# Converting Force Measurement to Pressure

Oseania
TL;DR Summary
A zip-tie like structure squeezes an elastic part. I can measure a force that is related to the squeezing pressure. I need to create a calibrator that would allow me to correlate the force to the squeezing pressure.
I have a zip-tie like structure, which when pulled, squeezes an elastic part. Think of it like a having a zip-tie around your finger.

I can measure a force that is related to the squeezing pressure. This relationship between force and pressure is quite linear. I would now need to create a calibrator that would enable me to correlate between the measured force (N) to the pressure (Pa) that is imposed to the elastic part. The diameter of the zip-tie is about 22mm and it squeezes to about 17mm diameter.

Now, I first started to think that I would have some inflatable balloon with fixed pressure. The zip tie wouldn't move when the pressures match. I would prefer to keep this calibrator relatively simple at first stage, so any crazy, easily built ideas are welcome ;-).

Thanks.

Now, I first started to think that I would have some inflatable balloon with fixed pressure. The zip tie wouldn't move when the pressures match. I would prefer to keep this calibrator relatively simple at first stage, so any crazy, easily built ideas are welcome ;-).
A flexible silicone tube, sealed at the bottom, filled with water from a reservoir with a large exposed water surface area above. The height difference sets the hydrostatic pressure at the bottom of the tube.
Bundle the bottom end of the tube in with the elastic material, tighten the zip-tie until the tube is half-collapsed under the tie. The tube collapse will occur over a narrow pressure range.

What range of pressure are you expecting ?

Mentor
Suppose you have a belt under tension T wrapped around a rigid cylinder of radius R. Let P be the normal force per unit area exerted by the cylinder on the belt. A force balance on the region of the belt between angular locations ##\theta## and ##\theta + d\theta## gives $$PRd\theta w=Td\theta$$where w is the width of the belt. from this it follows that $$P=\frac{T}{Rw}$$

Oseania
A flexible silicone tube, sealed at the bottom, filled with water from a reservoir with a large exposed water surface area above. The height difference sets the hydrostatic pressure at the bottom of the tube.
Bundle the bottom end of the tube in with the elastic material, tighten the zip-tie until the tube is half-collapsed under the tie. The tube collapse will occur over a narrow pressure range.

What range of pressure are you expecting ?
Thanks,

the pressure range is from 6 kPa to about 33kPa.

Oseania
Suppose you have a belt under tension T wrapped around a rigid cylinder of radius R. Let P be the normal force per unit area exerted by the cylinder on the belt. A force balance on the region of the belt between angular locations ##\theta## and ##\theta + d\theta## gives $$PRd\theta w=Td\theta$$where w is the width of the belt. from this it follows that $$P=\frac{T}{Rw}$$
Thanks, just to verify that w is the width?

Mentor
Thanks, just to verify that w is the width?
That's what I said.