Operation; Theory Of Operation; Pid Control - Tescom ER3000 User Manual

Electronic pressure controller

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5. OPERATION

The ER3000 is a microcontroller-based device that implements a digital control

algorithm to regulate pressure. Supply pressure is allowed into the ER3000 via a

pulse-width modulated solenoid valve at the inlet port, and pressure is reduced

via a similar valve at the exhaust port (normally the exhaust vents to ambient).

In a typical application, the ER3000 loads the dome of a dome loaded regulator

(air to open and a venting type regulator for the purpose of this example) and

senses pressure from a transducer mounted downstream in the process, as shown

in Figure 3. The ER3000 compares the feedback signal to the setpoint every 25

milliseconds. If the feedback is lower than the setpoint, the ER opens its inlet

valve, allowing pressure to flow onto the dome of a pressure reducing regulator.

This opens the main valve of the regulator, increasing pressure downstream. The

ER3000 will continue to increase pressure on the dome of the regulator,

increasing downstream pressure until the feedback signal is equal to the setpoint.

If the setpoint is lowered, so that the feedback is now higher than the setpoint,

the ER3000 will open its exhaust valve, reducing pressure on the dome of the

regulator. This will cause the regulator to self vent, thus lowering downstream

pressure. The ER3000 will continue to reduce pressure on the dome of the

regulator until the feedback signal is equal to the setpoint.

PID (Proportional/Integral/Derivative) control algorithm is widely used in the

process industry.

The most common example of a PID controller is a

temperature controller for an industrial oven. The basic control algorithm can

best be described through use of Figure 20:

Figure 20: PID Control

28 ER3000 User Manual

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