Dear Forum Members,

This thread is related to measuring several thousand Amperes of current using 8051 and controlling a process using the current feedback.

I would like to draw your kind attention towards a thread that I started some 6 months ago here is the link http://www.8052.com/forum/read.phtml?id=68903

Finally I have made two rogowski coils with following specifications.

Former Material - PVC [ Solid ].
Former Diameter - 5.6mm
Cu wire used for winding - 36 Guage armature winding wire.
Coil diameter after winding - 6mm
Length of coil when straight - 22 inches.
Number of turns - 2000.

Both the coils are made identical with very carefully winding [done manually] I tested these coils today with a resistance brazing machine output. & They produce following results.

Current Being measured - 1100 Amperes steady 50 Hz AC current.
The voltage across rogowski coil 1 : 90.5mV [RMS] AC
The voltage across rogowski coil 2 : 96.2mV [RMS] AC

I tested the two coils at other current values as well but in all cases coil2 showed higher voltage across terminals. I know whatever care is taken two coils can never be identical & thus it is not possible to have interchangeability with such coils. I have heard of some technique in which a resistor is used to bring interchangeability with these rogowski coils but don't know what exactly is that technique. If you friends can please help me with this trick/technique it will be a great help. Once I complete this project very soon I will post a detailed current measurement technique that can be used to measure several thousand amperes with good accuracy (less than 1% tolerance) and no analog integrator needed. Yes no analog integrator since I use the micro itself for integrating the rogowski output getting current and than find rms with this current all with software. Friends now the only hurdle left in this project is to some how achieve coil interchangeability. Thanks a lot to all of you for your kind support and cooperation.

Thanks & Regards,
Prahlad Purohit