Working principle

As the name suggests, TC or Dietze pliers are designed to measure the AC current in a circuit without breaking it. The operation of the current measuring instrument is based on the principle of a simple current transformer. In this case, the primary winding is a bus or cable with a measured current, and the tick pick, inside which there is a multi-turn winding, wound on a magnetic core made of ferromagnetic material, is the secondary. The alternating current in the wire (primary coil) creates an alternating magnetic field, the lines of force of which pass through the secondary winding, which excites an emf in it, proportional to the magnitude of the current in the primary coil. Thus, by measuring the resulting EMF, one can find the current strength in the first coil (wire).

Building

Modern multimeters, regardless of the manufacturer or modification, contain the following elements: magnetic cores with a movable lever, a switch for measuring measuring ranges, a display, output connectors for probes (in this case, the multimeter can be used as a regular multimeter) and a button for selecting Current measurements (image below)

Most modern current meters also include an internal transformer with a diode bridge. In this case, the terminals of the secondary winding are connected across the shunt. Depending on the range of measured current strengths, the current meter can be one-handed (for voltages up to 1000 V) and two-handed with additional insulated handles (for voltages from 2 to 10 kV inclusive). Current metering devices designed to measure more than 1 kV have an insulating length of less than 38 cm, and handles of at least 13 cm.

As a rule, the safety class and maximum current are indicated on the device case. For example:

• CAT III 600 V – this means that the device is protected against short-term surges in equipment during operation in fixed networks with a voltage of up to 600 V.
• CATIV 300 V – This means that the device is protected from power surges within basic level equipment for power supply voltages up to 300 V. An example of such equipment is a traditional electric meter.

Work safety rules

Mounting meters can only be used indoors or outside in dry weather. The strength of the current can be measured on both insulation-sheathed cables and bare cables. Before use, a person needs to wear protective gloves, put an insulating base under his feet and wear special shoes.

Measurement command

As a rule, the use of measuring instrument meters does not cause special difficulties. Before using the tool, it is worth paying great attention to safety measures, as mentioned earlier.

How to use the measuring instrument meters:

1. Set the desired range on the switch.
2. Press the button to open the magnetic circuit.
3. Install one connector in an AC or DC network (if the device supports this feature).
4. Position the current meter perpendicular to the direction of the wire.
5. Read the offer.

The difficulty of using instrument meters often lies in the isolation of a single conductor: when trying to take readings from a conventional cable coming from an outlet, zero should be displayed on the display. This is because the currents of the phase conductor and the neutral conductor are equal in magnitude and opposite in direction. Thus, the magnetic fluxes generated by them are mutually compensated. If the current readings are non-zero, this indicates the presence of  a circuit leakage whose value equals the value obtained. Therefore, for measurements, you need to find a place where the wires are separated and highlight one core. As such, you can use a switchboard or place to connect the phase wire to the circuit breaker. However, this cannot always be done, which limits the range of instrument meters.

If a unit is displayed on the screen during measurements, this indicates that the current in the wire is outside the measurement range. In this case, it is necessary to increase the range of current measurements with the switch. When taking measurements in hard-to-reach places, you can use the Hold button. With its help, you can record the result of the last measurement. By pressing Hold a second time, you can reset the value.

Useful “trick”.

If it is required to measure a small value of the current strength, it is necessary to make several turns of the wire on an open magnetic circuit, setting the range switch to a minimum. Next, it is necessary to take readings, and, determining the actual value, divide the resulting number by the number of wound cycles.

Example of use

Below is an example of how meters are used when measuring the load in a 220 V network, for example in an apartment. In this case, the switch should be set to the AC 200 position. Next, with the current measured, hold the insulated conductor and take the readings. Next, the obtained value of the current strength must be multiplied by the voltage in the 220 V network. For example, if the device shows 5 amperes, the power consumed in the network will be P = U * I = 5 * 220 = 1100 watts or 1.1 kW. The obtained value can be used to check the operation of electricity meters.