What are the techniques for using a multimeter?
Measure 220V AC power. Set the range switch to AC 500V. At this time, the full scale is 500V, and the reading is read according to the scale 1:1. Insert the two probes into the power socket, and the scale indicated by the probe is the measured voltage value. When measuring AC voltage, there is no positive or negative probe, and the selection of pointer and digital meters:
1. The reading accuracy of pointer meters is poor, but the process of pointer oscillation is relatively intuitive, and the amplitude of its oscillation speed can sometimes objectively reflect the size of the measured object (such as the slight jitter of the TV data bus (SDL) when transmitting data); The reading on the digital meter is intuitive, but the process of numerical changes appears chaotic and difficult to observe.
2. There are usually two batteries inside a pointer meter, one with a low voltage of 1.5V and the other with a high voltage of 9V or 15V. The black probe is the positive terminal relative to the red probe. A 6V or 9V battery is commonly used for digital watches. In the resistance range, the output current of the pointer meter is much larger than that of the digital meter. Using the R × 1 Ω range can make the speaker make a loud "click" sound, and using the R × 10k Ω range can even light up the light-emitting diode (LED).
3. In the voltage range, the internal resistance of the pointer meter is relatively small compared to the digital meter, and the measurement accuracy is relatively poor. In some high-voltage microcurrent situations, it is even impossible to measure accurately because its internal resistance can affect the tested circuit (for example, when measuring the acceleration voltage of a TV cathode ray tube, the measured value may be much lower than the actual value). The internal resistance of the voltage range of a digital meter is very high, at least in the megaohm range, and has little impact on the tested circuit. However, the extremely high output impedance makes it susceptible to the influence of induced voltage, and the data measured in some situations with strong electromagnetic interference may be false.
4. In short, pointer meters are suitable for measuring analog circuits with relatively high current and high voltage, such as televisions and audio amplifiers. Digital meters are suitable for measuring low voltage and low current digital circuits, such as BP machines, mobile phones, etc. It is not absolute, and pointer and number tables can be selected according to the situation.
