An Efficient Linearizing Demodulator Interface for LVDT

In this letter, we introduce an efficient linearizing demodulator circuit for linear variable differential transformers (LVDTs). A key innovation of this circuit lies in the integration of linearization and demodulation functionalities within simple electronics, while effectively addressing the limitations of traditional LVDT interfaces. It uses a simple saw-tooth excitation for LVDT and incorporates an enhanced inverse synthesis circuit as the core signal conditioner for processing the LVDT's secondary outputs. Further, this approach offers other unique features, including first, compensation for transients, rise-time, and other common LVDT errors, second, low component count, third, non-requirement of precision oscillator and demodulators, and fourth, a broad range. The efficacy of the proposed method was evaluated through simulation and experimental studies, showing a remarkable improvement in linearity (over six times) across a 100 mm span. The developed system achieved a nonlinearity error of 0.9%, a signal-to-noise ratio of 52 dB, and a repeatability error of 0.014%.