Variable Reluctance type Speed Sensor for Acidic and Radiation Environment

The sole objective of this work is to develop a speed sensor for acidic and radiation environment. The existing speed sensors available in market like Tacho-generator, Hall Effect type speed sensor and optical encoder type speed sensor has low life expectancies in acidic and radiation environment. The variable reluctance sensor available in the market uses a normal pickup coil around a permanent magnet. But the magnetic field of permanent magnet diminishes with time, ambient temperature and vibration. Insulation of the coil also gets damaged in acidic environment. The proposed variable reluctance sensor is more rugged and can be used in harsh environment with suitable design adaptations. As the behaviour of permanent magnet in acidic environment is not well studied, it is decided to use an electromagnet in place of permanent magnet and stainless steel sheathed Mineral Insulated copper core (MI Cable) for winding the coils so that it can withstand acidic and radiation environment. The Speed Sensor based on Variable Reluctance principle has been designed, analysed and fabricated. The effect of air-gap, exciting current, and speed of the motor on the output of the sensor was obtained in actual field condition. A signal conditioning circuit is developed and its response is also studied for conditioning the noisy output of the variable reluctance sensor.