Single capacitor integrator switch placement

[green]

https://www.geotech1.com/forums/attachment.php?attachmentid=50454&d=1591477213

I've spent a lot of time trying to understand the track hold differential integrator without much success. Good because it keeps the brain active, one of my reasons for being on the forum.

Think I understand a 1C integrator(output=Rfdbk/Rin*sample time*sample rate*average sample V) TC=(Rfdbk*Cfdbk). Sample rate and sample time effect output signal.

Using spice with constant 1V input with track hold differential integrator, output=1*6800/2200*((Rfdbk/(Rfdbk+10k))second stage. Doesn't appear sample time or rate effect gain with constant input. Wondering how sample time effects signal out when sampling a quarter? Don't know how to calculate TC.

[Carl-NC]

In general, slower integration can add depth but requires a slower sweep speed, and makes target responses a bit mushier. Fast integration gives a snappy response but with a little less depth.

[green]

I've always been intrigued by that circuit but have still never tried it. A cool way to have a variable TC.

Just trying to learn something. Why would I want a variable TC?

[Carl-NC]

My favourite sample and hold analog integrators [ATTACH]50454[/ATTACH]

Eric.

I've always been intrigued by that circuit but have still never tried it. A cool way to have a variable TC.

[Carl-NC]

I think it was one of those EDN design notes, possibly in one of their collection books. Is there a site that may have all these old design notes books online?

EDN has the Design Ideas archived back to 1969.

It's been awhile since I did it. First time I used a ceramic magnet, saw a reply where you suggested using a fridge magnet. Fridge magnet worked also. Some magnets don't work because they cause a target signal when not moving.

If you're talking about a flexible strip fridge magnet, those are Halbach magnets which have a low flux density except near the surface. Ideally, one surface has an alternating +-+-+- field and the other side has no magnetic field at all. I would avoid this for testing EFE. Find a good ceramic magnet that doesn't create any kind of target signal.

[green]

Thanks I tried it a couple of times by waving the fridge magnet across the coil from one side to the other, as thats how the coil moves in space but was not sure it worked properly, I will try your method.

It's been awhile since I did it. First time I used a ceramic magnet, saw a reply where you suggested using a fridge magnet. Fridge magnet worked also. Some magnets don't work because they cause a target signal when not moving.

[6666]

Held a fridge magnet near coil and pulled it away quickly. Watched scope trace, connected to integrator out.

Thanks I tried it a couple of times by waving the fridge magnet across the coil from one side to the other, as thats how the coil moves in space but was not sure it worked properly, I will try your method.

[green]

Thats very clever Green, how did you test the EFE ?, thanks.

Held a fridge magnet near coil and pulled it away quickly. Watched scope trace, connected to integrator out.

[6666]

Hi I am currently in the progress of putting together a PI detector schematic based on all the info I have learned from this forum

Just curious, is it a gold or coin machine ?

[6666]

Tried both ways. Switch after input resistors better for me, not sure why.

Thats very clever Green, how did you test the EFE ?, thanks.

[Ferric Toes]

My favourite sample and hold analog integrators

Eric.

[waltr]

Do you use integrators with new designs or sample with an A-D and digital filter?

I have been working on a PIC32MX design that does the Integrator in code.
Simply sampling and filtering did not have the sensitivity to small target changes.

[green]

Thanks Green

I was thinking in the 1C, the integrator capacitor is seeing 2X the samples as each capacitor in a differential circuit. Therefore a difference in integration time constants?

Think I'm correct, not positive.

[green]

Have forgotten why I think it looked better. Posted in another thread awhile back but couldn't find where I posted it.

The 100R pot worked for balancing EF signal. Trimming inverter gain should do the same?

Been trying to find reply where I explained why it was better. Have a hard time using search. Searched threads I started and didn't find it. Think maybe it is another thread. How do I search threads for the word integrator with my reply only? Or how should I go about finding it?

[Altra]

(R1, R2=1k) (R3, R4=100k) (C1, C2=470n)

Thanks Green

I was thinking in the 1C, the integrator capacitor is seeing 2X the samples as each capacitor in a differential circuit. Therefore a difference in integration time constants?