Even though this is a lesson about pressure sensors, let's talk about pressure gauges for just a moment. Pressure gauges are devices that react to pressure in a measurable way. Unlike sensors, which generally convert their results to a signal, gauges are usually read manually. Don't expect a gauge to interface with your PLC or ECM, but they can still be reliable, extremely useful, and cost-effective.
The manometer is a gauge that uses a liquid column to measure pressure. The first recorded manometer was developed in 1643.
Don't let those dates fool you; manometers have not been banished to museums. These simple pressure sensors are still in use today in classrooms, laboratories, and even on high efficiency furnaces. Their appeal is in their simplicity. Basic manometers have no moving mechanical parts, never need calibration, and don't require power to provide a reading. And because manometers rely on physical properties (density of the measurement liquid, and Earth's gravity), U-tube manometers are considered to be a NIST standard of accuracy.
NIST stands for National Institute of Standards and Technology. It has the distinction of being one of the oldest physical science laboratories in the United States, and is an authority on measurement accuracy.
The U-tube style manometer uses the displacement of a liquid to measure the pressure of a trapped fluid relative to the atmosphere, or another reference pressure. Try out this virtual manometer to see how it operates.
Manometers can be great for simple applications. As mentioned, basic manometers
Sorry, mobile machinery. This one's not for you.
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