While many of us think about closed-loop pressure control in process manufacturing operations, it’s also important for pneumatic-powered machinery control in discrete and hybrid manufacturing operations. A TESCOM ER5000 Series whitepaper, How Electronic Pressure Control Works, describes this control practice in these applications.
The whitepaper’s author describes different types of electronic pressure control. The first one is instead:
… of requiring operators to set pressure manually, a regulator may contain an electric motor that turns an adjusting stem until the desired outlet pressure is reached.
A second approach:
…sometimes referred to as an I/P, E/P or U/P transducer — accepts an electronic input signal (either I for current, E or U for voltage input), and produces an output pressure that is proportional to that signal.
If the command signal 4-20 mA (or 1-5 V DC) or 0-10 V DC calls for greater pressure, a valve in the regulator shifts to expose the outlet connection to the higher incoming pressure.
If lower pressure is called for, a valve shifts to open and bleed the outlet to atmospheric pressure.
With the I/P, E/P or U/P designs, the device controls regulator pilot pressure, comparing this pressure to the command signal and acting accordingly to either decrease or increase outlet pressure, which in turn, increases or decreases the regulator outlet (process) pressure.
The third type:
…“closes the loop” with an onboard microprocessor that takes an electronic signal from a pressure transmitter located on the outlet of the regulator, compares that signal to the command signal and automatically adjusts the pilot pressure to obtain the desired process pressure to compensate for any process disturbance.
The pneumatic controlled regulator will be selected to meet the needs of the application like inlet and outlet pressure range, flow capability, media compatibility, porting configuration while the electronic control head is common. By this combination a great variety of applications can be served.
Read the whitepaper and visit the TESCOM ER5000 Series Electropneumatic Actuator page on Emerson.com for more on this electropneumatic proportional-integral-derivative (PID) control and how it helps to provide robust and accurate pneumatic pressure regulation.