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GR 1864-1644 Megohmmeter Manual

1. ATH T n WH RD R23 m e IK 24 9K T me gn R230 R232 He 100KS IOM ss 22K atis Ti RM db RIO7 100 l WH BR BK 2k RR GUARD quo SRU R2 RIS Ria fo RIO Sek 58 R2TOKR 120K p 390K 12M i F 9K f EI Joe B 9 i 309F 310 I E c EBC CASElo 5 a dco 108 so sig os 7pDW0gF RIOS HI i RI24 g FOR WAVER Waves 226K BOTTOM VIEW OF BOTTOM VIEW OF BOTTOM VIEW OF 109F TOW Q102 Q103 QIOI Q201 Q202 0204 109 sio3 uj 0205 0205 sitio mie Lit R245 E or pF briog E 5103 c ge EN 470 o MEASURE sos T PN SEES CHARGE RIO 416103 eios 7 4T Fp gOS e NH ve o DISCHARGE i AT28 5202 08F RIO4 c104 Y RIO6 e 0 R235 WH GY BU J 70 5 B gt eos Taro CR S162265F DANGER Ra CRIOG Q20 wie a x SIO2 204R WH GY RD 00K STEP SOK STEP N 7 5 m pr 26729 RISO 133 ATIC e SIO2 2028 Sii so f 5 102 m on 209R 202F 209R 202F RIGI c 201 1 oxen GN SY zoon STEP 30K Oates I RD 109F R221 224 5101 et i IFIQ6F O4F 5 IO2F 101F 098 sio f so sioz S103 T WH OR BR jo 102 109R 102F iQIF i i 5 at ATWHGNBK r 5 136 9e WH RD BK WH RD BR CRIOB i sm 289 3888 OK PRECISION RESISTORS R220 68219 lt R26 R
2. R227 MIQH rd aw R Ya K 203R i oar eJ Z 174W R228 wo 806 A r R215 1 4w Je mI A WH RD BK RIOD RHO RHI 5 62K 68K 270k Ww oc iw RUS 39k sios WH VT Bk IW 104F D I 310F R224 R24 ARM oe N VT BU IWH GY RD Ru R213 d E d 1 390k _ RUZ 120K WH YE WH RD BK WH GN BK RI 5 3 100K VEN 4 4105 75 VIC BU Vew MIOI SIO3 I05F v AT23 Sio2 i09R ATS stor S101 Figure 7 4 Type 1864 switching diagram 1ejeuiugoBeyy Ajuejod eAnisod tt9L r98L 1864 1644 Positive Polarity Megohmmeter i 1 nM RRR 1 POSITION OF ROTARY SWITCHES SHOWN COUNTERCLOCKWISE 2 CONTACT NUMBERING OF SWITCHES EXPLAINED ON SEPARATE SHEET SUPPLIED IN INSTRUCTION BOOK 3 REFER TO SERVICE NOTES IN INSTR UCTION BOOK FOR VOLTAGES APPEARING ON DIAGRAM 4 RESISTORS 1 2 WATT NOG 200 ANCHOR TERMINALS USED AT 2A 2B 3 THRU 25 NOTE UNLESS SPECIFIED 3 RESISTANCE IN OHM s 1000 OHMS M 1 MEGOHM CAPACITANCE VALUES ONE AND OVER IN PICOFARADS LESS THAN ONE IN MICROFARADS O CONTROL 6 SCREWDRIVER CONTROL AT ANCHOR TERMINAL TEST POINT i25 550 tior REGULATED DC SUPPLY
3. 15 4 4 Resistance Measurement 16 4 5 Measurement of Voltage Coefficient 16 4 6 Guarded 3 Terminal Measurements eese 17 4 7 Remote Shielded Measuremensts eee 17 4 8 Measurements Under Humid Conditions esee 17 Chapt er5 THEORY 19 19 5 2 Circuit ee eO HR 19 PARE e r sus 19 5 2 2 Type 1863 Megohmmeter Figure 7 6 esses 19 5 2 3 Type 1864 Megohmmeter Figure 7 9 20 Chapter 6 SERVICE AND 21 21 6 3 Cabinet Removal sr yas uqapas maa aao mi a 23 6 4 Troubleshooting diets ten idea nai D De d e e dern 23 GAS General posts ertet ERR Ce De costs 23 64 2 Test Voltages edo Se etu ter REED ERI ar tad ture 24 6 5 Calibration Procedute 5r erri ei OR ER T Eee eder ure 24 qe 24 6 5 2 Meter Tracking sez 24 65 Voltage ACCUTACY 24 6 5 4 Range Resistor ACCUFACy iecit eoi ber ee c PEE RE Fea cect 25 6 5 5 Coarse co Adjustment isis er EP 25 6 6 MOD REMIO Val eevee E eases 26 6 7 Knob Was ta Wat Oth 27 6 8 Meter Cover Care a aaa ed EE 27 Chapter 7 PARTS L
4. 100V This voltage coefficient is usually negative except for reversed semiconductor junctions GUARD 1863 64 2 Figure 4 3 Guarded measurement of a three terminal resistor APPLICATIONS 4 6 Guarded 3 Terminal Measurements In many cases it is necessary to measure the resistance between two points in the presence of resistance from each of these points to a third point This third point can often be guarded to avoid error caused by the extraneous resistances This situation can be shown diagrammatically as a three terminal resistor Figure 4 3 Here R is the quantity to be measured in the presence of R and R If the junction of R and R is tied to a guard R is placed across the power supply and has no effect if it is greater than 500 R shunts R and causes a much smaller error than that which would be pres ent ifno guard were used The error is approximately RJR x 100 where R equals the value shown in Table 4 1 for the various ranges Ifa choice is pos sible the higher of the two stray resistances should be connected as R The guard terminal can be used whether the GUARD or the UNKNOWN terminal is grounded but note that if the UNKNOWN terminal is grounded the GUARD terminal will be a high positive voltage level Often the terminal to be guarded is a large chas sis and it is therefore safer to ground the GUARD terminal If this third terminal is true ground then the GUARD terminal must b
5. Recommended Equipment GR 1433 H Decade Resistor P N 1433 9733 GR 1644 Megohm Bridge GR 274 NP Double Plug Patch Cord Right Angle Plug 36 in long P N 0274 9980 GR 274 LLB Single Plug Patch Cord black 36 in long P N 0274 9468 Data Precision 3400 Digital Voltmeter Xcelite Type X 102 Phillips Screwdriver SHORTING LINK PATCH CORD N N UNKNOWN 22 cords 18 Connect the two ground terminals together with a third patch cord Figure 6 1 The megohmmeter shorting link should remain attached only to the ground terminal 19 Set the multiplier switch in the full ccw posi tion 1M 100k and the function switch to MEASURE 20 Measure the various standard resistors of the megohmmeter with the DMM according to the settings and tolerances of Table 6 2 Use the IET LOM 510A megohm meter for resistance values beyond the range of the DMM MEGOHM BRIDGE GR 1863 OR 1864 MEGOHMMETER UNKNOWN 1863 64 3 Figure 6 1 Connections for measuring standard resistors with a digital multimeter SERVICE AND MAINTENANCE 1864 1644 Positive Polarity Megohmmeter 6 3 Cabinet Removal Table 6 3 remove the instrument from the cabinet remove TYPE 1863 TEST VOLTAGES the two screws on the rear of the instrument cabinet and pull the instrument out of the cabinet Test Point 4 Test Point Voltage V CR105 Anode Q101 Emitter 174 Q101 Coll
6. CE tee ustedes 7 2 3 Repackaging for Shipments Or o T A E E E EET 8 2 5 Bench dee EEEE 8 ps Oliveti 2 7 Power Comme Ct Ons romei rai naic Chapter 3 OPERATION 9 3 1 Measurement Setup acces as 9 3 1 1 Ground Link Connection street ertet te dece rtt ice ded 9 3 1 2 Test Voltage Selection 9 3 1 4 entere seien ee 9 2 2 Measurement Procedee eierne u nter RR o Ee WIRED 10 PR E tes gol leper eee ners rere panas ESAE INDE 10 3 2 2 SCarch PrOCeGUIS 10 3 2 3 SOM OR 10 3 24 Shock Hazard uyana nayasa ep nates 10 3 3 O tput Jacekuy rierren 11 Chapter 4 APPLICATIONS J J J J J J 13 4 1 Insulation Testing au 13 4 2 Test Sample Resistivity Measurements sss 14 43 T General ce ORO SW 14 452 Charpgins Time Constant ios 5o eie Dante E 14 CONTENTS FIGURES AND TABLES 1864 1644 Positive Polarity Megohmmeter 4 3 3 Measurement Time Constant trt e e teg 15 4 34 Discharge TIME 5 eerte EUREN ER TREE REFERS ES REL EE EIE GROS 15 4 3 5 Large Capacitors Very High Resistance
7. The reading should be 0 5 3 that is 2 1 meter reading or 2 1 0 5 3 10 Set the decade resistor to 1 000 000 1 MQ The meter should read 1 496 11 Set the decade resistor to 5000000 5 MQ The meter should read 5 1296 12 Set the TEST VOLTAGE switch to 10 V 13 Set decades to 5 000 000 5 MO and the MULTIPLIER to 10M The meter should read 0 5 396 14 Increase the voltage to 20 V The meter reading should remain at 0 5 396 15 Continue to increase the voltage settings and observe that the meter reading remains at 0 5 396 NOTE When the light under the 1 M on the multiplier switch goes out the switch must be rotated so that the 1 M on the adjacent scale is lighted 21 1864 1644 Positive Polarity Megohmmeter Name DECADE RESISTOR MEGOHM BRIDGE PATCH CORD PATCH CORD EVM SCREWDRIVER or equivalent Table 6 1 TEST EQUIPMENT Function Standard resistor 0 02 for checking ranges 500 kQ to 10 MQ Bridge for measuring the standard resistors of the megohmmeter Connects decade resistor to megohmmeter Connect megohm bridge to megohmmeter 3 required Measurement of dc and ac voltages No 2 Phillips head screwdriver for internal adjustments 16 Set the POWER OFF switch to OFF and disconnect the decade resistor 17 Connect the Digital Multimeter between the GUARD and UNKNOWN terminals with two single banana plug patch GR 1644
8. PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT 1864 1644 Positive Polarity Megohmmeter User and Service Manual Copyright 2014 IET Labs Inc Visit www ietlabs com for manual revision updates 1864 1644 im October 2014 aaa ietlabs TEL 516 334 5959 FAX 516 334 5988 PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT e 0 aa ietlabs IET l ET LABS l NC 516 334 5959 FAX 516 334 5988 WARRANTY We warrant that this product is free from defects in material and workmanship and when properly used will perform in accordance with applicable IET specifications If within one year after original shipment it is found not to meet this standard it will be repaired or at the option of IET replaced at no charge when returned to IET Changes in this product not approved by IET or application of voltages or currents greater than those allowed by the specifications shall void this warranty IET shall not be liable for any indirect special or consequential damages even if notice has been given to the possibility of such damages THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE N WARNING N OBSERVE ALL SAFETY RULES WHEN WORKING WITH HIGH VOLTAGES OR LINE VOLTAGES Dangerous voltages may be present inside this instrument Do not open t
9. makes the instrument easy to analyze because the problem can usually be located quickly in either the voltage regulator or in the meter circuit t This value only appears as a fixed resistor in the 1864 Since the value is determined by feedback multiplication of the 200 M resistor in the 1863 no measurement should be made with the mogohm bridge This range only appears on the 1864 Its range value is determined from the feedback mul tiplication of the 2 G resistor therefore no mesurement should be made with the megohm bridge SERVICE AND MAINTENANCE 23 1864 1644 Positive Polarity Megohmmeter Ifthe instrument is completely inoperative be sure to check the power line connection and the fuse located in the IEC power input assembly on the rear panel 6 4 2 Test Voltages Tables 6 3 and 6 4 lista number of typical test voltages to assist in trouble analysis Figures 6 2 through 6 5 and the diagrams of Section 7 will assist in locating components for testing purposes 6 5 Calibration Procedure 6 5 1 General The accuracy of the 1863 and 1864 depends on the accuracy of the range resistors the accuracy of the applied voltages and the meter tracking accuracy The over all accuracy can be checked most easily by checking each one of these contributing quantities separately for to check all points on all ranges at all voltages would require a tremendous number of measurements 6 5 2 Meter Tracking The scale tracking ca
10. 1004 6081 1004 6081 1004 6081 1004 6228 4105 6228 4105 6100 4475 6100 4475 6100 4475 6100 4475 FMC 90201 90201 90201 90201 90201 90201 56289 14433 14433 14433 14433 14674 14674 81345 81349 81349 81345 MFGR PART NUMBER TCG LOUF 475V TCG LOUF TCG 10UF 475V TCG 19UF 475V TCG LOUF 475V TCG 10UF 475V 416P47296 1N4006 1N4006 1N4006 1N4006 FP 5 100 K 5PCT FP 5 100 K 5PCT RCR 2064745 RCR20G474J RCR206474J RCR206474 J PARTS LIST AND DIAGRAMS SINVYSVIC LSIT S LHVd Rotary switch sections are shown as viewed from the panel end of the shaft The first digit of the contact number refers to the section The section nearest the panel is 1 the next section back is 2 etc The next two digits refer to the contact Contact 01 is the first position clockwise from a strut screw usually the screw above the locating key and the other contacts PIO2 S102 209R are numbered sequentially 02 03 04 etc 103R gt or proceeding clockwise around the section A 4 yp i suffix F or R indicates that the contact is on v eoar the front or rear of the section respectively SS crios EEA S103 108F 2058 wH RD BU TORR fio2R WH BU BR IWH BR BK ATI ATIC O VOLTS S103 90 R226 R225 402 200 ew 1 4W
11. 3 Setthe multiplier dial to any range ground terminal to the GUARD paragraph 4 6 or 4 Makecertain that there nothing is connected the UNKNOWN terminal Figure 31 The ground to the UNKNOWN terminals f link should be connected to the GUARD terminal if 5 Adjust the SET oo control for an oo reading on the meter 6 Setthe multiplier switch to 10 1T 7 Setthe function switch to MEASURE 8 Adjustthe SET oo HIGHEST RANGE for an oo meter reading If this adjustment cannot be made electrically turn the instrument off and adjust the mechanical meter zero adjustment the center screw on the meter to give a meter reading of less than a line width beyond the sample to be measured is a small separate compo nent or if it is a component mounted in an enclosure that should be guarded see paragraph 4 6 However If one terminal of the unknown must be grounded then the link should tie the UNKNOWN terminal to the instrument case See Figure 3 1 GUARD 7 UNKNOWN oc Repeat steps 1 through 7 cer 3 1 4 Connection of Unknown UNGROUNDED OPERATION Small components should be connected directly to the UNKNOWN terminals Insulated leads can be GUARD UNKNOWN connected to a nearby unknown however if the un known resistance is high leakage between the leads will cause a measurement error and a change in ca pacitance to the high lead will cause a transient meter GROUNDED OPERATION deflection For such high resistance measurements a 1
12. N Do not pull on the dial to remove a dial knob as sembly Always remove the knob first To avoid damage to the knob and other parts of the control do not pry the knob loose with a screwdriver or similar flat tool and do not attempt to twist the Knob from the dial 2 Observe the position of the setscrew in the bushing with respect to any panel markings or at the full ccw position of a continuous control 3 Release the setscrew and pull the bushing off the shaft 4 Remove and retain the black nylon thrust washer NOTE To separate the bushing from the knob if for any reason they should be combined off the instru ment drive a machine tap a turn or two into the bushing for a sufficient grip for easy separation or any commercial equivalent SERVICE AND MAINTENANCE 6 7 Knob Installation To install a knob assembly on the control shaft 1 Place the black nylon thrust washer over the control shaft if appropriate 2 Mountthe bushing on the shaft using a small slotted piece of wrapping paper as a shim for adequate panel clearance 3 Orient the setscrew on the bushing with respect to the panel marking index and lock the setscrew with the appropriate hex socket key wrench NOTE Make sure that the end of the shaft does not protrude through the bushing or the knob won t bottom properly 4 4 Place the knob on the bushing with the retention spring opposite the setscrew 5 5 Push the knob in until it bot
13. R C product is 10 even under ideal conditions This can be calculated as C in uF x R in MQ or C in F x R in Q Table 4 1 contains values for R Measurements can be unsatisfactory even below this value for an product for several reasons 15 1864 1644 Positive Polarity Megohmmeter 1 Dielectric absorbtion paragraph 4 3 2 This is the main cause of erroneous readings Besides the difficulty in deciding what charging period should be used the previous history of the capacitor will greatly affect its Indicated leakage For example if a paper capacitor is charged to its rated value discharged for a short time and then its leakage current is measured at some low value it probably will give a reading beyond oc This is due to voltage recovery that is a consequence of dielectric absorbtion The voltage across the capacitor will increase above the test volt age causing current to flow in the reverse direction 2 Temperature coefficient If the temperature on the unknown changes and it has an appreciable tem perature coefficient the voltage on the capacitor will change in the MEASURE position If R is large the charge Q of the capacitor is more or less constant so if its capacitance changes its voltage must change Q CV A temperature controlled environment is recommended 3 Test voltage changes The test voltage can have rapid fluctuations due to large line voltage tran sients even though good regul
14. RES FLM 2M 1 2 PCT 1 2W 6451 4200 81349 RN65D200 4C R 129 RES FLM 2M 1 2 PCT 1 2W 6451 4200 81349 RN65D2004D R 130 RES FLM 49 9K 1 2 PCT 1 4W 6351 2499 81349 RN60D4992D R 131 KES FLM 100K 1 PCT 1 4W 6350 3100 81349 RN6001003F R 132 RES FLM 200K 1 PCT 1 4 6350 3200 81349 RN60D2003F R 133 RES FLM 200K 1 PCT 1 4W 6350 3200 81349 RN6002003F R 137 RES COMP 11 DHM SPCT 1 2w D 6100 9115 81349 RCR20G110J R 141 RES COMP 30 K OHM SPCT 1 4W D 6095 3305 81349 RCRO7G303J R 211 RES FLM 100K 1 PCT 1 8W 6250 3100 81349 RN55D1003F R 212 RES FLM 11K 1 PCT 1 8W 6250 2110 81349 RN5501102F R 213 RES FLM 1 02M 1 PCT 1 2W 6450 4102 81349 RN65D1024F R 214 RES FLM 2K 1 2PCT 1 8MW 6251 1200 81349 RN55D2001D R 215 RES FLM 20K 1 PCT 1 2 6450 2200 81349 RN65D2002F R 216 RES FLM 200K 1 PCT 1w 6550 3200 81349 RN75D2003F R 217 RES FLM 2M 1 PCT 1 2 6450 4200 81349 RN65D2004F R 218 RES FLM 20M 1 PCT 1w 6550 5200 81349 RN7502005F R 219 RES FLM 200M 1 100PPM LW 6619 3407 24655 6619 3407 R 220 RES FILM CARBON 26 OHM 1 PCT 6740 1504 63060 RX 1 R 221 RES FLM 1 91K 1 2 PCT 1 4W 6351 1191 81349 RN60D19110 R 222 RES FLM 3 83K 1 2 PCT 1 4W 6351 1383 81349 RN60D3831D R 223 RES FLM 7268K 1 2 PCT 1 4W 6351 1768 1349 RN6OD76810 R 224 RES FLM 7 68K 1 2 PCT 1 4W 6351 1768 81349 RN60D7681D R 225 RES FLM 209 OHM 1 PCT 1 4W 6350 0200 81345 R 226 RES FLM 402 OHM 1 PCT 1 8W 6250 0402 81349 RN5504020F R 227 RES FLM 806 CHM 1 PCT 1 4W 6
15. on the meter window paper based masking tape is recom mended rather than any kind of marking pen which could be abrasive or react chemically with the acrylic NOTE Electrical parts information in this section is present ed in such a way that all the data for a part numbered sub assembly are visible together in the manual Thus the parts list appears on left hand pages while the part location diagram on the apron and the schematic diagram tip out are on right hand pages REFERENCE DESIGNATOR ABBREVIATIONS B Motor P Plug BT Battery Q Transistor C Capacitor R Resistor CR Diode S Switch DS Lamp T Transformer F Fuse U Integrated Circuit J Jack VR Diode Zener K Relay X Socket for Plug In KL Relay Coil Y Crystal KS Relay Switch Z Network L Inductor M Meter MK Microphone 27 1864 1644 Positive Polarity Megohmmeter This page intentionally left blank 28 SERVICE AND MAINTENANCE 1864 1644 Positive Polarity Megohmmeter Chapter 7 PARTS LISTS AND DIAGRAMS ELECTRICAL PARTS LIST 1864 CHASSIS MOUNTED PARTS REFDES DESCRIPTION PART NO FMC MFGR PART NUMBER c 110 CAP MYLAR 047UF 10 PCT 1000V 4860 8255 75042 563UW 2 047 UF LOPCT C 111 CAP CER SQ elOUF 80 20PCT LOOV 4405 4100 72982 8131M1006511042 C 113 CAP CER CISC 6800PF 20PCT 1 4 4406 2689 72982 848 25U 6800PF20PCT CR 106 RECT 1N4005 600PIV amp 75A SI 6081 1003 14433 1N4005 CR 107 RECT 1N4005 600P
16. should become necessary 2 2 Dimensions The dimensions of the 1864 1644 are shown in both the rack and bench mounted configurations in Figure 2 1 INSTALLATION 2 3 Repackaging for Shipment Ifthe instrument is to be returned to IET Labs contact the Service Department at the number or address shown on the front cover of this manual to obtain a Returned Material Authorization RMA number and any special shipping instructions or assistance Proceed as follows 1 Attach a tag with the following Owner s Name Model Number Serial Number RMANumber 2 Wrap the instrument in heavy paper or plastic 3 Protectthe front panel and any other protru sions with cardboard or foam padding 4 Place instrument in original container or equally substantial heavy carton 5 Use packing material around all sides of instrument 6 Seal with strong tape or bands 7 Mark shipping container DELICATE IN STRUMENT FRAGILE etc 1864 1644 Positive Polarity Megohmmeter 2 4 Storage If this instrument is to be stored for any lengthy period of time it should be sealed in plastic and stored in a dry location It should not be subjected to temperature extremes beyond the specifications Extended exposure to such temperatures can result in an irreversible change in resistance and require recalibration 2 5 Bench Setup The bench portable model of the megohmmeter is cased in a Flip Tilt cabinet The cabinet opens by
17. the resistance being measured x TEST The output can be stored in a data file for plotting display or analysis It can also feed the user s go no go indicator The full scale voltage value for any test voltage can be calculated from the V formula using 0 5 times the measurement range as the R value These values are available on the 1864 along with the other levels that can be set with the variable TEST VOLTAGE switches see table 3 1 OPERATION 1864 1644 Positive Polarity Megohmmeter Table 3 1 OUTPUT VOLTAGE Lower Multiplier Dial Setting Upper Multiplier Dial Setting Test Voltage V Full Scale Output Voltage V VourT at 0 5 scale reading 11 1864 1644 Positive Polarity Megohmmeter This page intentionally left blank 12 OPERATION 1864 1644 Positive Polarity Megohmmeter Chapter 4 APPLICATIONS 4 1 Insulation Testing The insulation resistance of electrical machinery Table 4 1 transducers etc is one of several parameters that STANDARD RESISTOR VALUES RJ may indicate the condition of the insulation Routine A 2 Multiplier Range measurement of capacitance dissipation factor and Lower Dial Upper Dial leakage resistance provides useful data for monitor Value Q in i 50 100 V 200 250 500 V ing the condition of the insulation and for guarding 10 0 109 V 100 to 1000 vt against incipient breakdown 100 k 2k A routine test that has been widely ado
18. 1 to supply voltage levels to run the unity gain amplifier 1 Tube 101 is a series regulator that is controlled by the 5 6 V Zener diode CR112 REF and the setting of R140 The voltage picked off R 140 is fed into one side Q102 of the differential amplifier Q102 Q103 while part ofthe output voltage is fed into the other side Q103 The output of the amplifier is fed to the base of Q101 AMP and then to the grid of V101 for controlling the output voltage The output selection resistors are R124 through R133 These resistors determine the TEST VOLT AGE level Resistors R211 through R219 are the standard resistors R that determine the measure ment range The output from this circuit is fed through the SET HIGHEST RANGE control R241 to the FET amplifier 19 1864 1644 Positive Polarity Megohmmeter REGULATED OC SUPPLY ME PRECISION RESISTORS Figure 5 1 Megohmmeter block diagram Figure 5 1 Megohmmeter block diagram A unity gain FET input amplifier 1 follows the standard resistors in the circuit configuration R210 and C203 comprise a low pass filter input to FET Q204 The amplifier components include a differ ential amplifier Q202 Q203 a coarse oo control R244 the SET oo control R242 and an output transistor Q201 The signal then enters the series combination of R135 and R134 back to the GUARD terminal Resistors R221 through R223 R are meter sensi tivity resistors
19. 1006 14433 IN753A CR 201 DIGDE RECTIFIER 1N4003 6081 1001 14433 1N4003 CR 211 ZENER 1NS68B 20V SPCT e4W 6083 1018 14433 IN968B CR 212 ZENER INS65B 15V SPCT 4W 6083 1015 14433 IN965B Q 101 TRANSISTCR 2N3903 8210 1132 04713 2N3903 Q 102 TRANSISTOR 2N4250 8210 1294 07263 2N4250 Q 103 TRANSISTCR 2N4250 8210 1294 01263 2N4250 Q 201 TRANSISTCR 2N3903 8210 1132 04713 2N3903 Q 202 TRANSISTOR 2N3905 8210 1114 04713 2N3905 Q 203 TRANSISTCR 2N3905 8210 1114 04713 2N3905 Q 204 TRANSISTOR STATIC PRCTECT REQ 8210 1143 04713 2N4220 Q 205 TRANSISTCR MPS A14 8210 1246 041123 MPS ALl4 Q 206 TRANSISTCR 2N3414 8210 1290 56289 2N3414 R 107 RES COMP 2 0 K OHM 5PCT 1 2W 6100 2205 81349 RCR20G202J R 108 RES CCMP 1 0 K 5SPCT 1 2W 6100 2105 81349 RCR 20G 102J R 117 RES COMP 220 OHM 5PCT 1 2W 6100 1225 81349 RCR20G221J R 118 RES CCMP 200 K OHM SPCT 1 2W 6100 4205 813459 RCR20G204J R 119 RES CCMP 12 K 5PCT 1 24 6100 3125 81349 RCR206G123J R 120 RES COMP 8 2 K 5PCT L 2W 6100 2825 61349 RCR206G822J R 121 RES CCMP 10 K 5PCT 1 2W 6100 3105 81349 RCR20G103J R 122 RES COMP 10 K 5SPCT 1 2W 6130 3105 81349 RCR220G103J R 123 RES FLM 24 9K 1 2PCT 1 8W 6251 2249 81349 RN55024920 R 134 RES CCMP 68 K 5PCT 1 2W 6100 3685 81349 RCR 2066836 R 135 RES CCMP 16 K GHM SPCT 1 2W 6100 3165 81349 RCR206G163J R 138 RES CCMP 22 K 5PCT 1 2W 6100 3225 81349 RCR20G223J R 139 RES FLM 200K 1 PCT 1 4W 6350 3200 81349 RN60D 2003F R 140 POT WW TRM 5K OHM 10 PCT LT 6056 0142 24655 6056 0142 R 201 RES
20. 20 GQ The specifications are again broadened to allow for the tolerance variations of this multiplication The voltmeter uses a FET input four stage unity gain amplifier AMP Figure 5 2 to obtain high stability and low drift The SET oo control on both instruments is a voltage balance control while the SET oo HIGH EST RANGE control compensates for the FET gate current on the highest ranges 5 2 Circuit Description 5 2 1 General The following paragraphs will relate specific com ponents from the schematic diagrams of the 1863 Figure 7 6 and 1864 Figure 7 9 to the general components shown in Figure 5 1 THEORY 5 2 2 Type 1863 Megohmmeter Figure 7 6 The voltage supply section RECT of the 1863 consists offive different circuits three dc and two ac One ac circuit is a voltage source for the three pilot lamps used two to indicate the measurement range P101 P102 and the third to light the DANGER indicator P103 The second supplies filament volt age to the vacuum tube V101 The first dc supply is a half wave rectifier circuit with a 24 V Zener diode CR 111 that supplies voltages to the amplifier AMP circuit A second dc supply is a voltage doubler CR101 CR104 C101 C102 that supplies the plate voltage to V101 The voltage to the plate is the same for the 50 to 250 V ranges but R109 is eliminated from the circuit for the 500 V range The third dc supply is a half wave rectifier with a 20 V Zener diode CR21
21. 350 0806 81349 6 R 228 RES FLM 806 OHM 1 PCT 1 4W 6350 0806 861349 RN60D8060F R 241 POT COMP KNGB 1K OHM 10 PCT LIN 6000 0300 01121 JAINO56S1 02UZ R 242 POT COMP KNOB 2 5K OHM 1OPCT LIN 6000 0400 01121 JAINO56S252UZ R 245 RES WW AX LEAD 5 1K OHM 5PCT 3W 6680 2515 75042 5 2 5 1 K SPCT s 101 SWITCH RCTARY ASM 7890 5350 24655 7890 5350 s 102 SWITCH ROTARY ASM 7890 5360 24655 7890 5360 S 103 SWITCH RCTARY ASM 7850 5370 24655 7890 5370 S 201 SWITCH ROTARY ASM 7890 5380 24655 7890 5380 S 202 SWITCH ASM 1864 0400 24655 1864 0400 s 591 SWITCH TOGGLE 2POS DPST STEADY 7910 1300 04909 83053 s 502 SWITCH SLIDE 2 POS DPDT STEADY S 7910 0832 82389 11 1266 101 TRANSFORMER POWER 9345 4028 24655 0345 4028 PARTS LIST AND DIAGRAMS 29 1864 1644 Positive Polarity Megohmmeter ELECTRICAL PARTS LIST REGULATOR amp AMPLIFIER PC BOARD P N 1864 2701 REFOES DESCRIPTION PART NO FMC MFGR PART NUMBER C 107 CAP ALUM 30 UF 75V 4450 6173 56289 4303006075 C 108 CAP CER CISC OLUF 80 20PCT 100V 4491 3100 72982 080554025 U001032Z C 109 CAP CER DISC LOOPF 5SPCT 500V 4404 1105 72982 08310822 5D00101J C 261 CAP ALUM 30 UF 75V 4450 6173 56289 430300 0075 C 202 CAP CER CISC O01UF 80 20PCT 4401 3100 72982 080554025U001037 C 203 CAP MICA 160PF 10PCT 500V 4620 1000 81349 CM15FD101K CR 105 EIODE RECTIFIER 1N4003 6081 1001 14433 1N4003 CR 111 ZENER LNS70B 24V SPCT 4W 6083 1054 14433 IN970B CR 112 ZENER IN7TE3A 6e 2V 5PCT 6083
22. 6 1 Service The warranty attests the quality of materials and workmanship in our products When difficulties do occur our service engineers will assist in any way possible If the difficulty cannot be eliminated by use of the following service instructions please write or phone our Service Department see last page of manual giving full information ofthe trouble and of steps taken to remedy it Be sure to mention the type ID and serial numbers of the instrument Before returning aninstrument to IET for service please phone or e mail to our Service Department requesting a Returned Material Authorization Number and instructions for return 6 2 Minimum Performance Standards The following checks are provided for verifying the performance of the 1863 and 1864 Megohmmeters The test equipment necessary to perform these checks is listed in Table 6 1 To check an instrument proceed as follows 1 13 meter tracking check 14 19 voltage accuracy check 1 Connect the case to the GUARD terminal with the shorting link 2 Set the decade resistor to 0500000 500 kQ 3 Set the TEST VOLTAGE switch to to 1 0 0V 4 Set the multiplier switch to 1 M 5 Set the POWER OFF switch to POWER SERVICE AND MAINTENANCE 6 Adjust the two SET controls as described in Section 3 7 Connect the Decade Resistor to the UNKNOWN terminals with the dual banana plug patch cord 8 Set the function switch to MEASURE 9 Read the panel meter
23. 862 10 shielded system is preferable refer to paragraph 4 7 Figure 3 1 Ground link connection to GUARD terminal top and to UNKNOWN terminal bottom 3 1 2 Test Voltage Selection The TEST VOLTAGE switch es should be set to the desired measurement voltage The 1864 1644 Megohmmeter has a selection of 10 to 109 Vdc in 1 V steps or 100 to 1090 Vdc in 10 V steps On the 1864 the right hand TEST VOLTAGE switch must be set to the V position for the low voltages and to the 0 V position for the high voltages OPERATION 9 1864 1644 Positive Polarity Megohmmeter 3 2 Measurement Procedure 3 2 1 General Either of two measurement procedures may be used depending on whether or not the correct resistance multiplier range is known Ifthe range is not known the search procedure paragraph 3 2 2 should be followed If repetitive measurements are to be made on a given range i e if similar components are to be sorted the sort procedure paragraph 3 2 3 should be used 3 2 2 Search Procedure When the approximate resistance of the sample to be measured is not known proceed as follows 1 Setthe multiplier switch to the lowest range 2 Set the function switch to DISCHARGE 3 Connect the unknown between the UN KNOWN and terminals 4 Set the function switch to MEASURE 5 Rotate the multiplier switch cw until the meter gives a reading of less than 5 6 The resistance of the unknown is the meter reading multiplied b
24. 864 1644 Positive Polarity Megohmmeter 4 3 4 Discharge Time With the function switch set at DISCHARGE the UNKNOWN terminals are connected through 470 Q and the discharge time is approximately 0 0005 x C us where C is in uF The red DANGER light is turned off by the function switch so that the capacitor might be charged even after the light is extinguished However the discharge time is so short that this is not a practical consideration except for capacitors greater than 100 uF Capacitors with high dielectric absorption paragraph 4 3 2 can have a residual charge even after they are shunted and must be repeatedly shunted to be com pletely discharged Usually this voltage recovery is only a few percent i e 3 of the original applied voltage and therefore not dangerous to the operator but it can cause damage to sensitive circuit elements 4 3 5 Large Capacitors Very High Resistance Measuring insulation resistance of large capacitors that have very low leakage is difficult by any method Considering the basic circuit of Figure 4 2 if R is high the R C time constant can become very long on the high resistance ranges if C is large If R is low the voltmeter must be very sensitive for a given leakage resistance range and therefore the sup ply voltage E must be extremely stable to avoid large meter fluctuations The design of the 1864 is a compromise between these factors Measurements become difficult when the
25. CCMP 1 2 K 5SPCT 1 2W 6100 2125 81349 RCR20G122J R 202 RES CCMP 2 7 K 5PCT 1 2W 6100 2275 81349 RCR20G272J R 203 RES COMP 27 K 5PCT 1 2W 6100 3275 81349 RCR20G273J R 204 RES CCMP 43 K OHM 5PCT 1 2W 6100 3435 81349 RCR 20G433J R 205 RES COMP 3 3 K 5PCT 1 2W 6100 2335 81349 RCR20G3324J R 206 RES COMP 10 K 5PCT 1 28 6100 3105 81349 RCR20G103 J R 207 RES CCMP 24 K CHM 5PCT 1 2W 6100 3245 81349 RCR 20624345 R 208 RES COMP 20 K OHM 5PCT 1 2 6100 3205 81349 RCR206G203J R 209 RES CCMP 47 M 5PCT 1 2W 6100 6475 81349 RCR20G416J R 210 RES CCMP 47 M 5PCT 172W 6100 6475 81349 RCR20G476J R 229 RES COMP 1 2 K 5PCT 1 2W 6100 2125 81349 RCR20G6122J R 230 RES CCMP 100 K SPCT 1 2W 6100 4105 81349 RCR20G104J R 221 RES CCMP 1 0 M 5PCT 1 2W 6100 5105 81349 RCR206G105J R 232 RES COMP 10 M 5PCT L 2W 6100 6105 81349 RCR2 0G106 J R 234 RES CCMF 10 K 5PCI 1 4W 6999 3105 81349 RCROTG 103J R 235 RES COMP 100 OHM 5PCT 1L 4W 6099 1105 81349 RCRO7G101J R 236 RES CCMP 2 4 M OHM SPCT 1 2 6100 5245 841349 RCR20G245J R 237 RES CCMP 2 4 M OHM 5PCT 1 2W 6100 5245 81349 RCR20G245J R 238 RES COMP 2 4 M OHM 5PCT 1 2w 6100 5245 81349 RCR20G6245J R 239 RES CCMP 2 4 M OHM 5PCT 1 2W 6100 5245 81349 RCR20G245J R 243 POT WW TRM 500 CHM 10 PCT LT 6056 0136 24655 6056 0136 R 244 POT WW TRM 5K OHM 10 PCT LT 6056 9142 24655 6056 0142 V 101 TUBE VACLUM 6AB4 8360 0100 79089 6 AB4 PARTS LIST AND DIAGRAMS 30 1864 1644 Positive Polarity Megohmmeter Figure 7 1 Replaceable mechanical parts o
26. ISTS AND 5 29 ii CONTENTS FIGURES AND TABLES 1864 1644 Positive Polarity Megohmmeter Figures 1864 1644 Front panel Controls Connectors and Indicators iv Figure 1 1 Type 1864 1644 Front panel Controls Connectors and Indicators 2 Figure 1 2 Type 1864 1644 rear panel controls and connectors 4 Figure 1 3 Methods of connection to the measurement terminals 5 Figure 2 1 Dimensions of the GR IET 1864 1644 Megohmmeters 7 Figure 3 1 Ground link connection to GUARD and to UNKNOWN terminals 9 Figure 4 1 Electrode arrangement for resisitivity measurements 14 Figure 4 2 Basic megohmmeter circuit 15 Figure 4 3 Guarded measurement of a three terminal resistor 16 Figure 5 1 Megohmmeter block dH88rami n eee 20 Figure 6 1 Connections for measuring standard resistors 22 Figure 6 2 Top interior view of 1864 Megohmmeeter esee 26 Figure 6 3 Bottom interior view of 1864 Megohmmeter 26 Figure 7 1 Replaceable mechanical parts on the 1864 1644 31 Figure 7 3 Type 1864 rectifier circuit etched board assembly 32 Figure 7 2 Regulator and amplifier circuit
27. IV 75A SI A50A 6081 1003 14433 1N4005 CR 108 DIODE RECTIFIER 1N4003 6081 1001 14433 1N4003 F 101 FUSE SLC BLOw 1 8 250V 5330 0450 75915 313 125 F 102 FUSE SLO BLOW 1 16 250V 5330 0300 75915 313 062 J 101 BINDING POST ASM 0938 3003 24655 0938 30923 J 192 BINDING PCST ASM 0938 3022 24655 0938 3022 J 103 BINDING POST ASM 0938 3003 24655 0938 3003 J 104 BINDING POST ASM 0938 3003 24655 0938 3003 J 105 PHONE INS 281L 2 CKT 4260 1031 82389 N 111 M 101 METER 5730 1412 24655 5730 1412 P 101 LAMP FLANGE BASE 6V O 2A 1000H 5600 0300 71744 CM 328 P 102 LAMP FLANGE BASE 6V 042A 1000H 5600 0300 71744 CM 328 P 103 LAMP FLANGE BASE 6V 4 10000H 5600 0316 71744 CM 345 PL 501 CORD 3WR LOA 120V US 7FT HAMMER 4200 1800 24655 4200 18990 R 109 RES COMP 62 K 5PCT iw 6110 3625 81349 RCR32G623J R 110 RES COMP 68 K 5PCT IW 6110 3685 81349 RCR32G683J R 111 RES COMP 270 K 5PCT lw 6110 4275 81349 RCR32G2744J R 112 RES COMP 120 K 5PCT 1 2wW 6100 4125 81349 RCR20G124J R 113 RES COMP 390 K SPCT 172W 6100 4395 81349 RCR20G394J R 114 RES COMP 1 2 M 5PCT 1 2W 6100 5125 81349 RCR20G125J R 115 RES COMP 39 K 5PCT 6110 3395 81349 RCR32G393J R 116 RES CCMP 47 K SPCT 2W 6120 3475 81349 RCRA amp 2G473J R 124 RES FLM 226K 1 2PCT 1 8W 6251 3226 813459 RN55C2263D R 125 RES COMP 30 K OHM SPCT 1 2W D 6100 3305 81349 RCR20G303J R 126 RES FLM 499K 1 2 PCT 1 4W 6351 3499 81345 RN6004993D R 127 RES FLM 1M 1 2 PCT 1 2W 6451 4100 81349 RN 5D1004D R 128
28. O 26 zoom 20 s wW Ww 204F 203 oer i 207F aT 20 201 lw i Ccw SN i R202 ATS Gece RANGE 1 WH VT BU OUTPUT s WHVT BR FET INPUT VOLTMETER CIRCUIT Figure 7 5 Type 1864 schematic diagram PARTS LIST AND DIAGRAMS BOTTOM VIEW OF Q206 34 1864 1644 Positive Polarity Megohmmeter fl gt sails ws p ien fea 5210 0200 I l Ti e in FOOT PIVOT SHAFT a SPRING In E so CABINET BASE LO COMPLETE COVER ASM SIDE PLATE ASM GASKET Figure 7 6 Complete cabinet assembly 35 PARTS LIST AND DIAGRAMS 1864 1644 Positive Polarity Megohmmeter 36 Name Cabinet Base Complete Cover Assembly Handle Assembly Gasket base 2 required Gasket cover Foot round 2 required Foot square 4 required Hub Insert Side Plate Assembly Left Right Washer rubber 2 required Spring Pivot Shaft 2 required External Fastener Ring 2 required Part of Hardware Set 4182 3010 GR Part Number 4182 1328 4182 1425 4182 1503 5168 3620 5168 3605 5260 2051 5260 2060 4182 6010 4182 1455 4182 1475 8030 1642 4182 8000 4182 6000 5210 0200 PARTS LIST AND DIAGRAMS
29. ary Multiplier Selects resistance range 3 position toggle switch MEASURE 11 CHARGE DISCHARGE 3 rotary switches 10 position 9 position 2 position INTRODUCTION Selects the operating position applied to the unknown Select voltage in 1 V steps from 10 to 109 V and in 100 V steps from 100 to 1090 V 1864 1644 Positive Polarity Megohmmeter Figure 1 2 Type 1864 1644 rear panel controls and connectors Table 1 2 Figure 1 2 Type Reference Power Input IEC Standard Power input Power input and circuit protection receptacle Output Phone jack Provides a dc voltage output for recorder operation Line Voltage 2 position slide Connects wiring of power transformer for switch either 100 to 125 V or 200 to 250 V input 4 1 8 Amp Integral fuse Holder for 5 x 20 mm holder For 100 to 125 V operation 1 4 A fuse For 200 to 250 V operation 1 8 A fuse 4 INTRODUCTION 1 4 Symbols These instruments indicate the resistance of the unknown in multiples of ohms The relationship between ohms Q kilohms megohms MQ gigaohms GQ and teraohms TQ is as follows 1 MO 1060 10 kQ I GO 10 O 10 kO 10 MO 1 TO 10 Q 10 kQ 10 MO 1040 Banana plug stabilized by Shoulder 1864 1644 Positive Polarity Megohmmeter 1 5 Connections The UNKNOWN GUARD and ground terminals are standard 3 4 in spaced binding posts that accept banana plugs standard telephone tips alligator clips croc
30. ation is provided in the instrument because when R C is large the test voltage fluctuations are transmitted to the voltmeter unattenuated This difficulty can be reduced if the line voltage is regulated Slow drift of the test volt age can cause erroneous readings if R C is large because even a slow drift rate can be fast compared to the R C time constant A decreasing test voltage can cause a reading beyond Sufficient warm up time 30 minutes will allow the temperature inside the megohmmeter to stabilize and result in a more constant voltage at the UNKNOWN terminals 4 4 Resistance Measurements The recommended test voltage is 100 V for fixed composition resistors film resistors and wire wound resistors above 100 Refer to EIA Standards RS172 RS196 and REC 229 These resistors can be measured easily on the megohmmeter as long as the accuracy of the instrument is adequate If the resis tors are separate we suggest that they be measured ungrounded with the grounding link connected to the GUARD terminal 16 4 5 Measurement of Voltage Coefficient The 1864 Megohmmeter may be used to measure voltage coefficient as long as its accuracy is adequate The voltage coefficient of resistance 1s defined as R RV_ V x 100 where V1 gt V2 R1 is the resistance at V1 the higher voltage R2 is the resistance at V2 For example if V1 500 V and V2 100 V Reoov R ioov Voltage coefficient x 100 100V
31. ccuracy above Accuracy applies for gt 100 V For lt 100 V add 2 Meter Display Full mechanical zero at right end so 2 5 full scale is near right end and full scale is at left end However resistance values read naturally increas ing from left to right Voltage Accuracy across unknown For 2100 V 2 For 100 V 4 0 5 V CONTENTS FIGURES AND TABLES Short Circuit Current Approximately 5 mA Power 100 125 or 200 250 V 50 400 Hz 13 W Fuse For 100 to 125 V operation 1 4 A For 200 to 250 V operation 1 8 A Fuse holder is located under the IEC receptacle and holds a 5 x 20 mm fuse Dimensions 6 63 x 10 x 6 75 in Weight 9 5 Ib vi 1864 1644 Positive Polarity Megohmmeter This page intentionally left blank CONTENTS FIGURES AND TABLES 1864 1644 Positive Polarity Megohmmeter Chapter 1 INTRODUCTION WARNING High voltage is applied to the measurement terminals of N 1864 1644 Megohmmeters at all times except when the function switch is set to DISCHARGE While the current is limited to a value that is not dangerous under most N conditions the energy stored in a capacitor connected to the terminals may be LETHAL Always set the function switch to DISCHARGE before you connect or disconnect the unknown 1 1 Description The 1864 1644 Figure 1 1 indicates resistance from 50 to 200 TQ These ranges are suitable for leakage resistance measurements of most t
32. ded breathing on the terminals will cause a meter deflection because leak age from the insulator ofthe UNKNOWN terminal to the panel is measured Actually this problem is somewhat academic because the unknown to be measured is usually much more se verely affected by humidity than 15 the megohmmeter 17 1864 1644 Positive Polarity Megohmmeter This page intentionally left blank 18 APPLICATIONS 1864 1644 Positive Polarity Megohmmeter Chapter 5 THEORY 5 1 General The 1864 Megohmmeter basically consists of a regu lated dc power supply a set of precision resistors and a FET input voltmeter Figure 5 1 Switch S is closed in the DISCHARGE position of the function switch and open in the CHARGE and MEASURE positions while S is open only in the MEASURE position The regulated voltage E is controlled by a resistance R A meter sensitivity resistor R is ganged to the voltage control resistor R to make the meter read ing independent of applied voltage assuming that the unknown has no voltage coefficient An inverse scale is used on a reversed meter to give a reading proportional to R and not its reciprocal and yet have a scale that increases from left to right 0 to oo Metal film standard resistors are used on all ranges The top range of each instrument uses feedback to effectively multiply the value of the previous stan dard resistor by a factor of ten In the 1864 the 2 GO resistor is multiplied to
33. e grounded 4 7 Remote Shielded Measurements Measurements can be made on components that are some distance from the instrument if care is used to prevent leakage between the connecting leads and to avoid the shock hazard A convenient way to do this 1s to use a shielded cable If the unknown can be measured ungrounded make the connection to the UNKNOWN terminal with the shielded lead tie the shield to the GUARD terminal and connect the GUARD terminal to the panel ground with the connecting link If one side of the unknown must be grounded connect the grounding link to the UNKNOWN terminal shield the cUNKNOWN terminal and tie the shield to the GUARD terminal In this instance the shield is not at ground potential and should be insulated APPLICATIONS 1864 1644 Positive Polarity Megohmmeter 4 8 Measurements Under Humid Conditions The 1864 Megohmmeter has been designed to operate under conditions of high humidity but nevertheless a few simple precautions should be taken to ensure accurate measurements These precautions are 1 Allow several minutes warmup internal heat will reduce humidity inside the instrument 2 Clean the binding post insulation with a dry clean cloth 3 Use ungrounded operation tie the GUARD terminal to the panel ground To determine the presence of errors due to humidity measure the resistance between the binding posts with no external connections Note that with the UNKNOWN terminal groun
34. e other hand and then slowly release the handle 1 3 Controls Connectors and Indicators Figure 1 1 shows the front panel controls connectors and indicators of the 1864 Table 1 1 lists and identi fies them Figure 1 2 shows the rear panel controls and connectors and Table 1 2 lists and identifies them 1864 1644 Positive Polarity Megohmmeter Figure 1 1 Type 1864 1644 Front panel Controls Connectors and Indicators 2 INTRODUCTION 1864 1644 Positive Polarity Megohmmeter Figure 1 1 Type Reference 2 position toggle switch 4 in meter with plastic cover Knob rotated HIGHEST RANGE control Knob rotated control GUARD Insulated binding post SET o Ground Uninsulated binding post UNKNOWN Insulated binding Connects the side of the post unknown to the megohmmeter UNKNOWN Insulated binding post Indicated light Turn power on and off Indicates the value to be multiplies by the multiplier switch Adjusts high end of meter scale on highest resistance range to compensate for offset current Adjusts high end of meter scale on highest resistance range to compensate for offset voltage in the voltmeter For guarded measurements It can accept a shorting link to the ground post Grounds the Unknown or guard Contains a shorting link Connects the side of the unknown to the megohmmeter Glows red when the function switch is in the CHARGE or MEASURE position 8 position rot
35. ector Q101 Emitter 13 4 Warning Q101 Base Q101 Emitter 0 5 Q102 Base Q101 Emitter 18 8 Q102 Emitter Q101 Emitter 19 4 Be careful when troubleshooting the instrument Q103 Base Q101 Emitter 18 9 when it is out of its cabinet and connected to AT23 Guard 372 the power line Dangerous voltages are present CR101 Cathode Guard 744 ticularly at the t f t inals C CR102 Cathode Guard 533 particularly at the transformer terminals Con CR103 Cathode wa a ea nect the shorting link between the GUARD and CR104 Cathode Guard 0 3 ground terminals to keep the voltmeter circuitry CR201 Cathode Guard 30 3 near ground potential Q201 Collector Guard 14 3 Q201 Base Guard 0 6 AT6 Guard 8 9 AT10 Guard 8 4 Q202 Emitter Guard 9 4 Table 6 2 Q202 Collector Guard 6 2 STANDARD RESISTOR MEASUREMENTS Q203 Base Guard 8 7 Q204 Case Guard 0 Multiplier Switch Setting Standard Resistor Value 2 Measurement Q204 Drain Guard 8 7 Q204 Source Guard 0 3 Q204 Gate Guard 0 Voltages are dc and the values are typical Set TEST VOLTAGE switch to 200 function switch to CHARGE connect the shorting link between the ground terminal and GUARD and set the mulitplier switch to 1 M Measurements made with 1863 line voltage set at 115 Vac 6 4 Troubleshooting 6 4 1 General The following information is designed to assist in troubleshooting the 1863 and 1864 Megohmmeters An understanding of the theory involved in these instruments Section 5
36. he case Refer servicing to qualified personnel HIGH VOLTAGES MAY BE PRESENT AT THE TERMINALS OF THIS INSTRUMENT WHENEVER HAZARDOUS VOLTAGES 45 V ARE USED TAKE ALL MEASURES TO AVOID ACCIDENTAL CONTACT WITH ANY LIVE COMPONENTS USE MAXIMUM INSULATION AND MINIMIZE THE USE OF BARE CONDUCTORS WHEN USING THIS INSTRUMENT Use extreme caution when working with bare conductors or bus bars WHEN WORKING WITH HIGH VOLTAGES POST WARNING SIGNS AND KEEP UNREQUIRED PERSONNEL SAFELY AWAY A CAUTION DO NOT APPLY ANY VOLTAGES CURRENTS TO THE TERMINALS THIS INSTRUMENT IN EXCESS OF THE MAXIMUM LIMITS INDICATED ON THE FRONT PANEL OR THE OPERATING GUIDE LABEL 1864 1644 Positive Polarity Megohmmeter Contents Condensed Operating Instructions iv Specification S CRT 1864 1644 Specifications essent ener nre V Chapter 1 L LD8SGCFID H D 1 1 2 Opening and Tilting the Cabinet rete det ete bcne reete er rhet cus 1 1 3 Controls Connectors and INndiIC8at rS u eese eene 1 1 4 SYMBOLS 5 enne 5 Chapter 2 7 2 1 Initial Inspection ics nona cmi mee ede ota lates s 7 co
37. is resistance can be as low as 300 Q Note that any of the three insulated binding posts can be at high voltage depending on the position of the shorting link When capacitors are tested there is an especially dan gerous condition because a charged capacitor easily can have enough energy to cause heart fibrillation and death The capacitor should always be shunted before connection to the megohmmeter and the func tion switch should be set to DISCHARGE for a few seconds before the capacitor is disconnected We strongly recommend that additional precautions such as rubber gloves and insulated benchtops chairs and shoes should be used for anyone making repeti tive measurements with the megohmmeter particu larly measurements on capacitors These precautions should not take the place of careful discharge of the capacitors before and after measurement but should be used as an additional safety measure OPERATION 3 3 Output Jack The OUTPUT jack J105 on the rear panel makes accessible a dc voltage that is directly proportional to the reciprocal of the meter reading that is the highest value is at the 0 5 scale reading and the lowest value is atoo The output voltage for a particular multiplier switch setting can be calculated by Vopr 0 02 x V E RANGE R x where V r is the TEST VOLTAGE setting R vcr is the lower value for a particular multiplier dial set ting 100k for the 1 M 100 k range and R is the value of
38. itor under test 4 3 2 Charging Time Constant The time constant for charging a capacitor in the CHARGE position is determined by the value of the capacitor times the effective source impedance ofthe supply The supply resistance is approximately E a 00054 97 s kQ where E is the indicated test voltage in volts and I is the short circuit current which is approximately 5 mA Therefore the time constant is Cx T RC n seconds where C is in F As an example on the 500 V range R is approximately 100 so that the time constant for charging of a 1 uF capacitor is 0 1 s The time necessary for full charging depends on the type of capacitor and the leakage current that is to be measured A capacitor with no dielectric absorption will have a charging current that decreases by a factor of 2 72 the natural logarithm to the base e for every time constant it is left in the CHARGE position Thus the effective resistance at any moment is R EG The capacitor could be considered fully charged when this resistance is substantially higher than the true leakage resistance even though the charging current theoretically neverreaches zero As an example a 1 uF capacitor with a leakage resis tance of 10 Q measured at 500 V would have less than 196 error due to charging current if measured after seventeen time constants or 1 7 s APPLICATIONS Dielectric absorption dipole and interfacial pola
39. lists dial readings and resistor values APPLICATIONS 13 1864 1644 Positive Polarity Megohmmeter SAMPLE UNDER Figure 4 1 Electrode arrangement for resisitivity measurements 4 2 Test Sample Resistivity Measurements The megohmmeter can be used for measuring the resistivity of test samples as described by ASTM Standard D257 which describes in detail the tech niques for both surface and volume resistivity mea surements The most common electrode arrangement is that shown in Figure 4 1 In this configuration surface resistivity is measured with terminal 1 tied to the UNKNOWN terminal terminal 2 tied to the UNKNOWN terminal and terminal 3 tied to GUARD For volume resistivity measurements terminal 1 is tied to the UNKNOWN terminal terminal 2 to the GUARD and terminal 3 to the UNKNOWN terminal The formulas required to convert from measured resistance to resistivity are given in the ASTM standard Contact IET regarding the availability of resistivity test fixtures 4 3 Capacitor Insulation Resistance 4 3 1 General The insulation resistance IR of capacitors is mea sured by either the search or sort method paragraph 3 2 2 and 3 2 3 used for resistors except that some consideration must be given to the charge and dis charge currents 14 ANUS Capacitors being measured may be charged and may contain lethal energy Always set the function switch to DISCHARGE before connecting or disconnecting the capac
40. n a more important check is to see that the voltage and meter sensitivity track to give a cor rect resistance reading Such a check is generally adequate for it would be an unusual coincidence if both the voltage control and meter sensitivity resis tors were in error such that a good reading is obtained To check this tracking perform steps n through s of paragraph 6 2 If a reading is incorrect the voltages should be checked with a DMM connected between the UNKNOWN and UNKNOWN terminals The function switch can be set to either the CHARGE or MEASURE positions SERVICE AND MAINTENANCE If all the voltages are out of tolerance in the same direction they can be set within the tolerance by adjusting R140 located on etched circuit board P N 1864 2701 common to both the 1863 and 1864 Meg ohmmeters and shown in both Figures 6 2 and 6 4 The adjustment can be made as soon as the instru ment is removed from the cabinet paragraph 6 3 It is not necessary to move either of the printed circuit boards since the adjustment is on the top printed circuit board This adjustment affects all voltages by the same amount but adjustment at 200 V minimizes possible errors due to resistance tolerances If all the voltages are correct but all meter readings are in error in the same direction the meter sensitiv ity can be reset Adjust R243 Figures 6 2 and 6 4 located on the same etched circuit board as R 140 to correct the meter readings Thi
41. n be easily checked using a de cade resistance decade box with 100 kQ and 1 MQ steps Steps a through m of paragraph 6 2 should be performed to check the tracking If all readings are corrected by the amount of the error found at a read ing of 0 5 they should be better than the specification 24 TYPE 1864 TEST VOLTAGES Table 6 4 Test Point Test Point Voltage V Q101 Emitter CR105 Anode Q101 Emitter 16 0 CR112 Anode Q101 Ernitter 17 9 Q101 Collector Q101 Emitter 11 7 101 Base Q101 Emitter 0 6 Q102 Base Q101 Emitter 19 3 Q102 Emitter Q101 Emitter 19 9 Q103 Base Q101 Emitter 19 4 CR201 Cathode 35 7 Q202 Emitter AT5 14 9 Q203 Base AT5 14 3 CR104 Cathode Guard 294 CR103 Cathode Guard 590 CR102 Cathode Guard 888 CR101 Cathode Guard 1178 AT23 Guard 496 AT5 Guard 5 0 Q201 Collector Guard 15 4 Q201 Base Guard 0 6 Q202 Emitter Guard 10 0 Q204 Case Guard 0 Q204 Drain Guard 9 3 Q204 Source Guard 0 8 Q204 Gate Guard 0 AT6 Guard 9 6 AT10 Guard 9 1 CR201 Cathode Guard 30 6 Q203 Base Guard 9 3 Voltages are dc and the values are typical Set the TEST VOLTAGE switch to 200 function switch to CHARGE connect the shorting link between the gound terminal and GUARD and set the multi plier switch to 1 M Measurements made with a Data Precision 3400 Digital Voltmeter with 1864 line voltage set at 115 Vac 6 5 3 Voltage Accuracy While the voltage can be checked to be within its specificatio
42. n the 1864 1644 Replaceable parts list jrem 130002 Power switch O 2 5730141201 Meter assembly O 3 5520 5220 AS assembly for 1863 64 potentiometers 3 7 Red bindingpost_ O 5 9110081010 Gold bindingpost_ 6 jio Dialassemby j 8 1964 1220 Dial assembly for 1864 voltage range 9 18641230 Dial assembly for 1864 voltage setting B 10 i864 1210 Dial assembly for 1864 voltage setting A PARTS LIST AND DIAGRAMS 31 1864 1644 Positive Polarity Megohmmeter 32 Figure 7 3 Type 1864 rectifier circuit etched board assembly P N 1864 2720 REFDES C 101 C 102 C 103 C 104 C 105 C 106 C 112 CR 101 CR 132 CR 103 CR 104 R 101 R 102 R 103 R 104 R 105 R 106 CAP CAP CAP CAP CAP CAP CAP RECT 1N4006 800PIV IN4006 1N4006 800PIV 1N4006 800PIV RIECT RECT RECT RES RES RES RES RES RES RECTIFIER PC BOARE ELECTRICAL PARTS LIST DESCRIPTION ALUM 10UF ALUM 10UF ALUM 10UF ALUM LOUF ALUM 10UF ALUM 10UF PAPER FLM 100 FLM 100 COMP 479 COMP 470 COMP 470 COMP 470 m lt gt gt x gt 475V 475V 475V 475V 475V 475V 2 9047UF SPCT 7M 5PCT SPCT 1 2W 5PCT 1 2W 5PCT 1 2W SPCT 1 2W 10PCT 600v U 54 SI A50A 5 SI A50A 5 SI A50A e5A SI A50A P N 1864 2120 PART 4450 6175 4450 6175 4450 6175 4450 6175 4450 6175 4450 6175 4510 4300 6081
43. odile clips spade terminals and all wire sizes up to number eleven Figure 1 3 When several measurements of components with leads are to be made consult IET for an appropriate test jig or fixture when fully inserted For metal top binding post only Spade terminal Clamps ele Plug enters Slender with 1 throat all wire sizes telephone tip binding post bod f in ing po y alligator clip will clamp 2 upto No 11 assuring contact even fits inside jacktop j under nut j without cutting when nut is loose of all binding posts Figure 1 3 Methods of connection to the measurement terminals 5 INTRODUCTION 1864 1644 Positive Polarity Megohmmeter This page intentionally left blank 6 INTRODUCTION 1864 1644 Positive Polarity Megohmmeter Chapter 2 INSTALLATION Dimensions in inches BENCH MOUNTED Figure 2 1 Dimensions of the GR IET 1864 1644 Megohmmeters 2 1 Initial Inspection IET instruments receive a careful mechanical and electrical inspection before shipment Upon receipt verify that the contents are intact and as ordered The instrument should then be given a visual and operational inspection If any shipping damage is found contact the carrier and IET Labs If any operational problems are en countered contact IET Labs and refer to the warranty at the beginning of this manual Save all original packing material for convenience in case shipping of the instrument
44. pted for insulation testing calls for the measurement of the 1M 20k apparent leakage resistance after a test voltage has been applied for one minute and again after the test 10M 200 k voltage has been applied for 10 minutes The ratio 100 M 2M of the indicated resistances sometimes referred to as the Polarization Index can have some relation to 1G 20M the condition of the Insulation The results of such a measurement are apt to be more dependent on the 10G 200 M dielectric absorption of the insulator than on its true 1006 2G leakage resistance measured at equilibrium A com plete charge current vs time plot will provide more useful information 1T 2 G with feedback The 1864 1644 Megohmmeters can be used for ei multiplication ther true leakage measurements or for measurements at l or 10 minute intervals following the operating procedure described in Section 3 MIL STD 202C gives procedures for insulation resistance measurements of various components On large machinery one terminal must usually be grounded The 1864 1644 Megohmmeter is designed so that the binding post grounding strap should be connected between the ground terminal and the UNKNOWN terminal To determine the charge current divide the test voltage by the indicated resistance At the start of a charge current vs time plot the meter will be off scale The resistance in series with the insulator is the reading of the upper dial multiplier divided by 500 Table 4 1
45. pushing down on the handle and tipping the instru ment into the desired operating position paragraph 1 2 2 6 Rack Mounting Consult IET Labs 2 7 Power Connections The 1864 1644 Megohmmeter can be operated from either a 100 to 125 V or a 200 to 250 V 50 to 60 Hz power line Before connecting the 3 wire IEC power cord to the line set the slide switch on the rear panel to the proper setting as indicated by the position of the white line on the slide switch The slide can be actuated with a screwdriver blade Verify that the correct size fuse for the input voltage selected has been installed 1 4 A slow blow for 100 125 V input or 1 8 A slow blow for 200 250 V input If it is neces sary to use a 3 wire adaptor plug make certain that the third wire is connected to a good ground water pipe or equivalent If this is not possible connect the panel of the 1864 1644 uninsulated binding post to a good ground Plug the supplied IEC power cord into the instrument into a power receptacle The power cord may of course be selected to match the available receptacle INSTALLATION 1864 1644 Positive Polarity Megohmmeter Chapter 3 OPERATION 3 1 Measurement Setup 3 1 3 Set oo Adjustments 3 1 1 Ground Link Connection To adjust the SET controls proceed as follows 1 Turn the instrument on The grounding link connected to the uninsulated 2 Setthe function switch to DISCHARGE grounded binding post can be connected from this
46. riza tion is present in many capacitors and insulators especially those with a laminated structure When voltage is applied to such material the charge slowly diffuses throughout the volume and several minutes hours or even days are required for equilibrium in order to make the charging current small compared with the true leakage current A measure of this ef fect called the Polarization Index is the ratio of the resistance measured after 10 minutes of charging to that measured after 1 minute of charging Often the measured resistance after 1 minute of charging is called the insulation resistance even though charg ing current may be much larger than the true leakage current Some capacitor specifications say less than 2 minutes 4 3 3 Measurement Time Constant When the function switch is set from the CHARGE position to the MEASURE position the standard resistor is placed in series with the unknown ca pacitor If the supply voltage is fixed the capacitor must discharge by a voltage equal to that across the voltmeter at its final reading The time constant for this discharge would be C R Because 80 of the output voltage 1s fed back to the supply this time constant is reduced by a factor of 5 As a result the time necessary for an indication assuming an ideal capacitor depends on this time constant or that of the meter movement whichever is longer 1863 64 1 Figure 4 2 Basic megohmmeter circuit APPLICATIONS 1
47. s adjustment affects ail measurements but on the 1863 is most sensitive at 200 V and 250 V and least sensitive at 100 V In the 1864 it is most sensitive at the lower set tings of the first digit of the test voltage adjustment i e 100 V 200 V etc SERVICE AND MAINTENANCE 1864 1644 Positive Polarity Megohmmeter 6 5 4 Range Resistor Accuracy The range resistors can be checked by performing procedure steps in of section 6 2 6 5 5 Coarse o Adjustment If it is impossible to set the infinity controls on the front panel set both controls at their center positions and adjust R244 Figures 6 2 and 6 4 located on the etched circuit board with R140 for a reading as close to oo as possible Make the final adjustments with the front panel controls 25 1864 1644 Positive Polarity Megohmmeter ETCHED CIRCUIT BOARD FIGURE 7 4 VIO R242 RI40 R 4I FIO ETCHED CIRCUIT BOARD Figure 6 2 Top interior view of 1864 Megohmmeter 201 J05 S502 F102 TIOI 202 103 102 101 501 Figure 6 3 Bottom interior view of 1864 Megohmmeter 26 6 6 Knob Removal If it should be necessary to remove the knob on a front panel control either to replace one that has been damaged or to replace the associated control proceed as follows 1 1 Grasp the knob firmly with the fingers close into the panel or the indicator dial if applicable and pull the knob straight away from the panel N CAUTION
48. s etched board assembly 32 Figure 7 4 Type 1864 switching diagram asss 33 Figure 7 5 Type 1864 schematic diagram eene 34 Figure 7 6 Complete cabinet assembly eese 35 CONTENTS FIGURES AND TABLES 1864 1644 Positive Polarity Megohmmeter Condensed Operating Instructions GROJND UNKNOWN SET o HIGHEST RANGE GUARD MULTIPLIER DIAL FUNCTION SWITCH POWER OFF SWITCH TEST VOLTAGE SWITCHES 1864 1644 Front panel Controls Connectors and Indicators 1 Determine which ground link connection is to be 4 Connect the unknown to the UNKNOWN termi used paragraph 3 1 1 nals 2 Setthe TEST VOLTAGE switch es to the proper 5 Measure the unknown with either the search para voltage paragraph 3 1 2 graph 3 2 2 or sort paragraph 3 2 3 procedure 3 Set the oo adjustments paragraph 3 1 3 iv CONTENTS FIGURES AND TABLES 1864 1644 Positive Polarity Megohmmeter Specifications 1864 1644 Specifications Rmin Full Scale left end 0 5 rdg Voltage Setting Recommended Limit Resistance Accuracy min reading 0 5 Range 1 5 2 meter reading 1 Where meter reading is the actual number indicated at the scale e g for a reading of 900 kQ on the 1 GQ scale the accuracy is 2 9 1 or 3 8 Range 6 add 2 to accuracy above Range 7 add 3 to accuracy above Range 8 add 5 to a
49. that are ganged to the voltage resistors R124 through R127 R R222 is used for both the 50 V and 500 V ranges while the 200 V range uses the circuit resistance and has no added resistor The remaining two resistors R221 and R223 are used for the 250 and 100V ranges respectively Potenti ometer R243 is an adjustable control in the meter sensitivity circuit 20 5 2 3 Type 1864 Megohmmeter Figure 7 9 The circuit of the 1864 Megohmmeter is basically the same as that of the 1863 paragraph 5 2 2 The exceptions are explained in the following paragraphs In the 1864 the second dc power supply is a qua drupler This supply establishes the plate voltage of V101 with the use of resistors R109 through R114 The regulator circuit has a slightly different input when the TEST VOLTAGE switch is switched from V 1 to 0 V 10 Resistors R124 and R125 are switched out of the circuit in the 0V 10 position Voltage selection resistors for the 1864 are R126 through R133 and the meter sensitivity resistors are R221 through R228 An additional range resistor R220 is in the 1864 THEORY 1864 1644 Positive Polarity Megohmmeter Chapter 6 SERVICE AND MAINTENANCE WARNING Dangerous voltages are present inside this case When troubleshooting a ground strap should be connected between GUARD and GROUND on panel to keep the subpanel Guard at ground potential Refer all servic N ing to qualified service personnel
50. toms and pull it slightly to check that the retention spring is seated in the groove in the bushing NOTE If the retention spring in the knob comes loose reinstall it in the interior notch that has the thin slit in the side wall It will not mount in the other notch 6 8 Meter Cover Care N The clear acrylic meter cover can become susceptible to electrostatic charge buildup and can be scratched if improperly cleaned SERVICE AND MAINTENANCE 1864 1644 Positive Polarity Megohmmeter It is treated inside and out in manufacturing with a special non abrasive anti static solution Statnul which normally should preclude any interference in meter operation caused by electrostatic effects The problem is evidenced by the inability of the meter movement to return promptly to a zero reading once it is deenergized As supplied by IET the meter should return to zero reading within 30 seconds immediately following the placement of a static charge as by rub bing the outside surface This meets the requirements of ANSI standard C39 1 1972 If static charge problems occur possibly as the result of frequent cleaning the window should be carefully polished with a soft dry cloth such as cheesecloth or nylon chiffon Then a coating of Statnul should be applied with the polishing cloth N CAUTION N Do not use any kind of solvent Tissues or paper towels can scratch the window surface If it should be necessary to place limit marks
51. y the multiplier switch indication 7 Make measurements towards the low end of the meter scale whenever possible for best accuracy and resolution 3 2 3 Sort Procedure When the approximate resistance of the unknown is known proceed as follows 1 Set the function switch to DISCHARGE 2 Set the multiplier switch to the desired range 3 Connect the unknown between the UN KNOWN and terminals 4 Set the function switch to MEASURE 5 The resistance of the unknown is the meter reading multiplied by the multiplier switch indication For go no go checks it can be useful to make high and low limit lines on the outside of the meter case with strips of masking tape 6 Make measurements towards the low end of the meter scale whenever possible for best accuracy and resolution 10 3 2 4 Shock Hazard Every precaution has been taken in the design of 1864 Megohmmeters to reduce the possibility of shock However high voltage must be present at the terminals to make measurements at the required voltage levels and the operator should be aware of the dangers involved The current delivered by the megohmmeters under short circuit conditions is approximately 5 mA This 5 mA current is not lethal to most persons but might be lethal to those with poor hearts and it is painful to all The actual current that will flow through a person depends on the resistance of the part of the body that makes contact with the terminals Th
52. ypes of insulation used in electrical instruments electronic devices and components etc Section 4 The 1864 has a voltage range from 10 to 1090 V that can be set in 1 Vdc steps from 10 to 109 V and in 10 V steps from 100 to 1090 V by using the TEST VOLTAGE switches on the front panel The 100 volt setting is the EIA standard for measure ment of composition film and wire wound resistors above 100 kilohms The 500 volt setting is a standard value in the measurement of the insulation resistance of rotating machinery transformers cables capaci tors appliances and other electrical equipment A regulated power supply and charging circuit per mit rapid and accurate measurement of the leakage resistance of capacitors Guard and ground terminals permit measurement of grounded or ungrounded two or three terminal resistors A panel warning light indicates when voltage is ap plied to the test terminals and alerts users to the safe operation of the instrument INTRODUCTION 1 2 Opening and Tilting the Cabinet To open the cabinet refer to the pictorial graphic on the rear panel of the unit see Figure 1 2 The Flip Tilt cabinet can be opened by placing the instrument on its rubber feet with the handle away from you Push down on the handle and the instrument located in the upper part of the case will rotate to a vertical position While holding the handle down with one hand rotate the instrument to the desired position with th

GR 1864-1644 Megohmmeter Manual

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