How to Check the Disadvantages of Digital Multimeter

A multimeter can not only be used to measure the resistance of the object being measured, but also the AC and DC voltages and DC voltages. Some multimeters can even measure the main parameters of transistors and the capacitance of capacitors. Fully mastering the use of multimeters is one of the most basic techniques of electronic technology. Common multimeters include pointer multimeters and digital multimeters. Pointer multimeters are multifunctional measuring instruments with a meter head as the basic component, and the measured value is read by the meter head pointer. The measured value of a digital multimeter is directly displayed in digital form on the LCD display screen, which is easy to read, and some also have a voice prompt function. A multimeter is an instrument that shares a meter head and integrates a voltmeter, ammeter and ohmmeter. The defects of a multimeter are multi-factorial, and the problems encountered are random, there are not many rules to follow, and the repair is difficult. The front editor has sorted out some repair experiences accumulated in many years of work practice for your reference. The methods for cleaning the faults of Fluke multimeter can be roughly divided into the following categories:

　　(1) The voltage measurement method measures whether the operating voltage of each key point is normal, which can quickly find out the fault point. For example, measuring the operating voltage and reference voltage of the A/D converter.

　　(2) The touch method relies on the senses to directly distinguish the fault factors. Through appearance inspection, it can find broken wires, desoldering, short circuits, broken fuses, burned components, mechanical damage, copper foil lifting and cracking on printed circuits, etc.; it can touch the temperature rise of batteries, resistors, transistors, and integrated circuits, and refer to the circuit diagram to find out the factors of abnormal temperature rise. In addition, you can use your hands to check whether the components are loose, whether the integrated circuit pins are firmly inserted, and whether the switch is stuck; you can hear and smell whether there are any abnormal sounds or odors.

　　(3) The circuit-breaking method disconnects the suspected part from the whole machine or unit circuit. If the fault disappears, it indicates that the fault is in the disconnected circuit. This method is mainly suitable for the situation where there is a short circuit in the circuit.

　　(4) Short-circuit method The short-circuit method is usually used in the A/D converter inspection method mentioned above. This method is more commonly used when repairing weak current and micro-electric instruments.

　　(5) Component measurement method: When the defect has been reduced to a certain place or several components, it can be measured online or offline. If necessary, replace it with a good component. If the defect disappears, it means that the component is broken.

　　(6) The interference method uses the human body induced voltage as the interference signal to check the changes in the LCD display. It is often used to check whether the input circuit and the display part are complete.