How to use a multimeter correctly

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

They can measure AC and DC voltage, resistance, current and test the circuit.

How a multimeter works

As the name implies, a multimeter is used to measure several electrical quantities. A multifunctional device combines a voltmeter, ammeter, ohmmeter, continuity, and may also have additional functions such as a thermocouple or a low-frequency generator, checking capacitors and transistors.

Analog testers with a scale and an arrow are almost never found, since they have long been supplanted by available digital instruments. The latter, in addition to the accuracy and the number of modes, differ in the type of determination of values. The automatic ones show the result immediately after selecting the mode; in the manual ones, you need to additionally set the measurement range.

All multimeters have a similar design. On the front panel there is a screen, under it there is a rotary switch of modes, and just below - connectors for connecting probes. Some models have buttons for turning on the backlight, storing readings and for other additional functions.

Wires with probes, which need to touch the part during measurement, are connected to the corresponding connectors. The black wire is always to the socket marked COM, and the red one, depending on the current value. If it does not exceed 200 mA, then to the VΩmA connector, if it exceeds, then to 10ADC (10A MAX). In everyday life, such high currents are not found, so the VΩmA jack is mainly used.

The numbers on the scale indicate the maximum value that can be checked in this range. For example, in DCV 20 mode, DC voltage is measured from 0 to 20 V. If it is 21 V, then you need to switch one step higher, to position 200. It is important to select the range in accordance with the measured value, otherwise the multimeter will deteriorate.

How to measure DC voltage with a multimeter

Make sure the test leads are connected correctly.

Switch to constant voltage mode. It is usually denoted by the symbols V with a straight and dashed line, or DCV.

In multimeters with manual range selection, additionally set the approximate measurement value, or better one step higher. If unsure, start at the maximum and gradually lower.

Touch the probes to the contacts and look at the screen. If a minus sign is displayed along with a digit, it means that the polarity is reversed: the red probe touches the minus, and the black probe touches the plus.

In a handheld multimeter, you may need to adjust the measurement range.

If the display is one, you need to increase the measurement limit, if it is zero, the symbols OL or OVER - lower it.

How to measure AC voltage with a multimeter

Check that the probes are connected correctly.

Turn on AC voltage mode. It is marked with V ~ or ACV.

In handheld multimeters, also set the approximate measurement value. Better one notch higher or the highest.

Bring the probes to the contacts and read the readings from the display.

If the multimeter is with manual range and the display is one, increase the measurement limit, if it is zero (OL, OVER), lower it.

How to measure resistance with a multimeter

Make sure the test leads are connected correctly.

Set resistance measurement mode. It is denoted by the symbol Ω.

If the tester is hand held, select an approximate measuring range.

Touch the probes to the terminals of the resistor and see its resistance on the screen.

On a handheld multimeter, if necessary, adjust the measurement range up or down.

How to test a diode or circuit with a multimeter

Insert the test leads into the correct terminals on the multimeter.

Switch to the diode continuity mode, indicated by the arrow symbol with a vertical line.

Attach the needles of the test leads to the leads of the diode. The multimeter will show the voltage drop on the screen. If you swap the probes, then with a working diode on the screen will be one, and on a faulty one - any other number.

In the same mode, you can ring a circuit or wire, but you must first de-energize them. If the integrity is not violated, a beep will sound, if there is an open circuit, the screen will simply display a unit, OL or OVER.

On some multimeters, the audible dialing mode is turned on separately. For example, on a black tester, as in the photo above. This mode is indicated by a volume up symbol, a note, or a speaker.

How to measure current with a multimeter

Connect the test leads to the correct terminals of the multimeter, depending on the current value.

Set the current measurement mode (DCA, mA).

On a manual ranging multimeter, set the maximum threshold.

Connect the test leads in series. Unlike voltage and resistance, current is not measured in parallel. That is, you need not just touch two points of the circuit or the pins of the part, but connect the multimeter to the open circuit. If connected in parallel, the device may be damaged!

The current consumption is displayed on the screen. If the multimeter is hand held, then you may have to switch the range for more accurate results.