MPP Rev-D ‘Falsing’ on end of swing.

[green]

If Main & Sec samples widths are the same then all is good. Exact width is not that important.

There are discussions in the threads on this forum about what and how the integrator works. I just don't have links.

Since the main & sec sample widths are the same then re-check that the integrator Caps and resistors MATCH. That is the RC on the Op-amp Feed back (out to inverting in match the RC on the non-inverting in to ground). A mismatch of these components can cause the same effect as mismatched main vs sec sample widths. Again Exact values are not important but values Matching is very important.

Some detectors have a pot in series with input resistors to balance EF. Does anyone know how close(out to inverting in match the RC on the non-inverting in to ground)needs to be?

[waltr]

The Hammer Head I built has a pot to balance integrator inputs (pre-amp out to pot wiper, then each pot end into invert and non-invert integrator).
This is a touchy adjustment to get it working best so fairly critical. The pot has a much lower value than the integrator input Resistors so doesn't do much of a change.

If I remember correctly, to adjust this set sample delay out a bit (not minimum) then look at integrator output with O'scope.
The adjust so the two samples (main & EFE) give the same change but opposite direction.

May also be possible to look with scope on the sampling switch outputs and adjust so amplitude of each, when switch is on, to be the same but opposite direction.

These two samples are now Canceling each other so any EF affects should also cancel.

[Goaty]

Thanks for your info waltr.


I feel I am closing in on what needs to be done but don’t quite have the knowledge about the functioning of the circuit at a component level to tackle it. I understand what this section does but not how it does it.


You said - “ re-check that the integrator Caps and resistors MATCH. That is the RC on the Op-amp Feed back (out to inverting in match the RC on the non-inverting in to ground” and this is the part that I am having trouble getting my head around.
I think I will have to do a bit more study on op-amps first!


I noticed that Qiaozhi has posted an LTSpice simulation of the MPP sampling integrator but have never used a circuit simulator and unfortunately don’t really have the time to get into it at the moment.

[waltr]

Read this thread:
http://www.geotech1.com/forums/showt...ose+integrator