A multimeter comes in two types: one is a digital multimeter, and the other is an analog multimeter with a needle display. Regardless of the type, it generally has functions for measuring AC/DC voltage, AC/DC current, resistance, and more. Before measuring, it is essential to correctly select the measurement range of the multimeter; this is very important!
The diode measurement function of a multimeter is arguably the most commonly used. It is used to measure diodes and can measure the forward voltage of a diode. Generally, digital multimeters have a diode measurement function, which measures the voltage across a component when a certain current flows through it. When measuring a diode, it is the voltage when the diode is forward-biased; when measuring a transistor, it is the voltage across one junction of the transistor when it is conducting; when measuring resistance, it is the voltage across a resistor under a certain current. The measured value can roughly indicate the material and power rating of the diode.
A multimeter also has a very powerful function: when we need to discharge a capacitor, we can use a digital multimeter to do so!
To operate, connect the red and black probes to the positive and negative terminals of the large capacitor, continuously swapping the red and black probes. After a few seconds, when you hear a beep, the capacitor can be considered discharged.
Precautions for using a multimeter:
1. Before using the multimeter, perform a “mechanical zeroing”, which means ensuring that the multimeter’s pointer points to the zero voltage or zero current position when there is no measured electrical quantity.
2. During the use of the multimeter, do not touch the metal parts of the probes with your hands. This ensures measurement accuracy and also guarantees personal safety.
3. When measuring a certain electrical quantity, do not change ranges while measuring, especially when measuring high voltage or high current. Otherwise, it may damage the multimeter. If a range change is necessary, disconnect the probes first, then change the range before measuring.
4. The multimeter must be placed horizontally during use to avoid errors. Additionally, avoid external magnetic fields that may affect the multimeter.
5. After using the multimeter, set the selector switch to the maximum AC voltage range. If not used for an extended period, the internal battery should also be removed to prevent battery corrosion of other components inside the multimeter.