Hi all,

I'm looking for a way to get more resolution on a PIC32 A/D input (I'll=20
actually be using a Chipkit board) for a low-voltage input signal.=20
Official spec =3D as good as I can get it (in limited time). The=20
sensor/amp puts out a 0-10V signal for 0-to-10 Kg force, but I only need=20
to measure about 0 to 0.5kg (up to 0.5V), so only 5% of the full range. =20
Voltage-dividing the signal reduces the resolution/range, so I'll=20
protect the A/D input with a zener to clamp the signal instead.

Now, with a 2V external reference (lowest allowed by datasheet), 0 to=20
0.5V nets only 8-bit resolution.  I'd really like to get better. Other=20
than adding an op-amp into the circuit, is there any other trick to bump=20
the resolution up?

If I do happen to have a workable op-amp on hand (though I doubt) to=20
amplify the signal x4, I know that the zener will affect the linearity=20
of the signal as it gets close to the zener voltage, but would a 3-ish=20
volt zener cause any noticeable error at around 2V? Or is there some=20
parameter that indicates that a zener would have a "sharper" knee?

Cheers,
-Neil.


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