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Thickness Measurement

Short Stroke sensors offer a convenient, cost effective method of measuring material thickness, for example by measuring the separation between rollers illustrated below.

 

In this example, paper is fed through rollers that are sprung together with cantilever arms at each end to follow the paper's thickness profile.  The displacement of each cantilever is measured by a sensor and its target. Key features of this system include:

  • Non-contact measurement
  • Short stroke sensors measure linear displacement but also tolerate the angular displacement of the cantilever arms
  • Independent measurement of the displacement at each end of the rollers
    • Average displacement yields thickness measurement at centre of rollers
    • Difference in displacement yields roller angle, for example due to folded paper
  • Sensors are insensitive to lateral misalignment and wobble
  • Sensors require only 3 wire connections
  • A single CAM204 chip measures both sensors to ~ 5µm Noise Free Resolution
  • Immune to dirt and moisture
  • Simple and robust
Short Stroke sensor measures material thicknessbetween rollers  
Short Stroke sensors are similar to LVDTs in operating principle, but are more compact, simpler and cost effective.  Unlike Hall Effect sensors, they are not disturbed by stray magnetic fields and do not require special magnets and precise alignment.