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How to check the DC voltage with a multimeter. Checking the mains voltage: indication and measurement

To measure the value of the AC voltage 220v, acting in any electrical circuit, as well as to determine the current intensity in the load connected to it, special measuring instruments are used. They are called avometers, multimeters or testers. These products are fairly simple to handle devices, the order of work with which can be mastered by almost anyone.

By the method of measuring and recording of basic electrical quantities, such as, for example, current in the socket, voltage or resistance, all these devices are divided into analog (arrow) and digital. The second of these two samples of measuring equipment, often referred to simply as a multimeter, will be devoted to an article.

Application features

The digital meter of electrical parameters (or multimeter) is an electronic device that provides a digital indication of the recorded values with a display of readings on the LCD display. Such devices at a price are somewhat more expensive than arrow models. However, they provide a more accurate measurement of electrical parameters and are much more convenient in daily operation. In addition, digital multimeters have a large set of additional functions, some of which are missing from analog models. With their help it is easy to check the outlet in the apartment, make sure the supply of the required voltage.

Additional functionality includes such capabilities of digital multimeters as a test for the validity of semiconductor elements, "continuity" of electrical circuits with simultaneous duplication by an audio signal. They can also determine the nominal values of the capacitors (the latter function is found only in some models).

Please note, it is because of this multifunctionality that this device got its own custom name. "Multi" is translated as "a lot", and "meter" means "measure".

The purchase of a digital product includes the measuring device and two wires with special probes or "ends", the lower part of which is protected by non-conductive plastic heads (holders). Before checking the voltage in the outlet with a multimeter, first of all, it is necessary to properly assemble the measuring circuit. To do this, you should use the input sockets available on the case and labeled with the appropriate letters.

In the hole marked "COM", meaning in Russian "General", it is supposed to insert the end of the wire of black color. The red-colored connector is connected to the second (signal) socket.

Additional Information. If there is one more input connector marked "10 ampere" on the case of the device, you can measure the currents with the amplitude within the specified value. In some models, this limit is increased to 20 Amps. When measuring currents within the limits of the indicated values, the connector of the cord with the red color marking is inserted into this socket.

Step-by-step instruction

After connecting the wires, you can proceed to the measurements themselves, the sequence of which is as follows.

First, the required operating mode of the multimeter is set using the central rotary switch. The mode corresponding to measuring the AC voltage is in the sector under the designation "ACV" or "V ~".

Then within this sector, you should select the "750" position, which corresponds to the maximum value of the monitored parameter in the socket, that is, voltage up to 750 Volts inclusive. At the limit labeled "200", voltages not exceeding 200 volts are measured.

After selecting the mode and the measurement limit of the multimeter, both probes are taken over the insulated handles, and then their points are inserted into the socket sockets.

In the case of a good contact with the sockets of the socket, the result will immediately be the result of the measurements. It is displayed in the form of a series of figures to within a tenth of a fraction.

The order (polarity) of the position of the ends when measuring AC voltage in the network does not matter.

It should be noted that in the socket rarely when the voltage is exactly 220V. Usually it is somewhat higher or lower. By standards, the deviation should not exceed 22V, if it is a household network.

electrical safety

When working with a multimeter, it is mandatory to comply with the following rules for handling the device, providing protection in terms of electrical safety:

In conclusion, we should note that one more feature of the use of the multimeter should be attributed to the same problem (namely, to the issue of safety). The fact is that when working with this device you can not only measure the current voltage, but also establish the nature of the malfunction, manifested in the form of its absence. To do this, you will additionally require a conventional indicator screwdriver, through which you can determine the presence (or absence) of a "phase" on one of the female terminal blocks.

It happens that the indicator screwdriver shows the presence of a "phase", and when you insert both probes into the socket, the meter reading does not change. This means that there is a break in the "zero" conductor of the electrical wiring, or the contact in the connection with the female terminal block is broken.

When working with an indicator screwdriver, be sure that this accessory is in good working order. It should be checked on a known "working" outlet. To test the latter it is enough to connect a working table lamp or an iron to it.

Using a multimeter greatly simplifies the work of an electrician. And at the household level the device can come in handy if you need to check if the socket is working properly, and what voltage is in the network.

How to measure the voltage in the outlet or determine the value of the current flowing through it? This question has become almost in front of each of us. The answer to it is quite simple: it is a multimeter, a universal device for measuring the most varied electrical parameters.

The main feature of this device is a combination of a wide variety of devices that may be required for both professional and home-grown electrician. At the same time to use this device does not need to have any specific knowledge. It is enough to recall the school lessons of physics.

How to work with a multimeter?

Before measuring the voltage in the outlet with a multimeter, let's look at how this device works. And also we will understand with the values that he is able to measure.

Multimeters can be analog or digital. The answer to the question which of them is better obvious is a digital device. After all, digital multimeters always indicate the exact value of the measured value, they are loyal to the wrong connection of the probes, and not so demanding to the operating conditions. At the same time in favor of analog devices there is only one argument - price.

That's why in this article we will consider a digital multimeter. And begin our review with the test leads of the multimeter. For their connection, a conventional device has two or three sockets.

So:

The black test lead must be connected to the "COM" jack, which is negative or grounded. It depends on the measured value.

The red test lead is connected to one of the two remaining sockets. The abbreviation "VΩmA" means that this jack is intended for measuring voltage, resistance and amperage, but only at small values. To measure current strength in 1A or more, use a 10ADC socket that has a more powerful contact part.

Now let's talk about the values that a normal digital multimeter can measure. At different manufacturers the designation of some values may differ, so we will give all possible options.

So:

To measure the DC voltage, use the limit indicated by DCV. In this limit, there are usually several positions for measuring voltages from 200mV to 1kV. To measure AC voltage, use the limit labeled ACV. It usually also has several positions for measurements from 100V to 1000V.
To measure the currents, the DCA limit. It also has several positions of several hundred microamps, up to several hundred milliamperes. In addition, there is usually a position for measuring the current strength in up to 10A. However, to connect the device to this position, the instruction recommends that the red test lead be repositioned in the corresponding socket. This is necessary to ensure that the current in the 10A is sufficiently large and the weak contacts of the "VΩmA" socket just burn out from it.
To measure the resistance of the circuit, we have a limit of "Ω". It has several positions for measuring values from 200Ohm to 2MΩ.

Note! Any value can be measured with a larger limit. For example, a voltage of 100V can be measured in a position not 200V, but at position 1000V. But with an increase in the measurement limit, the error of the instrument also increases. In this connection, the obtained measurement results may not be reliable enough.

In addition to these basic values, many devices have additional limits for measuring the current transistor gain, short-circuit continuity, diode parameter measurements, and some others. These limits are more narrowly focused and we will not consider them in more detail.

Measurement of current and voltage with a multimeter

Knowing how to use a multimeter, you can consider how to make a measurement, depending on the measured quantities. After all, measuring the current in the socket is very different from measuring the voltage. In addition, we will consider other possible options for measuring these values in a domestic setting.

Voltage measurement with multimeter

Let's start by considering how to measure the voltage with a multimeter in a socket? This procedure will help you answer the question whether the network parameters correspond to the standards and whether it is possible to connect a certain electrical installation to it.

For this, first of all, we set the probes in the corresponding sockets. In our case, this is the "COM" socket for the black probe and the "VΩmA" socket for the red test lead.
Now we make the necessary switching on the multimeter itself. Since the current in the socket at us has a variable value, it is necessary to set the ACV limit.

The switch position must be higher than the expected voltage. That is, for an outlet in which there should be 220V, you must choose the nearest larger value. If we take our multimeter, then we choose a value of 750V. For two or three-phase sockets the nominal value of the voltage is 380V, that is, we also choose the position in 750V.

Note! If you do not know the expected value of the supply network, then it is better not to measure with a multimeter. If the voltage is above the maximum value, in our case 750V, then at best a multi-meter fuse can burn, and at worst everything can end with injuries and burns. Therefore, before making a measurement, determine the expected voltage value.

After the measurement limits are set, it is possible to proceed directly to the measurements. To do this, insert the plugs into the power contacts of the sockets and ensure a reliable contact between them.

After that, the multimeter display will display the instantaneous voltage value in our outlet. It can vary slightly within 1 - 2V, this is normal. If it fluctuates over a wider range, this indicates an unreliable contact of the probes and power terminals of the outlet, or of poor-quality contact in the electrical network itself.

If you are using an analog multimeter, then before you measure the voltage in the outlet you should determine the price of the scale division. After that, after a simple calculation to calculate the instantaneous value of the voltage.

Measuring the current with a multimeter

But the measurement of the current in the outlet with a multimeter is much more difficult. First of all, this is due to the peculiarity of the inclusion of a measuring device for measuring the amperage.

Let's look at the feature of connecting devices for measuring the amperage. The point is that for the measurement of the current strength, a multimeter or an ammeter should be connected in series with the electrical installation.
That is, in the outlet itself, there is no current without an electrical appliance connected to it as such. Therefore, we can not measure it. But when connecting the device through the outlet, a current directly proportional to the power of the device begins to flow.
In the end, it turns out that knowing the voltage of the supply network and the power of the device, it will be much easier for us to calculate the current of the electrical installation by calculations. For this we use Ohm's law.

Of course, this law is valid only for a DC network, and for an alternating current network, it is necessary to introduce another power factor. But for the simplest calculations it can be used.
But if you do not know the power of the device or you have doubts about its operation, then you need to know how to measure the current in the socket by the devices. In order not to cut the supply wire of the electrical installation and not to disconnect the socket from it, you can make a simple device.

	To create such a device we need a plug, two sockets and a piece of wire. The plug will connect to the outlet in which we make the measurement. It connects the wires that go to the socket number one.
	Connecting the socket number one is slightly different from the usual one. To one of the power clamps we connect the wire from the plug. And to the second power terminal we connect the wire going to the socket number two.
	To socket number two we connect one wire from socket number one. The second power contact is connected to the plug wire unplugged in the connection to the first socket.
	Now in stages. We insert the probes of our multimeter into the socket number one. We plug the plug of our device into the socket. Connect our electric appliance to the plug.
	If we did everything right, now we can measure the current in the socket with a multimeter. And when we remove at least one of the probes from the socket number one, our electric appliance stops working. But we do not recommend breaking the chain by removing the probe. Do it better with a fork.

If you are looking for an easier way to measure the current in the outlet or any other electrical installation yourself, then you will need electrical clamps. The peculiarity of this device is that you can measure the current without breaking the circuit. And you can do this at any convenient moment for you at any stage of the electrical installation.

The essence of this device is to measure the magnetic field around the conductor, through which it can determine the current flowing through the wire. To do this, it has an open magnetic circuit. An open magnetic circuit allows it to be closed around the conductor under investigation and to make measurements.

Note! If you have two-, three-, or other stranded wire, then you must measure each wire of one phase separately. If you close the magnetic circuit around the wires of all phases, the instrument will show zero. This is due to the fact that the magnetic fields around each of the conductors will compensate each other and the resulting value will be zero, or a very small value.

Conclusion

As you can see, the multimeter is quite a versatile device that allows you to produce a wide range of measurements. But it requires a correct approach and knowledge of the principle of operation of electrical installations.

A digital multimeter, often commonly referred to as a tester, is a device that is useful to have in every home. It is useful for testing batteries, car batteries, incandescent lamps, repairing, replacing wiring and simply necessary for both novice and advanced electronics enthusiasts. But for safe operation and obtaining adequate measurement results, you need to learn how to use a multimeter.

Varieties of multimeters

Multimeter is a device designed to determine the numerical values of various electrical parameters. The functions of even the simplest device include the measurement of constant and variable voltages, DC forces, and active resistances. In addition, there may be modes of checking transistors, diodes, measuring temperature, capacitance, frequency, AC power. Some professional multimeters have the ability to continuously record data in real time and export them for later processing on the computer, fixing the minimum, maximum and average values of the parameter, tools for providing accuracy in determining the values and a number of other additional options.

A set of instrument functions, a range of measured parameters and accuracy are the main characteristics on which its cost depends. Therefore, for those who do not have experience in the use of electrical measuring equipment, it is better to start with the simplest and inexpensive multimeter. For domestic purposes, enough options for measuring voltage, resistance, direct current, it is desirable to have the function of determining the integrity of the circuit ("drowsing"), the effective value of the alternating current.

What do I need to know before taking measurements?

When buying a multimeter, do not immediately try to determine the voltage in the outlet: it can be dangerous for life. Before you start working with the device, you need to understand the purpose of the connectors and controls, as well as to study the basic rules, the implementation of which will avoid electric shock, equipment failure and inaccuracy of results due to incorrect connection of the meter.

Device construction

Consider the purpose of the basic elements in the example of one of the simplest and affordable multimeters DT-838, shown in the figure. Its front panel contains a digital LCD display, connectors for connecting test leads, a mode switch. By turning the last element to the position indicated by the label, the monitored value and the upper limit of its measurement are selected. For convenience of use, the modes corresponding to homogeneous parameters are located side by side, their signatures are grouped and separated by lines.

The designations on the front panels of multimeters of other models may differ slightly, so it is necessary to study the main ones.

AC or ~ - characteristics of alternating current;
DC or ⎓ - DC characteristics;
V is the voltage in Volts;
A is amperage current;
Ω or Ohm - resistance in Ohms;
F or С - capacity in Farad;
Hz is the frequency in Hertz;
L is the inductance in Henry;
μ, m, k, M are prefixes indicating multiples (respectively, micro-10 -6, miles-10 -3, kilo-10 3, mega-10 6).

Examples for decoding the notation: ACV - AC voltage in Volts, ⎓ mA - direct current in miliamperes, Ω 2k - resistance measurement mode up to 2000 Ohm.

There are also multimeters with automatic selection of the measurement limit, for which it is sufficient to set the switch to the position corresponding to the type of the monitored value.

The stylus connectors are inserted into the sockets on the right at the bottom of the front panel. One of them, near which the inscription "COM" is applied, is used in any mode of operation, a black probe is connected to it. The upper contact is only used when measuring large DC values. For more details on the purpose of the sockets see the picture. In addition, below the rotary switch is a connector for connecting transistors to determine the current gain (hFE mode).

Rules for working with a multimeter

During the use of the device, it is impossible to touch bare areas of the test leads, while measuring current and voltage, this can cause harm to health. When checking large resistances because this indicator for a person's body is relatively low, there may be a significant error.
It is always necessary to ensure that the instrument's probes are inserted into the sockets intended for the type of measurement that is being carried out, as well as the position of the mode switch. It is necessary to pay attention to warning labels near the connectors of the device and not to exceed the specified values of current, voltage and duration of operation.
It is necessary to monitor the battery level of the instrument, since its low value can adversely affect the accuracy of the measurements. In some models of multimeters for this purpose there is a special indicator. After the operation is complete, turn the switch to the Off position or press the appropriate button on the housing to prevent the battery from prematurely discharging.
If the value of the detected value of voltage and current is not known even approximately, it is necessary to set the maximum possible limit of its measurement. After a preliminary evaluation, you can switch the switch to the mode closest to the received value of the parameter, since in this case the result will be more accurate.
With inefficient use of instrument probes in an operating device, it is likely that they touch several points of the electrical circuit at once, which can lead to a short circuit. Therefore, it is desirable to put on the conductive stings sections of tubes of insulating material, leaving only the most free ends.
It is necessary to know how to correctly use a multimeter when determining various electrical quantities. The current meter (ammeter) is connected in series to a break in the circuit, voltage (voltmeter) and resistance (ohmmeter) - parallel to the load - as in the figure. In the latter case, the power supply must be disconnected.

Voltage measurement

This mode does not require any switching in the circuit, so the most simple to implement. First, you need to determine the type of the measured voltage and its approximate value. For example, if a 9V battery is checked, then the DT-838 multimeter switch must be set to DCV 20. When determining the voltage at a household outlet having an effective value of 220V, the ACV 750 mode is selected. The black probe of the instrument should be inserted into the "COM" jack, red - in "VΩmA". Then it is necessary to touch the conductive stings of the element terminals by connecting the device in parallel and to see the readings on the display. Once again, it should be recalled that it is necessary to strictly observe the safety rules, especially when working with equipment that is under high voltage.

Features of the functioning of the multimeter in the voltmeter mode:

An ideal voltmeter must have an input resistance that tends to infinity, which is practically unattainable. Therefore, the device is capable of introducing a slight error, which in most cases can be neglected.
If you try to measure a DC voltage with a multimeter with the AC mode set, it will show a value of 0. Otherwise, the device may be out of order.
If the polarity is not respected, the sign "-" will appear on the indicator during the determination of the DC voltage.

Current measurement

Multimeter DT-838 allows you to estimate only the strength of direct current. First of all, you need to set the probes correctly: when measuring the value up to 200 mA, the red connector is inserted into the "VΩmA" socket, from 200 mA to 10 A - to "10A". And it is necessary to turn the switch in such a position that the limit was greater than the assumed value of the current. For operation in the ammeter mode it is necessary to disconnect the circuit and connect the device in series.

Also note the following features of the multimeter as a current meter:

Measurement of resistances

In the ohmmeter mode, you can determine the active resistance of the element by disconnecting it from the circuit and connecting the device in parallel. Unlike previously considered cases, exceeding the measured value of the selected limit will not cause a malfunction of the device.

When using a multimeter in the ohmmeter mode, you need to pay attention to the following:

In the case of determining small values of resistance, probes can make an error.
If you connect the device to a load connected to the source, it can fail.
If the measuring limit is exceeded, "1" appears on the screen, when the probes are closed with each other, the instrument should show a value close to zero.

Measuring voltages, currents, and resistances is the most commonly used function of a multimeter. Another very useful option is to check the integrity of the wires and other circuit elements. For this, the device must be connected in the same way as in the ohmmeter mode. If there is no rupture of the test conductor, an audible signal will be heard.

To determine the temperature with a multimeter, connect the sensing element - the thermocouple - to the "VΩmA" and "COM" sockets (some models have a separate connector), place it on the monitored object, and then read the readings from the indicator. You can learn more about this by watching the video:

Inexpensive digital multimeters are used only to troubleshoot equipment and are unsuitable for many professional jobs, such as calibration of sensors and other measuring instruments, since they have a large error for this purpose. But, having mastered the principles of using the simplest device, as you gain knowledge in the field of electrical engineering and electronics, you can proceed to the use of devices with an expanded set of functions, greater accuracy and reliability.

The electrical network today is an indispensable attribute of almost any structure and how well its installation will be implemented depends largely on the efficiency of the electrical equipment used and all electrocommunications. In view of which it is very important to understand how the house electrical system , and on what aspects should be paid attention in testing its performance. So, for example, many home masters are often interested in the question of how to test the outlet with a multimeter, in order to make sure of its performance. Let's discuss this together.

Step one: familiarize yourself with the network parameters

Immediately it should be noted that the quality electric power is an important indicator for the work of the majority of consumers, therefore, before you check the outlet with a multimeter, you should familiarize yourself with the following characteristics:

The voltage of the network should be 220V (a deviation from the indicated indicator is allowed +10% ...- 15%);
The frequency of the mains must be 50 Hz.

Phase two: taking measurements

The multimeter (measuring device) switches to ACV measurement mode. And the limit value of the installation should be more than 220 V.
The measuring probes of the device are applied to the contact groups of the socket, and the voltage indicators are fixed on the indicator board;
On the basis of the results obtained, conclusions are made about the operability sockets.

Sometimes, a simple measurement of the voltage level is not enough, which involves additional work, namely, grounding. For what it is recommended to perform the following actions:

Using the indicator screwdriver, determine the phase and zero contact of the socket;
Disconnect the household electrical system;
Set the multimeter to the resistance measurement mode (Ohm);
Measure resistance between the ground terminal and the sockets. With respect to the phase contact, the value of the resistance should tend to infinity, relative to zero - to zero.

To ensure that the process of diagnosing electrical equipment does not cause significant difficulties in the process of performing the work, it is desirable to adhere to the following recommendations:

Produce works only with appropriate experience;
Use approved electrical appliances;
Use personal protective equipment.

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If any of the household appliances does not turn on, then before you do its diagnostics and checking the entire electrical wiring diagram, you should make sure of the presence / absence of power. Even if the light in the room and burns, it does not mean that there is tension in a single outlet. Verify this (or reverse) with a special indicator probe (probe) or multimeter. The latter device is even better, since it allows you to determine the numerical value of this parameter of the intra-house network.

If you check the voltage in the socket with a simple multimeter, you can make sure that the voltage is acceptable, whether it is sufficient for the correct operation of technical devices.

Initial settings

Multimeters are different in execution (electronic, arrow) and modifications. But the order of work with them is absolutely identical.

The measurement mode (ACV) is the voltage variable (U ~). For those who forgot - there is no permanent network in the house network!
Limit of measurement (V) - 750. Characteristics of the industrial / voltage - 220V / 50 Hz. Therefore, the measurement limit is set to be large. In multimeters of the old type, the scale gradation is somewhat different, but in any case it is necessary to select the switch position to a value of at least 250.

Operating procedure

Insert the probes with which the instrument is completed into the corresponding sockets on its front panel. In some modifications of multimeters, they can be located on the front of the case, at the top. Polarity in this case is not important, since the voltage in the outlet is variable.

It is not necessary to remove the cover from it. You can insert the measuring ends of the probes (probes) into the sockets of the socket.

What to consider when checking

Tolerance. Our GOST provides for maximum deviation from the face value of 10% in any of the parties. That is, if the voltage in the socket is between 198 - 244 V, then this is considered the norm.
Before using the multimeter, you need to check the integrity of the insulation of the wires and knobs of the probes. Elementary precaution, since we are talking about tension - nothing more.
Especially expensive household appliances can be protected from breakage due to sudden jumps in the network, connecting them through a monitoring relay. These devices partly perform the function of the voltage regulator, allowing you to visually determine the current value of this network parameter. So, it is timely to take appropriate measures.

That's all. There is nothing difficult to check the voltage in the socket using a multimeter. Everyone can do this, and it is not necessary to wait for the arrival of an electrician. If there is no voltage, then one of the probable causes is knocking out the circuit breaker. .