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A multimeter is a device for checking the electrical parameters of various equipment and electrical components. With this tester, you can check the connection between conductors, measure voltage, current and resistance, and perform some other operations. How to use a multimeter – read our article!

Varieties of multimeters and the principle of their device

The most common types of multimeters are analog and digital. How they are equipped and work, we will consider further.

Analog

These are old-style testers that look like boxes with a glazed arc-shaped scale and a spring-loaded pointer. Often there is a mirror strip-arc on the scale so that when looking at the arrow it is possible to combine the arrow with its reflection. This way, when measuring, you look exactly perpendicular to the scale, and not at an angle, and it will be more difficult for you to make a mistake. The measuring panel has many parallel arc scales for different types of measurements:

Analog multimeter

One of the main advantages of an analog multimeter is its low price with quite sufficient measurement accuracy for domestic purposes. Moreover, in most analog multimeters, a special resistor is built in to adjust the position of the arrow exactly to “0”. For adjustment, a resistor head is used, similar to a screw slot, located below the measuring scale approximately at the point where the arrow is attached.

Digital

These multimeters are more modern and look like black oblong boxes with a large LCD display for digital indication of readings. These devices got their name because the analog signals entering the device in the analog-to-digital converter (ADC) are converted into digital form. Such devices are more expensive than analog ones, but their dimensions and weight are somewhat smaller, it is more convenient and faster to work with them.

Digital multimeter

Some models are well suited for working in complete darkness due to the ability to illuminate the indicator board (and electricians often have to work in dark rooms). You simply press a button and the panel is lit up. In addition, you can find a model with the ability to record the readings taken in the device’s memory and then transfer these data to a computer for further analysis. To do this, just press a special button.

Usually digital devices are used by professional electricians, electronics engineers and engineers.

The measurement kit includes two wires with terminals and pointed probes:

  • one black wire – “minus”, “ground”, “com” (common – common);
  • the second red wire is positive or “measuring”.

The black probe is usually applied to the body of the electrical appliance (common bus) or hooked with a special clip – a “crocodile”. The red probe is most often taken in the right hand and applied to different places in the circuit.

The probes supplied with the digital multimeter are the same as in the analog multimeter. Often the sockets are color-coded – red and black frames, so as not to accidentally confuse which probe to insert where.

Sometimes a multimeter is an integral part of another instrument, such as a digital clamp meter. Due to the need to be large, such devices have a large amount of free space in their case, where the multimeter is built.

Find out which multimeter is better to buy here.

Power supply for multimeters

Both types of multimeters require batteries to operate. Some types of indicators can measure voltage without batteries, but all other types of measurements still require a power source. It can be different types of batteries – AA, AAA, “Krona” (“6F22”) or rechargeable batteries. There are models with built-in batteries that can be recharged.

It is very good if the multimeter has an auto-off function when idle. It often happens that the measurements are made, the broken device is repaired, test / adjustment starts begin, and the multimeter is forgotten in the on state. In a few hours, the battery may well be discharged. Therefore, for those who constantly use the measuring device, it is better to choose a model with auto-off.

How to check the multimeter for performance?

To check the operation of the multimeter, as a rule, you need to perform the following steps:

  1. Set the probes to resistance test mode (R). In this case, the black wire must be inserted into the “COM” or “-” connector, and the red one into the “Ohm” (Ω) or “omega” connector.
  2. Move the large disk pointer to the “ringing” position.
  3. Align the metal ends of the probes with each other.

Multimeter operation

After these actions, a piercing sound signal should be heard. If there is no sound, then the multimeter is not working and is not even suitable for checking the wiring.

How to use a digital multimeter?

The DMM can be used for many common tasks: resistance testing, current readings, DC or AC voltage, transistor health. Instructions for use for beginners are as follows:

Principle of use

The general rule is this: start the measurement with a larger value on the pointer so as not to spoil the sensitive device. For example, if you want to measure the resistance of an element, knowing approximately that it is about 1 kΩ, then set the tuning knob to 2 kΩ.

Resistance measurement

Resistance is defined like this:

  1. The black wire is inserted into the “COM” connector, the red one into the “VΩmA” connector.
  2. Next, a black probe is applied to one leg of the element, and a red one to the other.
  3. If the element under test is soldered to the board, one leg must be unsoldered and raised so that there is no contact with the board.
  4. Which probe to which leg to apply does not matter.
  5. The disk pointer should be set to the voltage measurement sector (with the Ω sign) and the order of magnitude of resistance that you are counting on.

Voltage measurement

When carrying out measurements, it is necessary to distinguish between what kind of current is being measured – direct or alternating, and connect the probes accordingly. Direct current has the abbreviated name “DC” (direct current), graphically often depicted simply as a short horizontal line (-). Alternating current is abbreviated as “AC” (alternating current) and is usually represented by a wavy line (~) respectively.

Measuring voltage on a multimeter

Be careful when taking measurements, high voltage is life-threatening!

Voltage is measured like this:

  1. The black wire must be in the “COM” connector, the red one in the “VΩmA” connector.
  2. The disk must be installed in the sector for measuring voltage – for alternating in “ACV” (~), for constant in “DCV” (), and the exact position of the disc is determined in accordance with the magnitude of the measured voltage with a deliberate excess of the measured value. For example, to check the voltage in a 220 volt outlet, the disk must be set to 750 volts.
  3. Which probe to apply where – no difference. Just make sure that your fingers and hands do not touch the live parts and the tips of the probes.
  4. After the probes come into contact with the conductors, the measured voltage will be indicated on the display.

Remember that the more likely it is to be struck by a lightning strike or short circuit in circuits with high currents, the more care should be taken when measuring.

How to call with a multimeter?

This option is used for “dialing”, for example, wires and electrical wires. It is implemented as follows:

  1. The line is de-energized, for which plugs are unscrewed, or the central apparatus is turned off.
  2. The wires are released, for example, the twist is untwisted in the junction box, the terminals in the socket are unscrewed.
  3. The two ends are closed, and on either side.
  4. The tester is turned on and checked for operability, for which the tongs are connected, after which a signal should sound and the value “0” or close to this parameter will be displayed.
  5. Multimeter pins are applied to the ends of the wiring. If a sound is made and a value close to zero is displayed, then the wire is not damaged.

Using a multimeter, you can detect a line with a short circuit, for which the wires are disconnected and paired with a tester.

How this function of the tester is applied can be clearly seen in the following video:

Using other features

Most types of multimeters have a sound indication mode for a short circuit. If there is direct contact between the probes, the multimeter emits a piercing squeak. This mode is convenient to use when checking the integrity of the wires, the presence of contacts between the terminals, the “continuity” of diodes and other elements. In this case, you do not need to hold the multimeter in your hands; you can generally put it in your breast pocket, for example. If desired, you can pick up a multimeter with a light indication.

But be careful! The speaker or LED may be faulty, and you will think that the wires are open, but in fact they can carry current with unpredictable consequences!

In addition, some multimeters have the ability to determine the capacitance of capacitors, the inductance of coils, the gain of low-power transistors, the oscillation frequency (usually up to 20 kilohertz), the temperature in the room using the built-in thermistor, the temperature of objects and environments using the included thermocouple.

How to check the performance of a capacitor with a multimeter?

A capacitor is an element of an electrical circuit that has two conductive plates with a dielectric gasket between them. Most often, all these pads are rolled into a small roll, packed in a small cylinder. Two legs protrude from the cylinder – these are the conclusions of the storage plates. The working capacitor has no contact between the plates, so the capacitor simply does not pass direct current through itself. But the alternating current passes through the capacitor.

There are polar and non-polar capacitors. On polar ones, the marking is most often only on one leg, for example, only “+” on the side wall next to the leg. Polar ones must be used in the circuit only in the oriented state: “+” must be soldered to “+”, “-” to “-”. Incorrect positioning of the polar capacitor can even lead to a small explosion. And non-polar capacitors can be inserted into the circuit without worrying about the correct orientation.

So, the verification procedure is as follows:

  1. If the capacitor is soldered into the circuit, we solder one of its legs, which is more convenient.
  2. We set the multimeter to the “dialing” mode.
  3. We apply a probe to one leg of the capacitor. If the element is polar – respectively, the black wire to “-”, red to “+”. Do not confuse.
  4. If the number “1” is on the display, and the measuring device does not beep, this means that the capacitor is not “broken”, that is, the plates are isolated and, most likely, the capacitor is working. Otherwise, the capacitor has lost its efficiency, and it must be changed.

How to check an electrical capacitor using a conventional multimeter is described in the following video:

How to check the relay for operability with a multimeter?

A relay is an electrical device that allows you to switch more powerful electrical appliances using low power signals. Relays are often used in auto electrics, such relays usually have 5 flat pins-contacts. An inductor is usually used as a control element. The diagram of the mutual connection of the terminals to each other is usually shown directly on the relay case, especially if the relay is not small in size.

Some of the terminals should be in contact with each other, some should not. It will not be possible to fully check the relay for operability without using a power supply. It is needed to apply voltage to the control terminals.

Relay testing consists of the following steps:

  1. We turn on the multimeter in the “dialing” mode.
  2. First you need to make sure that in the off state there is no situation “all terminals are connected to all” or there is no contact where it should be. Which terminal should be connected to which depends on the specific circuit. If there is an “all to all” contact, the relay is faulty, this should not be.
  3. We check according to the diagram which terminals are shown as open. There should also be no contact between them.
  4. If, in the off state, the contacts between all terminals are in the state as they should be, the relay must be connected to the circuit or power must be supplied to the control terminals. The inductor should work and close the circuit, that is, a contact should appear between the controlled terminals where it was not there when the power was off, and vice versa. If the contact does not appear, then it is clear that the coil is not working and the relay cannot work properly.

Video for dummies: How to use a multimeter?

The following video will help you learn how to use a multimeter:

A multimeter is an indispensable tool for repairing and adjusting electrical appliances. It is necessary to use such a device according to the instructions, without fail observing all safety rules.