See LD-X for newest architecture.
The linear variable differential transformer (LVDT) is a type of electrical transformer/transducer used for measuring linear displacement (position). A counterpart to this device that is used for measuring rotary displacement is called a rotary variable differential transformer (RVDT). Both types provide output signals (voltages) based upon an AC excitation source causing a magnetic flux generated on transformer secondary(ies) by a moveable core proportional to the linear displacement position being gauged.
NAI offers multi-channel programmable, isolated excitation and signal input, LVDT/RVDT measurement LVDT / RVDT function modules, for all the multi-function intelligent I/O cards and platforms. Covering the range of excitation voltages/ frequency, interfacing to either two, three or four wire transducers and providing a normalized digital position word based on a percentage of full scale travel, the function modules are able to interface to virtually any type LVDT or RVDT. All LVDT / RVDT modules feature background wrap-around self-test capability and most platforms support an optional programmable AC excitation supply. Utilizing state-of-the-art technologies and specialized design algorithms, many useful application features such as excitation voltage and frequency measurement, excitation loss detection and many others are “built-in." Full scale operating signal and excitation voltages/frequency between 2-28 VRMS / 47 Hz and 10 KHz can be specified (see part number). Individual excitation inputs are supplied for each channel input.