A robust, −40° to +150°C wireless rotor temperature monitoring system based on a fully passive UHF RFID sensor tag

A novel wireless temperature monitoring system for electric machines is presented based on fully passive UHF RFID sensor tags. The system is composed of a custom designed IC UHF RFID sensor tag connected to an external μP and ADC through a master-slave series-peripheral interface (SPI) connection. The sensing element is a NTC 10kOhm thermal resistor (-40° to 300°C). The sensor tag, which includes an optimized meander dipole antenna, an analog front-end with a power consumption of 4.3uA and a digital core, communicates the temperature value to two EM optimized PIFA antennas located inside the stator of the electrical machine. The signal received by the PIFA antennas is demodulated by a commercial 1W RFID reader. The sensor is able to sense from -40° to 150°C and robust to the presence of the high electromagnetic disturbances generated by the electrical machine. Measured data rates are higher than 1 sample per second.