Six Ways to Troubleshoot Your Multimeter
1. Voltage measurement method
Measure whether the working voltage of each key point is normal to help quickly find out the fault point, such as measuring the working voltage and reference voltage of the A/D converter.
2. Feeling method
Use the senses to directly judge the cause of the fault. Through visual inspection, you can find such as disconnection, desoldering, short circuit, broken fuse tube, burnt components, mechanical damage, copper foil lifting and fracture on the printed circuit, etc. . You can touch the temperature rise of batteries, resistors, transistors, and integrated blocks, and refer to the circuit diagram to find out the cause of abnormal temperature rise.
In addition, by hand, you can also check whether the components are loose, whether the integrated circuit pins are firmly inserted, whether the switch is stuck, and whether there are any abnormal sounds and odors can be heard and smelled.
3. Circuit breaking method
Disconnect the suspicious part from the whole machine or unit circuit. If the fault has disappeared, it means that the fault is in the disconnected circuit. This method is mainly suitable for situations where there is a short circuit in the circuit.
4. Short circuit method
In the inspection methods of A/D converters introduced before, the short-circuit method is generally used, and this method is often used when repairing weak and micro-electric instruments.
5. Measuring component method
When the fault has been narrowed down to one or several components, online or offline measurement can be performed. If necessary, it can be replaced with a good component. If the fault disappears, the component is broken.
6. Interference method
Use the human body induced voltage as an interference signal to observe the changes of the liquid crystal display, and it is mostly used to check whether the input circuit and the display part are intact.
Troubleshooting method of digital multimeter
1. Waveform analysis
Use an electronic oscilloscope to observe the voltage waveform, amplitude, period (frequency), etc. of each key point of the circuit, such as measuring whether the clock oscillator starts to oscillate and whether the oscillation frequency is 40kHz.
If the oscillator has no output, it means that the internal inverter of TSC7106 is damaged, or the external components are open. Observe that the waveform at pin {21} of TSC7106 should be a 50Hz square wave, otherwise the internal 200 frequency divider may be damaged.
2. Measuring component parameters
On-line or off-line measurements of components within the fault range require analysis of parameter values. When measuring resistance online, it is necessary to consider the influence of components connected in parallel with it.
3. Hidden troubleshooting
Hidden faults refer to faults that appear and disappear from time to time, and the instrument is good and bad. This type of failure is more complicated, and the causes of the failure include weak solder joints, looseness, loose connectors, poor contact of the transfer switch, unstable component performance, and continuous breakage of the leads.
In addition, it also includes failures caused by some external factors, such as high ambient temperature, high humidity, or intermittent strong interference signals nearby.
4. Visual inspection
Touch the battery, resistors, transistors, and integrated blocks with your hands to see if the temperature rise is too high. If the newly installed battery heats up, it means that there is a short circuit in the circuit. In addition, it is also necessary to observe whether the circuit is disconnected, desoldered, mechanically damaged, etc.
5. Detect working voltage at all levels
Detect the working voltage of each point and compare it with the normal value. First, ensure the accuracy of the reference voltage. It is best to use a digital multimeter of the same model or similar to measure and compare.
