Explain the various functions and precautions of a multimeter in detail
(1) First of all, pay attention to personal safety, and the connection of the meter pen should not expose any metal wires. When measuring voltage and current online, it is important to develop a one handed operation habit, with one hand holding the pen like a chopsticks. For the convenience of measuring DC voltage, the black probe can also be fixed at the ground wire position (such as inserting it into the ground wire spring at the graphite layer of the TV picture tube, or some heat dissipation holes connected to the ground wire, and clamping it on the ground wire with an alligator clip is also acceptable).
During the voltage measurement process, do not let your hands touch the metal part of the probe, circuit solder joints, or component metal parts to prevent electric shock.
(2) The pointer type multimeter should be zeroed before use, that is, the pointer should be pointed at the zero scale.
Using a potentiometer to zero the ohm range: Short circuit the two probes and adjust the zero potentiometer so that the pointer is on the right zero scale. Note that every time the resistance range is changed, a zero adjustment must be made.
Zero adjustment of voltage and current range: Adjust the spring of the meter head, which is the central "one" character screwdriver adjustment point, so that the pointer is at the left zero scale.
(3) During the process of measuring voltage or current, if the two probes are still in the circuit, the gear and range cannot be changed, especially under high voltage and high current conditions. Otherwise, it may damage the multimeter and in some cases, circuit components.
(4) It is not allowed to measure with a resistance gauge when the circuit board is powered on (or when there is still power in large capacitors, etc.), otherwise the multimeter may be damaged.
(5) The current range of a pointer multimeter cannot be used to measure voltage and resistance when powered on, otherwise high current will damage the meter head. The measurement of current and voltage should not be rotated to the wrong gear. If the resistance or current range is mistakenly used to measure voltage, it is very easy to burn out the multimeter.
(6) If a digital multimeter is found to have battery symbol display, difficulty in zeroing when measuring resistance with a pointer multimeter, or a decrease in measurement accuracy, it indicates that the built-in battery of the multimeter is low and needs to be replaced. If not in use for a long time, remove the battery, and for pointer type multimeters, the gear should be set to the off position or the maximum range of AC voltage to prevent accidental operation and damage to the multimeter in the next use.
(7) When measuring the resistance range, generally do not touch the pins of the components and the metal part of the lead with your hands, especially when the resistance value of the components is high. Parallel connection of the human body resistance will reduce the resistance value, thereby affecting measurement accuracy.
(8) Another point is to cultivate the habit of regularly checking the safety and reliability of one's instruments and tools, as well as the normal measurement function and accuracy. Otherwise, it will cause trouble and misjudgment in the next use, leading to adverse results, and thus putting maintenance and testing in a difficult situation.
