Ideal for difficult sensing applications, this transducer can measure displacement and proximity of a metal target without physical contact. The measurement is unaffected by interposed nonmetallic, non-conductive materials, such as polymers and biomaterials.

The stainless shell of the device houses two coils; one for sensing and the other for temperature compensation. The coils and teflon cable are mounted on a stable PEEK substrate. This assembly is potted into the stainless housing using high-grade, vacuum-pumped epoxy and includes integral strain relief.

This packaging allows the sensor to be used in applications requiring long-term immersion in water and saline solutions.

Miniature "plug and play" signal conditioners provide linear DC output when supplied with unregulated DC power. Multichannel, OEM and digital display systems are also available.

Custom ranges are available on request.

How it works

Two coils within the non-contact DVRT's® housing form its sensing and compensation elements. When the face of the transducer is brought in close proximity to a ferrous or highly conductive material, the reluctance of the sense coil is changed, while the compensation coil acts as a reference.

The coils are driven by a high-frequency sinewave excitation, and their differential reluctance is measured using a sensitive demodulator. Differencing the two coils' outputs provides a sensitive measure of the position signal, while cancelling out variations caused by temperature.

Ferrous targets change the sense coils' reluctance by altering the magnetic circuit's permeability; conductive targets (such as aluminum) operate by the interaction of eddy currents induced in the target's skin with the field around the sense coil.