Part Number: INAEVM-SO8
in order to implement an analog-to-digital conversion (input range of at least -6V to +6V) I wanted to check and survey some instrumentation amplifiers which are intended for driving the ADC. Therefor, I used the INAEVM-SO8 „Universal Instrumentation Amplifier Evaluation Module“. The INA129UA and the INA828IDR (gain=1, Vref to GND) instrumentation amplifiers were evaluated in dual-supply configuration and performed well in case of single ended inputs (error less than 1mV). In terms of measuring differential input signals the results, so the output voltages of the amplifiers (supply = +/-12V, common-mode offset = 6V), were not satisfactory. Permanently an error of at least 2mV (rather around 3mV) occurred. E.g.:
input: 0.05V -> output: 0.046V
input: 3.25V -> output: 3.2465V
input: 5.2V -> output: 5.197V
Since I only have 3-channel power supplies, I used two, one for the supply voltages and one for the input signals. As it can be seen in the attached photo, 1.004V instead of 1V was transfered to the amplifier input (upper power supply). Maybe this is a reason for the deviation of the amplifier output signal, but I am not sure what causes this effect (electric coupling on the evaluation board?).
Perhaps someone can help me ensuring better results in measuring differential signals by means of instrumentation amplifiers!
(If it is unsuitable to use the mentioned instrumentation amplifiers as ADC driver in an data acquisition system, please inform me.)