Which integrator

[green]

This was posted by Eric. The same principle is used in Minipulse, Superscan, etc.
Notice the 200R (100R) trimmer, it may help balancing the signal. I would try diff. op amps, different switches.
Try different delay for EF sample.

http://www.geotech1.com/forums/showthread.php?20470-Integrator-Circuits-for-PI&p=171421#post171421

Might be the reason I've been using the #2 integrator. He didn't get to (more on that latter). Reply #1 is the same as your image.

http://www.geotech1.com/forums/showthread.php?21236-Replies-to-Minipulse-Plus&p=195781#post195781

Was trying to calculate gain and frequency response for the track and hold integrator. Not sure the calculations are correct. I've been trying to add GEB and I think changing sample time doesn't change gain so I think track-hold integrator is not a good choice.

Some of the PI's use integrator #1. Matching caps and resistors wasn't a problem. I still don't see why it doesn't cancel the magnet better.

[eclipse]

This was posted by Eric. The same principle is used in Minipulse, Superscan, etc.
Notice the 200R (100R) trimmer, it may help balancing the signal. I would try diff. op amps, different switches.
Try different delay for EF sample.

[green]

Including schematic for #1 and #2 integrators. Have been using #2 integrator. Looked good except for some output offset. Think switch charge injection was causing some of it. Tried #1 integrator. Matched caps and resistors. everything looked good until I wiped a magnet across the coil. For some reason I can't get integrator #1 to cancel the magnet even close to integrator#2. Is there something about the two integrators that would cause integrator #2 to cancel the magnet better or is there something I'm missing?