Sacramento CA 7 6 31433 Kemet Electonics Corp Simpsonville NC 31448 Army Safeguard Logistics Command Huntsville AL 31471 Gould Inc Semiconductor Div Santa Clara CA 31522 Metal Masters Inc Baldwin MS 31746 Cannon Electric Woodbury TN 31827 Budwig Ramona CA 31918 ITT Schadow Eden Prairie MN 32293 Intersil Cupertino CA 32539 Mura
89. eos 209 RIO V AK lt lt ROOG eco eoo V lt V lt 61127 28 2 23 2 RM25 RII24 5 PAZ 81126 Me 25 23 2 RII32 2 R4 61092 RIO93 SK R RIOJ ROSS RIO83 SK RIO90 oo RIOA SK RIO4 3 RIO4 T EA NOTES RESISTORS sica es a ARE ACTUALLY FOUR SHOWN BELOW RIAS 2 4140 2 44 2 4 4 I EA de A INDICATES INTERNAL AGU Ou gt ACCESSIBLE eer pas ig A DU gt SEA til a e ARE E 7 CHASSIS GROUND d OUTPUT Be J5 MI o G wt zt iat z i 26 T4 K AA E Sg as GND L a A sock di w Fe hale gt x A D E i 1 amp qus 2 qu A INL X a E Pe M ui c E i lan RS i xcd oue E f 4 4 I MEME 3 gt XE UA gos BES x Ge SIN 11 5 7 d E Ln 2 a e TE Y RTT ps C RU Qr 4 N B t d d E E 1 x Uy eC EN 4 d 2 4 mE 4 E Pa gat E y it 4 225m t t NA TE e
90. ete ums oae ns r em E Ne Susana de DS dcos Sorrow E aspi aa m BRIDGE POWER 312 380 GND I E 7 E m PLE 2 A g S26 Q 5 EN R203 2 K S GO s 3 3 m E _ ex a R 2 he 9205 33 536 ys E 155 204 15 314 soU ae BRIDGE Ha oe E Y J8 gt sd E d e 5 x i pen P 4 M r i BRIDGE BALANCE NULL DETECTOR CAL S3 s 5 v lt CRD US v M gue w 208 QN i gt ism RSIZ R1133 cass he og er eS AV IDE 150 PNIS RZQ opr te cas 39 536 K TO SE o lt TOU 2 UN TE be R207 TO SBA o x L s b ue i 4 23 CAL S3A 9 8 Po LY D E rR206 E gt 2 EMT 4 3873K SHUNT U WW A A l E RIIOO RIIO3 104 ROG 07 BE ns Riosst 25 23 2 25 23 2 25 23 2 25 25 2 now pt 4 O Rina ME RIIC2 RIOS lus a ES El 5 i 27 CAL C o sec o D EE MC RIO9 amp M 1 9 C
91. fg Co Inc Japan Branch Sumitomo Higashi Shinbashi Bldg 1 1 11 Hamamatsucho Minato ku Tokyo 105 Tel 81 3 434 0181 Korea Myoung Corporation Yeo Eui Do P O Box 14 Seoul 150 Tel 82 2 784 9942 Malaysia Mecomb Malaysia Sdn Bhd P O Box 24 46700 Petaling Jaya Selangor Tel 60 3 774 3422 Mexico Mexel Servicios en Computacion Instrumentacion y Perifericos Blvd Adolfo Lopez Mateos No 163 Col Mixcoac Mexico D F Tel 52 5 563 5411 Netherlands Philips Nederland Test amp Meetapparaten Div Postbus 115 5000 AC Tilburg Tel 31 13 352445 5 89 TECHNICAL SERVICE CENTERS New Zealand Philips Customer Support Scientific amp Industrial Division 2 Wagener Place Mt Albert Auckland Tel 64 9 894 160 Norway Morgenstierne amp Co A S Konghellegate 3 P O Box 6688 Rodelokka Oslo 5 Tel 47 2 356110 Pakistan International Operations PAK Ltd 505 Muhammadi House 11 Chundrigar Road P O Box 5323 Karachi Tel 92 21 221127 239052 Peru Importaciones amp Representaciones Electronicas S A Avad Franklin D Roosevelt 105 Lima 1 Tel 51 14 288650 Philippines Spark Radio amp ElectronicS Inc Greenhills P O Box 610 San Juan Metro Manila Zip 3113 Tel 63 2 775192 Portugal Decada Espectral Equipmentos de Elec e Cientificos Av Bomberios Voluntarios Lote 102B Miraflores Alges 1495 Lisboa Tel 351 1 410 3420 5 89 Singapore Rank O Connor s Si
92. following the instructions in paragraph 4 10 Only a minute amount of lubricating fluid should be applied After application exercise the switch by rotating it through all positions several times 4 14 Linearity Testing 4 15 The design of the 720A Voltage Divider is such that if the instrument is self calibrated if the leakage resistance is low and if the switch contacts display repeatable contact resistance the divider will meet its linearity specifications Because of the extremely tight over all specification 0 1 PPM of input very few laboratories will have both the necessary equip ment and the required technical skills to prove this The following linearity test using a second Model 720A as a standard is therefore intended only to indicate gross errors 0 2 PPM of input in the first decade and to prove specification on the lower decades The customer who hopes to prove more than this is referred to the following articles and papers 1 Andrew F Dunn Calibration of a Kelvin Varley Voltage Divider National Research Council Report No 7863 2 L Morgan and J C Riley Calibration of a Kelvin Varley Standard Divider IRE HIGH BALANCE PART OF 721A LEAD COMPENSATOR R LEAD NULL DETECTOR TEST DIVIDER 720A 845AB RLEAD lt LOW BALANCE PART OF T 721A LEAD COMPENSATOR 720A Trans on Instrumentation vol 1 9 pp 237 243 Sept 1960 4 16 compare divider li
93. ge source to the desired test voltage t Adjust the LOW BALANCE CONTROLS of the lead for testing D Decade compensator to obtain a zero indication on the null detector ac Turn the FUNCTION switch to CK D 720A SETTINGS PERMISSIBLE STANDARD DEVIATION MAX DIVIDER PPM of INPUT to TEST VOLTAGE B DECADE 8 9 999999X 9 Figure 4 7 DECADE LINEARITY TEST ad Set the standard divider to zero aj Set the divider under test to 1 0 99999X ae Set the divider under test to 1 0 990000 ak Adjust the HIGH BALANCE FINE control to obtain a zero indication on the null detector af Place the null detector in the zero mode adjust it for zero deflection and return it to operating al Set the divider under test back to 1 0 990000 and mode set the standard divider back to zero ag Adjust the LOW BALANCE controls of the lead am Re adjust the LOW BALANCE FINE control if compensator to obtain a zero indication on the null necessary to obtain a zero indication on the null detector detector ah Turn the HIGH BALANCE COARSE control to the an Set the null detector for the desired sensitivity same setting as the LOW BALANCE COARSE and make the linearity measurements given in control Figure 4 9 The null detector indications must be within the limits listed in the permissible ai Set the standard divider to full scale deviation column 4 9 720A ao ap aq ar as 4 10
94. he zero error at input low One microvolt equals 0 001 ppm d Connect the equipment shown in Figure 2 5 B e Adjust the input voltage to 1000 volts f With all dials set to zero measure the voltage between the OUTPUT HIGH and OUTPUT LOW terminals This is the zero error at output low One microvolt equals 0 001 ppm g Connect the equipment as shown in Figure 2 5 h Adjust the input voltage to 1000 volts i With dials set to 999999X measure the voltage between the OUTPUT HIGH and 1 0 terminals This is the full scale error One microvolt equals 0 001 ppm j Maintain the test set up of Figure 2 5 C except move the two leads connected to the 1 0 INPUT terminal to the 1 1 INPUT terminal k Adjust the input voltage to 1000 volts l With all dials set to 1 0 09999X measure the volt age between the OUTPUT HIGH and 1 1 INPUT terminals One microvolt equals 0 001 ppm 2 24 SELF CALIBRATION PROCEDURE 2 25 Performing this self calibration procedure ad justs the step resistance and overall resistance of the 720A Ht TH R ttt ot H 77 T 1012 FAUT SE SSR s H as ers MS tt tt e 5 HANK 05 THI Y Om 208 08 HH A H T
95. istance between the output high and low terminals When computing cor rection factors for loading of a particular instrument do not use the approximate resistance values given by Fig ure 2 3 Instead measure the output resistance at the desired dial setting The maximum amount of loading which will still be negligible for any dial setting may be calculated as follows a Divider specification 0 1 ppm of input b Maximum loading error limit 0 03 ppm of input d Maximum Ro 66 kilohms when S 454 SR 454 6 6 x 104 e Minimum R L EL 3 x 1078 1 x 1012 ohms 2 15 Similar calculations have been made for other dial settings and the results have been plotted in Figure 2 4 The choice of a loading error limit of 0 03 ppm was of course arbitrary and should vary over a wide range for different measurement applications In gen eral the error should be calculated and allowances made unless the errors are small compared to either the desired measurement accuracies or the divider specifications 2 16 It should be noted that resistances calculated are the parallel combinations of the load resistor and any leakage resistances which may exist from the tap point OUTPUT HIGH terminal to the input terminals of the divider 2 17 In applications where the load resistance must be supplied with a current this current may be supplied by either a stable power supply or a second voltage di vider in parallel with th
96. iv Cincinnati OH 95348 Gordos Corp Bloomfield NJ 95354 Methode Mfg Corp Rolling Meadows IL 95573 Campion Laboratories Inc Detroit MI 95712 Bendix Corp Electrical Comp Div Franklin IN 95987 Weckesser Co Inc Now 85480 96733 SFE Technologies San Femando CA 96853 Gulton Industries Inc Measurement amp Controls Div Manchester NH 96881 Thomson Industries Inc Port WA NY 97464 Industrial Retainer Ring Irvington NJ 97525 EECO Inc Santa Ana CA 97540 Whitehall Electronics Corp Master Mobile Mounts Div Fort Meyers FL 97913 Industrial Electronic Hardware Corp NY NY 97945 Pennwalt Corp SS White Industrial Products Piscataway NJ 97966 CBS Electronic Div Danvers MA 98094 Machlett Laboratories Inc Santa Barbara CA 98159 Rubber Teck Inc Gardena CA 98278 Malco A Microdot Co South Pasadena CA 98291 Sealectro Corp BICC Electronics Trumbill CT 98372 Royal Industries Inc Now 62793 98388 Lear Siegler Inc Accurate Products Div San Deigo CA 98978 IERC International Electronic Research Corp Burbank CA 99120 Plastic Capacitors Inc Chicago IL 99217 Bell Industries Inc Elect Distributor Div Sunnyvale CA 99378 ATLEE of DE Inc N Andover MA 99392 Mepco Electra Inc Roxboro Div Roxboro NC 99515 Electron Products Inc Div of American Capacitors Duarte CA 99779 Bunker Ramo Eltra Co
97. iving only the information specified in paragraph 5 4 4 40 The precision wirewound resistors used in the Model 720A are selected and matched during manufac ture to form a completely matched set Sufficient infor mation is marked on each of these resistors to permit replacement with a resistor which will match the others inthe set The following information should be given when one of these resistors is ordered from the factory a Serial number of the instrument b Reference designation of the resistor markings on the resistor If all markings on the defective resistor can not be read give the following information a Serial number of the instrument b Reference designation of the defective resistor c Reference designation and all part markings of the adjacent resistor on one side d Reference designation and all part markings of the adjacent resistor on the other side 4 41 SERVICE INFORMATION 4 42 The John Fluke Manufacturing Co Inc war rants each instrument manufactured by them for the period of one year upon making delivery of the instru ment to you the original purchaser Complete war ranty page located at the rear of this manual 4 43 I you should encounter any problem in the oper ation of your instrument please feel free to contact your nearest John Fluke Sales Representative or write directly to the John Fluke Manufacturing Co Inc with a statement of your problem 4 19 4 20 720
98. land Oy Philips AB Central Service Sinikalliontie 1 3 P O Box 11 SF 02630 ESPOO Tel 358 0 52572 France S A Philips Industrielle et Comerciale Science et Industry 105 Rue de Paris Bp 62 93002 Bobigny Cedex Tel 33 1 4942 8040 Germany F R G Philips GmbH Service fuer FLUKE Produkte Department VSF Oskar Messter Strasse 18 D 8045 Ismaning Munich West Germany Tel 49 089 9605 239 Greece Philips S A Hellenique 15 25th March Street 177 78 Tavros 10210 Athens Tel 30 1 4894911 Hong Kong Schmidt amp Co H K Ltd 18 FL Great Eagle Centre 23 Harbour Road Wanchai Tel 852 5 8330222 India Hinditron Services Pvt Ltd 1st Floor 17 B Mahal Industrial Estate Mahakali Road Andheri East Bombay 400 093 Tel 91 22 6300043 Hinditron Services Pvt Inc 33 44A Raj Mahal Villas Extn 8th Main Road Bangalore 560 080 Tel 91 812 363139 Hinditron Services Pvt Ltd Field Service Center Emerald Complex 1 7 264 5th Floor 114 Sarojini Devi Road Secunderabad 500 003 Tel 08 42 821117 Hindtron Services Pvt Ltd 15 Community Centre Panchshila Park New Delhi 110 017 Tel 011 6433675 Indonesia P T Lamda Triguna P O Box 6 JATJG Jakarta 13001 Tel 021 8195365 Israel R D T Electronics Engineering Ltd P O Box 43137 Tel Aviv 61430 Tel 972 3 483211 Italy Philips S p A Sezione I amp E T amp M Viale Elvezia 2 2005 Monza Tel 39 39 3635342 Japan John Fluke M
99. lead compensator to obtain a zero indication on the null bl Set the null detector for the desired sensitivity and detector make the linearity measurements given in Figure 4 11 The null detector indications must be within br Turn the HIGH BALANCE COARSE control to the the limits listed in the permissible deviation same setting as the LOW BALANCE COARSE column control bm Turn the FUNCTION switch to CK G bs Set the standard divider to full scale bn Set the standard divider to zero bt Set the divider under test 10 1 0 99999 4 12 720A PERMISSIBLE STANDARD DEVIATION MAX DIVIDER 120A PPM of INPUT to TEST VOLTAGE DECADE 8 9 999999X Figure 4 11 F DECADE LINEARITY TEST bu Adjust the HIGH BALANCE FINE control to obtain TION switch to OPR position the decade linearity a zero indication on the null detector tests are complete bv Set the divider under test back to 1 0 999990 and set 4 19 CALIBRATION the standard divider back to zero 4 20 Calibration of the Model 720A consists of cali bw Re adjust the LOW BALANCE FINE control if brating two standard resistance arms of the internal necessary to obtain a zero indication on the null Wheatstone bridge and calibrating the first three dec detector ades The bridge arms require calibration only if the BRIDGE BALANCE control has insufficient range bx Set the null detector for the desired sensitivity and to balance the bridge during
100. ley dividers cus tomarily are used in null balance systems in which minimum current is drawn from the divider output tap 2 1 720A o J pang itede veneesi s FUNCTION SWITCH Places instrument in operating mode or performs interr al switching for calibration or performs internal switching for decade linearity test DIALS Decade switches are used to set the ratio of output to input division ratio OUTPUT TERMINALS Provide output voltage of the divider LOW OUTPUT terminal is con nected to LOW INPUT terminal through low compensating resistance 4 BRIDGE POWER Used to connect the bridge power for calibration BRIDGE POWER TERMINALS terminal is used for low input during decade linearity testing BRIDGE DETECTOR Used to connect null detector for calibration TERMINALS INPUT TERMINALS Used to connect the input voltage across the resistance of the divider BRIDGE BALANCE _Used to balance bridge during self calibration and calibration ONTROL LT FUNCTIONS OF CONTROLS AND TERMINALS 2 10 Loading Errors If Ry gt gt Ro and is expanded in series 2 11 Figure 2 2 illustrates the Thevinin equivalent E Rr L for the Model 720A Kelvin Varley Divider then 2 Ro 3 To calculate the error in output voltage as a fraction 1 6 o 1 6 1 Ro E id of the input voltage the following ii are ds Ry Ry Ro Ro 281
101. lifier g Set both dividers to full scale and adjust the HIGH BALANCE FINE control to obtain a zero indication on the null detector h Set both dividers to zero and re adjust the LOW BALANCE FINE control if necessary to obtain a zero indication on the null detector 1 Set the null detector to the desired sensitivity j Set both dividers to the first comparison point and adjust the standard divider for a near zero indication on the null detector The dial settings of the two dividers plus the null detector reading shall agree within a tolerance of 0 2 PPM This criterion is applicable for input voltages of 100 volts or less k Continue to compare each setting of each decade until the comparison is complete The following dial setting combinations should be checked on each decade 0 all zeros 1 all zeros 1 dial 09 and all 9 except X in last 2 all zeros 2 dial 19 and all 98 except X in last 3 all zeros 3 dial 29 and all 9 except X in last 4 all zeros 4 dial 39 and all 95 except X in last 5 all zeros 5 dial 49 and all 95 except X in last 6 all zeros 6 dial 59 and all 95 except X in last 7 all zeros 7 dial 69 and all 95 except X in last 8 all zeros 8 dial 79 and all 9 except X in last 9 all zeros 9 dial 89 and all 9 except X in last 1 0 all zeros 10 dial 99 and ali 9 except X in last 1 1 dial 1 09 and all 95 except X in last 4 17 Decade Linearity Testing 4 18 The CK B through CK G
102. n an im pairment of linearity If evidence of this condition is present and exercising the switch fails to correct it the switch contact should be lubricated with a special purpose switch lubricant The product recommended for this pur pose is Rykon lubricant No 2 EP American Oil Co mixed with Tuluol It should be carefully applied in a very thin film with a camel s hair brush Rev 2 Rev 2 EREGI BALANTE DIELECTRIC SHEET EC oo wna sasan PERS RIE BOBS 11131 ait ae BABES 53 2 AAA MER CMPLGARTE 00141105 PERIS s que S8 cans nese CA 8 e 48 NOTE To prevent problems from current loops connect mr each instrument to a common mO grounding point preferably R k M on the power source On the 1 1 shielded cables connect one end of the shield to ground and leave the other end open 720A 3328 845AB Figure 4 2 EQUIPMENT CONNECTIONS FOR LEAKAGE RESISTANCE TEST 120A 332B 720A GRRE ETNA OIRO sassa Rev 2 k enti MD CDM UNUM NR AAN NAVARRA T UT o RAR SOOO HRSA A OOK KK PP OO IKE OCR SOOO N CODE CO s STO
103. nearity connect the equip ment as shown in Figure 4 3 and proceed as follows NOTE Figure 4 4 is a schematic diagram of the test set up obtained by interconnecting the equipment as shown in Figure 4 3 a Self calibrate the Model 720A 2 24 in Section II See paragraph b Set both dividers to zero c Set the voltage source to the desired test voltage turn on all equipment and allow it to warm up until it reaches temperature equilibrium d Place the null detector in the zero mode adjust it for zero deflection and return it to operating mode Adjust the LOW BALANCE controls of the lead compensator to obtain a zero indication on the null detector f Turn the HIGH BALANCE COARSE control to the same setting as the LOW BALANCE COARSE control NOTE If the dividers are set from one calibration point to the next while the test setup is energized the null detector meter will require several seconds to recover between readings Measurement may RIEAD STANDARD 332B DIVIDER VOLTAGE 720A STANDARD R LEAD Figure 4 4 SIMPLIFIED SCHEMATIC DIAGRAM OF LINEARITY COMPARISON TEST 4 5 720A be performed more rapidly if the VOLTAGE switch of the lead compensator is turned to OFF before switching Measurement may be speeded further by turning the ZERO OPR switch of the null detector to ZERO during switching This prevents the transient caused by turning the voltage on from saturating the null detector amp
104. ngapore PTE Ltd 98 Pasir Panjang Road Singapore 0511 Tel 65 4737944 South Africa South African Philips Pty Ltd Service Department 195 Main Rd Martindale Johannesburg 2092 Tel 27 11 470 5255 Spain Philips Iberica S A E Depto Tecnico Instrumentacion c Martinez Villergas 2 28027 Madrid Tel 34 1 4042200 Sweden Philips Kistaindustrier AB Customer Support Borgarfjordsgatan 16 S 16493 Kista Switzerland Philips A G Technischer Kundendienst Postfach 670 Allmendstrasse 140 CH 8027 Zurich Tel 41 1 482211 Taiwan Schmidt Electronics Corp 5th Floor Cathay Min Sheng Commercial Building 344 Min Sheng East Road Taipei Tel 886 2501 3468 Thailand Measuretronix Ltd 2102 63 Ramkamhaeng Rd Bangkok 10240 Tel 66 2 374 2516 374 1632 Turkey Turk Philips Ticaret A S Inonu Caddesi 78 80 Posta Kutusu 504 Beyoglu Istanbul Tel 90 1 1435891 Uruguay Coasin Uruguaya S A Casilla de Correo 1400 Libertad 2525 Montevideo Tel 598 2 789015 Venezuela Coasin C A Calle 9 Con Calle 4 Edif Edinurbi Apartado de Correos Nr 70 136 Los Ruices Caracas 1070 A Tel 58 2 241 0309 241 1248 West Germany Philips GmbH Department VSF Service fuer FLUKE Produkte Oskar Messter Strasse 18 D 8045 Ismaning Munich Tel 49 089 9605 260 7 13 7 14 X uncus ee r bh Ags Ma Dare m
105. nsilco Co RPC Div Hayesville NC 6L611 Allen Robert G Inc Van Nuys CA 6U850 Burgess Switch Co Inc Northbrook IL 6U095 AMD Enterprises Inc Roswell GA 6X403 SGS ATES Semiconductor Corp INpolis IN 6Y440 Micron Technology Inc Boise ID 60046 Power Dynamics Inc West Orange NJ 60197 Precicontact Inc Langhome PA 60386 Squires Electronics Inc Cornelius OR 60395 Xicor Inc Milpitas CA 60399 Torin Engincered Blowers Div of Clevepak Corp Torrington CT 60496 Micrel Inc Sunnyvale CA 60705 Cera Mite Corp formerly Sprague Grafton WI 60911 Inmos Corp CO Springs CO 60935 Westlake Capacitor Inc Tantalum Div Greencastle IN 60958 ACIC Intercomp Wire amp Cable Div Hayesville NC 61271 Fujitsu Microelectronics Inc San Jose CA 61394 SEEQ Technology Inc San Jose CA 61429 Fox Electronics Cape Coral FL 61529 Aromat Corp New Providence NJ 61752 IR ONICS Inc Warwick RI 61772 Integrated Device Technology Santa Clara CA 61802 Toshiba Houston TX 61857 SAN O Industrial Corp Bohemia Long Island NY 61935 Schurter Inc Petaluma CA 62351 Apple Rubber Lancaster NY 62643 United Chemicon Rosemont IL 62712 Seiko Instruments Torrance CA 62793 Lear Siegler Inc Energy Products Div Santa Ana CA 63743 Ward Leonard Electric Co Inc Mount Vernon NY 64154 Lamb Industries Portland OR 64155 Line
106. od MA 02395 Sonar Radio Corp Hollywood FL 02533 Leigh Instruments Ltd Frequency Control Div Don Mills Ontario Canada 02606 Fenwal Labs Division of Travenal Labs Morton Grove IL 02660 Bunker Ramo Eltra Corp Amphenol NA Div Broadview IL 02697 Parker Hannifin Corp O Ring Div Lexington KY 02735 RCA Solid State Div Somerville NJ 02768 ITW IL Tool Works Fastex Division Des Plaines IL 02799 Arco Electronics Inc Chatsworth CA 03296 Nylon Molding Corp Monrovia CA 03445 Lercon Electronics Inc Burbank CA 03508 General Electric Co Semiconductor Products amp Batteries Aubum NY 03797 Genisco Technology Corp Eltronics Div Rancho Dominquez CA 03877 Gilbert Engineering Co Inc Incon Sub of Transitron Electronic Corp Glendale AZ 03888 KDI Electronics Inc Pyrofilm Div Whippany NJ 03911 Clairex Corp Clairex Electronics Div Mount Vernon NY 03980 Muirhead Inc Mountainside NJ 04009 Cooper Industries Inc Arrow Hart Div Hartford CT 04217 Essex Intemational Inc Wire amp Cable Div Anaheim CA 04221 Midland Ross Corp Midtex Div N Mankato MN 04222 AVX Corp AVX Ceramics Div Myrtle Beach SC 04423 Telonic Berkley Inc Laguna Beach CA 04713 Motorola Inc Semiconductor Group Phoenix AZ 04946 Standard Wire and Cable Rancho Dominquez CA 05173 General Radio NY NY Replaced by 24655 Genrad INC
107. on Dynamics Div Torrance CA 73445 Amperex Electronic Corp Hicksville NY 73559 Carlingswitch Inc Hartford CT 73586 Circle F Industries Trenton NJ 73734 Federal Screw Products Inc Chicago IL 73743 Fischer Special Mfg Co Cold Spring KY 73893 Microdot Mt Clemens MS 73899 JFD Electronic Components Div of Murata Erie Oceanside NY 73905 FL Industries Inc San Jose CA 73949 Guardian Electric Mfg Co Chicago IL 74199 Quam Nichols Co Chicago IL 74217 Radio Switch Co Marlboro NJ 74306 Piezo Crystal Co Div of PPA Industries Inc Carlisle PA 74445 Holo Krome Co Elmwood CT 74542 Hoyt Elect Instr Works Inc Penacook NH 74840 IL Capacitor Inc Lincolnwood IL 74970 Johnson EF Co Waseca MN 75042 TRW Inc IRC Fixed Resistors Philadelphia PA 75297 Kester Solder Div Litton Systems Inc Des Plaines IL 75376 Kurz Kasch Inc Dayton OH 75378 CTS Knights Inc Sandwich IL 75382 Kulka Electric Corp Now 83330 Mount Vernon NY 75569 Performance Semiconductor Corp Sunnyvale CA 75915 Littelfuse Tracor Formerly Tracor Littelfuse Des Plaines IL 76854 Oak Switch Systems Inc Crystal Lake IL 71122 TRW Assemblies amp Fasteners Group Fastener Div Moutainside NJ 77342 Potter amp Brumfield Div Princeton IN 77542 Ray O Vac Corp Madison WI 77638 General Instrument Corp Rectifier Div
108. or Inc San Jose CA 005 7 Conductive Pkg Containers Inc Brookfield WI OCLN7 Emhart Fastening Group Shelton CT OFB81 S Mos Systems Inc San Jose CA OFFP1 Eveready LTD Ever Ready Special Battery Div Dawley Telford Salop UK 00199 Marcon Electronics Corp Keamy NJ 00213 Nytronics Comp Group Inc Darrlingon NC 00327 Welwyn Intemational Inc Westlake OH 00656 Aerovox Corp New Bedford MA 00686 Film Capacitors Inc Passaic NJ 00779 AMP Inc Harrisburg Pennsylvania 00853 Sangamo Weston Inc Components Div Pickens NC 01091 Allied Plastics Co Los Angeles CA 7 2 Federal Supply Codes for Manufacturers 01101 Wabash Inc Formerly Wabash Magnetics Wabash IN 01121 Allen Bradley Co Milwaukee WI 01281 TRW Electronics amp Defense Sector Devices Lawndale CA 01295 TX Instruments Inc Semiconductor Group Dallas TX 01526 Genicom Waynesboro VA 01537 Motorola Communications amp Electronics Inc Franklin Park IL 01686 RCL Electronics Shallcross Inc Electro Components Div Manchester NH 01884 Sprague Electric Co Now 56289 01961 Varian Associates Inc Pulse Engineering Div Convoy CT 01963 Cherry Electrical Products Corp Waukegan IL 02111 Spectrol Electronics Corp City of Industry CA 02114 Ampcrex Electronic Corp Ferrox Cube Div Saugerties NY 02131 General Instrument Corp Government Systems Div Westwo
109. rad Melrose Park IL 36665 Mitel Corp Kanata Ontario Canada 36701 Van Waters amp Rogers Valley Field Quebec Canada 37942 Mallory Capacitor Corp Sub of Emhart Industries INpolis IN 39003 Maxim Industries Middleboro MA 4F434 Plastic Sales Los Angeles CA 40402 Roderstein Electronics Inc Statesville NC 42498 National Radio Melrose MA 43543 Nytronics Inc Now 53342 43744 Panasonic Industrial Co San Antonio TX 43791 Datron Systems Wilkes Barre PA 44655 Ohmite Mfg Co Skokie IL 47001 Lumberg Inc Richmond VA 47379 ISOCOM Campbell CA 49569 IDT International Development amp Trade Dallas TX 49671 RCA Corp New York NY 49956 Raytheon Company Executive Offices Lexington MA 50590 Mostek Corp Replaced by SGS Thompson Microelec tronics 5F520 Panel Components Corp Santa Rosa CA 5P575 Nobel Electronics Suffem NY 5W664 NDK Div of Nihon Dempa Kogyo LTD Lynchburg VA 5U802 Dennison Mfg Co Framingham MA 50088 SGS Thomson Microelectronics Inc Carrollton TX 50120 Eagle Picher Industries Inc Electronics Div CO Springs CO 50157 Midwest Components Inc Muskegon MS 50356 Teac Corp of America Industrial Products Div Montebello CA 50364 MMI Inc Monolithic Memories Inc Military Products Div Santa Clara CA 50472 Metal Masters Inc City of Industry CA 50541 Hypertronics Corp Hudson MA 5055
110. rp Bames Div Lansdown PA 99800 American Precision Industries Delevan Div East Aurora NY 99942 Mepco Centralab A North American Philips Co Milwaukee WI 7 11 TECHNICAL SERVICE CENTERS U S Service Locations California Fluke Technical Center 16969 Von Karman Avenue Suite 100 Irvine CA 92714 Tel 714 863 9031 Fluke Technical Center 46610 Landing Parkway Fremont CA 94538 Tel 415 651 5112 Colorado Fluke Technical Center 14180 East Evans Avenue Aurora CO 80014 Tel 303 695 1171 Florida Fluke Technical Center 940 N Fern Creek Avenue Orlando FL 32803 Tel 407 896 4881 Illinois Fluke Technical Center 1150 W Euclid Ave Palatine IL 60067 Tel 312 705 0500 Maryland Fluke Technical Center 5640 Fishers Lane Rockville MD 20852 Tel 301 770 1576 New Jersey Fluke Technical Center East 66 Midland Avenue Paramus NJ 07652 0930 Tel 201 599 9500 Texas Fluke Technical Center 1801 Royal Lane Suite 307 Dallas TX 75229 Tel 214 869 2848 Washington Fluke Technical Center John Fluke Mfg Inc 1420 75th St S W M S 6 30 Everett WA 98203 Tel 206 356 5560 International Argentina Coasin S A Virrey del Pino 4071 DPTO E 65 1430 CAP FED Buenos Aires Tel 54 1 522 5248 Australia Philips Customer Support Scientific and Industrial 23 Lakeside Drive Tally Ho Technology Park East Burwood Victoria 3151 Australia Philips Customer
111. rve the range of the BRIDGE BAL ANCE control on the Null Detector and place the BRIDGE BALANCE control at the electrical center i Adjust R1130 Decade 0 for 0 10 microvolts NOTE The BRIDGE BALANCE control R205 and R1130 are now set to give a nominal 4007 6 ohm reference and the self cal procedure in paragraph 4 21 will make the other positions of the C Decade the same value If there is not enough range to trim the remaining posi tions of the C Decade to this nominal value repeat steps a through i with different settings for R205 and R1130 If calibration still is not possible retum the 720A to the factory for repair 1 Disconnect the test equipment calibration of the 4 kilohm bridge standard is complete 428 TROUBLESHOOTING 4 29 Troubles in the Model 720A may be located most easily by performing the decade linearity test described in paragraph 4 15 and analyzing the results Reference to the schematic diagram will greatly assist in the anal ysis Before attempting to locate the trouble the in strument should first be cleaned following the procedure described in paragraph 4 10 and the leakage resistance should be measured following the procedure described in paragraph 4 8 4 30 Because of the passive nature of the instrument troubles will be limited to defective resistors defective switches defective wiring and excessive leakage will usually be corrected by cleaning If repeated clean ing fails to correct
112. s Inc Orlando FL 14193 Cal R Inc Santa Monica CA 14301 Anderson Electronics Hollidaysburg PA 14329 Wells Electronics Inc South Bend IN 14482 Watkins Johnson Co Palo Alto CA 14552 Microsemi Corp Formerly Micro Semiconductor Santa Ana CA 14604 Elm wood Sensors Inc Pawtucket RI 14655 Comell Dublier Electronics Div of Federal Pacific Electric Co Govt Cont Dept Newark NJ Manufacturers cont 14704 Crydom Controls Division of Int Rectifier El Segundo CA 14752 Electro Cube Inc San Gabriel CA 14936 General Instrument Corp Discrete Semi Conductor Div Hicksville NY 14949 Trompeter Electronics Chatsworth CA 15412 Amtron Midlothian IL 15542 Scientific Components Corp Mini Circuits Laboratory Div Brooklyn NY 15636 Elec Trol Inc Saugus CA 15782 Bausch amp Lomb Inc Graphics amp Control Div Austin TX 15801 Fenwal Eletronics Inc Div of Kidde Inc Framingham MA 15818 Teledyne Inc Co Teledyne Semiconductor Div Mountain View CA 15849 Useco Inc Now 88245 15898 International Business Machines Corp Essex Junction VT 16068 Intemational Diode Div Harrison NJ 16162 MMI Southfield MI 16245 Conap Inc Olean NY 16258 Space Lok Inc Burbank CA 16352 Codi Corp Linden NJ 16469 MCL Inc LaGnange IL 16473 Cambridge Scientific Industries Div of Chemed Corp Cambridge MD 16733 Cablewa
113. t Equipment Connections for Linearity Comparison Test Simplified Schematic Diagram of Linearity Comparison Test Equipment Connections for Decade Linearity Test Simplified Schematic Diagram of Decade Linearity Test B Decade Linearity Test Decade Linearity Test Decade Linearity Test E Decade Linearity Test F Decade Linearity Test Decade Linearity Test Internal Function Switch Equipment Connections for Self Calibration 720A Kelvin Varley Voltage Divider Front Panel Assembly Trimmer P C Assembly Bridge P C Assembly Decade Switch Assembly Decade Switch Assembly D E F and Decades Switch Assembly PAGE 3 2 4 2 4 3 4 4 4 5 4 7 4 8 4 9 4 10 4 11 4 12 4 13 4 14 4 16 4 17 5 4 5 5 5 6 5 8 5 9 5 13 5 14 5 15 5 17 Rev 2 720A NEUE ROW MODEL 720A KELVIN VARLEY VOLTAGE DIVIDER 720A Section 1 Introduction amp Specifications 1 1 INTRODUCTION 1 2 The Model 720A Kelvin Varley Voltage Divider is a seven dial primary ratio standard which meets the most exacting requirements of the standards laboratory Absolute linearity of 0 1 ppm temperature coefficient of linearity of 0 1 ppm C and self calibration make the 720A the most accurate instrument available for the comparison of primary and secondary voltage and re sistance
114. t per million at the time of adjustment 1 5 ELECTRICAL SPECIFICATIONS RATIO RANGE 0 to 1 0 1 0 INPUT TAP and 0 to 1 1 1 1 INPUT TAP RESOLUTION 0 1 ppm of input with 7 decades ABSOLUTE LINEARITY at calibration temperature and without the use of a cor rection chart 0 1 ppm of input at dial settings of 1 1 to 0 1 0 1 108 1 3 of input at dial settings S of 0 1 to 0 See Figure 1 1 ABSOLUTE LINEARITY STABILITY without self cali bration 1 0 ppm of 1 0 108 2 0 1 to 0 See Figure 1 2 nput year at dial settings of 1 1 to 0 1 ppm of input year at dial settings S of NOTE The self calibration procedure may be used at any time to reset absolute linearity to 0 1 ppm of input TEMPERATURE COEFFICIENT OF LINEARITY 40 1 ppm of input C maximum at dial settings of 1 1 to 0 1 See Figure 1 3 SHORT TERM LINEARITY STABILITY Under typical conditions in a standards laboratory en vironment temperature maintained within 1 C and with an applied voltage of up to 100 volts stability of linearity is 0 1 ppm 30 days 1 1 720A 4567891 AN 14866 2 RT Uno n ug e i 4367891W E H 10 mum m _ N e aoron M 1 0 A 10 1 B 1072 a
115. tage of the Model 720A by the numerical setting of the readout dials For example if the input voltage is 100 volts and the dial setting is 8903174 the unknown voltage is 89 03174 volts 2 10 2 36 Simplified Method of Voltage Measurement 2 37 Voltages under 11 volts may be measured with comparable accuracy by the simpler equipment setup shown in Figure 2 12 This method standardizes the output voltage of the Model 720A by comparing it directly to a known standard cell When used with an input of 1 1 volts it is ideally suited to the accurate certifi cation of standard cells Typical associated equipment for this application is listed in Figure 2 11 2 38 To measure the unknown voltages connect the equipment as shown in Figure 2 12 and proceed as follows a Set the dc voltage source for an output of eleven or 1 1 volts depending on the desired range and allow to warm up b Set the readout dials of the Model 720A to the stand ard cell voltage c Connect the standard cell in place of the unknown voltage and adjust the dc source to obtain a null indication on the null detector d Disconnect the standard cell e Set the readout dials of the Model 720A to the ap proximate value of the unknown voltage f Connect the unknown voltage g Adjust the readout dials of the Model 720A to obtain a null indication on the null detector h Calculate the unknown voltage by multiplying by 10 or 1 depending on the range
116. the condition the instrument should be returned to the factory for repair 4 31 Not only may resistor defects be isolated toa particular step of a decade by the linearity test but also the nature of the defect may be determined A resistor may be shorted open over value or under value Because the switch contacts span two steps of resistance in all decades except the seventh the Rev 2 effect caused directly by a defective resistor will be seen at two adjacent switch positions In the through G decades the linearity test will isolate the defect to a particular resistor In the A B and decades each step is made up of several resistors and each resistor in the step will have to be measured to find the defect In these decades the variable trim mer resistor in the defective step should be checked by monitoring it and sweeping it from stop to stop several times If the variation is not smooth it should be re placed If one of the resistors in the oil tank or one of the factory selected fixed resistors is found to be defective the instrument should be returned to the fac tory for repair 4 32 resistance of the decade thereby increasing the pro portional value of all steps except the one containing the shorted resistor The proportional value of this step will be very low 4 33 An open resistor in any decade will prevent any output until the switch is advanced so the contacts span the open resistor
117. ve Systems Inc North Haven CT 16742 Paramount Plastics Fabricators Inc Downey CA 16758 General Motors Corp Delco Electronics Div Kokomo IN 17069 Circuit Structures Lab Burbank CA 17117 Electronic Molding Corp Woonsocket RI 17338 High Pressure Eng Co Inc OK City OK 17504 Aluminum Filter Co Carpinteria CA 17545 Atlantic Semiconductors Inc Asbury Park NJ 17745 Angstrohm Precision Inc Hagerstown MD 17856 Siliconix Inc Santa Clara CA 18178 E G amp Gvactee Inc St Louis MO 18235 KRL Bantry Components Inc Manchester NH 18310 Concord Electronics New York NY 18324 Signetics Corp Sacramento CA 18377 Parlex Corp Methuen MA 18520 Sharp Electronics Corp Paramus NJ 18542 Wabash Inc Wabash Relay amp Electronics Div Wabash IN 18565 Chomerics Inc Wobum MA 18612 Vishay Intertechnology Inc Vishay Resistor Products Group Malvem PA 18632 Norton Chemplast Santa Monica CA 18677 Scanbe Mfg Co Div of Zero Corp El Monte CA 18736 Voltronics Corp East Hanover NJ 18786 Micro Power Long Island City NY 18927 GTE Products Corp Precision Material Products Business Parts Div Titusville PA 19080 Robinson Electronics Inc San Luis Obispo CA 19112 Garry Corp Langhome PA 19315 Bendix Corp The Navigation amp Control Group Terboro NJ 19451 Perine Machine Tool Corp Kent WA 19482 Delta Electronics
118. vents the transient caused by turning the voltage on from saturating the null detector amplifier Set the standard divider to full scale Set the divider under test to 1 0 99999X Adjust the HIGH BALANCE FINE control to obtain a zero indication on the null detector Set the divider under test back to 1 0 000000 and set the standard divider back to zero Re adjust the LOW BALANCE FINE control if necessary to obtain a zero indication on the null detector Set the null detector for the desired sensitivity and make the linearity measurements given in Figure 4 7 The null detector indications must be Rev 2 o pee JUE HB pU PRLS BAERE 2g 384 m is SG 1118 HERB Beet v8 BREREOE nene 2 91 8 35 78 INESE 17 STEP OUTPUT STANDARD DIVIDER NOTE prevent problems from current loops connect Ae each instrument to a common grounding point preverably I on the power source On the shielded cables connect one end of the shield to ground and leave the other end open 720A BALANCE 364 8646525 ASA toot i 8 l r SBA KESIN Figure 4 5 EQUIPMENT CONNECTIONS FOR DECADE LINEARITY TEST 720A 4 7 720A R LEAD R LEAD C

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