The multimeter measures current, voltage, resistance, which file to adjust and how to read
1. Observe and understand the structure of the multimeter.
There are many types of multimeters with different shapes, but the basic structure and method of use are the same.
There must be a meter header and a selection switch on the multimeter board. There is also an ohm gear zero adjustment knob and a test lead jack. The following describes the role of each part:
(1) header
The head of the multimeter is a sensitive galvanometer. The dial on the head is printed with various symbols, scale marks and values. The symbol A-V-Ω indicates that the ammeter is a multimeter that can measure current, voltage and resistance. There are multiple scale lines printed on the dial, among which the one marked with "Ω" on the right is the resistance scale line, the right end is zero, the left end is ∞, and the scale value distribution is uneven. The symbol "-" or "DC" means direct current, "~" or "AC" means alternating current, and "~" means the scale line shared by AC and DC. Several rows of numbers under the scale line are the scale values corresponding to the different positions of the selector switch.
There is also a mechanical zero adjustment knob on the meter head, which is used to correct the zero position of the pointer at the left end.
(2) Selection switch
The selector switch of the multimeter is a multi-position rotary switch. Used to select measurement items and ranges. General multimeter measurement items include: "mA"; DC current, "V": DC voltage, "V": AC voltage, "Ω": resistance. Each measurement item is divided into several different ranges for selection.
(3) Test leads and test lead jacks
The test leads are divided into red and black. When using, insert the red test lead into the jack marked with "+", and insert the black test lead into the jack marked with "-".
2. How to use the multimeter
(1) Before using the multimeter, it should be done:
1. The multimeter is placed horizontally.
2. It should be checked whether the hands of the watch stop at the zero position at the left end of the dial. If there is any deviation, use a small screwdriver to gently turn the mechanical zero adjustment knob on the meter head to make the hands point to zero.
3. Insert the test lead into the test lead jack according to the above requirements.
4. Turn the selector switch to the corresponding item and range. It is ready to use.
(2) After using the multimeter, it should be done:
1. Pull out the test lead.
2. Turn the selector switch to the "OFF" position. If there is no such position, it should be turned to the maximum range of AC voltage, such as the "1000V" position.
3. If it is not used for a long time, the battery in the watch should be taken out to prevent the battery electrolyte from leaking and corroding the internal circuit.
(1) Measuring DC voltage
The measurement steps are:
1. Select the range. The DC voltage range of the multimeter is marked with "V", and there are five ranges of 2.5 volts, 10 volts, 50 volts, 250 volts and 500 volts. Select the range according to the power supply voltage in the circuit. Since the power supply voltage in the circuit is only 3 volts, 10 volts is selected. If you don't know the voltage, you should first measure with the highest voltage range, and gradually switch to the lower voltage range.
2. Measurement methods. The multimeter should be connected in parallel with the circuit under test. The red pen should be connected to the connection between the circuit under test and the positive pole of the power supply, and the black pen should be connected to the connection between the circuit under test and the negative pole of the power supply.
3. Correct reading. Carefully observe the dial, the scale line of the DC voltage scale is the second scale line, and when using the 10V scale, the measured voltage value can be directly read by the third row of numbers under the scale line. When paying attention to the reading, the line of sight should be facing the pointer.
