In situ self-calibration of an individual displacement sensor

This paper presents a new self-calibration method for displacement or angle sensors which are installed in the instruments. The principle of the method is based on the fact that the linearity error of the target sensor is very small. On every sampling point the derivative of the calibration curve function is measured simultaneously with output of the sensor. Input value of the sensor at every sampling point is approximately estimated first by using a straight calibration line which is given externally. The derivative is integrated with referring the approximate input to get the approximate calibration curve. Then the approximation of input value of every sampling point is improved with the obtained calibration curve. Next the integral of derivative is improved with, the newly estimated input values. Repeating these improving process the calibration curve converges to the correct one. Results of simulation and experiment have shown that the calibration error of the method is less than twice of the resolution of the calibrated sensor.