The simple circuit design in Figure 1 lets you measure all components of a current flowing in a dc servo motor. The rectified output of the circuit uses ground as a reference, so you can measure the output by using a single-ended A/D converter. The current-sense resistor, R1, has a value of 0.1. The Zetex (www.zetex.com) ZXCT1010 IC converts the differential signal across R1 to a single-ended signal. Two of these ICs form a signal rectifier. The single-ended signal makes measurement by an A/D converter cost-effective, small, and frugal in power consumption.