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# Measure compression of objects device

#### Dramarc

##### New Member
Hi
I need a device that should measure how many mm an object compress when a load is put onto it . Object size is approx 5*5*5 cm3 to 10*10*10 cm3 in size and the compression would be in ballpark 0.1 to 0.5 cm.
I’m thinking a a square metal plate with 4 rods . Placed in the corners. Object is placed on metal base plate and weights (thick metal parts with holes in corners so they can be held in place when put over rods. Somehow the distance should be measured between plates Vs load (number of weights on top plate ) . I haven’t found any good distance measuring devices for short distances. I’m also looking for a way to get signal into a computer in an easy way. Any tips of how to go about creating this device ? Other ideas of how to go about ? Thanks in advance / Andy

Possibly something like four small hydraulic pistons (or syringes) full of fluid, all linked to a single piston that has a spring return.

That would give the total of all four "sensors", so 4x the average displacement.

Then link that to either a precision linear pot, or an optical encoder via a cable and drum pulley.

Other than that you would need four separate linear (or cable/drum, or rack & pinion) position sensors or encoders, then do the maths on the result.

Or, if the top plate is on linear guides so it cannot tilt enough to throw off the reading, a single transducer linked to the plate should do.

These are some types of commercial sensors / transducers:

This type of thing, with a suitable amplifier, could be used to measure the compression force.

Thanks guys! Regarding the Ali express solution above , not sure how to always keep it vertical in test rig …

Construct a sturdy metal base plate with four rods attached at the corners. The rods should be rigid enough to support the weights and transfer the load evenly onto the object below.

Budget? You also make no mention of uncertainty?
I used quite a bit of Micro Epsilon laser sensors which work fine but also have a cost, they aren't cheap. Another less accurate solution for measuring displacement is using a LVDT sensor to measure displacement. Less knowing the uncertainty you need and the measured displacement you expect to see it's hard to suggest a solution. I did catch the 0.1 to 0.5 cm and I would be looking LASER but no clue on your budget? A Google of "Displacement Sensors" should get you some results. You can plot applied force against displacement.

Ron

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