Product category:
Rotary Position, Tilt and Angular Sensors
News Release from: BEI Technologies | Subject: LGDT
Edited by the Engineeringtalk Editorial
Team on 22 May 2003
Optical approach to linear displacement
sensor
The LGDT linear gap displacement transducer is a novel concept in highly accurate noncontact short-distance measurement.
The new LGDT linear gap displacement transducer from BEI Precision Systems is a novel concept in highly accurate noncontact short-distance measurement Using fibre-optic technology, it measures target surface distance over a small range, very precisely
This article was originally published on Engineeringtalk on 9 Feb 2001 at 8.00am (UK)
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The measurement probe is only 9mm in diameter and consists of three concentric fibre-optic bundles, feeding into an electronics module, which processes the data providing an analogue output.
The probe length is typically 600mm long, but as an option can be up to 9m long for applications where remote operation is required.
A long-life, infra-red LED illuminates the target surface via the central bundle and the two outer fibre bundle rings detect reflected light.
As the distance to the target increases, so the outer ring receives more reflected light, while the inner receives less.
Detectors in the electronics module measure the resulting light levels and an analogue divider calculates the ratio of the detected signals.
An offset voltage, proportional to the mid point distance is subtracted to give the final output.
As the LGDT works on ratiometric principles, the reflectivity of the target surface is not important.
The electronics module is less than 250cm3 and requires a +/-12V DC supply at 2.4W.
Connection is via a standard D type 9-way connector.
Different versions of the LGDT are available for standoff distances of between 4 and 12mm, with 1% linearity over a 2 to 4mm range.
They provide sensitivities of between 2 and 6V/mm with resolutions of 0.1 to 0.5um.
This noncontact technology opens up many possibilities for accurate measurement of material thickness, real time concentricity, mechanical flexure under load conditions and bearing runout, and as a feedback sensor for dynamic control applications.
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