Pressure Testing System

Here’s more followup to my previous post on the Hapmed Tourniquet Trainer. The data disparity I mentioned got me thinking about things we take for granted.

My college mentor used to say: “Believe nothing, trust no one”. And that has led me down this neurotic path. Thanks Thomas Morgan.

So stepping back just a bit, which pressure testing system below should I trust most?

A) Squeezed liquid bladder generating a water column that’s easily visualized, where pressure = fluid density x acceleration of gravity x column height. Bubbles can cause problems. Water density can vary. Bladders can leak. Tubes can kink. But it’s hard to game. No batteries. No wires.

B) Squeezed liquid bladder, connected to analog manometer. Same issues as above, plus difficulty zeroing. Lower resolution compared with a 3-4 meter water column.

C) Squeezed liquid bladder, connected to digital two port manometer that automatically subtracts the effects of atmospheric pressure. Same issues as A and B, plus you have to trust the digital device. However, the device can be calibrated and verified using a water column in parallel.

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