A 16-bit Tracking LVDT-to-Digital Converter with Programmable Frequency Reference Oscillator

Due to the usual LVDT to digital conversion method implemented with ADC being an analog conversion mode, it has a weak anti-interference ability. A Type II tracking strategy LVDT-to--digital algorithm is presented in this paper. In principle, a second-order servo closed-loop control loop is adopted to track the analog input position quantity automatically, and an internal excitation LVDT converter chip is designed. The frequency programmable excitation signal is realized by integrating the frequency division circuit and D/A conversion circuit. The over-range protection logical circuit is provided to eliminate ALL ZEROS changes to ALL ONES at LVDT stroke boundaries. Compared with the LVDT conversion method based on AD698, this method can effectively eliminate the chattering problem in the conversion circuit and has the advantages of a simple peripheral circuit structure and strong anti-interference ability. The design method of the conversion circuit and realization code of the look_up table is given. The test results show that the conversion resolution of the designed circuit reaches 16 bits, and the linearity reaches 0.15%.