Freitag, 15. Oktober 2010

Getting better aquainted with the Stretch Sensors

As mentioned in a previous post, I now have a stretch sensor by Images in my possession. Though I was first a bit skeptical I am beginning to see more and more ways of using this. I sort of had a hunch that the relationship between stretch and resistance might not be linear (yeah admitted, nothing strange in that, I would be more surprised *where* there a linear relationship.)

I am a visual person and I need to see things to understand them, so I made these graphs:

Stretched to 125 % of original length.

Stretched to 150 %

Stretched to 175 %

Stretched to 112.5 %, 125 %, 137.5 %, 150 %, 162,5 %, and 175%

Stretched with incrementions of 6.25 %

Due to the fact that I am lazy the graphs might be a bit confusing to read. The x-axis represents time and the white vertical lines represent seconds (I just double checked my math and the white lines are more like half seconds - maybe I will redo these if I get around to it. However you still get the generally picture). The y-axis measure the change in resistance. The light gray area is the resistance of the sensor. I did not add units, as the interesting part is the relative change and that is all I measured. 
The fact that the signal is non-linear can, with some tinkering, be used as a bonus. The resolution in the first couple percent of stretch is quite high - so if I where to use two stretch sensors simultaneously but in opposite phase (if one is loose, the other one is stretched) I should be able to maximize the resolution available :-)

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