B&K Model 290 Extended Range Solid-State Electronic Multimeter 电路图.pdf

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1、;.1t,:, i$ ;: ii ir+ iii=- iis RadioFans.CN 收音机爱 好者资料库 Deqr Friend: Congrotulqtions on your purchose of B d K-Precision Test Equipment, qnd welcome to the B 41 91 elBcs ilnI%9l+ epcs IInJ A00sI pu? A00s A0SI A0SASI AS ASI ArII00g (AuCISI AIII0S :uoqcafeg epon uoturuoJ :fcernccy :asuodseg cuenberg :a

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5、os e q 062 lapo1 11 T g eql sflumvgd IvISiIds otlv NolldruJsgo TvugNgc OHMS MEASI,JREMENT: 8 Lnw Voltage Ranges RXO.I, RXl, RXl0, RXl00, RXIK, RXI0K, (33mV): RX100K, ru(lM. 7 Normal Voltage Ranges RXl, RX10, RX100, RXIK, RX10K, RXI0OK, (1.25V): RxlM. Midscale Reading: l0 (timesmultiplier) Accuracy:

6、t3o of arc, (+4 of arc on RX0.1 and RXIM ranges). DC CURRENT: 10 Ranges 50pA, l50pA, 5001rA, l.SmA, 5mA, l5mA, 50mA, 150mA, 500mA and 1.5 Amp full scale. Accuracy: !37o full scale; + 4% on 1.5 Amp Range. Internal Voltage Drop: 50mV at instrument input terminals, to 50mA range. AC CURRENT: 10 Ranges:

7、 50pA, l50pA, 500pA, l.smA, smA, l5mA, 50mA, lsOmA, 50OmA, and 1.5 Amp full scale. Accuracy: !4% full scale 6011z, lsvo on 50pA and 1.5 unp ranges. Internal Voltage Drop: 50mV, at instrument input terminals, to 50mA range. Frequency Response: +.5d8, 20llz to 5kHz, 50ouA to l51 sqtt lvv c .8/s-g x A.

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9、durV SZI) asn; ,q uorlcelord puolreo rncrrJ sp?olreo tuorJ opop ,q pelcelord lndur lgg pue reew :IHCIIIA :SNOISNgIIIO :sINgI lgulnogu uirAod :SUOJJNCNOJIIIgS :NOIIJgIOUd OPERATING CONTROLS This Electronic Multimeter is as simple to operate as a conventional WVM. The following is a brief description

10、of each control and how it is used (refer to Figure 1). l. METER ZERO ADJUST (MECHANICAL): The mechanical meter zero adjustment must be made before the instrument is turned on. Insert a screwdriver (preferably non-metallic) into the slot located in the center of the front panel immediately below the

11、 meter face. While gently tapping meter, very slowly turn the mechanical zero adjust until the pointer rests at zero. 2. FI,JNCTION SWITCH: Used to select the desired function for the measure- ments to be performed. 3. RANGE SWITCH: Used to select the desired range of current, voltage, or resistance

12、 to be measured. 4. OFF-ON SWITCH AND ZERO CONTROL: To turn the meter on, pull the ZERO control shaft outward. The red lamp on the meter will glow, indicating the meter is ON. Rotate the ZERO control to position the pointer of the meter at zero on the meter scale or to position the pointer on the ze

13、ro center when using this feature. Push the ZERO control shaft in to turn the meter OFF. 5. OHMS CONTROL: The OHMS control is adjusted with the FUNCTION switch in one of the OHMS positions and with the test leads open. Rotate the OHMS control for a full scale indication, infinity (oo) on the ohms sc

14、ale of the meter. 6. PROBE SWITCH: This instrument is equipped with a strielded test lead to allow accurate AC measurements in the presence of strong electrical fields. When the switch is in the 100K position, a l00K resistor is switched in series with the test lead. This isolates the cable capacity

15、 from the circuit under test when making DC voltage measurements in RF, IF or sweep circuits. Set the probe switch to the DIRECT position for all measurements other than DC voltage. 7. ADJUSTABLE HANDLE: The carrying handle may be used to support the instrument in a convenient sloping position for e

16、asy viewing. The case also can be placed in either a vertical or horizontal position. OPERATING THE MODEL 290 SAFETY PRECAUTIONS A certain amount of danger is always present when working on electrical equipment and therefore, the user is cautioned to always familiarize himself as much as possible wi

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24、nOHS uflI p1gdsNvlil NOIIVIOSI NV sp?al 1sa1 Eullcauuoc eroJeq rarnod Eullerado eaoruer ol q actlcerd pooE V qrud runler punor3 z aprrrord plnoc rIJIr/t slcafqo qreau Eurlcetuoc pIoB ol InJer?o pelncpred ag slueuernsuaur Euprel olq,tr uo pu?ls o1 Suuo,roc roog ro roog pelelnsu fpadord ? eBr ol lrrul

25、rodury osp sr lI ryorls lulueplrc? Jo pr?zurl eql e4urlqtu ot 1a4cod rnof q pu?q euo Euldae1 Jo Uq?g aql dolaaep slrncrc atellol qErq tu4sel uar111 d. Set the RANGE selector switch fully clockwise and connect the test leads to the circuit the same as for DC voltage measurement. e. Observe the meter

26、pointer indication on the black scale marked O and rotate the RANGE switch counterclockwise to obtain the best useable meter deflection. Positive voltages will make the pointer deflect to the right of the center zero mark. Each side of the scale lepresents one-half of the range being used. For examp

27、le, when the .5 volt range is being used, each half r of the scale represents .25 volt and each division .01 volt. The purpose for the center zero scale is to indicate a balanced condition. For example, if this instrument is used in the alignment of an FM discriminator, the desired balanced conditio

28、n will result in a reading of zero on the meter. A misaligned condition will cause some deflection in either the positive or negative direction. 4. MEASURING AC VOLTAGES (RIvlS turrels lsrl ossda1s gpOI u! eru saEuer A CV uel eql (tugpO) uollpod ASI eW w qrlr/rrs 1ICNVU eql grlrr dde NOTE The dB sca

29、les of this meter and the charts in Figure 2 and Figure 3 only apply when the voltage being meazured is a pure sine wave. Complex waveforms such as those encountered in music material will not give a true RMS reading for the dB system to be accurate, however, the dB scales can be used for relative l

30、evel measurements. 6. MEASI.JRING RESISTANCES: CAUTION When making re$stance measurements be sure that the power to the equipment under test is disconnected. If voltage is accidentally applied to theohms ranges, fuse replacement may become necessary. a. Hi frms Measnuements. To measure resistance, s

31、et the FIJNCTION switch to the HI OHMS po$ition, and the RANGE switch to the range that will put the resistance to be measured as close to the center of meter scale as possible. When the FLJNCTION switch is placed in the OHMS functions, the meter pointer will move from the left hand edge of the mete

32、r (zero) to the infinity (c) mark on the right hand side of the meter. Short test leads together and rotate ZERO control until neter pointer rests over zero mark on ohms scale. Remove short from test leads and rotate the OHMS control to adjust the meter pointer to exactly the infinity (o) mark on th

33、e right hand side of the meter. Be sure that the probe switch is in the DIRECT position. When using the HI OHMS function in solid state circuits, the applied 1.25 volts will be high enough to cause diodes or transistors to conduct. On all resistance ranges, the probe tip is positive with reqpect to

34、the minus (-) test lead. Remember this when checking components which have a different forward and reverse resistance such as semiconductors and electrolytic capacitors. b. Cheching for Triggering of Inw-Power Silicon-Controlled Rectifiers (SCR): Low-power SCRs can be checked to see if they can be t

35、riggered to the ON.condition: To make this check, proceed as follows: (1) Set the FLJNCTION switch to HI OHMS and the RANGE switch to RXl. (2) Adjust OHMS control so meter reads full scale (oo). (3) Set the PROBE switch to the DIRECT position. (4) Connect Minus (-) test lead to the cathode of the SC

36、R and the Plus (+) test lead to the anode. (5) If the SCR is good, the meter willcontinue to read o. Now momentarily short the SCR gate lead to anode lead. The meter strould read a very low resistance, indicating that the SCR has been triggered and is conducting. Removing voltage from the anode lead

37、 of the SCR will return it to the non-conducting condition. c. .o Ohms llcasurements. The LO OHMS function is used to make resistance measurements in solid state circuits when the forward conduction of a diode or transistor junction can cause an objectionable error. When using this I I l l0 I I IoXU

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44、oqcunJ sI lHo oI aql u luaturu$u srll qllrla perns?au sacu?lslser erJ,suoqcunf rolcnpuoclues runrueuret pu? uocT.rs Jo ploqsaql uotlonpuoc oqt aolaq 11e,vi sl sql (atue1 IgXU uo sllolr1lur Zn) perns?eu tqeq ilnrrlc eql 01 paqddu s1 (11or 0) stlompu tE fluo uortrunJ t I I I (3) Connect a short heavy

45、gauge wire between the plus andminus jacks and adjust ZERO control until pointer rests exactly over zero mark on OHMS scale. (4) Remove short from test jacks. The.meter pointer will move from the left hand edge of the meter (Zerc) toward the infinity (oo) mark on the right hand side of the meter. Ro

46、tate the OHMS control to adjust the meter pointer to exactly the infinity mark. (5) Repeat ZERO and OHMS adjustments at least one more time to obtain the best accuracy. (6) Make solid connections between test jacks and device being measured and read resistance on OHMS scale (if device has no leads,

47、use short heavy gauge wire). (7) Multiply resistance reading by 0.1. For example, if the meter reads l0 ohms (center scale) the resistance being measured will be l0 x 0.1 = I ohm. NOTE It will be necessary to readjust the OHMS and ZERO controls when returning to the higher Ohms ranges. e. Measuring

48、Resistance of Thermistors: The I.o OHMS function strould be used for making accurate measurements of resistances of thermistors of low resistance value. If this measurement is made in the HI OHMS function, a changtrg resistance reading will result due to heating caused by the higher current flow thr

49、ough the thermistor. The thermistor strould not be held in the hand and should be kept away from any other heat to obtain the most accurate fesistance indication. 7. MEASI,JRING AC CI.JRRENT: a. Set the FUNCTION switch to the AC A position. b. Set the PROBE switch to DIRECT. c. Short test leads together and rotate ZERO control until meter pointer rests over zero mark on VOLTS/MA scale. d. Set RANGE switch to the desired range. If the approximate value of c