Linear range extension for LVDT using analog lookup table

A technique to extend the operating range of the linear variable differential transformer (LVDT) is presented in this article. The realization method is based on the analog lookup table achieved by the ramp signal generator where the frequency of ramp signal is equal to the excitation frequency. Therefore, the resolution of the resulting signal is very high. The output signals of the LVDT are provided to generate the reference signal to synchronize with the ramp signal. The proposed technique can extend the operating range of the LVDT from a normal operating range provided by the specification of the LVDT to maximum stroke range of the LVDT. The circuit of the proposed technique is simple and can be implemented using the commercial devices. The experimental results confirmed that the circuit performance are good agreement with the expected results. The response time of the proposed technique is about two periods of the excitation frequency.