A novel FPGA-based LVDT signal conditioner

This paper presents a phase compensated novel signal conditioner for a linear variable differential transformer (LVDT) and its FPGA based implementation. The LVDT output signal is a double-sideband suppressed-carrier amplitude-modulated (DSB-SC-AM) waveform, where the LVDT sinusoidal excitation is the carrier signal and the LVDT core position is the modulating signal. The proposed signal conditioner locates the carrier peaks in the LVDT output signal and provides a direct digital demodulation of the same at the said instants. Since the carrier component at the sampling instants equals the carrier amplitude, a simple gain scaling converts the read data to the LVDT core position measurement. The peak sensitive demodulation is insensitive to sensor induced phase lag and does not require external phase compensation network. This conditioner has better dynamic response than existing LVDT signal conditioners. Its overall error figures are also comparable with those of the existing solutions.