Design World – August 2019

108 August 2019 http://www.designworldonline.com DESIGN WORLD DESIGN WORLD http://www.designworldonline.com August 2019 109

Sensors report down to

the wire

The SGH50 draw-wire

sensor from SIKO is

an absolute position

sensor for hydraulic

cylinders, telescopic

cylinders, and piston

accumulators, based on

the company’s tried and

tested wire-actuated

sensor technology.

A draw-wire sensor

(far left) is shown

embedded in a

telescoping cylinder.

precision-machined drum. Threading on the

drum guides the wire to ensure consistent

unwrapping and retraction without overlap,

maintaining the exact relationship between

the wire’s motion and the linear distance

traveled. A coiled spring maintains tension

in the wire to prevent sagging, especially in

horizontal applications. A sensor is attached

to the axle of the drum and measures the

drum’s rotation.

When the target object moves, the wire

is extended (or retracted), and the drum

rotates. The sensor measures this rotation and

outputs a position signal proportional to the

drum’s rotation, and therefore, to the wire’s

movement. The type of sensor used depends

on the application requirements, with common

choices being optical or magnetic encoders, with

incremental or (for longer measuring lengths)

absolute output. For applications that require an

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