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When carrying out electrical work, it may be necessary to test the cable, for example, when marking the conductors and wires, checking the insulation and integrity of the wiring, as well as finding the place where the electrical cable is broken. Let us consider in what ways testing can be carried out, as well as the equipment necessary for this purpose.

Methods

Testing methods depend on the purpose for which it is performed. To check the integrity of the cable for an open circuit or electrical connection between its cores (short circuit), a continuity can be made with a tester based on a battery and a light bulb, or you can use a multimeter for this purpose. The latter is preferred.

Despite the fact that the price of a multimeter is higher than that of a primitive device, we recommend buying it, this device will always come in handy on the farm.

To check the cable, the multimeter must be turned on in the appropriate mode (display of a diode or a buzzer).

The testing technique is as follows:

When checking a wire for an open circuit, the tester is connected to its ends as shown in the figure. If the cable is intact, the light will glow (when testing with a multimeter, a characteristic sound signal will be heard).

Explanations for the figure:

• A –electric cable;
• B - cable cores;
• C - power source (battery);
• D - light bulb.

If the cable has already been laid, then on one side it is necessary to connect the cores together and ring the wires at the other end;

when the presence of electrical connection between the cable cores is checked, the tester probes are connected to different wires. Unlike the previous example, there is no need to twist the wires on the other side. If there is no short circuit between the wires, the light will not light (when testing with a multimeter, there will be no sound signal).

Continuity ringing of multicore cables for the purpose of their marking

When marking multicore cables, you can use the methods described above, but there are ways to greatly simplify this process.

Method 1: the use of special transformers, which have several secondary taps. The connection diagram of such a device is shown in the figure.

As can be seen from the figure, the primary winding of such a transformer is connected to the power supply, one end of the secondary winding is connected to protective shield cable, the rest of the leads - to its veins. To mark wires, measure the voltage between the shield and each wire.

Method 2: Using a block of resistors with different ratings, connected to the wires of the cable on one side, as shown in the figure.

To determine the cable, it is enough to measure the resistance between it and the screen. If you want to make such a device with your own hands, then you should select resistors with a step of at least 1 kΩ in order to reduce the effect of the wire resistance. Also, do not forget that the value of the resistors has a certain error, so first measure them with an ohmmeter.

When checking a multicore telephone cable, installers often use a headset for dialing, for example, TMG 1. Actually, these are two handsets, one of which is connected to a 4.5 V battery. Such a simple device allows not only checking the cable, but also coordinating their actions during installation and testing.

Insulation test

For testing insulation with a megohmmeter or multimeter, the principle of continuity is the same as when searching for an electrical connection between the cable cores.

The testing algorithm is as follows:

• set the maximum range on the device - 2000 kOhm;
• we connect the probes to the wires and see what the display of the device shows. Given that the wires have a certain capacity, until it is charged, the readings may change. After a few seconds, the instrument panel can display the following values:
• a unit, this indicates that the insulation between the wires is normal;
• zero - short circuit between the cores;
• some average reading, it can be caused by both "leakage" in the insulation, and electromagnetic interference. To determine the cause, switch the device to the maximum range of 200 kΩ. If the insulation is faulty, the display will display stable readings, if they change, then we can confidently talk about electromagnetic interference.

Attention! Before checking the insulation of electrical wiring, it must be de-energized. Second important point- when taking measurements, do not touch the probes with your hands, this can introduce errors.

Video: Wire ring - integrity check.

Finding the place of the cliff

After a break in the wiring has been detected, it is necessary to localize the place where this happened. For continuity in this case, you can use a tone generator, such as the Cable Tracker MS6812R or TGP 42. Such devices allow you to locate the breakage point with an accuracy of a centimeter, as well as determine the route of hidden wiring, in addition to this, the devices have other useful functions.

Devices of this type include an audio signal generator and a sensor connected to a headphone or speaker. When the sensor approaches the break point of the UTP cable pairs or wires of the electrical wiring, the tone of the sound signal changes. When a tone dialing is performed, before connecting the sound generator, it is necessary to de-energize the wiring, otherwise the device will fail.

Note that using this device, you can ring out both power and low-current cables, for example, check the integrity of a twisted pair, radio wiring or communication lines. Unfortunately, such devices will not allow determining the correctness of the connection; for this purpose, special equipment is used - cable testers.

Cable testers

This class of devices allows you to check both the integrity of the cable and the correctness of its connection, which is very important for the networks of Internet providers. It can be simple devices crossover testing or complex devices on a PIC controller that have an ADC and a built-in multiplexer.

Multipurpose cable tester Pro'sKit MT-7051N on a microcontroller

Naturally, the cost of such devices is not conducive to their everyday use.

Homemade contactless dial

Below is a schematic diagram of a simple non-contact breakage detector that can be assembled in one evening. Given the small number of parts, you do not have to bother manufacturing printed circuit board, but use a hinged installation.

List of required radio parts:

• variable resistance R1 - 100 kOhm;
• resistor R2 - from 4 to 8 MΩ;
• electrolytic capacitors: C1 and C3 - 220 μF, C2 - 33 μF;
• a ceramic-type capacitor with a capacity of 0.1 μF;
• D1 - LAG 665 microcircuit (preferably in a DIP package);
• SP is a regular earpiece from a telephone headset.

The circuit can be powered from a 2 to 5 volt source.

The probe (P) is based on a conventional bicycle spoke.

Correctly assembled non-contact cable continuity requires no configuration.

Video: Do-it-yourself cable dialing. How is the continuity of wires performed using a light bulb and a battery

In modern everyday life, situations are not uncommon when it is necessary to ring a certain circuit or electrical device with a tester. Most often, they occur when the socket or key switch stops working, as well as when the contact is lost or the power circuits of individual devices are interrupted. If the owner is used to doing everything on his own, he needs to get a very practical and easy-to-use device called a multimeter.

It can be used to check the serviceability of any electrical device, including an ordinary light bulb, a section of wiring, or a conductor included in it. But in order to correctly ring the circuit with a multimeter, you should first familiarize yourself with the basic methods of working with it.

In the following sections of the article, each of the possible options for using the multimeter will be discussed in more detail.

Integrity check (finding the correct conductor)

To check the integrity of the electrical wiring or to search for one core in a multicore cable, a digital tester turned on in the resistance measurement mode is quite enough. When carrying out such an operation, it is necessary to create a closed circuit consisting of directly from a multimeter (tester), a pair of measuring "ends" and the tested conductor itself.

In this case, a small electric current is passed through the tested section, and the multimeter determines the value of its internal resistance. This is not a dial tone yet, but a pretty convenient way.

In the process of such a check, according to the readings of the multimeter display, it will be possible to judge the integrity or open circuit in the tested section of the circuit or conductor. Zero or close to a few ohms readings mean that the wiring is not open; in this case, the electric current issued by the device flows freely through it.

It is also possible when, during the check, it is found that the device indicates readings in the megohm region, and does not give out an audible signal during the test call. This means that there is an internal breakage that cannot be detected visually in the wiring section.

In fact, a vertebra is a multimeter determination whether there is contact between the wires or not. The multimeter produces a small current, and if the circuit is intact, then the voltage is fixed, as a result, a sound signal sounds - a bell, and zeros are displayed on the display of the multimeter. By dialing, they check fuses, light bulbs, wires, and the integrity of the circuits.

Likewise, with the help of a continuity with a multimeter, a short circuit of the conductors is fixed, which, in working condition, should not have contact with each other. In a working cable, each individual core during testing should show a small resistance (from fractions to several ohms).

The resistance value is determined by the total length of the cable item being tested with the multimeter. At the same time, there should be no contact between all of the multicore cable and the adjacent conductors, which checks the continuity.

Checking the wiring

Continuity of conductors with a multimeter is functionally provided in most digital devices of this class. To set the dialing mode, it is enough to set the switch to the position marked with the "Buzzer" icon and prepare the measuring chain shown in the figure.

If current flows through the tested piece of wire, the multimeter will emit a sound signal (buzzer). Naturally, for continuity of a circuit section several meters long, an additional wire is required, which is used to build up the measuring circuit.

Another option for testing phase and neutral linear conductors of considerable length involves twisting them at the remote end of the wiring.

In this case, to check the circuit for an open, it is enough to connect the measuring probes of the multimeter to the free contacts of those ends of the electric line that are located closer to the device.

The last of the proposed options has the following advantages:

• in this way, it is possible to ring with a multimeter both wires of the electrical wiring at once, connected in a serial chain;
• it is much easier to check the wire in this way than the first one, since you can do without an additional segment that provides a build-up of the measuring circuit.

Before checking the electrical wiring hidden in the thickness of the walls, first of all, you should carefully read the diagram of its laying. In addition, it is necessary to remove the operating voltage from it by disconnecting the machine corresponding to this line.

With the help of improvised means

Testing the wires with a multimeter is not the only possible way to test them for continuity or breakage. You can make sure that any linear conductor is in good working order without the help of this universal device.

To carry out such a check, you will need:

• an ordinary battery (preferably a square 4.5 Volt);
• a 3.5 Volt light bulb, by means of which the investigated linear section of the wire is checked (controlled);
• a pair of connecting wires and a gripping type connector (the so-called "crocodile").

After preparing everyone necessary elements on their basis, a simple measuring chain is assembled, consisting of a control lamp, a battery and a tested conductor. With a correctly assembled circuit and in case of serviceability of the tested section, the control lamp will light up. The absence of a glow with all working elements of the circuit indicates an open circuit in the conductor itself.

When testing in this way, the same principle is used as when testing with a multimeter included in the dialing mode.

Features of checking the wires that make up various devices

First, we will consider the features of work in conditions when the on-board wiring of a modern car is checked by means of a continuity with a multimeter.

Car wiring

The specificity of this situation lies in the fact that the wiring in this case consists of one linear conductor with a supply voltage of 12 Volts. In this case, the metal body of the car is used as the second (common or "earth") conductor, where, as a rule, there is nothing to break off.

To prepare the on-board network for examination, first of all, it is necessary to disconnect the positive terminal from the battery, after which you can safely start work. Testing of the on-board wiring is organized according to the previously described continuity circuit for linear circuits.

When checking the "mass" of the car, the main attention is paid to the quality of contact of the supply terminals with the body.

Electric heating element

Focusing on the readings of the indicator on the multimeter, it is possible to make a continuity of such an element as a water heating heating element. In the process of checking with the control probes of the device, touch the two contact plates of the heater and evaluate it internal resistance by indicator.

If the display shows the order of a few ohms, then no doubt the element is working properly. At large values on the screen corresponding to the break of the tested line, you can immediately say that the heating element is damaged and must be replaced.

In addition to the heating element itself, when checking boilers and similar devices, it is very important to ring the supply cable for its unwanted contact with the device body. For this purpose, one of the multimeter probes is alternately connected to the input contacts; while the other end is constantly held on the heater body.

In the case when the digital multimeter shows some resistance during measurement, this means that the protective sheath of the supply cable is damaged. To prevent electric shock to the user, it should be replaced with a new one.

Other household appliances and parts

Using a multimeter, you can also test the power circuit of any lighting device by testing the wiring and auxiliary elements (switches, in particular) for a short circuit or open circuit. To do this, first of all, you should ring two linear chains ending directly at the contacts of the light bulb.

Additional Information! Before ringing the lighting device, first of all, make sure that the bulb itself is in good working order by rearranging it into a known working device.

In the process of dialing the linear chains, be sure to check the serviceability of the switch in one of them, as well as the reliability of the connection of the conductors with its contacts.

We also note that in this way it will be possible to ring the windings of a linear transformer or an electric motor and make sure that they are intact or there is an open circuit (short circuit).

In conclusion, we recall once again that by means of a multimeter it is possible to check not only individual wires or wiring hidden in the thickness of the walls, but also any other electrical devices and parts.

Content:

While in the apartment overhaul performed and full check the state of the wiring. Diagnostics of the wiring is carried out when it is completely or partially replaced or if a malfunction is suspected. Some apartment owners try to carry out this procedure on their own, in connection with which they often have a question of how to correctly ring the wires with a multimeter.

General information about the multimeter

Before you start working with a multimeter, you first need to familiarize yourself with its capabilities. A cheap Chinese model with a minimum set of functions is quite enough to check the wiring.

Most the best option there will be a simple multimeter with the ability to work in continuous mode. To do this, the adjustment knob of the multimeter must be turned in the direction of the icon indicating the diode. On some models, a sound wave is displayed instead. When the condition of the wire is checked, the closure of the contacts is accompanied by an audible signal.

It is not only the beep that indicates the integrity of the wiring. An open circuit is indicated by the number one shown on the display. It shows that the resistance between the probes is higher than the measurement limit. In the absence of damage in the tested area, the display shows the resistance, which in ideal conditions should tend to zero. First of all, this applies to household electrical networks with a short length.

Procedure for checking the network with a multimeter

Before the continuity of the electrical circuit, the handle of the multimeter is set to the desired position. Further, the ends of the test leads are connected to the corresponding sockets. The COM jack is for the black wire, and the jack with the Ω sign is for the red one. After that, the multimeter must be turned on using a special button. Turning on can be carried out in automatic mode when the handle is in the right position selection of operating mode or measurement limits.

The measuring ends are closed together. The presence of a sound signal means that the device is working properly and is ready for operation. The tested wires or cables are pre-cleaned of insulation, and the cores are stripped to a shine. Dirt and oxidation is removed from metal surfaces. After that, the measuring wires need to touch the bare areas on which the check is carried out.

If the wires are intact, this will be confirmed by an audible signal, and the display will show zero or the resistance value. The presence of a unit on the screen and the absence of a sound signal indicates a damaged wire. When working with electric current, you must strictly follow the safety rules. This fully applies to all actions performed with a multimeter. When dialing, it is recommended to equip the ends of the wires with tips - the so-called "crocodiles". This contributes to a more stable contact and provides freedom of action when taking measurements.

The electrical circuit must be de-energized before testing. Even batteries with a weak current must be removed without fail. If capacitors are present, they must be discharged by short-circuiting. If such measures are not taken, then during the check, the multimeter will simply burn out.

If the tested conductor is long, it is very important not to touch its bare ends with your hands during measurements. In this case, the readings obtained may be incorrect and inaccurate. When multicore cables are ringed out, all available conductors are separated and stripped. The entire circuit is then checked for short circuits. Each core in turn is connected to the "crocodile", and all the rest are connected to the other measuring end in various combinations. If the indicator shows one, and there is no sound signal, then there is no short circuit.

If suddenly the light went out

Situations when the light suddenly disappears is best considered on the example of a modern apartment, where all current norms and requirements were observed when laying cable lines. This means, depending on its purpose. Each such group is connected to a common apartment board using a separate circuit breaker.

In case of a sudden disappearance of light in the apartment, you must first check the health of the lamp. First, the dashboard and the machines located in it are checked. If they are on, then it is likely that the malfunction has arisen from the switch, socket, or the lamp itself. The wiring in this situation is most likely not damaged. When the machine is triggered, all circuit elements are checked, except for the room switch.

Before checking the lamp, it must be unscrewed from the socket. One dipstick touches the threaded base and the other touches the center contact at the end of the base. Wait for the signals described above, and in case of a malfunction, replace the lamp. If the lamp is working properly, the cartridge is then checked by disassembling the lamp and checking the connected contacts and wires. Next, the room switch is checked, in the absence of external damage, the contacts are checked with a multimeter. If the machine is triggered, the wires are checked for a short circuit.