Structure, Operation, and Operating Procedures of a Multimeter
1. The basic structure and appearance of a multimeter
A multimeter mainly consists of three parts: an indicator, a measuring circuit, and a conversion device. The indicating part is usually a magneto electric microampere meter, commonly known as the meter head; The measuring part converts the measured electricity into a small direct current suitable for the meter requirements, usually including a shunt circuit, a voltage divider circuit, and a rectifier circuit; The measurement of different types of electricity and the selection of measurement ranges are achieved through conversion devices.
2. Instructions for using a multimeter
(1) The selection of terminal buttons (or sockets) should be correct
The red probe connecting wire should be connected to the red terminal (or the socket marked with a "+" sign), and the black probe connecting wire should be connected to the black terminal (or the socket marked with a "-" sign). Some multimeters are equipped with AC/DC 2500 volt measuring terminals, and when in use, the black test rod should still be connected to the black terminal (or the socket marked with a "-" sign), while the red test rod should be connected to the 2500 volt terminal (or the socket marked with a "-" sign).
(2) The selection of the switch position should be correct
Turn the conversion switch to the desired position according to the measurement object. If measuring current, the conversion switch should be turned to the corresponding current range, and the measured voltage should be turned to the corresponding voltage range. Some multimeters have two toggle switches on the panel, one to select the measurement type and the other to select the measurement range. When using, the measurement type should be selected first, and then the measurement range should be chosen.
(3) The range selection should be appropriate
According to the approximate range being measured, turn the conversion switch to the appropriate range for that type. When measuring voltage or current, it is recommended to keep the pointer within the range of half to two-thirds of the measuring range for more accurate readings.
(4) Read correctly
There are many scales on the dial of a multimeter, which are suitable for different measured objects. Therefore, when measuring, while reading on the corresponding scale, attention should also be paid to the coordination between the scale reading and the range range range to avoid errors.
(5) Correct use of Ohm gear
1) Choose the appropriate magnification range
When measuring resistance, the selection of the magnification range should be such that the pointer stays in the thinner part of the scale line. The closer the pointer is to the middle of the scale, the more accurate the reading will be. The closer it is to the left, the tighter the scale line will be, and the worse the accuracy of the reading will be.
2) Zero adjustment
Before measuring resistance, the two test rods should be touched together and the "zero adjustment knob" should be turned at the same time to make the pointer just point at the zero position of the ohm scale. This step is called ohm zeroing. Every time the ohm range is changed, this step must be repeated before measuring the resistance to ensure measurement accuracy. If the pointer cannot be adjusted to zero, it indicates that the battery voltage is insufficient and needs to be replaced.
3) Cannot measure resistance with electricity
When measuring resistance, the multimeter is powered by a dry battery, and the measured resistance must not be charged to avoid damaging the meter head. Do not short circuit the two test rods in the Ohm gap to avoid wasting the battery.
(6) Pay attention to operational safety
1) When using a multimeter, be careful not to touch the metal part of the test rod with your hands to ensure safety and measurement accuracy.
2) When measuring high voltage or high current, do not turn the conversion switch with power on, otherwise it may cause the switch to burn out.
3) After using the multimeter, it is recommended to turn the conversion switch to the higher range of AC voltage. This range is the safest for the multimeter to prevent damage during the next measurement due to negligence.
4) Before the test rod comes into contact with the tested circuit, a comprehensive inspection should be conducted again to see if there are any errors in the position of each part.
