How to – multimeter

Reading time 4 minutes

Updated – January 10, 2024

How to - a multimeter is a universal electronic measuring device for measuring voltage, current, continuity, diodes, transistors, and possibly even capacities, frequencies, temperatures, etc.

The generally used functions are continuity, voltage and current measurements, which are explained below.

Of course there are clear differences in quality, ultimately the price ranges from around 20 euros to the four-digit range.

If you prefer a branded product, the price for the multimeter shown is 300 euros Voltcraft VC-891, or 200 euros for that Voltcraft Clamp multimeter VC-750E. The same products are available at correspondingly higher prices, including a calibration certificate, which is certainly unnecessary in the applications mentioned here.

FLUKE is another well-known manufacturer of professional measurement technology that has been tried and tested for decades. The prices quoted there are consequently at least twice as high.

However, if you just need a “guess” iron, devices between around 40 and 90 euros will probably serve you well. If it ever gives up the ghost, maybe... Especially outside the warranty period, it may be possible to purchase a replacement instead of a repair. the usual way.

Practical examples

Check fuse

Some fuses can be seen at first glance as to whether they are defective or not, while others appear to be OK. A continuity measurement provides certainty.

To check whether the fuse is complete, turn on the meter and select the setting according to a symbol similar to the one shown above. If you touch the metal end of the black measuring tip with the metal end of the red measuring tip, an acoustic signal sounds and the digital display shows “0.0000”.

The measuring device reacts in the same way if the fuse is intact. If there is no acoustic signal and the display shows “1.0000”, then the fuse has no continuity and is defective.

The sign (Ω = ohm) stands for the SI unit of electrical resistance, after the German physicist Georg Simon Ohm (* March 16, 1789 – † July 6, 1854).

Assign lines

The above function also enables the allocation of lines that cannot be traced visually. For example, cables in cable harnesses that are laid behind panels, furniture or cable ducts and are not marked to distinguish them.

Here a measuring tip is connected to the cable in question via an “extension cable”. With the other measuring tip you scan one cable after the other. Once you have found the corresponding end, the acoustic signal sounds and the display shows “0.0000”.

measure the voltage

Whether battery or socket, “voltage” must be measured in both cases, either direct voltage (DC – direct current (direct current)) or alternating voltage (AC – alternating current (alternating current)), which is intended to supply power to connected devices.

Alternating voltage changes in time with the mains frequency (50 / 60 Hz = oscillations per second) between + 230 and - 230 volts, while direct voltage, here for example + 24 V, is always constant over time.

The test probes and sockets of measuring devices are usually colored black (-) and red (+). If you measure the voltage of a battery, the red (V) is connected to the plus pole and the black (COM) to the minus pole.

When the selector switch is set to DC V(volt), the display shows, for example, “13.242 V” with a 12V battery. If you swap the two measuring tips, the display changes to “- 13.242 V”.

The SI unit volt stands for electrical voltage, named after the Italian physicist Alessandro Giuseppe Antonio Anastasio Volta (* February 18, 1745 – † March 5, 1827), among others the inventor of the battery.

Measure current

If the battery is empty faster than you would like and you apparently hardly have any consumers switched on, the question often arises: what draws how much current?

When measuring current with a multimeter, the maximum current carrying capacity according to the data sheet must be observed!

By setting the measuring device selector switch to DC A (mpère) and connecting the black measuring line to COM and the red line to the red socket marked “A”, the current flow in a line carrying DC voltage can be measured.

To do this, disconnect the cable at an accessible connection (e.g. behind the battery fuse, which must be removed before the measurement!) and connect the red plus cable to the now open output of the fuse, the black negative cable to the unscrewed one Cable end. After inserting the fuse, the meter shows the current flowing.

Now one consumer after the other can be switched off and the difference in the measured values, which represents the respective electricity requirement, can be noted. After all – obvious – consumers have been switched off, the display should show “0.0000”. If a value greater than zero is still displayed, there is still a consumer that has not been taken into account...

The SI unit Amp describes the electrical current strength and the derived quantity magnetic flux, named after the French mathematician and physicist André-Marie Ampère

Clamp multimeter

There are so-called clamp multimeters with which you can measure the current in a cable by positioning it as centrally as possible in the area enclosed by the two clamp arms and then reading the value.
It is therefore not necessary to disconnect the cable, as with the type of multimeter described above.

These devices usually contain the same functions as the multimeter shown at the beginning. The associated measuring lines are connected to the lower face of the clamp multimeter.