What are the common faults of the digital multimeter and how to fix it after the fault?

1. The meter has no display.

First check if the battery voltage is normal (usually a 9V battery, the new one should also be measured). Next, check if the fuse is normal. If it is not normal, replace it. Check if the voltage regulator block is normal. If it is not normal, replace it. Is the current limiting resistor broken? If it is broken, replace it.

Check again:

1)Check the circuit board for corrosion or short circuit, open circuit (especially the main power circuit line). If so, the board should be cleaned and dry and soldered in time.

2)If everything is normal, the measurement shows the power input of the integrated block. Is the test voltage normal? If it is normal, the integrated block is damaged and the integrated block must be replaced. If it is not normal, is there any other short-circuit point? If so, it must be handled in a timely manner; if it is not normal after it is processed or not, then the integration has been internally short-circuited and must be replaced.

2. Electrical blocking cannot be measured.

First check the circuit board from the appearance, is there any connection resistor burned in the electric blocking circuit? If it is, it must be replaced immediately; if not, it should be measured for each connected component, and if there are bad components, it should be replaced in time; If the periphery is normal, the measurement integrated block is damaged and must be replaced.

3. The voltage block is inaccurate when measuring high voltage, or the measurement is not accurate or even unstable for a long time. Most of these faults are caused by insufficient working power of one or several components. If within a few seconds of stopping the measurement, the components are found to be hot during the inspection, which is caused by the thermal effect caused by insufficient power, and the component variable (include the integrated block), the component (or integrated circuit) must be replaced.

4. The current block cannot be measured.

Most of them are caused by improper operation. Check if the current limiting resistor and the voltage dividing resistor are burnt out. If it burns out, it should be replaced. Check if the connection to the amplifier is damaged. If it is damaged, reconnect it: if it is not normal, replace the amplifier.

5. The indication value is unstable and there is a jump phenomenon.

Check if the entire board is wet or leaky. If so, you must clean the board and dry it. Check whether there are bad or weak soldering phenomena (including test pens) in the input circuit, and if so, they must be re-welded.

Check for resistor enomenon is caused by a decrease in power. If this is the case, replace the component.

6.The indication is not accurated.

This phenomenon is mainly caused by the resistance value or capacitance failure in the measurement path, so the capacitor or resistor should be replaced.

1)Check the resistance value (including the resistance value in the thermal reaction) in the path. If the resistance value  or the thermal reaction value changes, replace the resistor.

2)Check if the resistor and capacitor in the reference voltage loop of the A/D converter are damaged. If it is damaged, replace it.

This article is from Allicdata Electronics Limited. Reprinted need to indicate the source.

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