I need a compact and inexpensive sensor that can measure small tensile forces (less than a couple grams). There are plenty of cheap IOT sensors for pressure and/or compressive force, but I have been unable to find anything for measuring tension that is suitable for incorporation into the design of a small, low-cost Arduino-based device.
The ideal device would look like a small (< 1cm) chip or capsule with an eyelet or similar for attaching a wire or fiber. The device would measure the force with which the fiber is pulled. If you hung a small object from the fiber, you would be able to weigh it and/or measure its vertical acceleration.
I would be happy with either analog or digital output, as long as it's possible to maintain better than 5% precision without frequent recalibration.
It seems to me that a product like this digital spring scale must be based on a sensor similar to what I described, but maybe it's using the hook to impart compressive rather than tensile force to an internal sensor.
It occurred to after posting the above that it might be possible to use a solenoid with positional feedback -- just measure the amount of current that has to be supplied to keep the solenoid from being displaced by the load. But this is just a random thought -- I have no idea whether it's practical or whether commercial sensors exist based on this principle.
Get a small kitchen scale from your local home appliance shop, and start deconstructing. There are small load cells in there (usually four per scale), maybe you can repurpose those. They should be small enough for you. Higher precision (for smaller weight) scales can be found in e.g. office supplies and stationery shops, I have a scale that has a 0.1 gram resolution, and I think there are 0.01 g versions available as well.
You have to check the mechanics as these cells are designed to measure compressive force rather than tensile force, but a little bracket that goes around the cell to suspend the load below it can take care of that.
I guess you can find such small loads cells on ebay or aliexpress as well.
I teach atmospheric physics and am fully aware of that. If you look at a lot of commercial offerings of tension sensors, they cite the capacity in grams or kilograms. Many people have a better understanding of what a gram is than they do of a newton.
wvmarle:
Get a small kitchen scale from your local home appliance shop, and start deconstructing. There are small load cells in there (usually four per scale), maybe you can repurpose those. They should be small enough for you. Higher precision (for smaller weight) scales can be found in e.g. office supplies and stationery shops, I have a scale that has a 0.1 gram resolution, and I think there are 0.01 g versions available as well.
You have to check the mechanics as these cells are designed to measure compressive force rather than tensile force, but a little bracket that goes around the cell to suspend the load below it can take care of that.
I guess you can find such small loads cells on ebay or aliexpress as well.
Thank you for the good suggestions. I had already thought about doing what you suggested with compressive load sensors, but it involves an extra layer of amateur engineering that I had hoped to avoid. I'm genuinely surprised that there is not already an existing niche for IOT-compatible tension sensors.
