An accurate source of calibration air pressure

[Tony]

When experimenting with pressure measurement systems, a constant accurate source of air pressure is a very handy thing to have.

Probably the simplest way to generate an accurate calibration air pressure source is from a water bubbler. This works exactly like an aquarium tank air bubbler, where a submerged air pipe blows bubbles into a fish tank.

The trick is to know exactly how deep the open end of the pipe is below the water surface. It then requires an exact amount of air pressure to force the water column down the pipe and blow bubbles. Any excess pressure just blows more bubbles. The air pressure within the pipe will always remain constant as long as a slow steady stream of small bubbles are being forced out of the bottom.

A small air compressor and needle valve could supply the air, and you can then generate a very accurate and repeatable air pressure reference source for testing your pressure measurement system.

[86rocco1]

My brother uses that exact method to measure the water height in a cistern. He has a tube running to the bottom of the cistern, he pumps air into the tube and when the pressure stabilizes, he reads off the air pressure on a gauge he's calibrated in inches of water.