KEI150(Model150and150R) 电路图.pdf

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1、MODEL 150 and MODEL l5OR DC MICRO VOLT-AMMETER INSTRUCTION MANUAL KEITHLEY INSTRUMENTS, INC. “1, CLEVELAND, OHIO . RadioFans.CN 收音机爱 好者资料库 SECTION INTRODUCTLON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .I. 1 . SPECIlICAIONS .,.,.*.*.*.*. II OPJ3RATION . . . . . . . . . . . .

2、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III A. Operating Controls B. Preliminary Set-up C. General Precautions 1. source Reoistance 2. Shielding 3. Thermal EMF 4. Input Noise 5. Checking the Zero Point D. Meaouring Voltage 1. Direct Moaswement 2. Small varib.tions 3. Differen

3、tial Voltages E. Measuring Current 1. Dire F. Power Supply MAINTENANCE ,.*.*,.*.,.*. V General Notes Trouble Shooting Volta:- treme power nensitivity. Typical applications include mca,suring the output from strain gages, thermopilos, thermocouples, bolometers, phototubes, ionization chanlbtirs, ocln

4、tillation countors, and barrier layer cells. Other applications are found in cell studies, measurement of electrochemical potcn-cials, electrolytic corrosion studies, molecular weight analysis and Hall effect studies. In addition to its use as a direct indicator of minute potentialo and currents, th

5、e Mod01 150 may also be used as a null detector In Wheatstone or Mueller bridges, or with an external voltage source ao a meg-mecps from 1 microvolt to 1 volt full wale on n zero-cqnt.cr mster. Zl:ill Cc.ncra1l.y drift off scale on any voltage range. On current ranges ihis does not happen bocauso of

6、 the input ohuntinC resistors. 2. Shielding - Since the instrument operates with a mo3lo.t fx- quoncy of 120 cps, it is not generally sensitive to 60 cpn pickup unless it is large enough to overload the amplifier. The pickup :n;y be a source of difficulty when using the amplifier Tith high imPeri- a

7、xes ox the more sensitive voltage rzngcs and on the t-.zo or three most sensitive current ranges. In these cases it is desirable to shiold,thc leads and the source 3s completely as possible. In ooiae cases a simple low-pass filter at the input to eliminate frec,uoncies of about 1 cps and above will

8、be helpiul. No use is made of an inout filter in this instrument since any input series impcdxince 13.x to :he filter will increase the input noise and the thermal drift. When o,p - eratine above ground, the case of the instrument must be Croundcd. 3. Thermal EKF - Extreme precautions have been take

9、n in the input circuit to minimize thermal EMFs so that the residual FXF is less than 0.6 microvolt. The material used in the input circuit is pure copper. Any other metal will generat a thermoco)u?le potential. Load solder is perticularly troublesome. lihero thermal EXFs are a problem, soldering sh

10、ould be done with the cadmium-tin solder supplied with the instrunont. 4. Input Noise: The noise at the input is a function of input re- sistance and is approximately given by E = 1.29 x 10-10 (R+2000)$ where E Is the IWS noise, and R is the source resistance. It Is as- sumed that the bandwidth of t

11、he instrument is about 1 cps and the temperature is 80F. If noise is observed, calculate the theoretical noise and compare results. Also bear in mind that only wire-wound resistors approxil the ideal resistor. norrcvc r ) Lf Evx.o!13 or m or with a phototube, shield the tube from light. III - 2 D. M

12、I?ASUlING VOLTAGI? I.- 1. Direct Voltngc Meanurcmontn - Place the FUNCTION switch at MILLIVOLTS or MICROVOLTS ao nocossary for tho mousuroment to bc taken. Thon turn tho RANQ? switch to more sensitive ranges until the meter gives a uoablo dofloction. 2. Monsuring Voltagc Variations - Set the PUNCTIO

13、X switch and RAI:GZ switch to obtain the best deflection of the mster. Use the ZXRO SUP- PRESS controls as described in B to increase the sensitivity of tho meter. Then small changes In a relatively large steady signal may be disnlayed with a large scale deflection. 3. Masswing Differential Volt thi

14、s voltage being applied through ap- propriate dropping resistors to the feedback point. to achieve zsro suppression. The potentiometer is the front panel control xarked ZERO SET, while switch bW3, which determines the portion fed back, is labeled ZERO RANGE. N-l E. Other Controls Three controls are

15、set at the factory and should rcqulro only lnfro- qmnt attention by the user. Hll8 Is an internal control marked DC AMP BAD. It is used to zero the DC amplifier, I.e., to set the output voltage to zero when the domodulator output is zero. This is not very critical since an un- balance will simply be

16、 fed back tc the in;lut to produce a s:aall error signalto correct itself. Pi127 is msrked CAD. Thlo is the variable portion of the mGter multiplier resistance to allow for motcr-to-nu3ter sensitivity differences. R177, marked CURXENT BALAWE, my be sot at some voltngo which will cause a current to f

17、low through R175 to the chopper ar:n. This cur- rent is used to componsato for a small gcnoratod chopper current which would otherwise flow in the input circuit. This chopper current differs from chopper to chopper but is fairly stable for long periods of tirce. Its effect on any current range could

18、 be rc- moved with the ZERO SUPPRESS controls, but the Current 3alancc :%othod used here gives an effective zero input current for all ranges. I?. Pwer Supply A standard half-Irave rectifier followed by an R-C filter is used to supply unregulated Bt and B- to the output cathode follower. The unregul

19、ated B- is regulated to -150 volts in V7, OA2, and is used for ths negativ: returns for the dc wplifier. Unregulated B+ is fed to the plate of V8, 12Rll.A, the series tube in a 225-volt electronic regulator. The output voltage from this rcgu- lator is divided by R510 and R511 and compared to referen

20、ce tuba V9, a 5651. The difference signal is amplified by cascade amplifier VlO, a 12AX7, and applied to the grid-cathode circuit of the series tubs. This regulated 225 volts supplies B+ directly to the dc amplifier, through a decoupling filter (2176, CllO) to the second and third ac amplifier stage

21、s, and through another decoupling filter (R103, ClO4) to the first ac amplifier stage, Regulated B+and B- also supply currents to the 10 volt zener diodes which are used for zero suppression. This gives two-stage regula- tion for these very critical voitages. The first two ac amplifier filaments and

22、 the first dc alnplifior filaments are driven by a bridgo-rectified 6-volt d.c. supply. The R-C filter sections R5l2, C507, R513, C508, insure low ripple. IV-2 SECTION V - MAINTENANCE Rxccpt for occasional tube or chopper replacement, very little mainton- ante is required by the Models 150 and 150R.

23、 Components are operated. well below rating and solid-stato devices arc employed where possible to achieve long, trouble-free service. Certain portions of the input circuit are wired using copperwlre and special cadmium-tin solder. These special joints are painted red. If, for any reason, those join

24、ts must be unsoldered or re-soldcrod, USE ONLY CfZ?4IUM-TIN SOLDER AND A COPPZR-TIP?ED SOLDERING IRUN WHICH iuS hWJER BLTV; USZD WIUf 0FJI:IARY L,E!D-TIN SOLDRR. A small 301 Of cadmium-tin solder is supplied with each instrument. What may seem to be circuit failure in the Micro Volt-kmxeter is quite

25、 often found to be an unusual condition in the entire test set-up. Therefore; before trouble-shooting the instrur;ont, :hock to sei: wh;cthcr it operates correctly with: . 1. All other circuitry disconnected. 2. Input shorted (with copper loads). 3. power line voltage and frequency correct. If the d

26、ifficulty persists, the following systematic procedure may be employed to determine the fault. TROLDLF-SHOOTING Reference is made to the Schematic Diagram, DR 12188-D, and the Voltage- Resistance Diagram enclosed at the rear of tho manual. To bogin trouble-shooting, short the input teninLls, strap c

27、hassis ground to LO with the link provided, and switch ZERO R;L:CZ to CItF . :; Zero offset of a few tenths of a microvolt is normal. on CJrront func- tions with the input terminals open but shielded, it should be possible to sot zero current with the CURPJNT BALANCE control at the rear of tho instr

28、ument. EXCESSIVE OUT?UT NOISE (mUI IBRMINALS SHORTED) Short the input grid of the dc amplifier, pin / of VI+, to ground. If this stops the noise, it is being generated in the ac amplifier. unfor - tunately, because of the very low signal levels involved, noise in the ac amplifier is difficult to tra

29、ce by other thanthe s.ubstitution method. Most logical noise sources are Vl or the chopper. To replace the chop- per, unplug the cap at the top, and unscrew the three thumb-screw nuts which clamp the chopper loads. Unscrew the two chopper mounting screws and lift out the chopper. When inserting the

30、new chopper, make sure that the chopper leads are preol q.-ed against the copper terminals and that the insulating washers are between the leads and the thumb-screw nuts. Observe color-coding on the leads. V-l If thu no-isc Pornl.oto aftor shortn(j the dc amplifier input, the noise So being :riratod

31、 in the dc nm,lif!.er or power nupply. A stnce-hy- stn search should reveal tho source. OUTPUT NOT I,I?RO (I?tT,TuT IYRMINALS SHOR!l?;,) Be 8ure that ZERO RANGE is set to OFF. Short the dc amplifier inpue erIcI, fier or power oupply are at fault. If It can be sot to zero, the trouble may be in the R

32、C amplifier or demodulator cj,rcuit. a. Power Supply - B+ should be about +225 cn pin 1 of Jr, arxi B- should be -130 on pins 2, 4 or 7 of V7. If V7 Is cot firing, correct the fault in the unreo1 c502 c503 CTjO4 csolj C506 c507 508 cyog CHl CSl cs2 CUl Dl D2 D3 n4 Fl M RlOl R102 RlO3 n104 R 105 R105

33、 tiloT RlOO lx109 I?110 Rlll RcplacecLbla Part.0 List Model 150 - 15m Deficription I i Part ND. Capacitor, mylar colected, .047 to .33 rd, 600 VQCW Capacitor, ceramic disc, .OCb7 mfd, 600 VDCW same a3 Cl14 Capacitor, padding 780 -2110 mmf Capacitor, metalized paper, 1.0 mfd, 200 VIEW Capacitor, tubu

34、lar, electrolytic, 20 mfd, 600 VEW SHm3 an Cl04 Same I38 c501 same as cl08 Same as Cl04 Capacitor, mylar dieiectric, 4.0 mfd, 600 VDCW Capacitor, tubular, elec.trolytic, 1000 mfd, 12 VECW depwited carbon, 333 ohms, 1% lW $ f.w Resistor, deposited carbon, 100 ohms, lp, 2 Renjstor, deposited carbon, 3

35、3.3 ohms, l$! +W Resiotor, deposited carbon, 10 ohms, l%, 2W Resistor, deposited carbon, 3.33 ohms, l$, , 2W Sam as R501 Resistor, wirewound, 5K, lC$, 1OW Same as R503 Resistor, composition, 22K, I-$, 2W Resistor, composition, 10 meg. lC$, $W Resistor, deposited ccrbon, 220K ohms, l$ $W Same as RlOl

36、 Same as RlOl Seam s.8 R106 Resistor, dep0oited carbon, HOOK, l$, $W Resistor, wirewcnnd, 6 ohms, I, 5 Resistor, wirewound, 5 ohms, l, 5W Rectifier, selenium, 13Ov, 65ma Rectifier, bridge, 26 volt, 6OOma Function switch, 4 pole, 4 position Rongo switch, 9 position Zero suppress, zero range 5 positio

37、n Power switch, D.P.D.T. Power transformer Central KI-129 Demodulator transformer Central KI-128 Input transformer, #James Cl635 special Pilot lamps (2) 6.3. 0.15 amps G.E. type 47 Vacuum tube, type 6084 Vacuum tube, type EF86 Same as V2 Vacuum tube, type 12.4X7 Vacuum tube, type 12AT7 Vacuum tube,

38、type 6CM6 Vacuum tube, type OA2 Vacuum tube, type 12B4A Vacuum tube, type 5651 Same as V4 HP4-1OK R14-1OOM R12-75K RIG-&!l-1COK R12-1M R3-100 n5-5If R3-22K Rl-1OM R12-22CK 12-60m R4-6 R4-5 RF6 RF7 SW56 SW54 sw58 SW14 TR27 26 Tn2a PL4 6084 EV-RPa6 w-12.2X7 EV-12AT7 EV-6Cfr6 EV-OA2 EV-12B4A -5651 EV-5651 . I- _._ v- -