Keithley 148 User Manual Download

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Summary of Contents for 148

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Page 2: ...fectsresulting from unauthorized This warranty does not epply to defectsresulting from unauthorized mpdification or misuse oft any product or part This warmnty al o does mpdification or misuse oft any...

Page 4: ...CONTENTS...

Page 5: ...148 Input Compartment 26 15 Correct Wave Form in dc to dc Inverter 31 16 correct wave Form at Point F in Oscillator circuit 32 17 Improper wave Form af point F in Oscillator Circuit 32 18 NOf Used 19...

Page 6: ...SPECIFICATIONS MODEL148 SPECIFICATIONS iv 0375...

Page 7: ...en previously required Meter accuracy is 2 of full scale on all ranges Noise is less than 1 nanovolt peak to peak on the lo nanovolt range Zero drift is less than 10 nanovolts per 24 hours after warm...

Page 8: ...ll changes in dc potentials from low impedance sources These are found in fundamental or applied research laboratory standards work cryogenic experiments and instrument development for space research...

Page 9: ...MODEL148 GENERALDESCRIPTION FIGURE lb Front Panel With Model 1481 Input Cable 0972 3...

Page 10: ...GENERALDESCRIPTION MODEL148 ZERO s PPmssIoN POWER SWITCH 5201 COARSE 5103 FINE R168 4 FIGURE 2 Front Panel Controls 0972...

Page 11: ...peration for the power supply 1 AC position The Nanovoltmeter will operate from the ac power lint The battery will be charged if needed then the BATTERYCHARGINGLamp will light 2 OFF position The Model...

Page 12: ...tween the positive and negative values of the maximum voltage set by the COARSEControl g INPUT Receptacle The INPUT Receptacle is of a special low thermal design Use only the Models 1481 1482 and 1486...

Page 13: ...h the power cord connected Also use battery operation to reduce the 8 cps ripple which may appear at the output with the input shorted in ac operation See paragraph Z 13 NOTE Before using the battery...

Page 14: ...PROCEDURES a Set the front panel controls as follows POWERSUPPLY Switch OFF FUNCTION Switch MILLIVOLTS RANGESwitch 100 ZERO SUPPRESSCOARSEControl OFF NOTE Make sure the ZERO SUPPRESSCOARSEControl is O...

Page 15: ...rovolts 300 krl 3kn 5O l 0 01 millivolt 1 I 2 10 kn 100 1 0 03 millivolt 1lQ 10 kcl 5O l 0 1 millivolt l Sl 10 kn 2O l 0 3 millivolt 1 Ma 10 kn 2O l 1 millivolt 1Kl 10 kn 2O l 3 millivolts 3Kl 30 m 1O...

Page 16: ...the soldering iron used is clean and that it has not been used with regular solder before Use only rosin solder flux If possible heat sink all cadmium soldered joints together to reduce generated the...

Page 17: ...FUNCTION Switch Setting MICROVOLTS MICROVOLTS MICROVOLTS MICROVOLTS ZERO SUPPRESSCOARSE Control Setting 1 2 3 4 Maximum Suppression Voltage 0 24 microvolt 1 2 microvolt6 12 microvolt6 120 microvolt6...

Page 18: ...1 Remove the link from the LO or GND terminal on the rear panel 2 Connect the voltage source to the Nanovoltmeter i L wt Make measurements as de scribed in paragraph 2 5 The zero suppress controls ma...

Page 19: ...e furnished Model 3701 Input Cable mates with the output connector on the Model 148 On the most sensitive ranges of the Model 148 under some conditions a 8 cps beat may appear This condition can be el...

Page 20: ...3 are nearly correct If the source resistance is composed of other materials it may be necessary to include other terms in the equations to account for flicker l f and current noise over and above th...

Page 21: ...the wave form shown in Figure 6 If excessive pick up occurs the wave form will resemble that of Figure 7 The circuit will operate reasonably well as long as the wave formis not clipped as shown in Fi...

Page 22: ...to cause loop instabilities and it may be used to filter ac components in some cases 2 14 THERMALEMF S a Junctions between two dissimilar metals form a thermocouple and will de velop an emf if there...

Page 23: ...g Four terminal connections can often be used to eliminate this error Refer to Figure 9 j it the zero suppress may be used If an unwanted IR drop is con 1 M d 48 1 to nullify the voltage d If the curr...

Page 24: ...ved Insert the top cover assembly 1 in place and fasten to he chassis with the two pawl type fasteners at the rear Store the top cover with handles feet and tilt bail for future use I Item Keithley kS...

Page 25: ...by a saturated transistor switch and enters a dc amplifier which has a feedback capacitor to filter out the demodulator ripple The dc amplifier output is connected to the meter the output terminals a...

Page 26: ...nal is initially applied to the Model 148 Vf is zero and the voltage across the primary is entirely Vin As the output voltage rises Vf increases and Vd decreases to a small value Vf Vinj OrgV Vin Only...

Page 27: ...nd bias point of Vl are selected for low noise oper ation at 94 cps The high Q tuned circuit in the plate of Vl has a good signal to noise ratio and it provides a narrow bandwidth around 94 cps The tu...

Page 28: ...sformer drives transistors Q24 and Q25 through a phase compensa ting network resistors R308 to R310 R323 and capacitor C309 which compensates for the chopper phase shift The transistors alternate betw...

Page 29: ...202 has a saturable ferrite core The inverter circuit supplies voltages to the three regulated supplies which are basically the same series regulator design d For the 12 volt supply diodes D206 and D2...

Page 30: ...the h2 and 12 volt supplies Except for the comparator stage npn transistors are used 3 9 BATTERYCHARGINGCIRCUIT a The battery charging circuit operates when the POWERSUPPLY Switch 5201 is in AC or OFF...

Page 31: ...stributors b The physical location of components in the input compartment is critical Place replacement parts in the exact position shown in Figure 14 Circuit loops will introduce extraneous ac signal...

Page 32: ...t replace ment is necessary b Removal Procedures 1 Disconnect the chopper drive coil at connector 5302 Figure 20 Carefully remove the three thumb screws in the input compartment and the three chopper...

Page 33: ...parts Table 7 lists equipment recommended for troubleshooting If the trouble cannot be readily located or repaired con tact Keithley Instruments or its representatives Paragraph 2 17 describes how to...

Page 34: ...alligator clips are connected 3 Set t lh Z KRDSUPPRESSCOARSEControl to OFF b 1f hac operation is trouble free set the POWERSUPPLY Switch to BATTERY li sconnect the power cord from the power line Batte...

Page 35: ...es 1 Connect the low thermal shorting plug to the INPUT Set the Model 148 controls as follows POWERSUPPLY Switch OFF RANGESwitch 100 FUNCTION Switch MILLIVOLTS ZERO SUPPRESSCOARSEControl OFF Line Volt...

Page 36: ...r See paragraph 4 8 points B C and D Fig 21 Defective D204 D212 Check components replace if D205 433 434 Q38 faulty or Q39 High ripple only at Defective Q43 and or Check components replace if point D...

Page 37: ...djustment is required 4 8 OSCILLATOR CHECKOUT AND CALIBRATION a The oscillator circuit drives the demodulator and the chopper If the power supplies check out continue on the oscillator If the oscillat...

Page 38: ...nd 423 The wave form at point F should resemble Figure 16 If it does not but resembles Figure 17 use a 15 kilohm resistor for R307 Fl in Oscillator Circui t 2 msec cm horizontal Scale is 2 v cm rtIcal...

Page 39: ...319 Check components replace if C301 C302 C303 or faulty Q17 or R319 are most R321 R320 R303 R318 likely parts TABLE 10 Oscillator Circuit Troubleshooting Table 4 9 AMPLIFIER CHECKOUT AND CALIBRATION...

Page 40: ...e of this calibration depends very much on the source If one is not available it is recommended that the gain be calibrated by Keithley Instruments If a source should be constructed here are some guid...

Page 41: ...e outputs as shown on the differential voltmeter on any range from 1 microvolt and above Adjust potentiometer R136 Figure 25 for exactly full scale meter deflection Range Resistor Used In RANGESwitch...

Page 42: ...UT Receptacle Clean INPUT Receptacle with non metallic sensitive shorting plug or connection abrasive If contamination goes below in input compartment plated surface replace connector Clean lugs with...

Page 43: ...18 base Q9 and QlO Replace faulty componentr Greater than 20 1 peak to peak Instrument located near high Try turning off possible sources one ripple at output terminals on HO cps magnetic field such b...

Page 44: ...INTENANCE MODEL148 NANOVOLTMETER FIGURE 20 Top View of Model 148 Chassis Location of components printed circuits and some test points is shown above Refer to Parts List for circuit designations 38 036...

Page 45: ...iew of Model 148 Chassis Locations of components and some test points is shown above The input compartment is shown without its shield Refer to Parts List for circuit designations Connect to point F a...

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Page 47: ...NCE FIGURE 24 Resistor Locations on Printed Circuit 76 Figure 25 contains callouts for the other resistors FIGUM 25 Resistor and Test Point Locations on Printed Circuit 76 Figure 24 contains callouts...

Page 48: ...OLTMETER FIGURE 26 Resistor and Test Point Locations on Printed Circuit 74 Bottom Face 9 Connect to point E at either place not to both points simultaneously FIGURE 27 Component Locations on Printed C...

Page 49: ...DIETER MAINTENANCE FIGURE 28 Resistor and Test Point Locations on Printed Circuit 75 An alternate location for point H is shown in Figure 20 FIGURE 29 Capacitor and Transistor Locations on Printed Ci...

Page 50: ...FIGURE 30 Resistor Locations on RANGE FIGURE 31 Resistor Locations on Switch S102 Figure 31 shows resistors RANGESwitch 5102 Figure 30 shows on opposite side resistors on opposite side 0 0 FIGURE 32 c...

Page 51: ...manufacture 80164 must be ordered from Keithley Instruments Inc In ordering a part not listed in the Replaceable Parts List completely describe the part its function and its location b Order parts th...

Page 52: ...25 I if 16 v 15 v 20 20 v 10 v ETB 56289 EAZ 29309 ETT 05397 ETT 05397 ETT 05079 non polar C104 25M C210 100M C80 10M C80 10M C106 25M 23 23 23 23 23 23 23 23 23 23 Cl16 Not Used Cl17 Cl18 Cl19 Cl20...

Page 53: ...Desig Description Mfg Keithley Fig Code Part No Ref GlOl Chopper JlOl Receptacle INPUT Special Plug Special Mate of JlOl 5102 Jack Telephone DEMODULATOR TEST Mfg 83330 17689A 17638A CS 132 CS 65 No 2...

Page 54: ...mer 80164 Transformer 80164 RESISTORS CH 1 20 CH 5 20 MB 14 20 2 16323A SW 157 2 17632B 163238 SW 58 2 17626B 14838A SW 158 2 14838A SW 151 15110A 2 17623B 20 TR 65 20 Circuit Desig Value Rating TYPO...

Page 55: ...112 w C0mp 01121 Rl 470 24 R134 100 0 lO l 2 w Comp 01121 Rl 100 24 R135 8 6 ko l l 2 w DCb 79727 R12 8 6K 25 R136 R137A B RI38 R139 R140 2 kn 1 kn li Not Used 111 0 1 11 ks lO l 2 w WWVar 80294 RP35...

Page 56: ...l 2 w DCb 79727 RlZ 10K w l 1 8W MtF 07716 R88 15K0 32 R206Not Used R207 1 kn R208 6 98 kb2 R209 6 98 kn R210 4 7 kn lO l 2 w l 112 w l l 2 w lO l 2 w lO l 2 w lO l 2 w lO l 2 w lO l 2 w lO l 2 w lO l...

Page 57: ...esignations Q17 to 925 and to page 53 for Q26 CO 229 930 2N1381 01295 TG 8 22 431 2N1381 01295 TG 8 22 432 2N1381 01295 TG 8 22 Q33 2N1381 01295 TG 8 22 434 2N1381 01295 TG 8 22 Q35 PNP Case TO 540139...

Page 58: ...N713 lN645 lN645 lN746A lN746A lN4148 1 4148 83125 RF l 4 27 83125 RF 14 27 12954 DZ 14 27 83125 RF 14 27 83125 RF 14 27 01295 DZ 40 01295 DZ 40 01295 RF 28 01295 RF 28 Circuit Desig MISCELLANEOUSPART...

Page 59: ...9 1K 27 R229 1 8 ku l l 2 w DCb 79727 R12 1 8K 27 R230 680 12 lO 112 w camp 01121 Rl 680 27 R231 10 n l 2 w ww 01686 R92 10 26 R232 18 n l 2 w ww 01686 R92 18 26 R233 100 1 lO l 2 w CCJlllp 01121 Rl 1...

Page 60: ...oov CerD 71590 DD 471 Circuit Desig MISCELLANEOUSPARTS Description Mfr Keithley Part No Fig Ref 5301 J302 __ L302 T301 T302 Circuit Desig Connector Mfg No 02 016 013 5200 91662 Connector Nut Mfg No 41...

Page 61: ...2 2K 28 R321 R322 R323 R324 R325 4 ka Lamp 3v 4 7 kn 10 kn 10 kn l l 2 w lO l 2 w lO l 2 w lO l 2 w DCb 79727 R12 4K 28 CM 2158 CM PL 37 28 camp 01121 Rl 4 7K 28 camp 01121 Rl 1OK 28 camp 01121 Rl 1OK...

Page 62: ...484 10 76545 AC 9 1483 1484 10 feet 80164 SC 5 1483 1484 100 feet 80164 ws 1 1483 1484 3 pads 80164 17774A 1483 1484 TL 1 mm I01121 Allen Bradley Corp 05397 Kemet Co Milwaukee Wis Cleveland Ohio I 012...

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Page 66: ...ents connected whether power is turned on or not Also describe signal source Where is the measurement being performed facton controlled laboraton out of doors etc _ What power line voltage is used Var...

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