Digital Multimeter Kho Cov Lus Qhia
Rau cov cuab yeej faulty, thawj zaug xyuas thiab txiav txim siab seb qhov tshwm sim txhaum puas muaj tshwm sim (tag nrho cov haujlwm tsis tuaj yeem ntsuas tau) lossis tus kheej (tus kheej lub luag haujlwm lossis tus kheej ntau yam), thiab tom qab ntawd paub qhov txawv qhov xwm txheej thiab daws nws cov tsos mob.
⒈ If all gears cannot work, focus on checking the power supply circuit and A/D converter circuit. When checking the power supply part, you can remove the laminated battery, press the power switch, connect the positive test lead to the negative power supply of the meter under test, and connect the negative test lead to the positive power supply (for digital multimeters), switch the switch to the diode measurement gear, if the display shows If it is the forward voltage of the diode, it means that the power supply part is good. If the deviation is large, it means that there is a problem with the power supply part. If there is an open circuit, focus on checking the power switch and battery leads. If there is a short circuit, you need to use the circuit breaking method to gradually disconnect the components that use the power supply, focusing on checking operational amplifiers, timers, and A/D converters. If a short circuit occurs, more than one integrated component is generally damaged. The A/D converter can be checked at the same time as the basic meter, which is equivalent to the DC meter of an analog multimeter. The specific inspection method is as follows:
⑴The range of the meter under test is turned to the lowest level of DC voltage;
(2) Ntsuas seb qhov ua haujlwm voltage ntawm A / D converter yog qhov qub. Raws li A / D converter qauv siv nyob rau hauv lub rooj, sib xws rau V ntxiv tus pin thiab COM tus pin, sib piv cov nqi ntsuas nrog nws cov nqi raug.
(3) Ntsuas qhov siv voltage ntawm A / D converter. Kev siv hluav taws xob ntawm cov khoom siv digital multimeter feem ntau yog 100mV lossis 1V, uas yog, DC voltage ntawm VREF ntxiv thiab COM yog ntsuas. Yog tias nws deviates ntawm 100mV lossis 1V, nws tuaj yeem hloov kho los ntawm lwm tus potentiometer.
⑷ Check the displayed number of input zero, short{{0}}circuit the positive terminal IN plus of the A/D converter with the negative terminal IN-, make the input voltage Vin=0, and the meter displays "00.0" or "00.00".
⑸ Check the full bright stroke of the display. Short-circuit the test terminal TEST pin with the positive power supply terminal V plus to make the logic ground become a high potential, and all digital circuits stop working. Because DC voltage is applied to each stroke, all strokes are bright and the alignment table displays "1888", and the alignment table displays "18888". If there is a missing stroke, check the corresponding output pin of the A/D converter and the conductive glue (or connection), and check whether there is poor contact and disconnection between the A/D converter and the display.
⒉ If there is a problem with individual files, it means that the A/D converter and the power supply part are working normally. Because DC voltage and resistance files share a set of voltage divider resistors; AC and DC current share a shunt; AC voltage and AC current share a set of AC/DC converters; others such as Cx, HFE, F, etc. are composed of independent different converters . Understand the relationship between them, and then according to the power diagram, it is easy to find the fault location. If the measurement of the small signal is inaccurate or the displayed number jumps greatly, focus on checking whether the contact of the range switch is good.
3. If the measured data is unstable, and the value always increases cumulatively, the input terminal of the A/D converter is short-circuited, and the displayed data is not zero, which is generally caused by the poor performance of the 0.1μF reference capacitor.
According to the above analysis, the basic sequence of repairing the digital multimeter should be: digital meter head→DC voltage→DC current→AC voltage→AC current→resistance gear (including buzzer and checking diode positive voltage drop)→Cx→HFE , F, H, T, etc. But it should not be too mechanical. Some obvious problems can be dealt with first. But when making adjustments, be sure to follow the above procedure.
Nyob rau hauv luv luv, ib tug faulty multimeter, tom qab kev ntsuam xyuas kom zoo, yuav tsum xub soj ntsuam qhov ua tau ntawm qhov txhaum, thiab tom qab ntawd nrhiav qhov chaw txhaum raws li daim duab kos rau kev hloov thiab kho. Vim hais tias cov multimeter digital yog cov cuab yeej siv tau zoo, cov khoom siv hloov pauv yuav tsum tau hloov los ntawm cov khoom siv nrog tib qhov tsis zoo, tshwj xeeb tshaj yog kev hloov pauv ntawm A / D converter, yuav tsum siv cov kev sib xyaw ua ke uas tau soj ntsuam nruj me ntsis los ntawm cov chaw tsim khoom, txwv tsis pub muaj ua yuam kev thiab yuav tsis ua raws li qhov yuav tsum tau ua. Qhov tseeb. Tus tshiab hloov A/D converter kuj yuav tsum tau soj ntsuam raws li txoj kev tau piav saum toj no, thiab yuav tsum tsis txhob ntseeg vim hais tias ntawm tus tshiab.
