Ah okay... but I'll have to investigate creating a noise source... which=20 I believe I can do with a zener. The issue with the op-amp is finding a suitable one in my junk bin.=20 Cringing at the thought of paying for overnight shipping for a $0.50=20 op-amp, but I need to get this running this weekend. Will investigate the LED as a clamp. Cheers, -Neil On 5/5/2016 3:24 AM, Richard Prosser wrote: > Hi Neil, > > You can add dither (noise) to the wanted signal and then average the > results to give intermediate steps. Generally OK for a couple of bits > of extra resolution. > > Low voltage zeners tend to have a fairly soft turn on point - not what > you want. You may even find a LED of the right type could be better, > or a string of std. diodes. Better again might be an opamp to clamp > the maximum level. (And amplifiy). > > RP > > > On 5 May 2016 at 17:53, Neil wrote: >> Hi all, >> >> I'm looking for a way to get more resolution on a PIC32 A/D input (I'll >> actually be using a Chipkit board) for a low-voltage input signal. >> Official spec =3D as good as I can get it (in limited time). The >> sensor/amp puts out a 0-10V signal for 0-to-10 Kg force, but I only need >> to measure about 0 to 0.5kg (up to 0.5V), so only 5% of the full range. >> Voltage-dividing the signal reduces the resolution/range, so I'll >> 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 >> 0.5V nets only 8-bit resolution. I'd really like to get better. Other >> than adding an op-amp into the circuit, is there any other trick to bump >> the resolution up? >> >> If I do happen to have a workable op-amp on hand (though I doubt) to >> amplify the signal x4, I know that the zener will affect the linearity >> of the signal as it gets close to the zener voltage, but would a 3-ish >> volt zener cause any noticeable error at around 2V? Or is there some >> parameter that indicates that a zener would have a "sharper" knee? >> >> Cheers, >> -Neil. >> >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .