An Adaptive Analog Circuit for LVDT's Nanometer Measurement Without Losing Sensitivity and Range

A self-adaptive circuit for the linear variable differential transformer (LVDT) has been developed to enhance its nanometer measurement range without loss resolution. By applying a fuzzy-proportional-integral-derivative controlled programmable gain amplifier array to produce a reference signal, which can adjust itself according to LVDT's core position, the conditioning circuit has ensured the signal to analog-to-digital converter varying in a very small interval over full-scale operating range. Thus, the sensitivity of the measurement system can be improved without losing measurement range. The simulation result demonstrated that the proposed circuit has solved the contradiction between resolution and range, which usually occurs in weak signal detection. Moreover, the signal-to-noise ratio has been ameliorated greatly. Additionally, the DSP-based signal conditioner, which utilizes the self-adaptive circuit, demonstrates the performance of the novel design and nanometer precision is obtained in a wide range.