Low-cost linearity range LVDT read-out circuit using LC Wien bridge oscillator and microcontroller with parasitic insensitive

Abstract

The paper addresses the issue caused by the phase shift between the excitation coil voltage and the output voltage at the secondary coil of the LVDT. The goal is to develop a read-out circuit based on an LC Wien bridge oscillator to reduce the phase shift, making it insensitive to parasitic resistance. Additionally, the paper proposes to enhance the linearity range by using an approximate inverse hyperbolic sine function with the microcontroller Atmega328p to improve the linearity range further. Experiments were conducted to measure the oscillation frequency and validate the circuit prototype. The measured oscillation frequency errors were approximately 0.097 %. The comparison of linearity between the ideal case and the proposed system can demonstrate that the percentage error is lower than 0.1 %. The simulation and experimental results are agreeable with the theory, indicating that the proposed technique enhances the linearity range.