How to use a multimeter to measure resistance
When measuring resistance with a multimeter, the following methods should be used*:
a. Mechanical zero adjustment. Before use, the pointer positioning screw should be adjusted so that the current indication is zero to avoid unnecessary errors.
b. Select the appropriate magnification file. The scale line of the ohm gear of the multimeter 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. Under normal circumstances, the pointer should be pointed at 1/3~2/3 of the scale.
c. Ohm zero adjustment. Before measuring the resistance, the two test pens should be short-circuited, and the "ohm (electrical) zero adjustment knob" should be adjusted at the same time, so that the pointer just points to the zero position on the right side of the ohm scale line. If the pointer cannot be adjusted to zero, it means that the battery voltage is insufficient or there is a problem inside the meter. And every time the magnification gear is changed, the ohm zero adjustment must be performed again to ensure accurate measurement.
d. Reading: The reading of the meter multiplied by the magnification is the resistance value of the measured resistance.
At first glance, the multimeter is very complicated. In fact, it is composed of an ammeter (commonly known as a meter head), a dial, a range selection switch, and test pens.
When using, if the range selection switch is pointed to the DC current range, the ammeter M is connected with some shunt resistors to achieve the purpose of expanding the range, making it an ammeter with several ranges of different sizes.
The measurement result depends on the DC current scale on the dial to read. Usually the second row on the dial is the current scale. Similarly, if the range selection switch points to the DC voltage range, the meter head is connected to some other resistors in series (the principle of dividing the voltage by series resistors makes it a multi-range voltmeter). The reading depends on the DC voltage scale on the dial. Most multimeters share a scale for voltage and current.
If a rectifier is connected to the circuit that measures the DC voltage, the AC voltage can be measured. The principle of measuring resistance is similar to that of measuring DC voltage, except that a set of batteries must be added during the test. When the selector switch points to the resistance range, look for the first line of resistance-specific scale readings on the dial.
