Maintaining ADC resolution while accounting for weight scale tare.

Other Hardware Sensors
1

G'day,

Wondering if anyone has any solutions to a little problem I foresee with my simple weight scale project. I aim to use a number of load cells to measure the weight of water in a vessel, up to 100 kg. A 16 bit ADC will probably give me the resolution I'm after (~1.5g increments). The problem is that the vessel itself will exert some force on the load cells which will need to be 'zeroed' out. Let's say I get 1V with an empty vessel from my load cells amplified by an In-amp, and 5v when 100kg of water is added. My usable range will only be 4V, or 4/5 of the resolution of the ADC. If I could somehow set the minimum reference voltage for the ADC (default 0V) to the tare voltage (e.g 1V) then the entire resolution of the ADC would be from 1V to 5V. Is this possible, or does anyone know of another way to solve this problem.

Thank you,

2

I could also use a 24 bit ADC and ignore the problem, since there is so much more resolution available. If anyone knows a good low cost 24 bit ADC that works well with the Arduino, let me know.

3

Try the HX711. It's very cheap and there's lots of information on the web about it.

By the way, it looks like you want a final resolution of 1:67,000 (100 kg / 1.5 g). Look at this and this for some difficulties associated with achieving that level of precision.

4

Thanks Dave,

I'll check them out.

Cheers