Problems with building P.I. Treasure Hunter

[DerrickLail]

I am a senior at Western Carolina University and for my senior project i am building a magnetometer that will go on an underwater autonomous vehicle. To get a better understanding of P.I. magnetometers i am currently building a magnetometer using the Treasure Hunter plans. I have the front end of the circuit breadboarded however the induced voltage signal is ringing like crazy instead of being critically damped as shown in his documentation. If anyone could help it would be greatly appreciated.

[Sid]

I met this problem once. The ringing was independent on damping because the ferrite core showed some magnetostriction. Could it be this case? Sid

[Carl-NC]

Are you using an Ace-type breadboard?

[DerrickLail]

Yes, i am using an Ace type breadboard. Also i mispoke earlier, when i look at the actual induced voltage signal at the search coil it is critically damped. However, when i look at it after it has gone through the clipping diodes it is ringing very badly.

[Carl-NC]

Plug-in breadboards have horrific capacitance between rows... try spreading out the input components to the opamp. Sometimes, I ground every other row of contacts to prevent feedthrough.

- Carl