A Noncontact Rotational Speed Sensor for Bearing Cages in a High-Temperature and High-Speed Environment

The bearing is a crucial component of the engine, and monitoring the rotational speed of the bearing cage during its operation can play a vital role in preventing potential damage and failure of the bearing. However, realizing the real-time monitoring of cage state parameters in a high-temperature environment is still a significant challenge. Herein, a rotational speed sensing system based on the eddy current effect is proposed in this paper, in which the eddy current sensor probe adopts a helical coil structure without skeleton support, the excitation is provided by a signal source, and the coupler and envelope detector converts the impedance change into a voltage signal. The real-time visualization of rotational speed is attained through processing the data acquisition card and the host computer. Based on the rational design, the sensor can measure the rotational speed from 0 to 9000 rpm in the temperature range of 20 to 400 °C, and the maximum hysteresis error, nonlinearity error, and repeatability error of this non-contact sensor are only ±0.24%, ±0.127%, and ±0.113%. Hence, the advantages of its self-supporting structure, high accuracy, and real-time display undoubtedly lay an experimental foundation for online monitoring of the rotational speed of bearing cages in high-temperature and high-speed environments.