The current strength in the electrical circuit is measured by the device. How to work with current clamps? Electric Current Meters

During the operation of the mains or of any device, it is necessary to measure the current strength.

In this article you will learn what is meant by this term and what tools are used for this purpose.

At the same time, we’ll talk about safety measures during such work.

Current unit

The strength of current in physics is the value of the charge crossing the cross section of a conductor per unit time. The unit of measurement is ampere (A). A current of 1 A has a current at which in 1 second a charge of 1 pendant (C) passes through the cross section of the conductor.

The current strength can be compared with the pressure of water. As you know, in the old days small rivers were blocked by dams to create a pressure that could rotate the mill wheel.

The stronger the pressure, the more productive the mill could be set in motion with it.

In the same way, amperage characterizes the work that electricity can do. A simple example: when the current in the circuit increases, the light bulb will burn brighter.

Why do you need to know how much current flows in a conductor? The strength of the current determines how it will act on a person in case of accidental contact with live parts. The effect produced by electricity is displayed in the table:

Here are a few more reasons:

1. The current strength characterizes the load on the conductor. The maximum throughput of the latter depends on the material and the cross-sectional area. If the current is too large, the wire or cable will become very hot. This can lead to melting of the insulation followed by a short circuit. This is why wiring is always protected against overload by circuit breakers or fuses. Owners of apartments and houses with old wiring should pay special attention to the current flowing in the wires: due to the use of an increasing number of electrical appliances, it is often in an overloaded state.
2. By the ratio of the current strength in various circuits of the electrical appliance, we can conclude that it is serviceable.   For example, currents of equal strength must flow in the phases of the electric motor. If discrepancies are observed, then the engine is faulty or is operating with overload. In the same way, the state of the heating device or electric “warm floor” is determined: the current strength in all components of the device is measured.

The work of electricity, more precisely, its power (the amount of work per unit of time), depends not only on the strength of the current, but also on the voltage. In fact, the product of these quantities determines the power:

W \u003d U * I,

• W is the power, W;
• U is the voltage, V;
• I - current strength, A.

Thus, knowing the voltage in the network and the power of the device, we can calculate what current strength will flow through it under the condition of a working condition: I \u003d W / U. For example, if it is known that the heater power is 1.1 kW and it works from a regular 220 V network, then the current in it will be: I \u003d 1100/220 \u003d 5 A.

Current measurement formula

It should be borne in mind that, according to the laws of Kirchhoff, the current strength in the wire before branching is the sum of the currents in the branches. Since in an apartment or house all devices are connected in parallel, then, for example, if two devices with a current of 5 A work simultaneously, then a current of 10 A. will flow in the lead wire and in general zero.

The reverse operation, that is, the calculation of the consumer's power by multiplying the measured current by voltage, does not always give the correct result. If there are windings in the consumer device, such as in motors with inductive reactance, part of the power will be spent on overcoming this resistance (reactive power).

To determine the active power (the useful work of electricity), you need to know the actual power factor for this device, which is the ratio of active and reactive powers.

Instruments for measuring current and voltage

Here are some measuring tools that will help an electrician in this matter:

Ammeter

There are several varieties of this device, which differ in the principle of action:

1. Electromagnetic:   inside there is a coil, flowing through which a current creates an electromagnetic field. This field draws the iron core connected to the arrow into the coil. The greater the current strength, the more the core will be drawn in and the more the arrow will deflect.
2. Thermal:   a tensioned metal thread connected to the arrow is installed in the device. The flowing current causes the filament to heat up, the degree of which depends on the current strength. And the more the thread heats up, the more it will elongate and sag, respectively, the stronger the arrow will deviate.
3. Magnetoelectric:   the device has a permanent magnet, in the field of which there is an aluminum frame connected to the arrow with a wire wound around it. When an electric current flows through a wire, the frame in a magnetic field tends to rotate by a certain angle, which depends on the strength of the current flowing. And the position of the arrow, which indicates the value of the current strength on the scale, depends on the angle of rotation.
4. Electrodynamic:   Inside the device there are two series-connected coils, one of which is movable. When current flows through the coils as a result of the interaction of the electromagnetic fields that arise during this process, the moving coil tends to turn relatively motionless and at the same time pulls an arrow. The angle of rotation will depend on the strength of the flowing current.
5. Induction:   current is passed through the windings of the fixed coils connected by a magnetic system. As a result, a rotating or running electromagnetic field is formed, acting with some force (depending on the current strength) on a movable metal cylinder or disk. He is associated with the arrow.
6. Electronic:   such devices are also called digital. Inside there is an electric circuit, information is displayed on the liquid crystal display.

Current meter multimeter

So it is customary to call a universal electronic meter of current parameters. It can be switched both to the ammeter mode and to the voltmeter, ohmmeter and megger mode (large resistances are measured, usually insulation).

Multimeter Current Measurement

The measurement results are displayed on a liquid crystal display. To operate the device requires battery power.

Tester

In terms of functionality, this is the same multimeter, but analog. The measurement results are indicated on the scale using the arrow, batteries are required only with an ohmmeter.

Measuring pliers

Measuring ticks are more practical. They just need to clamp the portion of the tested wire, after which the device will show the strength of the current flowing in it.

It should be borne in mind that only the tested conductor should be in the ticks. If you clamp several conductors, the device will show the geometric sum of the currents in them.

Measuring pliers

Thus, when the entire 1-phase wire is placed in the clamp meter, the device will display “zero”, since in the phase and zero conductors the opposite directions of the same magnitude flow.

Measurement methods

The first three devices for taking measurements should be included in the load circuit in series with it, that is, in a wire break. For a 1-phase network, this can be either a phase or a neutral wire. For 3-phase, it is only phase, since in the zero phase the geometrical sum of currents flows in all phases (at the same load it is equal to zero).

We note two important circumstances:

1. Unlike a voltmeter (voltage meter), the ammeter cannot be used without load, otherwise it will result in a short circuit.
2. The probes of the device can touch the wires or contacts only in the absence of voltage, that is, the tested line must be de-energized. Otherwise, an arc may arise between the closely spaced probe and the wire with the release of heat sufficient to melt the metal.

All measuring instruments have a range switch that controls sensitivity.

  Grounding is necessary for the safe operation of electricity. - The most important component of the electrical network.

Transformer 220 to 12 Volts - the purpose and recommendations for the manufacture you will find.

Note that the current consumed by some devices, such as television and computer equipment, energy-saving and LED lamps, is not sinusoidal.

Therefore, some measuring instruments, the principle of operation of which is oriented to alternating voltage, can determine the value of the strength of such a current with an error.

Related videos

Clamp meters are a device whose main purpose is to measure the electric current without breaking the electric circuit and disrupting its functioning.

Additionally, this device is also capable of measuring voltage, frequency, temperature (on some models).

In accordance with the measured values \u200b\u200bare divided into ammeters, voltmeters, wattmeters, phase meters, ampere voltmeters.

The most common include tick ammeters for measuring alternating current, called clamp meters. With their help, you can quickly measure the current in the conductor without breaking or disconnecting the electrical circuit. Electrical measuring clamps can be used in electrical installations up to 10000V.

Every inhabitant knows the purpose of many electrical appliances and tools - everyone knows why a soldering iron or an electric drill is needed. But far from everyone, not even at every enterprise, there are clamp meters.

Despite this, current clamps are intended for widespread use, just very many do not know about the existence of such a device and do not know how to use it.

Where are electrical ticks used?

Clamp meters can become an indispensable tool for both household consumers and enterprises of various sizes. With their help it is possible:

• - determine the actual load on the network. To determine the load of a single-phase network, the measurement is carried out on the input cable, the obtained current value in amperes is multiplied by the voltage in the network and the cosine of the angle between the phases (cos φ). If there is no reactive load (powerful inductive elements, chokes, motors), then the last value is taken equal to unity (cos φ \u003d 1).
• - for measuring the power of various devices. In case of need, the current strength of the circuit section with the connected consumer is measured. Power is determined by the above formula.
• - to check the operation of electricity consumption meters, for example, reconciling meter readings with actual consumption.

Design and notation

Part electrical ticks   any modification includes the following main parts: clamp pliers, range and function switch, display, output connectors, measurement fixation button. This article discusses brand current clamps mastech M266.

The switch can be installed in one of the provisions of the measurement modes:

1. - DCV - constant voltage;
2. - ACV - alternating voltage;
3. - DCA - direct current;
4. - ACA - alternating current;
5. - Ω is the resistance;
6. - diode icon - check diodes;
7. - signal icon - buzzer with a buzzer.

Three input connectors of the device are protected against overload. When connecting the device, the black wire of the probes is connected to the “COM” connector, and the red wire to the “VΩ” connector. The third connector, labeled “EXT,” is used to connect the insulation meter.

Current measurement procedure

The limit switch is set to the appropriate AC measurement range. Current clamps are connected to the measured conductor.

If the display shows only the value “1”, then it is necessary to set the limit switch to a higher value, since an overload has occurred.

Voltage Measurement Procedure

Connect the red wire of the probe to the “VΩ” connector, the black wire to “COM”. Set the limit switch in the position corresponding to the measured range.

Connect probes to the measured load or voltage source. The measured voltage and its polarity will be observed on the screen of the device. If only the value “1” is observed on the screen, then the limit switch must be switched to a higher value, since an overload has occurred.

Resistance Measurement Procedure

The probes of the device are the same as when measuring voltage. Set the range switch to the range “Ω”. If the device is used for dialing, then the switch must be set to the appropriate position. If the resistance of the measured section of the circuit is less than 50 Ohms, the buzzer will sound.

Electrical meter - principles of operation

The principle of a single-turn current transformer is put into the work of the simplest current-measuring clamps of alternating current.

Its primary winding is nothing more than a wire or bus in which current is measured. The secondary winding, which has more turns, is wound on a detachable magnetic circuit and is located in the pincers themselves. An ammeter is connected to the secondary winding.

By measuring the current that flows in the secondary winding, taking into account the known transformation coefficient of the measuring transformer, it is possible to obtain the amount of current measured in the conductor.

Note that using clamp meter   measuring the current (and in fact the load) in the circuit is not at all difficult and very convenient. The measurement process itself is as follows.

Using the knob, the measured value is set. The pincers open, a conductor is passed through them, the handle is released and the pincers close. The further procedure for using the meter is exactly the same as when using a conventional tester.

Clamps can be connected to both insulated and uninsulated wires. Most importantly, only one bus should be covered. The meter displays the current value of the measured circuit.

Thus, if you grab the conductor and press the button, then after the magnetic circuit is opened, the recorded measured reading of the device will be saved on the device screen.

An alternating current passes through the current-carrying part, which is covered by the magnetic circuit. An alternating magnetic flux is created in the magnetic circuit, as a result of which electromagnetic induction occurs in the secondary winding - current (measured by an ammeter) begins to flow through it (secondary winding).

Modern clamp meter   are carried out according to a scheme in which a current transformer and a rectifier device are combined. It allows the leads of the secondary winding to be connected to the measuring device through a set of shunts, and not directly.

How to use clamp meters

How to measure the network load in the apartment?

The range switch is set to ACA 200. Having opened the current clamp, at the entrance to the apartment cover them with an insulated wire, record the readings that appear on the screen of the device.

The resulting value is multiplied by a voltage of 220 V, the cosine is taken to be unity.

Example. Let's say the device shows 6A. This means that the network load of the apartment is:

P \u003d 6 · 220 \u003d 1320 W \u003d 1.32 kW.

Based on these data, it is possible to check the correct operation of the meter of consumed electricity, the correspondence to the actual load of the input cable, etc.

A little trick when measuring

How can a small current be measured with an electrical clamp?

In order to measure clamp meter   a small current strength, you need a wire on which you need to find out the current, wrap it several times on an open magnetic circuit. Set the measuring range to the minimum value.

Determine the measuring interval of your digital multimeter. A multimeter is a small hand-held device that allows you to measure voltage, resistance and current. Each model is designed to measure the current strength lying in a certain range, and this range should correspond to the electrical system that you are going to test. For example, passing 200 A through a multimeter, rated at a maximum of 10 A, will cause the multimeter fuse to fail. The maximum measured current is indicated on the multimeter itself or in the instructions for it.

Select the appropriate multimeter mode.   Most multimeters can work in several modes, measuring different values. To measure the current strength, you must switch to mode A (current measurement) and AC (alternating current) or DC (direct current), depending on the circuit being tested. The type of current is determined by the power source of the circuit. For example, a household source gives AC, and a battery gives DC.

Set the measurement interval on the multimeter.   To ensure that the multimeter fuse is not guaranteed to burn, set the upper limit of this interval well above the expected current. You can always lower the maximum if the multimeter shows nothing when connected to a circuit.

Insert the connectors into the appropriate slots.   Your cable comes with 2 cables, with a probe at one end and a connector at the other. Connect both cables to the sockets designed for measuring current strength; If these sockets are not clearly marked on the multimeter itself, you can install them by looking at the instructions.

To measure current, connect a multimeter to a circuit. This is extremely dangerous and can lead to electric shock when measuring household AC current or current generated by other sources of high voltage or current, and sometimes low-power sources. Before touching any wires, especially bare wires, turn off all switches and check with an AC current probe so that the alternating current in your circuit is zero. Do not work in a wet environment or even in high atmospheric humidity - moisture can conduct current. Wear rubber gloves on your hands. Additional precautions may be required. Consult a serious book on working with electricity (but not in a network resource) before starting work. Keep in mind that the electrical insulation of the wire could be broken during chain assembly or as a result of prolonged use. Insufficient insulation can cause electric shock. Always have someone near your mobile phone who could call the emergency service if necessary. Your partner should also be able to provide first aid and cardiopulmonary resuscitation. If you are shocked, your partner should pull you aside using some non-conductive material (for example, dry clothes, but you may need something else), otherwise it will also be shocked when you touch you through your skin, or possibly and through clothing (or other insufficiently insulating material). In any case, consult the book on electrical safety before proceeding with measurements, and find out what type of electrical signal you have to deal with. Read in a book on electrics (but not in a network resource) about the dangers that await you, and how to avoid them. Cut the wire in a suitable place. Fasten both loose ends of the wire and strip them. Firmly connect one of them to one probe of the multimeter, the other to the second, so that they do not touch each other. Before measuring, make sure that the ends of the wire are firmly pressed against the probes of the instrument. Make sure that the wire, especially its bare ends, does not touch you. Turn on the circuit switches that you previously turned off, and if there are no readings on the multimeter, adjust its scale.

Not expensive, but very useful at home and not only, a universal multimeter device will help in various situations. Regardless of price, they solve various tasks related to electricity. You can measure the current strength with a multimeter, the main thing is to know how to do it.

For beginners, you need to understand what and where to connect, why you need value switches, how to take measurements in a domestic environment.

Briefly about the device

Each tester has two outputs. For connecting wires with probes. There may be more sockets for connection, but we need red to connect the probe to phase and black to the neutral wire. There may be slots for taking measurements of all values. Namely:

To designate the nests, the designation using the unit of measure is used. It is impossible to make a mistake if you have not skipped physics lessons.

The second main element of the device of the measuring device is a scale of settings and a switch. As a rule, a certain sector is allotted for measuring the value of current strength. Amps with various numerical values \u200b\u200bare indicated here.

Multimeters are available in digital and analog versions. Digital instruments have a greater number of adjustable amperage values, and they are also equipped with sound signals and other options. But this concerns the choice of type of device. Each of them will allow you to take measurements, for us this is important.

Let's move on to the main topic.

Step-by-step instruction for measuring current strength with a multimeter

All work should be performed according to the following algorithm:

• We determine the value available for measurement on this device. If the tester has a limit value of 10 A, and you measure, passing through it 100 A - this "work" will lead to failure of the fuses. The maximum value is indicated on the scale of the multimeter and in the instructions for it.
• We select the necessary mode for measurement. To do this, switch the device to the desired sector on the scale. To do this, set the switch to sector "A", or "AC" this mode of measuring the values \u200b\u200bof alternating current. When measuring the constant, the flag should be set in front of the DS sector.

This must be done. To determine the type of circuit, you need to know the power source. For measurement on a household appliance we set “A”, and measuring on the chain of industrial equipment, we set up the “DS” sector.

• We set the limits of the value of the force when measuring on the tester. It is guaranteed impossible to damage the multimeter by setting the maximum possible level. It is better to reduce it during improper operation to a normal value during measurement.
• We insert the wires with the probes into the corresponding sockets on the device body.
  

  Important. Cables with probes should be connected to the connectors to measure the magnitude of the current strength and accurately in color. We insert the wire with the probe for connecting to the phase (red) in the desired socket, insert the black for the earth in a specific place.

  For safety reasons, if in doubt, it is better to look at the instructions and check that the connection is correct.

• We measure current. Performing this work, it is necessary to remember the safety rules when working with electricity. Electric shock can occur even when working with small power devices. This is especially important when performing work in conditions with high humidity. It is better to work in rubber gloves and boots.

For a better understanding of the measurement, we will analyze a typical operation by measuring the current strength on any household appliance. This must be done under load. To do this, you need a set of additional wires with crocodiles. We need to open the network. Therefore, when measuring AC, we connect any additional wire from the outlet to one of the contacts of the plug of the device.

We attach the tester probe to the second contact of the socket. We attach the second probe of the tester, using a crocodile on an additional wire, to the second pin of the instrument plug. We get a network with a connected multimeter.

When the household appliance is turned off, the tester scale will be 0. After switching on, on the multimeter we get the indication of the measurement we are interested in.

The practical value of measuring current in the home

By measuring the current strength on a microwave oven, we can determine with its help a malfunction of two nodes at once. When turned on, the value on the scale will be small, then the amperes will increase. This is due to the fact that when we turn on the furnace, we start the fan first, and only then the magnetron of the furnace turns on. If the value on the scale of the current is less than 5. A - this means that the magnetron does not work. When turned on, the measurement value must be at least 1.5 A. If this is not the case, the device fan should be repaired.

In the same way, you can measure this value on a finger battery to determine its charge level. But here you should take care of the battery. On the scale we set the measurement of direct current. It is important to use the probes according to their polarity. We put the battery on the black probe with a minus, and touch the plus for a short time with a red probe.

If the value is less than Ampere, the battery can be disposed of. Why should the touch be short? When measuring, we apply a load to the battery, from a long exposure, it discharges and in this case it can be discarded immediately after measurement.

In the same way, having received the current value of the phone’s charger, we can find out the serviceability of protecting it from short circuit. In the same way, but with the use of more powerful testers, the current value is determined in industrial plants and machines. The principle of operation is the same, regardless of the type of equipment.

In conclusion, we summarize the information by making a small memo for people taking a multimeter for the first time.

Before work, make sure that the device is in good working order. To do this, select the switch flag in the network resistance measurement sector and short-circuit the probes between each other. At 0 on the scale, you can begin to work.

Set the maximum current value on the scale to prevent the fuse of the device from burning. Install the switch in the current measuring sector and set it according to the marking. "A", "AC" - for measurements of alternating current. We put on the value of "DS" when measuring direct current.

It is possible to measure the serviceability of household appliances and equipment only under load. Therefore, you should remember the circuit for connecting the tester to the power supply circuit and observe safety measures when working with a powered mains.

When working in a damp room with high humidity, use rubber shoes and gloves. Place a rubber mat on the floor. These measures will save your life.

After finishing work, be sure to turn off the device to preserve the battery charge.

By following all these simple recommendations, you get the opportunity to save money by completing the work of a specialist yourself. It is easy to do this, but once again I want to remind you, take care of your life by measuring current with a multimeter.

Let your house always be bright and joyful.

One of the main parameters in electrical engineering is the current strength, which is an electric current in a certain amount passing through a conductor of a certain section. This value is of great importance for the normal operation of electrical systems, so the question of how to measure the current strength with a multimeter often becomes relevant. This procedure is necessary in order to know exactly about a particular current level set for a particular circuit. A multimeter is the main instrument with which measurements are taken.

How to measure the current strength in a socket with a multimeter

Before starting measurements, the test leads are connected to the device first. Each of them has its own color - black and red. The black probe is usually common, zero or minus, so it is connected to the lower connector, marked with COM symbols. The other red probe is connected to the middle connector during measurements. There is a connector located at the top of the multimeter, into which a red probe is connected when an alternating current of up to 10 amperes is measured.

After connecting the probes, the desired operating mode is selected by turning the circular switch and setting it to the desired position. If the value of the measured parameter is known in advance, then the set measurement limit should slightly exceed it. This measure allows you to protect the multimeter from burnout. In the event that there is no information about the possible readings of the device, the maximum possible measurement limit is set.

When measuring voltage, the device is connected in parallel to the circuit, and for current measurements, in series. The measurement of semiconductors or resistance parameters is performed when the power is off in this circuit. can also be measured with a multimeter. To do this, the switch must be moved to the ACV position at 750 volts, and then measure. In the same way, a measurement is performed on a 380V network. The current strength at the outlet is measured by setting the instrument in AC metering mode.

How to measure transformer current with a multimeter

The current flow in the transformer is carried out exclusively in a closed circuit. In order to make current measurements, you first need to connect some kind of load, and then a multimeter is connected in series with it. In this case, the switch is also set to AC measurement mode. The red wire connects to a separate output.

At the preparatory stage, you need to do the following:

• A probe with a black wire is installed in the corresponding black socket, and a probe with a red wire is installed in the red socket, where there is a designation "A", that is, amperes.
• The toggle switch switches to the desired position: for AC measurements - AC, DC - DC.
• The measurement limit is set so that it is higher than the expected current level in the circuit. This will help protect the device from burnout.

After preparation, you can proceed to direct measurements. For this purpose, the multimeter must be sequentially included in the open circuit between the transformer and the load. The amount of current passing through the device is displayed on the display of the multimeter. In the absence of load, a limiting resistance can be included in the chain - an ordinary bulb or resistor.

If the current value is not displayed, the measurement limit is chosen incorrectly and must be reduced by one position. If there is no result, the procedure must be repeated and continue to do so until a value appears on the display.

How to measure battery current with a multimeter

Despite the resemblance, all batteries have different parameters and specifications. In this regard, quite often there is a need to verify the operability of these elements, in particular, in measuring the current strength.

The main test method concerns new batteries, allowing you to determine their performance at the time of purchase. To take measurements, the multimeter is set to the position corresponding to direct current. Further, the procedure will be as follows:

• The multimeter should be installed at the maximum measurement limit.
• The multimeter probes are applied to the battery terminals.
• After the increase in current on the screen stops, after about 1-2 seconds the probes are removed.

The normal current in a new battery is usually 4 to 6 amperes. If the indicators are from 3 to 3.9A - this indicates a decrease in battery life. Therefore, it can only be used in devices with reduced power. At lower rates, batteries can only be used in very weak devices or not at all.

How to measure DC current with a multimeter

The DC current measurement is carried out in the same manner as when measuring batteries. Just in this case, the multimeter is also used to check more powerful devices. First of all, these are rectifiers used in industry and in everyday life.

For measurements with a multimeter, any two points are selected between which the measuring device is connected in series. The connection must be made with the correct polarity. If the multimeter is connected incorrectly, the value with a minus sign will be displayed.

In the event that the value of the estimated current strength is greater than the highest measurement limit, it is necessary to set the switch to position "10A". At the same time, from the “V ΩmA” socket, the measuring probe moves to the “10A” socket.

How to measure AC power with a multimeter

Before starting measurements, it is necessary to determine exactly which current will be measured - alternating or constant. After that, the multimeter switch is set to the desired position. Next, you need to set the approximate force in this circuit in order to connect the measuring probe to the corresponding connector. If the current is assumed to be up to 200mA, the probe is plugged into the “V ΩmA” socket, and with a current of more than 200mA, into the “10A” connector.

Sometimes it happens that there is no information about the current strength at all. Therefore, measurements should be started from the maximum value. If a current of a lower value appears on the display, then the plug needs to be moved to another connector. In the case when the current is again less than required, the plug is rearranged again. If necessary, the control knob should be set to a lower current mark. Before starting measurements, you need to carefully study all the signs printed on the multimeter and in the future choose only the desired symbolism. All measurements should be carried out from maximum to minimum, this is a mandatory requirement when working with a multimeter.