How to Measure Current with a Clamp Meter

This article introduces you to a clamp meter, who use them, and why they use them. We will explain the different features and various functions of a clamp meter.

How to Measure Current with a Clamp Meter

What is a clamp meter?

A clamp meter is a kind of test equipment. It is also known as Tong Tester. A clamp meter is the most straightforward equipment to use and operate efficiently. The main function of this device is to measure a live conductor in the circuit without damage or power loss. A clamp meter can measure a high value-current in a component without turning off the circuit power. The negative drawback of the tong tester meter is the “accuracy” is significantly low.

This convenient device uses to measure current efficiently and safely without using test leads, known as a clamp meter.  We know that the magnetic field can occur when the current flows throughout a conductor.  This device uses the magnetic field, which can be detected to provide the reading of the corresponding current.

These devices do not disrupt the current flow so that the technician can measure very safely and very quickly.

Read more: Best Clamp Multimeter For Electricians

Working principle of a clamp meter

The working principle of the clamp meter is the magnetic induction principle, to create AC measurements,  without contact the flow of current throughout a wire. It generates a magnetic field hall, that effect sensor, mainly detects the magnetic field that is caused by the flow of current, to cause less voltage across the sensor.

Clamp meter construction

The construction of this meter can do by using different components which are discussed below:

Jaws or clamps transformer

Clamps or jaws are used to detect the magnetic field. While the current flow in the conductor.

Camp opening trigger

A clamp opening the trigger is used to open or close the clamps power switch. The power switch is used to switch on or off the meter.

Backlight button

The backlight button is used to activate the LCD display, to read the displayed value easily at night or in dark places.

Hold button

The hold button mainly holds the final value on the LCD display.

LCD display

The LCD display is used to show the measured value.

Functional rotary switch

This switch is used to choose the current based on the range and type being measured.

Read more: Best Multimeter For HVAC

How do a clamp meter measures A/C current?

Clamp meters measure alternating and direct current or in combination. It consists of static D/C and charging D/C, and charging A/C voltage. Clamp meters measure D/C voltage using Hall effect sensors. A Hall effect sensor is a kind of magnetometer, and It can sense the strength of an empowered magnetic flux.

Like a simple induct sensor, the Hall effect sensor will work when the empowered magnetic flux is static, not changing. It will work for alternating magnetic fields as well. A clamp meter contains a toroidal iron core that clamps together with a Hall effect chip in the gap between the two halves. The induced magnetic flux from the current-carrying wire is channelled through it.

What do a clamp meter measure?

Alternating current (AC) and Direct current (DC), voltage, resistance, continuity, and, with some models, direct current, capacitance, temperature, frequency, and more tests are done.

Steps to follow while measuring A/C current with a clamp meter

  • For the measurement of current, we are taking a lamp with a wire.
  • The neutral and current wire should be split or separated to clamp around both the cables separately.
  • First of all, turn on the clamp meter and set the dial meter to 20 amps A/C.( Amp clamp meter measures A/C current in 1 conductor) At the end of the lamp wire, it is attached to the plug.
  • Now plug in the outlet.
  • We will clamp the meter around both the wires.
  • Nothing is measured at zero. This is because the current in the neutral wire cancels out the current in the phase wire.If we measure current in the separate wire, neutral wire gives the reading of 0.3 Amps energy consumed.
  • Phase wire also giving us the reading of 0.3 Amps with the lamp ON.
  •  when we turn off the lamp, the reading on the clamp meter screen is zero, which means no amps consumed.
  • Similarly, we are testing the same process on a laptop. Again, we will attach the laptop plug to the same two-line splitter, the consumer is a laptop, and our outlet is 220Volts.
  • We will turn ON the laptop, and the clamp meter is around a single splitting wire showing a reading of 0.18 Amps.
  • When the laptop is turned ON, when we take out the plug, the reading is zero. Or we clamp around both the wire; the reading is zero.
  • 0.18A x 220V = 39 watts. This is how we calculate the consumed amperage and 39 watts of current.

Likewise, we may check as many appliances of household usage. The measured value is slightly influenced by the positioning of the wire inside the clamp meter.


How does the clamp meter measure current?

Clamp meters perform the principle of magnetic induction to make non-contact A/C current measurements. Electric current flowing through a wire circuit can produce a magnetic field.

Can we measure D/C current with a clamp meter?

Hall Effect clamp meters could measure both A/C and D/C current up to the kilohertz (1000 Hz) range. Like current transformer types, Hall Effect clamp meters use jaws to concentrate the magnetic field that encircles the conductor measurement.

How do you measure power using a clamp meter?

We need a clamp meter, can test A/C power. By using clamp meter to check A/C current and Voltage probes connected to the line.
Measure current x voltage= VA which is the total power.

Why do we use a clamp meter instead of a multimeter?

Clamp meter can protect electrician from the old school of thought; cut the wire and test the voltage and current through probes. It is more safe time saving and convenient.


In this article, we have described a clamp meter. What is a clamp meter, and why it is being used? The most important features of a clamp meter. We explain to you in detail what are the working principles of a clamp meter.

 We have given some examples; complete procedure to test the current of a lamp and a laptop. You can check many appliances like a mobile phone charger, Iron, and kettle. These practicals tell you how to measure current with a clamp meter and what else we can measure with a clamp meter. Meanwhile, we show you how to calculate current, voltage and total power used by appliances.

The article is very informative, to learn to measure voltage and current with a clamp meter. In addition to this, its calculation and various functions and application of a clamp meter will tell you the significant usage of this device. Here is the list of some best-featured clamp meters one should be delighted to buy them.

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