Right... I'm hoping resolution gets me more of a finer change that I can=20 detect and respond to quicker. And I'm more concerned about linearity=20 that ultimate accuracy. Cheers, -Neil On 5/5/2016 1:30 PM, Dwayne Reid wrote: > I'd use a LED plus signal diode: LED (c) to ground, LED (a) to Vdd > via suitable resistor, diode (c) to LED (a), diode (a) to > signal_to_be_clamped. Pick the appropriate LED color for the desired > voltage drop (plus 0.6V for the diode drop). > > Bonus: you get a power indicator. > > I regularly use a/d over-sampling to increase my signal's resolution > but you need to be aware that accuracy does not increase at the same > rate as resolution. In other words, accumulating enough samples to > double your apparent resolution does NOT give the same increase in accura= cy. > > dwayne > > > At 01:24 AM 5/5/2016, Richard Prosser wrote: > >> 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 nee= d >>> 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 bum= p >>> 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. > --=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 .