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I would like to measure the a small amount of tension (less than a newton) in a line. I've found products that do this for much much larger amounts of tension. I've also seen "stretch sensors" but they don't seem to provide an easy way to convert "amount of stretch" measured in ohms to newtons.

I suppose I could buy a stretch sensor and a spring scale, come up with some kind of regression to convert inches to amount of stretch and then I can convert ohms to inches based on the data provided, but thats a good deal of work, and I'm also worried the stretch sensor can degrade over time.

Anyone have any good suggestions on how to sense small amounts of tension?

The device I'm building is designed to measure thrust output by a quadcopter propeller. I'm sure I could rig it to push down into a scale or something rather than pull, but I would much rather have a system where the prop creates tension in a line. That way I can also have the propeller free rotating and could potentially measure p-factor

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  • \$\begingroup\$ Would a digital pocket scale do the trick? \$\endgroup\$ – Nick Alexeev Oct 27 '16 at 1:07
  • \$\begingroup\$ @NickAlexeev maybe but thats not a sensor \$\endgroup\$ – OneChillDude Oct 27 '16 at 1:11
  • \$\begingroup\$ There are inexpensive spring scales designed to measure pull force. Just FYI. \$\endgroup\$ – mkeith Oct 27 '16 at 2:36
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    \$\begingroup\$ You can get loadcells for very low ranges. That would be the most accurate. \$\endgroup\$ – R Drast Oct 27 '16 at 6:26
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Simple thing to do would be to use digital pocket scale. This is frequently done on the R/C world. This may be enough for a start.

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(Source. There are more photos of this setup, as well as other ones.)

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