Hi team
I am experimenting with an INA122 In Amp with a view to measuring input voltages of fractions of a mV. I'm using two bias resistors of 330K on the inputs and gain of from 25 to 200. Ultimately I'd like to use this with sensors such as a thermopile, but currently I'm using a wheatstone bridge of 3 x 100K resistors with an 83 K resistor + 25K and 1 K pots in series as the 4th arm. By varying the 1 K pot, I am able to graph Vin vs Vout and get good linearity from about Vin = 1mV upwards. However, with anything less than Vin= 1 mV, the graph levels off and certainly does not pass through the origin. I would have thought that an in-amp should be able to give good results with input down to microvolts. Any suggestions?
I am experimenting with an INA122 In Amp with a view to measuring input voltages of fractions of a mV. I'm using two bias resistors of 330K on the inputs and gain of from 25 to 200. Ultimately I'd like to use this with sensors such as a thermopile, but currently I'm using a wheatstone bridge of 3 x 100K resistors with an 83 K resistor + 25K and 1 K pots in series as the 4th arm. By varying the 1 K pot, I am able to graph Vin vs Vout and get good linearity from about Vin = 1mV upwards. However, with anything less than Vin= 1 mV, the graph levels off and certainly does not pass through the origin. I would have thought that an in-amp should be able to give good results with input down to microvolts. Any suggestions?