Minipulse Plus Rev My time has come!

[6666]

C24 is not needed

[mushaba]

Thanks guys for spending your time trying to spread your knowledge!!As i said before please be as patient as possible for each one...

Another question,what is the difference between Earth Field Elimination and Ground Balance??

A few posts back:

Question of the day,how does the EFE work?I imagine it takes a sample of the field,then invert it and substract it from original sample?To achieve that it should drive three op-amps one with sample another to produce the inverted sample and a third to substract them?

The main sample will contain a signal from the target plus a contribution from the Earth field. The EFE sample is usually taken a few hundred microseconds later, when the target signal has substantially died away, whereas the EF signal will remain the same. By subtracting the EFE sample from the main sample you are then left with the target signal.

The thing i cant get sometime now and i need help is how the EFE signal is the same during first sample and EFE sample,isnt it an ac signal??How it can stay exactly the same a few hundred microseconds later??There must be something left of the EFE after the substaction..There goes GB??

[waltr]

As George stated: "The EFE sample is usually taken a few hundred microseconds later" than the main sample ", when the target signal has substantially died away".

Think of the EF as causing an OFFSET to the entire time of TX off. This offset is caused ob moving the coil through the Earth's Magnetic field which induces a current to flow in the coil wires.
Since the sampling cycles (pps rate) is quite quick and your swinging the coil is much slower then this EF current is close to a steady DC offset. So a late sample (EFE) subtracted removes the offset and leave the signal from a target's eddy current decay.
The other reason to do and EF sample is that the current flow in the coil is in one direction when you sweep the coil to the left and the opposite direction when sweeping the coil to the right. Without subtracting the EF sample there can be a 'target detection' at the ends of each coil sweep.

GEB sampling is typically done at a different time and when there is still a response from minerals in the ground. However, the EF & GB samples can be combined and taken and various times.

Check the three sample GEB method in my HH2 thread (following the links on the theory) for a discussion.
https://www.geotech1.com/forums/show...ake-on-the-HH2

Then study the TDI timing and circuits on when the samples are taken and how these are processed. TDI schematic attached.
The TDI does do two EFE samples (D,B) and then combined with two GEB samples(A,B). The "main" samples are C with A detecting longer TC targets.
Also the SD2000 timing and circuits. Also attached.

TDI PRO PROTO.pdf
Full SD2000 schematic Part one.pdf
Full SD2000 schematic Part two.pdf

[waltr]

Forgot about this paper that covers GB in detail. It starts with VLF but then goes into PI detectors.
https://www.minelab.com/__files/f/11...S_&_THEORY.pdf

[mushaba]

Thanks waltr thanks a lot you gave me a lot to study.Day by day I understand more why Pi's constructed this way!