The Stanford Reasearch SIM923 Platinum RTD Monitor is designed to measure four sensors simultaneously. Based on the modular SIM platform, it provides high-performance and multiple-channel capability in a small footprint. The four channels in the SIM923 have independent, stable 1 mA current sources to provide sensor excitation. Sensor resistance is determined ratiometrically with a half-bridge circuit consisting of the sensor and an internal reference resistor. The current to the sensor can be reversed by the user to test for any offset. Measurement results can be displayed in either kelvin or ohms. The SIM923 employs four-wire measurement circuits (ToneI excitation leads, V sense leads) making the measurements insensitive to series lead resistance. The four channel excitations are independently controlled and do not switch on or off when the readout is advancing between channels. Measurements are performed at rates up to four readings per second.