The low input bias current of the INAx191 provides accurate monitoring of small-value currents. To accurately monitor currents in the microamp range, increase the value of the sense resistor to increase the sense voltage so that the error introduced by the offset voltage is small. The circuit configuration to monitor low-value currents is shown in Figure 8-6. As a result of the differential input impedance of the INAx191, limit the value of R_SENSE to 1 kΩ or less for best accuracy.

Figure 8-6 Measuring Microamp Currents