What Is a Leakage Current Meter?
A leakage current meter is a device that measures leakage current from electrical equipment. Generally, it is a clamp meter that can measure minute currents of mA or less.
Uses of Leakage Current Meters
Leakage current meters are used in electrical equipment and medical devices. Generally, they are used to determine whether they conform to the standards outlined in laws and regulations.
Leakage current has a significant impact on the human body, and even a weak leakage current can lead directly to death, so accurate measurement is necessary from a safety perspective. It is also important from the viewpoint of quality because it can cause noise in communication equipment.
Principle of Leakage Current Meters
Leakage current meters are capable of non-contact measurement with circuit conductors and measure current by clamping a copper wire with a clamp meter.
The principle of current detection is to detect the magnetic field generated by the current and extract an output proportional to the measured current. The most common detection methods include the CT method, Rogowski coil method, Hall element method, and fluxgate method.
The principle of each method is as follows.
1. CT Method
This method converts the current to be measured into a secondary current corresponding to the turn ratio.
2.Rogowski Coil Method
This method converts the voltage induced in an air-core coil by an alternating magnetic field created around the current to be measured.
3. Hall Element Method
This method combines the Hall element and CT methods to measure from DC current.
The Hall element is an element that measures the voltage generated when a current flows through a point where a magnetic field is generated, and this method is the mainstream for DC measurement.
4. Fluxgate Method
This method combines the fluxgate (FG element) and CT methods to measure DC current.
The fluxgate is an element that measures the magnetic field generated by winding two coils in opposite directions around an iron core and calculates the current value backward from the magnetic field.
Difference Between Leakage and General Ammeters
The most important feature of a leakage current meter is its resolution.
Ammeters that measure load currents measure large currents of 1A or more in the case of the clamp method. leakage current meters, on the other hand, need to measure weak currents, so they can only measure weak currents of 1A or less.
There are load current meters that measure weak currents for semiconductor manufacturing processes, but for such applications, devices that are connected in series to a circuit are commonly used.