Magnetom. coil tune cap?

I am out here in the middle of nowhere with no one to ask about this.

I need to wire up a magnetometer sensor coil. It is about the size of

2 beer cans end-to-end and, since it is full of thin wire, weighs about the same.

Measured resistance is 142 Ohms.

I need to tune it to a bandwidth of 2-40Hz for Earth micropulsation readings. It is attached to a high gain instrumentation amp.

Without doing elaborate calculations, can anyone give me a ball park figure for a mylar cap value to put in parallel with the winding?

I have no equipment on hand to test the response but can hopefully tell from the readings if I get close enough.

Noel Wilson

Furthermore, one needs to know the *inductance*; the resistance is not relevant, unless it is excessively high.

You can't resonate it with a cap and get over four octaves of bandwidth. They may use shunt capacitors just to trap out signals from radio stations that may cause your inst amp to do strange things. Try a .001uF cap. With 147 ohms of coil resistance, that should give you about 40 dB of attenuation at lower AM broadcast band freqs.