What are the requirements for using a multimeter
(1) Familiarize yourself with the meanings of various symbols on the dial and the main functions of various knobs and selector switches.
(2) Perform mechanical zero adjustment.
(3) Select the gear and range of the transfer switch based on the type and size of the measurement, and find the corresponding scale line.
(4) Select the position of the probe socket.
(5) Measuring voltage: When measuring voltage (or current), it is necessary to choose a good range. If a small range is used to measure a large voltage, there is a risk of burning the meter; If a large range is used to measure a small voltage, the pointer deflection is too small to read. The selection of measuring range should try to deflect the pointer to about 2/3 of the full scale. If the magnitude of the measured voltage is not clear in advance, the highest range should be selected first, and then gradually reduced to the appropriate range.
Measurement of AC voltage: Place one transfer switch of the multimeter in the AC/DC voltage range, and the other transfer switch in the appropriate range of AC voltage. The two probes of the multimeter can be connected in parallel with the circuit or load being tested.
Measurement of DC voltage: Place one conversion switch of the multimeter in the AC/DC voltage range, and the other conversion switch in the appropriate range of DC voltage. Connect the "+" probe (red probe) to the high potential and the "-" probe (black probe) to the low potential, allowing current to flow in from the "+" probe and out from the "-" probe. If the pen is connected in the opposite direction, the pointer on the head will deflect in the opposite direction, making it easy to bend the pointer.
(6) Current measurement: When measuring DC current, place one switch of the multimeter in the DC current range and the other switch in a suitable range of 50uA to 500mA. The selection of current range and reading method are the same as voltage. When measuring, the circuit must be disconnected first, and then the multimeter must be connected in series to the tested circuit in the direction of the current from "+" to "-", that is, the current flows in from the red probe and out from the black probe. If the multimeter is mistakenly connected in parallel with the load, the internal resistance of the meter head is very small, which can cause a short circuit and burn the instrument. The reading method is as follows:
Actual value=indicated value × Range/full deviation
(7) Resistance measurement: When measuring resistance with a multimeter, the following methods should be followed:
Select the appropriate magnification gear. The scale line of the multimeter's ohm gear is uneven, so the selection of the magnification gear should make the pointer stay in the thinner part of the scale line, and the closer the pointer is to the middle of the scale, the more accurate the reading. In general, the pointer should be positioned between 1/3-2/3 of the scale.
Zero the b ohm. Before measuring resistance, two probes should be short circuited and the "Ohm (Electrical) Zero Adjustment Knob" should be adjusted so that the pointer is exactly at the zero position on the right side of the Ohm scale line. If the pointer cannot be adjusted to the zero position, it indicates insufficient battery voltage or an internal problem with the instrument. And every time the magnification is changed, the ohm should be reset to zero again to ensure accurate measurement.
C reading: The reading on the meter head multiplied by the magnification is the resistance value of the measured resistance.
(8) Precautions
When measuring current and voltage, it is not allowed to change the range with power
When selecting the measuring range, the larger one should be selected first, followed by the smaller one, and the measured value should be as close to the measuring range as possible
When measuring resistance, it is not possible to measure it with electricity. Because when measuring resistance, the multimeter is powered by an internal battery, if it is charged for measurement, it is equivalent to connecting an additional power source, which may damage the meter head.
After use, the transfer switch should be placed in the maximum AC voltage position or neutral position.
