I am trying to understand the nature of the non-linearity of the INA116 amplifier.
I have a voltage measurement instruments which uses the INA116 as the front end sensor at unity gain due to its high input impedance and ultra low input bias current. The data sheet indicates +- 0.0005 of FSR (which I assume is the supply +-15V) giving ~7.5mV. What I am seeing is a 20 mV positive to negative jump in the residuals within 30mV of zero Volts. Is this a known feature of this device? All of the non-linearly occurs near the zero difference of the inputs?
The testing is done with one input grounded and the input signal on the other and then the test is switched.
I have seven different builds of the same instrument and the residuals from a linear voltage sweep on each build are within about 1mV of each other. The instruments and testing are essentially identical. They all show a very sharp jump from +10mV to -10mV when within +-30mV of zero.