> I am looking for a sensor that can be used with a pic that will measure
> tension. I thought about a spring and a pot but that leads to a lot of
uncertainty
> when it comes to accuracy.  Has anyone used such devices or know of a
> reasonable source for such a sensor?

What force range and accuracy do you require?

You can buy "fishing scales" which perform the same function as the
traditional spring scales. There will be an analogue voltage somewhere
inside and possibly a voltage to frequency converter which makes interfacing
to any PIC easy.

You can use kitchen digital scales - typically 2 kg and 5 kg ratings
available. Similar but higher precision and more expensive ones are
available. These scales typically contain a load cell - 4 strain gauges in a
bridge - and an analog to digital converter. In cheaper scales this is a
voltage to frequency or pulse width converter. These are made as compression
scales BUT they also work in tension just as well. Suitably connecting  to
the face of the load cell will allow a proper in-line tension device to be
produced.

You can buy bare load cells but getting them from scales will almost
certainly be cheaper. The load cell and electronics can be (and may well
need to be) removed from the scale body. I'm currently using such a load
cell in compression but tension would be almost as easy.



    RM

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