How to ring a computer network cable with a tester. Testing twisted pair cables at home. How to check for a broken internet cable

A local network with an Internet connection is now available in almost every home. Network problems happen, and unfortunately, it’s not possible to identify the problem right away. It is necessary to check each network component at the software and hardware level.

Algorithm of actions

Let's consider the situation. There is a computer in the room. It is connected via a patch cord to the router, which, in turn, is connected via an Internet cable to the provider’s equipment to access the global network. At one point, the network checker on the computer shows that the connection is unavailable or not connected.

What to do:

Check the local interface of the computer you are working on - rule out software errors in Windows or hardware failure of the network card.
Check the operation of the section from the computer to the router - rule out a network break in the PC - router section, a malfunction of the software or hardware of the router responsible for the local network.
Send requests to one or more remote servers of large companies to check the functionality of the cable or equipment that goes and is located outside your home.

To walk through the troubleshooting algorithm, work with the network commands.

Troubleshooting

A superficial check can be done using the command ping all nodes home network and several remote Internet servers. For these purposes, open command line on behalf of the administrator. Next, enter the commands, focusing on the algorithm of actions:

Testing the operation of the network card of the computer itself is done by exchanging test packets with itself. If there are no losses, then everything is in order. Team ping 127.1.1.0.

You can add the -t option to make the packets go on forever until you manually stop them with the Ctrl+C key combination.

Next, ping the area to the router. It is important to ensure that the Internet cable between the computer and the router does not break. If there are packet losses, reboot the router and try pinging again. If local IP address the router has not changed, which means it is 192.168.0.1 or 192.168.1.1.

When 100% of the number of packets reaches the router, the next step is to ping one of the remote servers. This way you can check if you can access the Internet. It is recommended to ping the IP address of the server of a large corporation, as this eliminates the fact that it is unavailable on the network. It is not necessary to know the IP address; you can ping by domain name.

Analyze the information received.

Fault Analysis

We will start from the losses received when sending packets. It is important to understand that the ping command is a protocol of the fourth level according to the nesting of the OSI model, that is, software, network and hardware errors are excluded, but data levels 5-7 according to the OSI model are not checked.

It turns out that a cable break, if present, can be identified in this way and is the easiest to do. But the programs do not allow you to identify the specific location of the cable failure, but only indicate the area.

How to check an Internet cable or local cable and understand that there is a break? Eliminate other options related to a faulty network card or router. If there were packet losses when scanning the computer itself:

Restart your network connection.
Disconnect from all network add-ons (VPN, proxy).
Do a Network Reset.

Update or reinstall the network card driver.

If packets are lost in the PC-router section:

Reboot your router.
Check that the Ethernet cable connectors are securely seated in the port of the router and the network card ( motherboard).
Switch the Ethernet cable to the next port on the router.
Restore the router to factory settings.

Check the connected port indication on the router. If it doesn’t light up, there are two possibilities: the capacitors on the router board have malfunctioned (or another hardware failure of the router) or the cable is faulty.

If packets are lost when accessing the Internet:

Reboot your router.
Free up a dynamic IP address in your router settings.

Turn off VPN and proxies.
Ping other remote servers to ensure that the server is not accessible.
Load Internet pages through another browser.
Restore your router to factory settings.
Call your provider to find out the cause of the problem.

If packets are still not being passed through, there are three possible reasons: a faulty Internet cable, a problem with DNS processing, or problems with the provider’s equipment.

Checking twisted pair breakage and insulation integrity

The following video describes 5 ways to test twisted pair cables:

If all indications are that there is a problem with the cable, it must be identified and corrected. If a short cable is faulty, you can simply replace it. For wires several tens of meters long, you can use special devices to help identify the problem.

Tester

MicroScanner2 is a professional solution for identifying the location of cable faults. By connecting one connector to the port, graphical information about the length of the patch cord to the fault location will be displayed on the tester screen.

Other methods require removing the connector and taking measurements directly on the twisted pair contacts. It would also be a good idea to check the quality of the cable crimp with the connector. If the crimp is weak or the insulation is broken, problems with signal transmission are guaranteed.

Multimeter

In resistance mode, you need to ring the orange and green twisted pair to check the integrity of the cable:

Remove the second connector from the PC network card or other network equipment.
Remove the connector from the end to be measured and expose the wires.
Apply the tester probes first to the orange and white-orange conductor of the twisted pair. Normal resistance is 1-2 ohms.
Next, apply to green and white-green. The resistance should also be 1-2 ohms. The polarity is not important.
Then attach the multimeter probes to the orange and green conductors. The multimeter should read more than 100 ohms. Multimeters usually indicate infinity.

Regular potatoes

If you don’t have any devices at hand, and you need to find out if the cable is damaged right now, do the following:

Cut the potatoes in half.
Immerse each pair as close together as possible into the potatoes, 1.5 cm deep.
If the wire is connected to the positive, the area around the immersed conductor will begin to turn green.
If the conductor is connected to minus, then white foam will appear near the conductor. If you pull out the negative wire, it will begin to darken.
With zero changes in the state of the potato, the twisted pair is most likely shorted or broken.

Conclusion

If you have problems accessing the global network, you need to identify the cause of the problem. It happens that Internet access is blocked because there was a cable break at the site local network or with a patch cord connected to the WAN. It is best to check the integrity of a twisted pair cable using a tester, since it does not require removing the crimped connectors. If there is no such device, use a multimeter or more accessible methods.

In a pop-up window on the computer monitor, the message “Network cable is not connected” appeared, the LED on the network card did not light up. You insert and remove the RJ-45 plug in the hope of poor contact in the connection and realize that the cable is faulty. If you do not have a separate network card installed in your computer, and the network cable plug is inserted directly into the motherboard, the LED will not light if the connection is disabled by software.

Nowadays, a twisted pair network cable is often first connected to the router, which sometimes freezes. Therefore, first of all, you need to reboot the router. To do this, just disconnect it from the power supply for a minute and then turn it on again. It is quite possible that access to the Internet will be restored after this.

A shutdown can occur without your direct participation, for example due to unstable network voltage, running unlicensed programs or a virus. To check in Win XP you need to go to: Start / Settings / Control Panel / Network connections and make sure the connection is connected. Less often, but it also happens, the network card driver does not work correctly. You can check: Start / Settings / Control Panel / System / Hardware / Device Manager / Network Cards. There should be no warning signs.

Network cards very rarely fail; this sometimes happens after a severe thunderstorm. You can check the functionality of the network card by connecting it to a known-good line or installing it in another computer, not forgetting to install the driver for it. Sometimes it is possible to get a network card to work by moving it to an adjacent slot on the motherboard.

A call to the provider's technical service will help check the functionality of the line on their part. If everything is in order with the computer and the provider, it means that the twisted pair cable has failed and requires repair. You can, of course, call specialists and wait, but if you wish, it is possible to diagnose and repair the twisted pair cable yourself.

The most likely malfunctions of the twisted pair cable are:
- complete break of one or more wires - occurs often;
- a short circuit between the conductors of one twisted pair or between the wires of adjacent pairs is less common.

Program for checking Internet access
Network Traffic Monitor

IN search engines People often look for the answer to the question: “a program for testing twisted pair cables.” On a computer with installed system Windows already has a program that displays the message “Network cable is not connected” if the twisted pairs in the cable are broken or shorted. You will have to look for the location of the break or short circuit yourself; there is no program that would indicate the exact location and cause of the malfunction. There are special testers for this, for example MicroScanner Pro.

It’s another matter if there is a connection to the Internet, but it is unstable or the download speed has suddenly dropped. For monitoring network traffic there is an excellent free program, more precisely a utility called Network Traffic Monitor.

It allows you to measure data transfer speed in real time, observe changes in speed over time, save data on a hard drive, rubber windows, extensive customization options and many others useful services. Supports many languages, including Russian.

Installing the program on your computer is simple, just run the EXE file and press the confirm button several times. Network will automatically be added to startup and will monitor and save all data. To display any of the windows on the monitor screen, just click right click mouse on the tray icon and select the desired window. Network Traffic Monitor is the best utility for analyzing and diagnosing network quality that I came across during my search. I have tested the functionality of the Network Traffic Monitor program with Windows HP and Windows 7. You can download the Network Traffic Monitor program with one click from my website.

Diagram of connecting a computer to a network
UTP twisted pair cable

To check twisted pair cables with knowledge of the matter, it is advisable to represent electrical diagram connecting a computer's network card with a twisted pair cable to other devices, a hub, a switch or another computer. The figure shows a diagram of a section of the network connecting a computer to active equipment, a hub or switch.

To check the twisted pair cable, the part of the network card or hub circuit to which the RJ-45 twisted pair cable connector is connected is of interest. As you can see, each pair is connected to the transformer in a symmetrical circuit (a tap is made from the middle of the transformer winding, which is connected to a common wire, sometimes through a resistor or capacitor). Thanks to this connection, all induced noise in the cable arrives at the input in antiphase and is mutually destroyed, while the useful signal arrives in phase and its magnitude does not change. The transformer circuit has another advantage: it protects active equipment from short circuits and entanglement of wires in a twisted pair cable when connected.

Range and shape of the information signal
twisted pair cable

Some people have a question, what shape and scope does the signal in twisted pairs have? The photograph shown is an oscillogram of the information signal. On twisted pairs, both Rx and Tx signals have approximately the same shape and a swing of about two volts. The signal is transmitted via one pair, and received via the second, which is why two pairs are needed for communication. If one of the RJ-45 connectors of the twisted pair cable is removed from the equipment, signal transmission automatically stops.

Theoretically, the signal in a twisted pair cable should have a rectangular shape, but since there is capacitance and resistance of the conductors, the signal shape is rounded. For this reason, the distance between communication points is limited, usually no more than 100 meters. The 2 V signal is not dangerous to humans, nor is a short circuit between pairs dangerous to network equipment, so you can troubleshoot a twisted pair cable without disconnecting it from the network. The network card, switch or hub will not fail.

How to find a break in a UTP twisted pair cable

There are several ways to find a break in a twisted pair cable: external inspection, continuity testing with a multimeter or pointer tester, and folk methods.

Checking the twisted pair cable by external inspection

Checking a UTP cable should begin with an external inspection of the cable along its entire length, Special attention you need to pay attention to the quality of crimping in RJ-45 plugs. If crimped carelessly, the conductors may not be inserted into the plug all the way, and the contact will be poor. Or the conductors overlap with each other at the point of fixation (this happens with the green pair, since its conductors are crimped at a distance of two contacts) and the twisted pairs can short-circuit in this place. If a visual inspection does not reveal a fault, then it is necessary to test the twisted pair cable.

If you had at your disposal a modern cable tester with an LCD display, for example, MicroScanner Pro, which allows you to determine not only the type of defect in a twisted pair cable, but also its location, or at least a homemade LED tester, then no questions would arise. However, in everyday life you have to make do with improvised means.

Checking a twisted pair cable with a tester or multimeter

The easiest way to check is to test the orange and green twisted pair with a pointer tester. To do this, you need to remove the RJ-45 plug from the computer's network card. Next, with the probes of the tester turned on in the resistance measurement mode, first touch the orange and white-orange conductor of the twisted pair. The tester should show a resistance of 1-2 ohms, then to green and white-green. The resistance should also be 1-2 Ohms. The polarity of the tester connection does not matter. Next, the resistance between the orange and green conductors of the pair is measured. It should be more than 100 ohms, usually equal to infinity. If the measurement results correspond to the above values, then the twisted pairs in the cable are working.

Here is another method, more complex, but reliable and indispensable if the twisted pair network cable being tested is not connected to the equipment. You need to bring the ends of the cable with RJ-45 plugs into one place and ring the conductors. It is necessary to set the switch on the device to the resistance measurement position and, according to the diagram, check the integrity of the conductors and the absence of a short circuit between them.

The photo shows a twisted pair cable crimped into an RJ-45 connector according to color-coded option B.

The end of one probe of the device is touched to the contact of one RJ-45 plug, and the other probe is touched to the contact of the same name of the second plug. The resistance should be zero. The wires of each color are called in turn and each wire is checked to ensure there is no short circuit with any other. The test for short circuits is carried out on one plug. To do this, one end of the probe is connected to contact, say number 1, and the second in turn to all the others. Next, the probe is connected to pin 2 and in turn to 3, 4, 5, 6. Since only two pairs are involved in signal transmission (orange and green, plug contacts 1, 2, 3, 6), you need to pay attention to them when checking Special attention.

But it is not always possible to connect the UTP cable connectors to one point. In this case, it is difficult to do without additional devices. Of course, you can extend the end of the tester probe to the entire length of the cable and perform the test together, or cut off one of the RJ-45 plugs, strip the wires and twist them together in pairs. But it is more expedient to make a simple device from an RJ-45 socket, short-circuiting the pairs in it with pieces of conductors with a diameter of 0.5 mm or resistors, as shown in the photo. It is better to use resistors, as this allows you to check not only the integrity of the twisted pair conductors, but also the presence of a short circuit between them. If the measured resistance value is zero, and not the value installed in the socket, it means that the conductors are shorted together. It is better to take different resistor values for twisted pair jumpers, for example 50, 100, 150 and 200 Ohms. Then the measurement results will be more informative.

The RJ-45 plug of one end of the twisted pair cable is inserted into a socket with jumpers, touching the tester probes to the contacts of the second plug, and checking each twisted pair in turn to ensure there is no short circuit between adjacent pairs using the technology described above.

Thanks to different resistance values, it is easy to check the correct crimping of twisted pairs when checking a newly manufactured cable. If any pairs are swapped, then the magnitude of the resistance will immediately show this. For example, if, when checking the orange pair, the multimeter shows a resistance of 100 Ohms instead of the required 50, it means that instead of the orange pair, another pair is crimped into contacts 1 and 2 of the RJ-45, or the cable is crimped in a different way.

It is very inconvenient to check a twisted pair cable by touching the RJ-45 plug. If there is a free RJ-45 socket available, the measurement conditions can be improved. Insert the other end of the cable into the socket and take measurements by touching the probes to the contacts inside the socket.

Based on the results of the inspection, a decision is made on further actions. If the orange or green pairs are broken or shorted, then you can replace them with one of the unused ones, brown or blue, if they are working. To do this, you will first have to cut one plug and ring all the pairs again, then the second one and re-check the pairs, since a break or short circuit may be in the plugs themselves. Short circuits occur at the point where the cable is clamped by the clamp in the plug when the wires are improperly prepared. Break if the conductors are cut when cutting the outer sheath of the cable. This is where they often break. If, after cutting the plugs, all pairs turn out to be defective, you need to more carefully inspect the cable along its entire length; if the damaged area cannot be detected, you will have to replace the twisted pair cable with a new one.

Checking UTP twisted pair cable without devices

If you don’t have a tester or multimeter at hand, you can check the serviceability of the twisted pair cable without them using the proposed method below. It is necessary to cut off 10-15 cm pieces from the ends of the cable along with the connectors. Release the ends of the cable from the sheath by 5 cm and remove the insulation from each wire to a length of 2 cm.

Pour a little water with table salt dissolved in it into a small container made of dielectric material (glass, plastic, plastic bag) at the rate of a quarter of the volume of salt from the volume of water. The more salt, the better. Salt is added to water to reduce its electrical resistance. Immerse all conductors of one end of the cable in a container with solution. You can immerse each twisted pair one by one. The distance between the twisted pair conductors should be minimal, but they should not touch.

The twisted pairs of the opposite end of the cable are connected in series to the poles of any battery or power source with a value of more than 3 V. If the salt concentration in the heated water is very high, 1.5 V will be sufficient. This voltage is produced by any AA battery, for example from a TV remote control. A battery from cell phone, its voltage is about 3.7 V. A battery from the motherboard will also work, it has a voltage of 3.2 V. If you have a resistor with a nominal value of 50-100 Ohms, it is better to connect the battery through it, for protection in case of short circuit of the twisted pairs. The polarity of the connection does not matter.

The telephone network can be used as a power source. Voltage in telephone network about 40 volts and the current is constant, limited at the telephone exchange to 40 mA. This connection is safe for humans and the telephone line. This option is convenient to use if you need to supply voltage to a twisted pair cable in a hallway where there is a telephone box nearby.

Anything is suitable for testing. Charger from a cell phone, USB port computer, there is 5 V at the outer terminals. It is not permissible to connect to USB without a current-limiting resistor; you can damage the computer. To test twisted pairs, a current of 2 mA is sufficient.

After applying voltage, the following picture will be observed at the opposite ends of the twisted pair, which are in water.

As you can see, on the conductor that is connected to the minus (cathode), small white bubbles of hydrogen are released, and on the conductor connected to the plus (anode), yellow-green bubbles of chlorine are released. It is obvious that the pair is fine and there is no short circuit with other conductors. In the event of a short circuit, depending on which wire, white or yellow bubbles also came from the other wire.

If damage is found, then you can finish checking the twisted pairs and replace the faulty twisted pair with a blue or brown one. For example, when checking twisted pairs, a break was detected in the orange pair. Then connect the orange pair coming from the connectors to the blue pair of the cable. The connection technology is described on the page “Extending twisted pair cables”.

Of course, it is better to crimp the cable with new connectors rather than splice it. Or crimp using the old method, described on the page “How to crimp an RJ-11, RJ-45 plug onto a twisted pair cable.”

If the orange and green pairs are ok, and you don't want to bother with crimping the connectors, you need to check the cut pieces of cable with the connectors. To do this, all colored wires of twisted pairs, stripped of insulation, and separately white wires are twisted together.

The connector is immersed in a saline solution to such a depth that the contacts are completely submerged in water. Twisted wires are connected to the battery.

On four of the eight contacts, white bubbles should form one after another. When you change the polarity of connecting the battery, bubbles should form on the contacts on which they did not appear before and also strictly after one. Deviation from this immediately indicates a malfunction. For example, if there are no white bubbles on one of the contacts, then the wire is broken; if there are no white bubbles on any contact, then there is a short circuit between the conductors. To clarify, you can perform individual testing of pairs by unwinding previously made twists.

Depending on the results obtained, you will have to crimp or splice the wires.

Checking a twisted pair cable using a potato

The cable is prepared as described above, only the container with the saline solution is replaced with half a potato. Each pair is stuck sequentially into the potato to a depth of 1-1.5 cm. The distance between the conductors should be minimal.

As you can see in the photo, the wire that is connected to the positive terminal of the battery turned green around the wire, and white foam appeared around the negative terminal. When the wires are removed from the potato, you will notice a darkening of the wire to which the minus was applied. If there are no changes in the cut of the potato, it means that the twisted pair conductors are broken or shorted to each other.

Just for fun, I poked the wires into the slice of an apple. Not so obvious, but it is obvious that the wires are in order.

Using the described twisted pair testing method, you can check wires of any type, cross-section and length.

– an indispensable tool for every network communications installer. It is also present in the mandatory kit of a network engineer. And there are often cases when an ordinary ordinary user has this at hand useful tool. Imagine an ordinary day at work, when the network signal suddenly disappears. On the provider's side, everything is in order, software problems are excluded - all that remains is to check the cable. This is where this measuring device comes in handy, with which you can check the integrity in a couple of minutes

Functionality of twisted pair testers

A modern twisted pair tester can have a number of useful functions. In addition to checking the conductor for a break, such a device can search for a route, measure the level of signal attenuation and return loss. The tester is also capable of crosstalk at the near end of the cable. However, for ordinary daily needs, most often only one function will be required - ringing the cable, that is, a standard check of the coil for serviceability. The most primitive models, in addition to directly ringing, can indicate a possible source of the problem, such as a broken pair or a poorly crimped connector.

How to use a twisted pair tester

The entry-level twisted pair cable tester consists of two conditional blocks. The main block is the master unit - this is where the signal indicators are located, as well as options for selecting operating modes. The second block is the response one - there are also light indicators there that indicate which conductor is being called at the moment. Both blocks usually have RJ45 and RJ11 connectors installed.

Now we will explain how a regular twisted-pair LAN tester works using the example of a cable consisting of four pairs of conductors.

Our cable is already ready for use within the configured network, and is crimped on both sides with the necessary connectors.
To check, you need to insert one end of the cable with a crimped connector into the connector of the tester's master unit.
The second crimped end of the cable is, accordingly, inserted into the mating block.
Then we switch the tester to operating mode and observe the readings of the device.
The indicator lights on both parts of the tester will begin to blink, indicating a connection on each pin.
If everything is correct and the signals pass through, the cable has no breaks, is crimped correctly and is completely ready for work.
If any pair or several pairs of light indicators do not respond during the testing process, this means that the signal is not transmitted through specific wires and there is no contact.
Next, you need to look for the reason for the lack of contact - a broken wire, poor-quality crimping, or change the cable section being tested.

The described method is suitable for home use, where most often a LAN connection uses one piece of cable leading from the network outlet to the device. If you have a more complex network consisting of several devices and a number of cable sections, it is important to understand that in order to determine the break, you need to ring each section separately. Also, do not forget that the described operating scheme is relevant if you have the most common standard twisted pair tester at hand. To obtain detailed information about a technical malfunction, you should use a device of a higher level.

Multifunction twisted pair testers

If you have already chosen a twisted pair tester, you can buy it by placing an order with eServer. In stock you will find cable testers for any technical needs, capable of serving both simple home networks and complex cabling systems with multi-level structures. How a multifunctional twisted pair tester can differ from a less advanced one, we will tell you in more detail and point by point.

Different models of lan tester for twisted pair cables may have individual sets of capabilities, so we will describe the most relevant ones:

The advanced twisted pair tester has the ability to generate a tone. The locator function makes it easy to determine if there is a hidden cable nearby. To do this, the device must be connected to an outlet, after which it will send a signal directly to the wiring. Next, the tone generator is activated, which begins to make sounds as the device approaches the wires that are connected to the outlet.
Such a tester is able to determine the length of the cable section being tested, so there is no need for mandatory visual inspection.
A multifunctional tester can not only determine the presence of a wire break, but also indicate the location of this break.
Most often, advanced testers are equipped with a liquid crystal display, which displays the most detailed information about the current connection test. In this case, you no longer need to watch the blinking indicators; the tester simply detects a malfunction and displays all possible data on it.

A shutdown can occur without your direct participation, for example due to unstable network voltage, running unlicensed programs or a virus. To check in Win XP you need to go to: Start / Settings / Control Panel / Network Connections and make sure that the connection is connected. Less often, but it also happens, the network card driver does not work correctly. You can check: Start / Settings / Control Panel / System / Hardware / Device Manager / Network Cards. There should be no warning signs.

Program for checking Internet access
Network Traffic Monitor

Search engines often search for the answer to the question: “a program for testing twisted pair cables.” On a computer with Windows system There is already a program that displays the message “Network cable is not connected” if there is a break or short circuit in the twisted pair cable. You will have to look for the location of the break or short circuit yourself; there is no program that would indicate the exact location and cause of the malfunction. There are special testers for this, for example MicroScanner Pro.

It’s another matter if there is a connection to the Internet, but it is unstable or the download speed has suddenly dropped. To monitor network traffic, there is an excellent free program, or rather a utility called Network Traffic Monitor.

It allows you to measure data transfer speed in real time, observe changes in speed over time, save data on a hard drive, rubber windows, extensive customization options and many other useful services. Supports many languages, including Russian.

Installing the program on your computer is simple, just run the EXE file and press the confirm button several times. Network will automatically be added to startup and will monitor and save all data. To display any of the windows on the monitor screen, just right-click on the tray icon and select the desired window. Network Traffic Monitor is the best utility for analyzing and diagnosing network quality that I came across during my search. I have tested the functionality of the Network Traffic Monitor program with Windows HP and Windows 7. You can download the Network Traffic Monitor program with one click from my website.

Diagram of connecting a computer to a network
UTP twisted pair cable

To check a twisted-pair cable, it is advisable to competently imagine the electrical diagram of how a twisted-pair cable connects a computer’s network card to other devices, a hub, a switch or another computer. The figure shows a diagram of a section of the network connecting a computer to active equipment, a hub or switch.

Range and shape of the information signal
twisted pair cable

How to find a break in a UTP twisted pair cable

There are several ways to find a break in a twisted pair cable: external inspection, continuity testing with a multimeter or pointer tester, and folk methods.

Checking the twisted pair cable by external inspection

Checking a UTP cable should begin with an external inspection of the cable along its entire length; special attention should be paid to the quality of crimping in RJ-45 plugs. If crimped carelessly, the conductors may not be inserted into the plug all the way, and the contact will be poor. Or the conductors overlap with each other at the point of fixation (this happens with the green pair, since its conductors are crimped at a distance of two contacts) and the twisted pairs can short-circuit in this place. If a visual inspection does not reveal a fault, then it is necessary to test the twisted pair cable.

Checking a twisted pair cable with a tester or multimeter

The photo shows a twisted pair cable crimped into an RJ-45 connector according to color-coded option B.

Checking UTP twisted pair cable without devices

The twisted pairs of the opposite end of the cable are connected in series to the poles of any battery or power source with a value of more than 3 V. If the salt concentration in the heated water is very high, 1.5 V will be sufficient. This voltage is produced by any AA battery, for example from a TV remote control. A battery from a cell phone will work well; it has a voltage of about 3.7 V. A battery from the motherboard will also work, it has a voltage of 3.2 V. If you have a 50-100 Ohm resistor, it is better to connect the battery through it to protect the case of short circuit of twisted pairs. The polarity of the connection does not matter.

The telephone network can be used as a power source. The voltage in the telephone network is about 40 volts and the current is constant, limited at the telephone exchange to 40 mA. This connection is safe for humans and the telephone line. This option is convenient to use if you need to supply voltage to a twisted pair cable in a hallway where there is a telephone box nearby.

Any charger from a cell phone, a USB port on a computer, will be suitable for testing; there is 5 V at the outer terminals. It is not permissible to connect to USB without a current-limiting resistor; you can damage the computer. To test twisted pairs, a current of 2 mA is sufficient.

After applying voltage, the following picture will be observed at the opposite ends of the twisted pair, which are in water.

The connector is immersed in a saline solution to such a depth that the contacts are completely submerged in water. Twisted wires are connected to the battery.

Depending on the results obtained, you will have to crimp or splice the wires.

Checking a twisted pair cable using a potato

Just for fun, I poked the wires into the slice of an apple. Not so obvious, but it is obvious that the wires are in order.

Using the described twisted pair testing method, you can check wires of any type, cross-section and length.

When carrying out electrical installation work, it may be necessary to test the cable, for example, when marking cores and wires, checking the insulation and integrity of the wiring, as well as searching for a broken electrical cable. Let's consider the ways in which 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 a break or electrical connection between its wires (short circuit), the continuity test can be done with a tester based on a battery and a light bulb, or you can use a multimeter for this purpose. The latter is preferable.

Despite the fact that the price of a multimeter is higher than a primitive device, we recommend buying it; this device will always be useful in the household.

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

The testing methodology is as follows:

When checking a wire for a break, 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 picture:

A – electrical 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 wires together and ring the wires at the other end;

when checking the presence of an electrical connection between the cable cores, 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, no beep will sound).

Testing multi-core cables for the purpose of marking them

When marking multi-core cables, you can use the methods described above, but there are ways to significantly simplify this process.

Method 1: the use of special transformers that have several secondary winding taps. The connection diagram for 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 network, one end of the secondary winding is connected to the protective shield of the cable, and the remaining terminals are connected to its conductors. To mark the wires, it is necessary to measure the voltage between the screen and each wire.

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

To identify 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 in increments of at least 1 kOhm to reduce the influence of 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 multi-core telephone cable, installers often use a dialing headset, for example TMG 1. Actually, these are two telephone handsets, one of which is connected to a 4.5 V battery. Such a simple device allows you not only to check the cable, but also to coordinate your actions during installation and testing.

Insulation check

To test 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;
connect the probes to the wires and see what the device display shows. Considering that the wires have a certain capacitance until it is charged, the readings may vary. After a few seconds, the device display can display the following values:
one, this indicates that the insulation between the wires is normal;
zero – there is a short circuit between the cores;
some average readings, this can be caused either by a “leak” in the insulation or by electromagnetic interference. To determine the cause, switch the device to the maximum range of 200 kOhm. 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 the electrical wiring, it must be de-energized. The second important point is that when taking measurements, do not touch the probes with your hands, this can introduce errors.

Video: Wire continuity check - integrity check.

Finding the break point

After a break in the electrical wiring has been discovered, it is necessary to localize the place where it happened. For dialing in this case, you can use a tone generator, for example, the Cable Tracker MS6812R or TGP 42. Such devices allow you to determine the location of the break with centimeter accuracy, as well as determine the route of hidden wiring; in addition, the devices have other useful functions.

Devices of this type include an audio signal generator and a sensor attached to an earphone or speaker. When the sensor approaches the place where the UTP cable pairs or electrical wiring wires are broken, the tone of the sound signal changes. When a tone test is performed, the wiring must be de-energized before connecting the sound generator, otherwise the device will be damaged.

Note that with the help of this device you can test both power and low-current cables, for example, check the integrity of twisted pair cables, radio wiring or communication lines. Unfortunately, such devices will not allow you to determine the correct connection; special equipment is used for this purpose - 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 Internet provider networks. These can be simple devices that check crossover 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 does not encourage their household use.

Homemade contactless dialing

Below is a diagram of a simple non-contact break detector; it can be assembled within one evening. Considering the small number of parts, you don’t have to bother making a printed circuit board, but use wall mounting.

List of required radio components:

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

The circuit can be powered from a source with a voltage of 2 to 5 volts.

The dipstick (P) is made on the basis of a regular spoke from a bicycle wheel.

Properly assembled contactless cable testing does not require adjustment.

Video: Do-it-yourself cable testing. How to test wires using a light bulb and battery

Computer tips for novice users

Algorithm of actions

Troubleshooting

Fault Analysis

Checking twisted pair breakage and insulation integrity

Tester

Multimeter

Regular potatoes

Conclusion

Program for checking Internet access Network Traffic Monitor

Diagram of connecting a computer to a network UTP twisted pair cable

Range and shape of the information signal twisted pair cable

How to find a break in a UTP twisted pair cable

Checking the twisted pair cable by external inspection

Checking a twisted pair cable with a tester or multimeter

Checking UTP twisted pair cable without devices

Checking a twisted pair cable using a potato

Functionality of twisted pair testers

How to use a twisted pair tester

Multifunction twisted pair testers

Program for checking Internet access Network Traffic Monitor

Diagram of connecting a computer to a network UTP twisted pair cable

Range and shape of the information signal twisted pair cable

How to find a break in a UTP twisted pair cable

Checking the twisted pair cable by external inspection

Checking a twisted pair cable with a tester or multimeter

Checking UTP twisted pair cable without devices

Checking a twisted pair cable using a potato

Methods

Testing multi-core cables for the purpose of marking them

Insulation check

Finding the break point

Cable testers

Homemade contactless dialing

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