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I want to measure weight of some objects which range from 50 grams to 20 Kg. So what kind of sensor should I use to get values with a precision of 1 gram. I tried a strain-gauge load cell of 20Kg, connected it to hx711, and this to arduino. But I get values which are not much accurate.(I may have not done it properly maybe). They show me different values every time I put the same weight.
I wanted to know if there is any good sensor for weight measuring sensor with a good precision of 1 gram.
The main mechanical differences between an expensive 20 kgf load cell and a cheap one will be -
Repeatability
You load it with 10 kg, take it off, load it again. How well do the readings agree?
Drift
You load it 10 kg, and leave it on there. Read it now, read it in an hour, read it in a month. How well do the readings agree?
Hysteresis
You load it with 10 kg. Read it. Add another 5 kg. Now remove the 5 kg. Read it again. Does the increasing load reading match the decreasing load reading?
Linearity
You load it with 5 kg. Add another 5 kg. Is the second reading twice that of the first?
With a cheap one, you may get many 10s of grams error at any one of these steps. With an expensive one, you may get sufficient mechanical goodness to be able to use the reading range of a 20 bit ADC to give you 20 kg full scale with an accuracy of a gram.
You won't get a such precision with an load cell and DAQ that you will buy it on eBay or Ali. These are very expensive industrial load cells and DAQ. For example legal to trade cell C6 has 6000 intervals, i.e 20,000g/6000=3.3g per interval.
