Patented Technology
Elegance in Sensor Design
The DIST sensor consists of a double coil wound on a round non- conductive rod (usually fiberglass). The wire is wound as a helix with a large pitch. Upon reaching the end of the shaft, the pitch is reversed and a returning helix is laid over the first coil. This is shown below where the enlarged view shows the position of both coils. Its system also contains electronics producing a resonant circuit oscillating in the 2 – 4 Mhz range. This configuration results in having two coils in series with one having current flowing clockwise and the other counterclockwise. Based on their orientation the magnetic fields of the two coils virtually cancel each other out while the electric fields reinforce each other. This results in an external field that is mostly electric with a minimal magnetic component.
The frequency of the electric circuit is dependent on the inductance and capacitance of the two coils. Based on the design of the coils the inductance is low and constant. The capacitance is significant and can easily be varied by the motion of any adjacent conductive surface, which in our case is a metal tube covering the insulated rod. As that tube is moved we can see changes in the output of the resonant circuit of about 1 Mhz over the full length of the sensor. The change in the frequency is linear with the motion of the tube, so the system can deliver resolution of one micron over a sensor length of one meter.
The system (coil and electronics assembly) can be housed in a stand-alone assembly or embedded into an OEM system such as a hydraulic or pneumatic cylinder or other subsystem. The coil/electronics assembly is typically mounted as the stationary component with the metallic tube–which we refer to a target tube–being mounted to the moving component.
Traditional analog outputs used in LVDT’s and magnetostrictive sensors are supported as well as our patented one-wire frequency output. More detail about available outputs is available on the “Tech Info” section of this site as well as though our selection of published White Papers.