In radio engineering practice, checking the voltage with a multimeter is an ordinary procedure that allows you to control its level in the operating circuits in the selected measurement mode. When carrying out this operation, novice ham enthusiasts have a number of questions regarding the procedure for working with the meter at their disposal. Ordinary users are mainly interested in how the necessary modes are selected and how to measure the voltage in the household network of a city apartment so as not to endanger their lives.
How to connect multimeter wires
When taking measurements, it is important to understand where the multimeter probes are inserted and how to connect them correctly. It is recommended to remember the following points:
- most universal measuring instruments on their front panel have three sockets for connecting wires;
- the kit includes two measuring cords with a set of probes, one in black and the other in red insulation;
- the first is inserted into the socket under the designation "COM" or "General", and the second - into the connector with several characters (among them there is a voltage icon "V");
- the third socket with a set of built-in shunts is intended for measuring currents of large ratings (up to 20 Amperes and above).
To measure voltage, only the first two sockets are used, in which the black wire always remains in place. To change the type of work (determining the capacitance or current, for example), only the probe in red insulation is poured.
The difference between AC and DC voltage
Before measuring the voltage in a car battery or outlet, it is important to understand its characteristics. According to their physical manifestations in electrical circuits, voltages are divided into constant and variable. The first type is characterized by a constant amplitude and the flow of the current caused by it in only one direction. Therefore, when measuring it, the appropriate type is selected, indicated on the front panel of the device as “DC”.
Alternating or pulsed current and the corresponding voltage are usually denoted by the symbol "AC". They are distinguished by a continuous change in the instantaneous value (amplitude) over time. In existing electrical networks, its value varies from 220 volts to zero 50 times per second. Before measuring the AC voltage, the device must be switched to the appropriate view.
How to measure the voltage at the outlet
In domestic conditions, it is often necessary to check the magnitude or absence of voltage in the outlet, which is explained by its frequent disappearance and deviations from the norm. If a user has a multimeter in their household, checking the network will not be difficult. Procedure:
- Measuring ends are inserted into the device as provided for voltage testing.
- The “AC” mode is selected and the desired limit is set to 250 or 750 Volts of alternating current.
- The sharp ends of the probes are neatly inserted into the sockets of the outlet without regard to polarity.
- As a result, the value of the measured value is displayed on the indicator board.
When inserting the ends into the openings of the outlet, do not touch their exposed parts with your hand. Keep the probes only by insulating nozzles.
The value displayed by the device usually differs from the nominal value of 220 volts - at normal load it will be equal to 230-235 volts.If there is no mains voltage, the device will display a value of zero or one.
How to measure battery or battery voltage
To measure the voltage in a car battery or miniature battery, it should be borne in mind that they relate to DC sources. In this case, voltage measurements with a multimeter will be carried out correctly if the following conditions are observed:
- when connecting the ends of the device to the poles of the battery, it is important to observe a certain polarity of connection;
- a measuring probe in red insulation is connected to the plus of the power source, and black to its minus;
- To take readings on the measuring device, you need to turn on the “DC” mode.
As in the alternating voltage version, in this case it is important to set the limit required by the measurement conditions. If this rule is violated, if the measured value exceeds the set value, the multimeter steadily displays “1”. This means that the limit must be increased to larger values than the value being checked.
Possible malfunctions
If the unit icon appears immediately after turning on the device and does not disappear, the ADC chip has burned in it and it needs to be repaired / replaced. In addition to this characteristic malfunction, the following problems may occur during voltage measurement:
- the tester overestimates the readings, when compared with the data of a serviceable device, they differ by a significant amount;
- random numbers are displayed, the multimeter does not show voltage at all;
- in the upper limits of measurement, the readings are greatly underestimated.
In the first case, the multimeter does not correctly measure the voltage due to the discharged battery installed in the supply compartment. It should be checked and replaced if necessary with a new one. To determine the nature of the second problem, the ADC test will help, which most often fails with just such a malfunction typical of it. The third error is most likely due to the breakdown of one of the electrolytic capacitors, which stands out among other parts by the characteristic bloating of the case.
Is it possible to measure voltage without a multimeter
There are various ways to determine the voltage value in the absence of the device. The most difficult of them is the use of a conventional voltmeter or a modern electronic oscilloscope as a meter. However, the likelihood that these not-so-simple measuring instruments will end up in the user's home at the right time is very small. If they are absent, it is possible to check the voltage in the network or on the battery using the old "old-fashioned" method - by means of a light bulb of the appropriate rating. With its help, you can even measure the magnitude of the voltage, but only approximately.
When checking the network, the 220-volt lamp should burn fully. By the brightness of its glow, it is only possible to roughly estimate the measured value: half the glow is approximately 120-140 Volts. They act similarly in assessing the battery voltage, only in this case a 12 volt bulb is taken.
It is possible to check miniature batteries at 4.5 or 9 Volts (KBS or KRONA) by simultaneously touching their contacts with the tip of the tongue. It usually causes a “sour” taste characteristic of a lemon. The stronger this sensation, the better the battery is charged.
