Multimeter failure methods can be roughly divided into the following types:
A multimeter can not only be used to measure the resistance of the object being measured, but also AC and DC voltages can be used to measure DC voltage. Even some multimeters can measure the main parameters of transistors and the capacitance of capacitors. Fully mastering the usage of a multimeter is one of the most fundamental skills in electronic technology. Common multimeters include pointer multimeters and digital multimeters. A pointer multimeter is a multifunctional measuring instrument with the head as the core component, and the measured value is read by the pointer of the head. The measured values of a digital multimeter are directly displayed in digital form on the LCD screen, making it easy to read. Some even have voice prompts. A multimeter is an instrument that uses a common meter head and integrates a voltmeter, ammeter, and ohmmeter. The malfunction of a multimeter is caused by multiple factors, and the randomness of encountering problems is high. There are not many rules to follow, making it difficult to repair. Here are some accumulated repair experiences summarized,
(1) The voltage measurement method measures whether the working voltage of each key point is normal, which can quickly identify the fault point. Measure the operating voltage, reference voltage, etc. of the A/D converter.
(2) Sensation method relies on sensory perception to directly determine the cause of faults. Through visual inspection, it can detect issues such as broken wires, desoldering, short circuits in grounding, broken fuse tubes, burnt components, mechanical damage, copper foil warping and breakage on printed circuits, etc; You can touch the temperature rise of the battery, resistor, transistor, and integrated block, and refer to the circuit diagram to find the cause of the abnormal temperature rise. In addition, you can also check by hand whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the conversion switch is stuck; You can hear and smell any unusual sounds or odors.
(3) The circuit breaking method interrupts the suspicious part from the entire machine or unit circuit. If the fault disappears, it indicates 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) The short-circuit method is generally used in the inspection of A/D converters mentioned earlier, and it is more commonly used in repairing weak and micro electrical instruments.
(5) When the fault has been reduced to one or several components, the component measurement method can be used for online or offline measurement. If necessary, replace with good components. If the fault disappears, it indicates that the component is broken.
(6) The interference method uses human induced voltage as an interference signal to observe the changes in the LCD display, and is commonly used to check whether the input circuit and display part are intact.
