Error minimization of an angle sensor using LabVIEW based calibration

In this paper, a method to calibrate an anisotropic magneto resistance (AMR) angle sensor in order to bring down the error to minimum is presented. The measurement system consists of the sensor and a permanent magnet. The main area of application for the sensors is the position sensing of Brushless DC motors (BLDC) motors. The sensor has an evaluation board where the output of the AMR sensor via an analog to digital converter (ADC) can be taken into a PC via USB. By making using of LabVIEW we did signal processing on the incoming data to obtain the sine and cos, calculates the angle. The process has two stages. This paper explains the first phase, the offset calibration. Once offset calibration is done with the raw data, angle is again calculated and compared with the raw angle obtained. The maximum angle error is calculated as the maximum mean deviation of angles calculated. The offset calibration resulted in considerable reduction in angular error. As the next phase, the authors propose the use of optical encoders to obtain real time reference for the sensor output and there by determining the actual error instead of taking the theoretical max mean deviation.