Coil Field Examiner.
Coil Field Examiner.
(OP)
I would like to setup a coil field examiner to test the strength of magnetic fields from metal detector coils.
First up
Is there a difference between AC & DC magnetic field detection equipment?
What is the best cost effective method to do this simply, is there a simple circuit i can use to get the field strength to a data acquision card in a PC.
Thanks
First up
Is there a difference between AC & DC magnetic field detection equipment?
What is the best cost effective method to do this simply, is there a simple circuit i can use to get the field strength to a data acquision card in a PC.
Thanks





RE: Coil Field Examiner.
E= N * d(phi)/dt
N turns.
phi is the total magnetic flux through the coil
d(phi)/dt is the calculus expression for the rate of change of magnetic flux.
phi = flux density * area of coil
None of this works for a DC field. For a DC field you need either a Hall effect device of a GMR (Giant Magneto Resistive) device.
Hopefully these points can be googled to get you more data.
RE: Coil Field Examiner.
http://my.execpc.com/~rhoadley/magmeter.htm
As was mentioned, to detect ac what you need is a coil connected to a high impedance voltmeter (draws virtually no current).
V = d/dt (Phi) = d/dt (N*A*B(t)*cos(theta)
where N is number of turns, A is area, B is flux, theta is angle of coil plane compared to flux... we will from this point forward assume the coil is tilted until max measurement -> cos(theta)=1
V = N*A*d/dt(B)
Assuming B (and hence V) are a single frequency sinusoid with B and V representing peak values, at frequency f, then Vrms = V/sqrt(2) and ||d/dt(B)|| = ||2*Pi*f* B||
Vrms = N * A * 2 * Pi * f * B / sqrt(2)
Vrms = Pi*sqrt(2) * N * A * f * B
Vrms = 4.44 * N * A * f * B
B= Vrms/(4.44 * N * A * f)
Everything in SI units. Else add appropriate unit conversions.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Coil Field Examiner.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.