Patent ID: 7248994

Claim:
An apparatus for determining a linear position of a movable component of a linear variable differential transformer (LVDT), which includes a primary coil driven by an excitation signal at an excitation frequency, a first positional output, and a second positional output, the apparatus comprising: a first signal analyzer including an analog input operably coupled to the first positional output and a second signal analyzer including an analog input operably coupled to the second positional output, each of the first signal analyzer and the second signal analyzer comprising: a feedback loop configured to generate a digital estimate that substantially tracks an amplitude of the analog input, the feedback loop comprising: a comparator configured for comparing the analog input to an analog feedback signal and generating a comparison result; a digital estimator, operating at an estimation frequency and configured to sample the comparison result and modify the digital estimate by an incremental adjustment amount responsive to the comparison result to reduce a difference between the amplitude of the analog input signal and an amplitude of the analog feedback signal; and a digital-to-analog converter configured to convert the digital estimate to the analog feedback signal; and an amplitude analyzer configured to collect a digital estimate history by sampling the digital estimate at a sample frequency that is a binary multiple of the excitation frequency and analyze the digital estimate history to determine an amplitude of the digital estimate substantially near the excitation frequency; and a result calculator configured to evaluate the amplitude of the digital estimate from the first signal analyzer and the amplitude of the digital estimate from the second signal analyzer to generate a numerical representation of the linear position of the movable component.