On 08/08/2019 14:50, T i m wrote:
Peeps,

I would like to read the output of a strain gauge (measuring weight
(0-5kg) in this instance) from a PC as part of a general experiment
but not sure what bit does (and maybe limits), what.

So, strain gauge (or gauges) connects to a SG amp and that turns the
output into volts?

Then you could read said volts with say an Arduino and then have a USB
interface to PC, effectively streaming the output of the strain gauge
in ASCII (numbers) to the PC (and the rest is software etc) .

However, I understand the Arduino's only have a 10(12 with a tweak)
bit ADC and so with 10 bits I'm only going to get 1024 output values?

eg, If that was a 1kg 'scale' then I could read around 1g increments
but if it was a 5kg scale then ~5g would be the smallest increment
(that may be fine but I am just testing my understanding here).

Yes. You should be able to get 12bit or 16bit ADCs relatively cheaply
provided that you don't want fast ones and can live with a bit of
non-linearity. I you want strict linear then you will have to calibrate
it against a reliable voltage reference source.

Or is the output of the little eBay strain gauge amps already serial
so if it was a 24 bit device (16777216) it would be resolving down to
~1/3000 of a g (mathematically at least) and so would just use the
Arduino to turn it into ASCII over a USB interface (no ADC needed)?

I'd expect a simple strain gauge to output either a resistance value,
voltage or current depending on its internal design. Yo will have to
think about shielding from air currents and all sorts of mechanical
details if you want to go more precise than 10mg.

I know you can buy commercial strain gauge to ASCII over USB devices
but they aren't exactly cheap (~£250+).

Cheers, T i m

Decide what resolution and accuracy you need first and work from there.

--
Regards,
Martin Brown