Digital multimeters have high sensitivity and accuracy and are used in almost all businesses. However, due to the fact that there are many factors in its failure, and the randomness of the problems encountered is large, there are not many rules to follow. To find faults, you should first look for the outside and then the inside, first easy and then difficult.
Sensory method
By means of the senses to directly judge the cause of the failure, through the visual inspection, it can be found such as disconnection, desoldering, short circuit, broken fuse tube, burned out components, mechanical damage, and copper foil on the printed circuit is lifted and broken, etc. ; The temperature rise of batteries, resistors, transistors, and integrated blocks can be touched, and the cause of abnormal temperature rise can be found out by referring to the circuit diagram. In addition, you can also check by hand whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the transfer switch is cassette; you can hear and smell whether there is any abnormal sound or smell.
Voltage measurement
Measure whether the working voltage of each key point is normal, and the fault point can be found quickly. Such as measuring the working voltage of the A/D converter, the reference voltage, etc.
Short circuit method
The short-circuit method is generally used in the method of checking the A/D converter mentioned above, and this method is used more when repairing weak and micro-electrical instruments.
Circuit breaker
Disconnect the suspicious part from the whole machine or unit circuit. If the fault disappears, it means that the fault is in the disconnected circuit. This method is mainly suitable for short circuits in the circuit.
Measuring element method
When the fault has been narrowed down to a place or a few components, it can be measured online or offline. If necessary, replace with good components. If the fault disappears, the components are broken.
GVDA Digital Clamp meter GD108A:
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