General use of electrical instruments: multimeter
The multimeter can measure DC current, DC voltage, AC voltage and resistance, etc. Some can also measure power, inductance and capacitance, etc. It is one of the most commonly used instruments for electricians.
1. The basic structure and shape of the multimeter
The multimeter is mainly composed of three parts: an indication part, a measurement circuit and a conversion device. The indication part is usually a magnetoelectric micro-ampere meter, commonly known as a meter head; the measuring part is to convert the measured electric quantity into a small DC current suitable for the head requirement, usually including a shunt circuit, a voltage dividing circuit and a rectifying circuit; And the choice of the range is achieved by the conversion device.
500 type multimeter↓
2, the use of the multimeter
(1) The button (or jack) should be selected correctly.
The red test lead cable should be connected to the red end button (or the “+†jack), and the black test lead cable should be connected to the black end button (or the jack marked with “—â€). Some multimeters are equipped with an AC 2500 volt measuring terminal. When used, the black test stick is still connected to the black end button (or "-" jack), and the red test stick is connected to the 2500 volt end button (or Inside the jack).
(2) The selection of the switch position should be correct
Switch the selector switch to the desired position according to the measuring object. If the current is measured, the transfer switch should be turned to the corresponding current level, and the measured voltage is transferred to the corresponding voltage level. Some universal surface boards have two transfer switches, one for measuring the type and the other for measuring the range. When using, you should first select the measurement type and then select the measurement range.
(3) The range selection should be appropriate
Depending on the approximate range being measured, the transfer switch is turned to the appropriate range for that category. When measuring voltage or current, it is best to make the pointer within the range of one-half to two-thirds of the range, and the reading is more accurate.
(4) Correct readings
There are many scales on the dial of the multimeter, which are suitable for different objects to be tested. Therefore, when measuring, the reading on the corresponding scale should also pay attention to the cooperation between the scale reading and the range file to avoid errors.
(5) Correct use of ohm files
1Select the appropriate magnification file:
When measuring the resistance, the magnification gear should be selected so that the pointer stays in the thin part of the scale line. The closer the pointer is to the middle of the scale, the more accurate the reading, the more to the left, the more the scale line is squeezed, the more accurate the reading. difference.
2 zero adjustment:
Before measuring the resistance, the two test rods should be touched together, and the “zero adjustment knob†should be turned at the same time so that the pointer just points to the zero position of the ohm scale. This step is called ohmic zero adjustment. Each time the ohmic file is changed, this step is repeated before measuring the resistance to ensure measurement accuracy. If the pointer cannot be adjusted to zero, the battery voltage is insufficient and needs to be replaced.
3 can not be charged measuring resistance:
When measuring resistance, the multimeter is powered by dry battery, and the measured resistance must not be charged to avoid damage to the meter. In the ohmic gap, do not short the two test bars to avoid wasting the battery.
(6) Pay attention to operational safety
1 When using the multimeter, be careful not to touch the metal part of the test rod to ensure safety and measurement accuracy.
2 When measuring a higher voltage or a larger current, the transfer switch cannot be turned on, otherwise the switch may be burned out.
After the 3 million meter is used up, it is best to turn the switch to the highest range of the AC voltage. This file is the safest for the multimeter to prevent the multimeter from being damaged in the next measurement.
4 When the test rod touches the line under test, it should be checked again to see if there is any error in the position of each part.
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