To assist with the understanding of how the EA002 2,10, 50 turn clamp coil adapter operates we have filmed a short video demonstrating how multiple turns of wire increase the magnetic field causing a clamp meter to read higher currents.




The Transmille EA002 coil works on the premise of multiple loops of wire increase the size and force of the magnetic field radiated by current flowing in a single conductor. By making multiple winding's, the current can be multiplied by the number of windows (i.e. 10)


To verify the number of turns inside an EA002, simply pass a higher current (as in the video 10A) through a single conductor and measure this with a clamp meter. Then put the divisor through the coil (in this case 1A) and verify that the multiplication factor is correct.


A turn of a coil cannot be incomplete, so it must be a full number (i.e. 9 or 10, it cannot be 9.5 turns). Even low cost clamp meters have suitable resolution to identify if a turn is missing.


For example, in a faulty coil the 50 turn winding has actually only been wound with 49 turns.


We verify our clamp meter at 19A through a single conductor, and then apply 380mA to the 50 turn winding of the coil


The clamp meter originally read 18.8A against the single conductor, however it is now reading 18.6A, a 200mA difference, or 0.2 counts if the clamp meter only has a resolution of 100mA.


This is easily identifiable as an error, as it is outside of the repeatability and alignment errors of the clamp itself.


Most 17025 bodies accept that the number of turns that a coil has is a physical property that does not change with time, current level or with frequency. Therefore Transmille reccomend that unless your quality system necesitates it, the EA002 coil does not need re-calibration/re-certification unless it has been physically damaged.


Unless the case is pried open, or excessive current is applied (which would result in an open circuit rather than a shorted turn), if the coil was manufactured with 50 turns then there will be 50 turns from that point forwards. The variables are your current source which may be varying in its current output with the load that is being applied, but this can be verified by connecting a multimeter in series with the current, verifying the current which is being applied to the clamp coil adapter.