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Hi everybody,
For a load cell amplification I'm using the INA321 with a gain of 500. Following datasheet, I've set R2 = 99 kOhm and R1 = 1 kOhm. Reference is set to GND and voltage supply is 4V.
It seems that everything works fine, except for the low frequency output noise which is around 2mV. It is a very low frequency noise, I can see the variation with the multimeter. The input of the amplifier (load cell) is surely stable because I'm using an high precision calibrator.
What can cause this noise?
I've seen from the datasheet that the input Voltage noise (last graph at page 5 https://www.ti.com/lit/ds/symlink/ina321.pdf?ts=1643184446359&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FINA321 ) could be aroud +/- 5uV. In this case, if I multiply this value for the gain ( 500 ), I obtain 2,5mV peak of output noise. Am I right with my argument?
If yes, I thing that there can't be any solution for this and obviously I need to change the instrumentation, searching another one that could be less noisy.
My goal is to achieve a noise what can be 10 times less.
Which is your advice?
Thank you in advance,
Mattia
Hi Mattia,
for lowest noise you should not take a micropower instrumentation amplifier. Compare the noise data of INA321 with the INA337, e.g. There's a gigantic difference between them in the low frequency noise performance.
Kai
Hi Mattia,
Thanks for your post, I can help you.
The voltage noise spec you see in the datasheet is inherent to the INA. As you have uncovered, this noise is amplified with gain. If you are searching for lower noise performance, I would suggest a different INA like the INA337 like Kai suggested.