Inputs are applied to the INA using test points TP14 and TP17 for channel A, and TP20 and TP22 for channel B. The inputs for the op amp are applied through test points TP3 and TP13 for REFA, and TP16 and TP19 for REFB. To maintain linear operation, the INA must remain within the common mode voltage range with respect to the power supplies and differential inputs. A useful tool to calculate whether the INA is operating within safe limits can be found in the TI’s Analog Engineer’s Calculator. Click the + symbol next to Amplifier and Comparators and then click on INA VCM v VOUT.