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I'm starting to learn about automatic process control, and there are types of signals transmitted in a control system. Among that is pneumatic signal that is a pressure signal. But I still don't know what a pressure signal means? How does it work? If you could give me a simple reference to learn more about signals(not a book to read, I'm already reading a book about control..)

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For a pneumatic system, information is carried by the pressure of a gas (or air) in a pipe, instead of electrical current. In antique Greece, pneuma was used in medicine to describe air circulating for the functioning of living systems.

I am not sure the term is very common, although there are several related concepts such as pneumatic actuator, pneumatic controller, pneumatic signal transmitter or amplifier, (fundamentals of) air logic, etc.

By a form of metonymy, I'd consider a pressure signal as the measure, as a given location over time, in certain units (psi, psig for pound/square inch [gauge]).

Apparently, due to pressure/temperature conservation laws in constant volume, pneumatic controllers can also work on temperature.

In addition to the above link, the short document Pneumatic Systems describes in Chapter Different kinds of basic circuits: Flow amplification, Signal inversion, Memory Function, Delay function.

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They are small pipes with pressurized air. They typically are on or off and typically control actuators but not just control, they supply the required force for the actuators. You see them a lot in manufacturing production lines. A jig will hold a part for some machining step and the jig will open or close under pneumatic control. They are used where electric wires aren’t suitable such as creating a fire risk and don’t require speed

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  • $\begingroup$ Thank you. If we kept sending a pneumatic signal , one after another, just like in an electric signal , electron after electron be transmitted, can the pneumatic signal then be not functioning as " on and off" ? And why is it considered not fast (don't require speed)? $\endgroup$ – hello there Aug 6 '18 at 7:39
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    $\begingroup$ Slow compared to an electrical signal. A pneumatic Signal is mechanical. The gas is typically expelled by the actuator, It’s a cycle, $\endgroup$ – Stanley Pawlukiewicz Aug 6 '18 at 12:51

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