TX coil saturation formula

[bklein]

I came across this discussion:
http://www.daycounter.com/Calculator...lculator.phtml

In our use of the coil as a TX coil head, do we consider the coil as having a variable core material - air when above ground and ground mineralization content when close to the ground? Thus placing the coil near the ground affects its inductance?

Has anyone done tests where you drive the coil with a squarewave signal and look at the current waveform with a scope to determine the saturation point? I wonder if this would be a tool for us to optimize the TX coil design and pulse timing parameters for our given coil and also perhaps explain issues some people are having with MOSFETs getting hot in their tests (coil inductance too low).

Barry

[chemelec]

I came across this discussion:
http://www.daycounter.com/Calculator...lculator.phtml

In our use of the coil as a TX coil head, do we consider the coil as having a variable core material - air when above ground and ground mineralization content when close to the ground? Thus placing the coil near the ground affects its inductance?

Has anyone done tests where you drive the coil with a squarewave signal and look at the current waveform with a scope to determine the saturation point? I wonder if this would be a tool for us to optimize the TX coil design and pulse timing parameters for our given coil and also perhaps explain issues some people are having with MOSFETs getting hot in their tests (coil inductance too low).

Barry

Placing one of my 8" Radial, PI Coils Directly on the Ground in my yard, does Not change the Inductance by any measureable Amount, as Compared to Free Air.

But If the Soil was Highly Mineralized and the Coil in Direct Contact with it, It Might somewhat Affect the Inductance.
But Most Often, the Detector Coil is an Inch or Two, Above the ground, so it would have little, If Any effect on it.

Still, "An Interesting Calculator"!

Thanks.