Hi, i have trouble measuring low voltages (0 to 100mV) with INA122.
As input, I have several shunts (some are copper bus bars) with different values and 100A full rectified (pulsating 100Hz, not filtered) passing through them.
With the INA122 I measure the voltage drop across them, and then get their value in micro Ohms.
So, I am measuring 0-100mV full rectified (not filtered) with INA122, after the IA I have 2 Sallen Key filter i series to get the "mean value" then to the microcontroller ADC.
The input is a shielded twisted pair (I have 100A (100Hz) and their noise in the same box...), I have 2 5k6 1% resistors from both inputs to ground, the INA122 is powered single supply 24V, and then a voltage divider to the sallen key filters. Also I have the reference pin (5) with a trimmer to adjust voltage reference.
Gain resistor are 2k2+220 1% (gain approx 87).
I cant get values to repeat, or to be consistent. I recently read about (V-)+0.15, so I´ll change gain resistors.