Types of current clamp
– Current transformer: Comprises a split ring made of ferrite or soft iron with a wire coil wound around it.
– Iron vane: Uses a moving iron vane that is directly affected by the magnetic flux in the core.
– Hall effect: More sensitive and able to measure both DC and AC, up to the kilohertz range.
– Rogowski coil: Resembles a current clamp and gives a voltage proportional to the rate of change of current.
– Clamp meter: An electrical meter with integral AC current clamp used by electricians.
Current transformer
– Works only with AC or pulse waveforms.
– Can be used in reverse to inject current into the conductor.
– The subject conductor forms the primary winding and the coil forms the secondary.
– Used in electromagnetic compatibility susceptibility testing to induce an interference current.
– Requires a specifically designed injection probe for this purpose.
Iron vane
– Measures both AC and DC and gives a true root mean square (RMS) value for non-sinusoidal AC waveforms.
– Limited to power transmission frequencies up to around 100Hz.
– Usually fixed directly to the display mechanism of an analogue clamp meter.
– The calibration of the instrument is non-linear.
– Provides accurate measurements for non-sinusoidal or distorted AC waveforms.
Hall effect
– More sensitive and able to measure both DC and AC, up to the kilohertz range.
– Often used with oscilloscopes and high-end digital multimeters.
– Increasingly common for general use.
– Provides accurate measurements for various waveforms.
– Suitable for measuring low currents, with units available that can read down to 1mA.
Rogowski coil
– Resembles a current clamp and is used in clamp meters and power monitoring loggers.
– Better linearity and flexibility due to having no core to saturate.
– Does not require any magnetic or electrical contact at the opening end.
– Gives a voltage proportional to the rate of change of current in the primary cable.
– Requires additional signal processing before displaying the sensed values. Source: https://en.wikipedia.org/wiki/Clamp_meter
In electrical and electronic engineering, a current clamp, also known as current probe, is an electrical device with jaws which open to allow clamping around an electrical conductor. This allows measurement of the current in a conductor without the need to make physical contact with it, or to disconnect it for insertion through the probe.
Current clamps are typically used to read the magnitude of alternating current (AC) and, with additional instrumentation, the phase and waveform can also be measured. Some clamp meters can measure currents of 1000 A and more. Hall effect and vane type clamps can also measure direct current (DC).
