How to connect a multimeter: instructions for the correct operation of the device when carrying out various measurements

When working with electronics and wires, it is often necessary to measure constant and variable amperage, voltage, resistance and other network parameters. In order not to buy a bunch of different equipment for this, a multimeter was invented. This small and easy-to-use appliance can be connected and used by any amateur electrician at home.

Types of devices

Multimeters are digital and analog. The former are more modern, accurate and convenient, but the latter are still used due to the fact that with some measurements, electrical devices simply stop working. The function of the device always includes the calculation of voltage, current and resistance. In addition to this minimum program, manufacturers of different models often add additional features, including:

• measurement of additional quantities: capacitor volume, current frequency, inductance, temperature, electrical capacity, some parameters of semiconductor triodes;
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• continuity of diodes;
• automatic selection of the measurement limit;
• sound probe;
• built-in simple frequency generator for checking the health of transmission lines or signal amplification;
• the ability to check the circuit for a short circuit and the integrity of the wires;
• fixation and recording of results;
• the ability to connect the device to a computer, transfer measurement data directly to it and save it in digital form.

Also on sale are probes - "nozzles" for multimeters in the form of terminals, pliers, clamps, needles different lengths and thicknesses, as well as other shapes for more convenient use of the device in different situations.

Most hobby electricians and DIYers use multimeters from the M-830 and DT-830 series. These are fairly cheap devices with an average accuracy class (1%) and a bit depth of 3.5. The model number indicates the novelty of the device modification., but the differences in functionality are quite insignificant and will not be particularly noticeable when taking measurements at home. Work with all of them is carried out according to the same scheme - general instructions and procedures do not differ, the only difference is in additional features.

Principle and modes of operation

At the top of the device, you can see a seven-segment LCD display that will display the results of your work. Below is the dashboard, in the center of which there is a switch that controls the type and range of the measured value. By default, it is set to Off. From it, in a clockwise direction, there are sections for the following operating modes:

• V ~ - definition of alternating voltage. The maximum value can be 200 or 600 volts.
• A- or ACV - DC current measurement. The limits can be 200 or 2000 microamperes, as well as 20 or 200 milliamperes. Some models have a section for high values ​​up to 10 A.
• A ~ - alternating current. The mode is not available on all devices.
• Speaker icon - wire continuity. Reacts with a characteristic sound if the resistance in the area is less than a certain value.
• Anode and cathode symbol - checking the health and polarity of the diode. Shows the difference in its plus or minus transition.
• Ω - definition of resistance. Range modes: 200 and 2000 Ohm, 20, 200, and 2000 kOhm.
• V- or DCV - definition of constant voltage. It has five limits: 200 and 2000 mV, 20, 200 and 600 V.

There may be other designations that will be indicated in the instructions for a particular model. Below the control panel are the device connectors:

• Top socket 10 A. A positive probe is connected to it when measuring current with a value of up to 10 amperes.
• The middle socket with the designation VΩmA or similar is for the positive lead in all other modes.
• Bottom COM socket - connector for common or negative wire in all cases of using the device.

In addition, to the left of them is a connector for testing transistors, if the device has such a function. There is also an additional socket for measuring microcurrents up to 200 μA.

Measurement of various quantities

The multimeter always comes with two probes - black and red. The first one has a negative charge, the second one is positive. With the help of them, measurements are carried out: one end of each of the wires is connected to the device, and the other to an element or section of the electrical circuit.

General rules

When measuring different quantities, the algorithm for working with a multimeter will differ, but there are several general recommendations. These include, for example, safety rules:

• The probes can only be held by the insulated part, without touching the metal needle. This may not only affect the measurement results, but also lead to electric shock. The integrity of the insulation must be checked every time it is used. If it is damaged, the wire must be wrapped with electrical tape or replaced. It is especially dangerous to use damaged test leads when measuring voltage.
• Before connecting the multimeter to the network section, it is necessary to carefully check the correctness of the settings of the magnitude and measurement limits, as well as the correspondence of the probes to the required connectors. It is important to never measure voltage while the probe is connected to socket A10 - this will cause a short circuit.
• If you are uncertain about the range of values, start with the largest value and gradually decrease it until the display shows numbers. The reason for this is that if you try to measure a current or voltage that is much higher than the limit, the multimeter may fail.
• When changing the range, it is advisable to remove the probes or de-energize the circuit, otherwise the device will break. An exception is resistance measurement.

The units of measurement shown on the display of the multimeter take into account the limit selected on the device, that is, they can be shown, for example, immediately in kilo-ohms or microamperes. The result is displayed with an accuracy of hundredths, so if too small values ​​are received, it may not be displayed - to fix this, you need to reduce the range.

Current strength

To measure the current, the multimeter must be connected to an open in the electrical circuit. To do this, it will need to be opened and closed with the help of probes, which at the time of measurement will become one wire - certain difficulties may arise with this. 2 terminal blocks for soft wires, which are temporarily attached to the probes, can help solve the problem.

First, the system is disconnected from the power supply, then one of the wires in it is cut. Then a multimeter is connected - the red probe is connected to the positive pole of the power source, and the black one to the element next to it. Then they are inserted into the corresponding connectors on the measuring instrument. For the first, this will be the top or middle slot, for the second, the bottom. You need to choose them based on the estimated current strength.

After that, power is supplied to the system, the arrow on the device is turned, and it measures the required value. It is advisable to carry out this procedure as quickly as possible - with a delay of 10 seconds, the wires begin to heat up, which may cause problems. During the entire process, care should be taken to avoid any contact with non-insulated elements of the system.

DC and AC are measured in the same way. If you specify the wrong type, then the device will not show any numbers.

Resistance of circuit elements

Measuring resistance with a multimeter is the easiest and safest way. To do this, connect the device probes to the element, move the switch arrow to the Ω sector and wait for the numbers to be displayed on the display. The only nuance that should be taken into account is that the circuit must be disconnected from the power supply and completely "discharged" before the procedure, otherwise the readings may be incorrect. This is because the multimeter detects that the circuit is obstructing the passage of electricity through it for the expense of self-creation of a small voltage in the wire and calculates by its drop resistance.

When the device, when trying to measure this value, gives 0, the measurement range must be reduced. And if the display shows 1, ol or over, then, on the contrary, increase. These procedures do not harm the device in any way.

DC and AC voltage

To change the voltage with a multimeter, you need to determine whether it is variable or constant, and then put the arrow of the device in the appropriate position. The range is selected in the same way as in the case of the current - if the numbers are uncertain, the highest limit is selected, which then gradually decreases, if necessary. This will protect the device from overheating, which could blow the fuse or internal components.

The multimeter must be connected to the measured element of the circuit in parallel, touching it with the probes on both sides. The device will measure the potential difference and display the voltage calculated with it. If this value is negative, then the black probe is connected to the cathode.

Additional features

Having figured out how to correctly use a multimeter to calculate the basic values, you can proceed to the study of additional functions of the device. The most popular of them is the determination of the integrity of the wires using the so-called continuity. This procedure is not difficult to carry out. First, you need to set the arrow of the device to the appropriate mode - usually it is indicated by the image of a speaker or sound waves. Then connect the probes (black to the bottom jack, red to the middle) and place them along the edges of the circuit. If it is intact, the device will beep.

Power on the site must be turned off before testing. In addition to calculating problems using this function, you can check which wires are connected to each other in an apartment, where several cables with insulation of the same color pass.

You can also check the health of the diode with a multimeter. If a specific device model does not provide a separate function for such purposes, this can be done in the resistance or continuity determination mode. The black probe must be connected to the negative end of the diode, and the red one to the positive. Resistance should be present in only one of them. If it is present in both directions or is absent at all, then the diode is faulty.

The situation is more complicated with checking the LED. It starts to work only when a current arrives in a certain voltage range, therefore, during a normal check, the values ​​may not work. In order to reliably check it, you need a multimeter with a connector for connecting transistors. You need to turn on the LED with "plus" in hole C (collector) and "minus" in E (emitter) on the NPN section and vice versa on PNP. If it is working properly, it will start glowing. You can determine the positive and negative electrodes of the LED by their length - "minus" is usually shorter than "plus".

Some multimeters have a function for checking the capacitance of a capacitor. Its ranges are in values ​​from 2 nF to 20 μF, and the measurement principle is no different from others. If there is none, then you can indirectly check the serviceability of this device using the resistance determination mode. The measurement limit must be set to 20-2000 kOhm, and connect the probes to the capacitor.

If it works, then the resistance will be at zero at first, but then it will start to increase slowly until it reaches the maximum value, and the device will show the number "1". However, this method is unreliable - it does not show the capacity of the device and cannot determine whether the capacitor can handle the voltage.

It is recommended that the meter itself be checked for accuracy once a year. To do this, you need to measure their resistance, current and voltage in calibration circuits, where this value is known in advance. Such a procedure is done in laboratories, but many home craftsmen believe that such accuracy is not needed to work with household electrical appliances, and they neglect it.