Hi All, I have this idea to make a valve spring tester with a 200Kg disc load cell. My question is, does the load have to hit the centre of the point? Or can I make a disc to straddle the centre/point?
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Hi Peter,
Glad you asked! You’ve avoided a situation like this:
I’ve only ever used the bar-style ones, however I’d say the concept here is the same, it’s the deformation and stretch of the whole structure that gives the output. Keep in mind that load cells need calibration too
Keen to see where you go with this one!
-James
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Hey Peter,
Yes, it’s based on the change in electrical characteristics of that part of the load cell when the material is deformed very slightly (so as James said, it is important to calibrate these sensors to ensure that your results are accurate as well as being precise).
As for the idea that you have to introduce a disk, I suggest sitting it flat against the cell like this:
That way all of your reaction forces centralise at that point rather than being able to support part of the load onto the rest of the cell through your material that would invalidate your results as only part of the resultant weight vector actually passes through onto the point which is required to deform:
As James said, a bar load cell may be a better choice here, that way you can simply leverage the support of your weight off of or against it to get a much more reliable measurement in my experience.
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My thoughts are that the capacity would be reduced, as the strain is being measured across the radius. I’ll probably make a cylinder & piston to constrain the load radially. I’ve also bought the HX711 amplifier and an arduino to calibrate, convert and display the load.
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Hey Peter,
That small node that sits out the top of the cell is essentially being crushed when you’re measing the weight-force applied across it, the best analogy I know for it that it acts like a Bosu ball that you can measure how crushed it is based on the change in electrical characteristics.
It’ll require calibration as we’ve discussed a few times throughout this thread, but any rigid setup that you come up with that applies the entirety of the force onto that node and doesn’t allow it to be transmit anywhere else should produce accurate readings.
Let us know how you go with it, I’m curious to see what set up you land on 
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