Probe, multimeter and current clamp – what it is and why these tools are needed

Electricity and electrical appliances surround us on all sides. So devices that determine certain parameters of an electrical circuit are needed today by everyone: you won’t call an electrician to check a battery or a light bulb. Which appliance is best for your most common household tasks?

There are several types of probes that differ significantly in functionality:

1. No power indicator screwdrivers with neon light or LCD indicator . This is the simplest and most inexpensive type of indicator screwdrivers, but their functionality is small.
With such a probe, you can only determine the phase wire. To do this, touch the tested conductor or terminal with a sting, pressing your finger to the contact on the handle.

If there is 220V on the conductor, the light will light up. But nothing else can be done with a probe without power – neither find the neutral wire, nor check its integrity, nor even determine the presence of a voltage below 60-70 V.

2. Indicator screwdrivers with their own battery power and a field-effect transistor circuit. Outwardly, they may be very similar to those discussed earlier, but it is quite easy to distinguish them: firstly, in models with a transparent case, batteries-tablets are visible inside.

Indicator screwdriver FIT 56531 170 *
Secondly, if you touch both the tip and the contact on the body at the same time, the indicator will light up.
HP2-I05
312-85
5V0-32.21
JN0-1332
156-585
PEGAPCDS86V1
ISMP
PRINCE2-Foundation
AIE02
NS0-603
NSE5_FSM-5.2
5V0-21.21
CISM
TCP-BW6
AZ-700

 

Thirdly, some models are equipped with a switch, which also indicates the presence of autonomous power supply.

This is already a more functional tool with which you can perform many tasks:

Phase detection – for this you need to touch the tested terminal with a sting, without touching the contact on the case. If there is voltage at the terminal, the LED will light up.
Grounding check. To check if the appliance is grounded, touch the tip of the probe to the metal of its case (you need to find an unpainted area or scratch the paint to metal in an inconspicuous place). In this case, the device must be connected to the network. If there is no ground, the LED will light up.

Determination of the neutral wire or grounding conductor. Touch the sting to the tested wire, if there is no indication, make sure that the wire is not phase. Now, pressing the contact on the probe body with your finger, touch the sting to the test wire. If it is neutral or ground, the LED will light up. If the LED does not light up, it means that the wire is not connected anywhere or is broken.

Wire breakage detection. To check the integrity of the wire, strip both ends of it, take one end in your hand, and touch the other with the tip of the probe, pressing your finger to the contact on the body. If the wire is intact, the indicator LED will light up.

Checking bulbs, fuses, heating elements, etc. To check if the fuse is intact, touch one of its terminals with your fingers, and touch the other with the tip of the probe. With the other hand, you need to touch the contact on the probe body. If the fuse is intact, the indicator will light up. Light bulbs, heating elements and other elements with free flow of electric current are also checked.

Non-contact phase detection. If you touch the contact on the body with your finger, the probe will detect the presence of voltage in the wire already at a certain distance – it is enough to bring the sting 1-2 cm to the conductor.

Finding wires in the wall. The previous method allows you to look for live wires under a layer of plaster – only not very thick, no more than 2 cm. To do this, press your finger to the contact on the body and guide the sting along the wall. In the place where the wire runs under the wall, the indicator will light up. Sometimes it is more effective to look for the wire in another way – to hold the probe by the sting and lead it along the wall close to the contact on the case. The contact area is larger than the tip area, and in this mode the probe sensitivity can be higher.

3. Non-contact probes with high sensitivity that do not require contact with the wire to determine phase or ground.

Electrical test probe CEM AC-8

[200 V – 1000 V, 180 mm]
840 *
11In stores: tomorrow
They are characterized by maximum safety, since they do not require access to bare wires to work with them. Also, with the help of non-contact probes, you can usually find hidden wiring, and not necessarily live – they can work as a metal detector.

At the same time, when working with electrical equipment or checking multicore cables, using such probes can be inconvenient, since it is difficult to separate the signal of the desired wire from the interference generated by other closely spaced conductors.

Multimeter
If the probe allows you to determine only quality indicators (there is voltage / no voltage, there is a contact / no contact), then a multimeter can find out the numerical values ​​of these characteristics. Therefore, multimeters are often used by electronics engineers, but it can also come in handy in the household.

 

With a multimeter, you can measure the exact voltage value in the outlet. To do this, set the appropriate measurement mode on it (alternating voltage – ACV, limit at least 300 V), connect the probes correctly and insert both probes into the socket. Usually one probe is connected to the common connector, the other to the AC voltage connector.

 

According to GOST, the voltage in the outlet should be in the range of 210-250 V. If the voltage in your outlet greatly exceeds the specified limits, this is a reason to call the power supply organization. Both undervoltage and overvoltage are harmful to household appliances.

Do not try to check the current in the outlet with a multimeter (in mode A) – at best, the multimeter’s fuse will blow, at worst, the wiring will melt and ignite, and the device will fail.

A multimeter can help in determining the health of a laptop power supply or other gadget with a round power connector. To do this, you need to look at the output voltage on the power supply case and set the corresponding DC voltage measurement limit (DCV) on the multimeter. 20 V is usually sufficient, but if the power supply is supplying 36 V for example, the limit should be higher than this value. After that, you should turn on the power supply to the network and touch the probes to the connector pins. Typically, one of the contacts is located inside the cylinder of the connector in the form of a pin or metal tube, and the other is outside.

 

You can not follow the polarity, if you confuse “minus” with “plus”, nothing bad will happen, just the values ​​on the screen will be displayed with a “-” sign. If after that the screen remains 0, the value is lower than that indicated on the power supply case, or it is constantly changing – the power supply is faulty and requires replacement.

Multimeter Master Professional M832

[manual, up to 1000 V, error – 0.5%, continuity check, diode check]
550 *
34 2
In stores: tomorrow
In continuity mode with a multimeter, it is convenient to determine the integrity of the wires and look for the ends of one wire in multicore cables. To do this, set the dialing mode and touch the probes to different ends of the wire. Conveniently, in most multimeters, a successful dial tone is accompanied by a sound signal, that is, you do not need to look at the device during operation.

 

You can check the batteries with a multimeter. The easiest and safest way is to check the voltage in the DC voltage measurement mode with a range of 2-20 V (depending on the rated voltage of the battery). For a fully charged “finger” or “little finger” battery, the voltage should be in the range of 1.4-1.6 V. Slightly discharged cells can give a voltage of 1.2-1.4 V, and completely discharged – 1.1 V or less …

 

However, this method is not highly reliable – batteries that give 1.4 V may well get caught, while practically not retaining their charge. A more reliable way is to measure the short-circuit current. It is necessary to switch the multimeter to the DC current measurement mode at the maximum limit (10-20 A, you may need to move the probe to another socket on the multimeter) and briefly touch the battery poles with the probes. You need to touch until the maximum value on the scoreboard is reached, but in any case, no longer than 1.5-2 seconds. It is recommended to check only batteries in this way, battery cells can have a high short-circuit current, which will lead to a blown fuse in the multimeter and damage to the battery itself.

 

A short-circuit current of 3-6 A indicates that the battery is charged and can be used in gadgets with high power consumption: flashlights, digital cameras, toys with electric motors, etc.
A battery with a short-circuit current of 2-3 A can also be used in electrical appliances with low energy consumption: remote controls and radio controls, electronic clocks, thermometers, etc.
A short-circuit current of 1A or less signals a low battery – in the remote control it may also work, but not for long. It makes no sense to put such batteries in anything more power-consuming.

CEM DT-9908 multimeter

[manual, up to 1000 V, error – 0.5%, continuity check, diode check, temperature measurement, display backlight, auto power off]
3 999 *
7 1
In stores: tomorrow
Also, a multimeter can more accurately determine the health of heating elements of boilers, kettles, washing machines and other equipment than when using a probe. First you need to turn off the power to the electrical appliance and remove its cover to gain access to the heating element. It is not worth checking the integrity of the heating element through the plug of the power wire – in a de-energized state, the power circuit can be interrupted by the electronics of the device, and no check will work. Next, you should disconnect the wires suitable for the terminals of the heating element so that other elements of the device do not distort the measurement results. Next, you should check:

Resistance between TENA terminals in resistance measurement mode with a limit of 200 Ohm. Depending on the power, it can be from 20 to 60 ohms, but in any case less than 200.
If the resistance is close to 0 (0-2 ohms), there is a short circuit in the heating element, you cannot use it. High resistance indicates a break in the heating element.

Resistance between the body (ground) and the heating element terminals in the resistance measurement mode with the maximum limit. The device should show the maximum or measurement error.
Any positive value below the upper limit, in principle, indicates the breakdown of the heating element onto the case and the unsafe use of it. In general, the insulation resistance has quite finite values, but household multimeters cannot measure it.

The windings of electric motors are checked according to the same principle. Unless the spread of resistances of serviceable windings is higher – in low-power electric motors it can be in units of Ohm, in motors more powerful – tens and hundreds.

Also, a multimeter can measure the characteristics of various electronic components – capacitors, diodes, transistors, etc., but this is a topic for a separate article.

Current Clamp
Sometimes it becomes necessary to measure the current (or power) consumed by an electrical appliance. Theoretically, the current can be measured using a multimeter, but in practice this is not always possible. First, not all multimeters are capable of measuring alternating current. Secondly, thin standard wires are not suitable for measuring currents from 1A and above in a 230 V network – they have too high resistance. Thirdly, measuring the current with a multimeter is associated with the danger of electric shock, since for measuring the device must be included in the break of the power circuit. Therefore, it is much easier and safer to use a current clamp .

 

Modern current clamps are usually a versatile tool and can function as a conventional multimeter. Accordingly, you can do everything listed in the previous section with them.

Clamp meter UNI-T UT210B True RMS

[manual, up to 600 V, error – 2.5%, continuity check, diode test, display backlight, auto power off]
2 199 *
3In stores: tomorrow
The main difference between such a device is those very clamps – a non-contact current measuring coil. To measure the current with a clamp, it is not at all necessary to open the circuit – it is enough to place a single wire inside the coil. This is the main inconvenience of measurement – usually, for electrical equipment, the neutral and phase conductors are laid in the same cable under common insulation. Therefore, for the convenience of using a current clamp, electricians often use a specialized (usually homemade) extension cord with separate wires.

 

With the use of such an extension cord, current measurement with a clamp is an absolutely safe and simple procedure.