They can measure direct and alternating voltage, resistance, current and check the circuit.
How is the multimeter
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 like a thermocouple or low-frequency generator, checking capacitors and transistors.
Analog testers with a scale and an arrow are almost never found, since they have long been superseded by available digital devices. The latter, in addition to the accuracy and number of modes, differ in the type of determination of quantities. Automatic show the result immediately after selecting a mode, in manual you need to additionally set the measurement range.
All multimeters have a similar design. There is a screen on the front panel, under it is a rotary mode switch, 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 that need to touch the part when measuring are connected to the corresponding connectors. The black wire is always to the socket marked COM, and the red wire, depending on the amount of current. 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, therefore, the VΩmA socket 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, a direct voltage of 0 to 20 V is measured. If it is 21 V, then you need to switch one step higher to position 200. It is important to select the range according to the measurement, otherwise the multimeter will deteriorate.
How to measure DC voltage with a multimeter
Make sure the probes are connected correctly.
Switch to constant voltage mode. Usually it is denoted by the letters V with a straight and dashed line or DCV.
In multimeters with manual range selection, additionally set the approximate measurement value, and preferably one step higher. If you are not sure, start with the maximum and gradually lower.
Touch the contact probes and look at the screen. If a minus sign is displayed together with a number, then the polarity is reversed: the red probe touches the minus, and the black – the plus.
In a handheld multimeter, you may have to adjust the measuring range.
If the display is one, the measurement limit must be increased; if zero, the OL or OVER symbols should be lowered.
How to measure alternating voltage with a multimeter
Check that the probes are connected correctly.
Turn on AC voltage mode. It is marked with V ~ or ACV.
In hand-held multimeters, also set the approximate measurement value. Better one step higher or the maximum.
Bring the probes to the contacts and read the readings from the display.
If the multimeter with manual ranging and is on the screen is one, increase the measurement limit, if zero (OL, OVER) – lower.
How to measure resistance with a multimeter
Make sure the probes are connected correctly.
Set the resistance measurement mode. It is indicated by the symbol Ω.
If the tester is manual, 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 measuring range up or down.
How to check a diode or circuit with a multimeter
Insert the probes into the correct multimeter connectors.
Switch to diode dialing mode marked with a vertical arrow symbol.
Attach the probe needles to the terminals of the diode. The multimeter will show the voltage drop on the screen. If you swap the probes, then with the working diode on the screen there will be one, and on the 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 broken, a sound signal will sound, if there is a break, the unit will simply display a unit, OL or OVER.
On some multimeters, the sound mode of dialing is turned on separately. For example, on a black tester, as in the photo above. This mode is indicated by a volume up symbol, note, or speaker.
How to measure current with a multimeter
Connect the probes to the required connectors on the multimeter, depending on the magnitude of the current.
Set the current measurement mode (DCA, mA).
In a multimeter with manual range selection, 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 findings of the part, but connect the multimeter to the circuit break. When connected in parallel, the device may fail!
The screen displays the current consumption. If the multimeter is manual, then you may have to switch the range for more accurate results.