Method for Identifying Type of Eddy-Current Displacement Sensor

Eddy-current (EC) displacement sensors are used in a device for measuring the shaft vibration of turbines. An EC displacement sensor is composed of a sensor probe and an impedance/output voltage (Z/V) converter. In a power plant in the U.S., the type of the sensor probe and the displacement x from the turbine shaft to the tip of the sensor probe (displacement x ) are not controlled. For this reason, when only the Z/V converter breaks down, the plant is stopped and dismantled, and both the Z/V converter and the sensor probe are replaced. This results in two problems, i.e., the unstable supply of electric power when the power plant is stopped and the high cost of dismantling the plant. If both the type of the sensor probe and x are identified during turbine operation, the aforementioned problems could be solved. In this paper, we describe that the three types of the sensor probe and x can be identified by comparing the measured the maximum quality factor Q_EC (max) and frequency f₀ at Q_EC (max) with the Q_EC (max) versus f₀ characteristics of sensor probes.

I. Introduction

Eddy-Current (EC) displacement sensors are used in a device for measuring the shaft vibration of turbines [1], [2]. An EC displacement sensor is composed of a sensor probe and an impedance/output voltage converter [3].