Fyrir gallað tæki, athugaðu og ákvarðaðu fyrst hvort bilunarfyrirbærið sé algengt (ekki hægt að mæla allar aðgerðir) eða einstaklingsbundið (stök aðgerðir eða einstök svið) og greina síðan aðstæður og leysa vandamálið.
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:
⑴ The range of the meter under test is turned to the lowest level of DC voltage;
(2) Mældu hvort vinnuspenna A/D breytisins sé eðlileg. Samkvæmt A/D breytilíkaninu sem notað er í töflunni, sem samsvarar V plús pinna og COM pinna, berðu saman mælda gildi við dæmigerð gildi þess.
(3) Mældu viðmiðunarspennu A/D breytisins. Viðmiðunarspenna hins almenna notaða stafræna margmælis er almennt 100mV eða 1V, það er DC spennan milli VREF plús og COM er mæld. Ef það víkur frá 100mV eða 1V er hægt að stilla það með ytri styrkleikamæli.
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.
Í stuttu máli, gallaður margmælir, eftir rétta prófun, verður fyrst að greina hugsanlega hluta bilunarinnar og finna síðan staðsetningu bilana samkvæmt hringrásarmyndinni til að skipta um og gera við. Vegna þess að stafræni margmælirinn er tiltölulega nákvæmt tæki, verður að skipta um varahluti fyrir íhluti með sömu breytur, sérstaklega skipti á A/D breytinum, verður að nota samþætta blokkina sem hefur verið stranglega skimuð af framleiðanda, annars verður vera villur og munu ekki uppfylla kröfur. Nákvæmni. A/D breytirinn sem nýlega hefur verið skipt út þarf einnig að athuga samkvæmt aðferðinni sem lýst er hér að ofan, og má ekki treysta honum vegna þess nýja.
GVDA Digital Multimeter GD108A:
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