Maintenance and repair of the digital multimeter
A digital multimeter is a commonly used measuring instrument that can have many special functions, but its main function is to measure voltage, resistance, and current, and it is widely used in multiple fields. How should users maintain a digital multimeter? Below, the editor will introduce the maintenance methods of digital multimeters in detail, hoping to help everyone.
1. Maintenance
A digital multimeter is a precision electronic instrument. Do not change the circuit at will and pay attention to the following points:
1. Do not connect to DC voltage higher than 1000V or AC RMS voltage higher than 700V
2. Do not connect the voltage source when the function switch is in the Ω and position
Do not use this meter when the battery is not properly installed or the back cover is not tightened
Repair method
Digital multimeters have high sensitivity and accuracy, and their applications are almost ubiquitous in all enterprises. However, due to the multifactorial nature of its failures and the high randomness of encountering problems, there are not many rules to follow. Therefore, some repair experience accumulated in practical work is compiled for reference by colleagues engaged in this profession.
Finding faults should start with the outside and then the inside, starting with the easy and then the difficult, breaking down the whole into small parts and focusing on breakthroughs. The methods can be roughly divided into the following categories:
1. Sensory method relies on sensory perception to directly determine the cause of faults. Through visual inspection, it can detect factors 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.
2. 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.
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.
4. 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.
When the fault has narrowed down to one or several components, it can be measured online or offline using the component measurement method. If necessary, replace with good components. If the fault disappears, it indicates that the component is broken.
