The 6 most common faults of digital multimeters
(1) The instrument has no display Firstly, check whether the battery voltage is normal or not (generally used 9V battery, the new one should also be measured). Secondly, check whether the fuse is blown, whether the voltage regulator is normal, whether the current limiting resistor is open. Then, check whether the circuit board is corroded or short-circuit, disconnection phenomenon (especially the main power supply circuit), if so, the circuit board should be cleaned, and do a good job of drying and welding in a timely manner; if the circuit board is normal, you can measure the display of the integrated block of the power supply input of the two pins, test whether the voltage is normal? If the test voltage is normal, the integrated block is damaged, the integrated block must be replaced; if the test voltage is not normal, check the other there is no short-circuit point? If there is, it should be dealt with in a timely manner; if there is no or dealt with is not normal, then the integrated block has been short-circuited internally, it must be replaced.
(2) resistive block can not be measured First of all, check the appearance of the circuit board, in the resistive block circuit, there is no connection resistance burned? If there is, then it must be replaced immediately; if not, then each of the connecting components to be measured, there is a bad timely replacement; if the periphery are normal, then the measurement of the integrated block is damaged, it must be replaced.
(3) voltage block in the measurement of high-voltage display value is not allowed, or the measurement of a long time display value is not allowed or even unstable Most of these failures are caused by one or several components of the work of insufficient power. If you stop measuring in a few seconds, check these components found hot, which is due to the lack of power and thermal effects caused by the components must be replaced (or integrated circuits).
(4) current block can not be measured Most of these failures are caused by improper operation, you can check the current-limiting resistor and voltage-dividing resistor burned out? If burned, it should be replaced; and then check whether the connection wire with the amplifier is damaged? If damaged, it should be reconnected; if not normal, then replace the amplifier.
(5) unstable display value, the phenomenon of jumping words Check whether the overall circuit board moisture or leakage phenomenon? If so, the circuit board must be cleaned and dry treatment; input circuit with or without poor contact or soldering phenomenon (including the test pen), if so, it must be rewelded; check for deterioration of the resistance or just after the test, there is no component of the occurrence of ultra-normal scalding phenomenon, this phenomenon is due to the reduction of its power caused by the phenomenon, if there is this phenomenon, it should be replaced with the component.
(6) display value is not allowed This phenomenon is mainly caused by the measurement circuit resistance or capacitance failure, the capacitor or resistor must be replaced. Check the resistance value of the circuit (including the resistance value of the thermal response), if the resistance value changes or the thermal response to change the value, the resistor should be replaced; check the reference voltage circuit of the A/D converter resistance, capacitance is damaged? If damaged, replace them.
