Source for inexpensive strain gauges

[Brian Smith 1Participant @briansmith1]

Hello

Does anyone know of a source for inexpensive strain gauges? I want to play around with some sensors. The cheapest ones I can find on the net are around $6.00 US, yet I read of some that cost pennies, just cannot find them.

regards

Brian

[Brian Smith 1Participant @briansmith1]

Source for strain gauges

[Speedy Builder5Participant @speedybuilder5]

ebay on the Uk site about 36p each (350 ohm)from China. Even the amplifiers are only 3.59pounds
BobH

[Neil WyattModerator @neilwyatt]

Broken bathroom scales, pound-shop baggage scales?

[MuzzerParticipant @muzzer]

Yes, you can find half decent bathroom scales (100kg or so) in places like Aldi, Lidl, B&M etc for under a tenner. These contain 4 strain gauges and the complete amplifier / display etc. The baggage scales (~40kg) are pretty much the same deal except they only have one load sensor. You couldn't buy the bits for that price. The other cheap source is kitchen scales (~5kg) , if you need a more sensitive system.

When I say "sensor", in fact they usually have a dual strain gauge with elements at 90 degrees. Once you get into the details you will find that's actually what you want. The metal part has to be fairly compact and is typically a sort of spiral shape. I modelled one up not so long ago and in this picture, the element is where the yellow patch is and the force is applied to the blue spot:

The other thing to consider is that scales usually are measuring a load force, not a stretching or simple bending force, so the load cell element is not a simple beam with a strain gauge on the outside. It's worth picking up a set of scales just to see what the strain gauge system looks like – at as little as a fiver it's hardly an extravagance. Yes I've got a few….

Murray

[Brian Smith 1Participant @briansmith1]

Thanks Bob…I tried ebay here in Canada…but that did not show up at the time…I will look again

The scales idea is interesting…have you managed to remove the sensor and attach to another surface?

 

regards

Brian

 

Edited By Brian Smith 1 on 06/05/2017 14:54:59

[MuzzerParticipant @muzzer]

No I didn't – I don't think that would be practical. They are glued on and are very thin, so would almost certainly disintegrate. Possible that heat would loosen them, depending what was used to attach them. Have you checked out the dollar stores, Canadian Tire etc for cheap scales and luggage scales?

One helpful piece of info would be what you hope to measure with them. If it's just to measure a force, you could remove the load cell thing from a set of scales and integrate it into what you are making. If you are looking at strain on an existing structure, you could get some gauges from ebay etc and wire them up to the electronics from some scales. But you'd need to use the same type of sensors ie a right angle pair in this case.

Murray

[Dave Smith 14Participant @davesmith14]

One thing to think about is how are you going to calibrate it all?

[MuzzerParticipant @muzzer]

That may be another reason for simply reusing the cells from a set of scales….

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