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Description
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.
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