The three R’s of analog position sensor-based mechanical measurements: Page 5 of 5

July 12, 2019 //By Edward Herceg
position sensor
Those of us old enough to remember the “good old days” recall that grade school focused on learning the 3 R’s: reading, ‘riting, and ‘rithametic.

Typically the effects of stiction in position measuring systems can be non-linear and are often not very repeatable, so determining or characterizing system resolution can be much more complicated, if even possible. And because the system resolution interacts with system repeatability, as was noted above, measurement errors can increase substantially, particularly if the system is providing position feedback for closed-loop control. Of course, any effects caused by stiction will also appear as non-linearity in the sensor's output. But because stiction effects are not very repeatable, digital linearization techniques to offset the non-linear effects will not be practical.

For this reason, efforts to reduce stiction are usually necessary to minimize any measurement errors caused by stiction in very slow-moving or intermittent-motion positioning systems. These efforts can involve applying techniques such as "dither", a low amplitude signal of high frequency that is input into the system to supplant stiction with much reduced dynamic friction, or by decreasing friction on the moving surfaces of the sensor by improving their surface finishes and by coating them with a lubricant.

About the author:

Edward Herceg is Chief Technology Officer for the Alliance Sensors Group - www.alliancesensors.com

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