> Hi Mohit, does the signal come out of IC3B (it says COND1 on
> that label but AN1 has COND label)
Yes COND1 -> COND. Eagle doesn't let you duplicate names, so the numeric
suffix.

> What are the values of C8, 13, 14, and is R4 10k or 10R ? Have
> you tried removing those capacitors ?
Since this was a prototype board and I wasn't sure what quality of
rectification IC3 would do, I put in C8, C13, C14 just in case I needed to
connect capacitors (of different values/sizes) to filter the rectifier
output. R4 and C8 would form a LPF. In the boards that were working
previously, and the present ones, C8 is 470uF; C13,C14 are not connected and
R4 is just a wire (0 ohm).

> I'm not clear as to why you'd want them on a square wave
Actually, IC3 rectifies the square wave to a signal that can be fed into the
PIC analog pin. And these capacitors are there to final-smoothen the output.


This is basically a conductivity meter. The Cell1/Cell2 dips into a
solution. Depending on the conductivity of the solution, the 1V p-p square
wave amplifies through IC4C. IC4D is for calibration. And IC3 for
rectification so that the PIC can read the analog signal.

Point is: I cannot understand why the square wave should get distorted by
putting in the PIC.

Thanks,
Mohit.


Jinx wrote:

Thanks for your time,
Mohit.


Hi Mohit, does the signal come out of IC3B (it says COND1 on
that label but AN1 has COND label) ?

What are the values of C8, 13, 14, and is R4 10k or 10R ? Have
you tried removing those capacitors ? I'm not clear as to why you'd
want them on a square wave
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