A DSP-based modified Costas receiver for LVDT position sensors

A novel signal conditioning system for Linear Variable Differential Transformers (LVDT) is presented. This system considers the signals involved in the operation of the LVDT to be analogous to a Double Sideband Suppressed Carrier AM (DSBSC-AM) communication system, where the position information is akin to the signal to be transmitted and the input sine wave excitation to the LVDT is akin to the carrier wave. Signal conditioning is achieved through a modified digital signal processor-based Costas receiver. This system has better dynamic response than existing solutions and better noise rejection than commercially available solutions. Static testing of the system using both 4-wire and 5-wire LVDTs verifies that the conditioner meets or exceeds the linearity performance of existing signal conditioning systems over the full-scale operating range. In addition, this system requires no phase compensation network or manual tuning