Troubleshooting a digital multimeter in five ways
Digital multimeter is a kind of measuring instrument that uses analogue/digital conversion principle to convert the measured quantity into digital quantity and display the measurement result in digital form. Compared with the pointer multimeter, digital multimeter has the advantages of high precision, speed, large input impedance, digital display, accurate reading, strong anti-interference ability, measurement automation and is widely used. However, if not used properly, it is easy to cause failure.
Digital multimeter troubleshooting should generally start from the power supply. For example, after turning on the power supply, if the LCD yuan display, you should first check whether the voltage of the 9V laminated battery is too low; whether the battery lead is disconnected. Looking for faults should follow the "first inside and outside, first easy after the difficult" order. Digital multimeter troubleshooting can be carried out in the following way.
Digital multimeter troubleshooting general five methods
First, appearance check: you can touch the battery, resistor, transistor, integrated block temperature rise is too high. If the newly loaded battery is hot, the circuit may be shorted. In addition, the circuit should also be observed whether the broken wire, desoldering, mechanical damage, etc..
Second, test the working voltage at all levels: test the working voltage at all points, and compared with the normal value, first of all, the accuracy of the reference voltage should be ensured, it is best to use the same model or a similar digital multimeter for measurement and comparison.
Third, waveform analysis: using an electronic oscilloscope to observe the circuit voltage waveforms, amplitude, period (frequency) of the key points. For example, such as measuring whether the clock oscillator vibration, oscillation frequency is 40 kHz. if the oscillator has no output, indicating that the TSC7106 internal inverter is damaged, it may also be an external component open circuit. Observe TSC7106 foot {21} waveform should be 50Hz square wave, otherwise, it may be internal 200 frequency divider damage.
Fourth, the measurement of component parameters: for components within the scope of the fault, online measurement or offline measurement, the parameter values should be analysed. For resistance online measurement, should consider the impact of its parallel components.
Fifth, hidden troubleshooting: Hidden faults refers to the faults are hidden, the instrument is good or bad faults. Such failures are more complex, common causes include solder joints, loose, loose connectors, transfer switch contact **, unstable component performance, the lead will be broken and so on. In addition, also includes some external factors caused by. Such as high ambient temperature, excessive humidity or intermittent strong interference signals nearby and so on.
