Process variable
Value of a given part of a monitored or controlled process
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In control theory , a process variable ( PV ; also process value or process parameter ) is the current measured value of a particular part of a process which is being monitored or controlled . An example of this would be the temperature of a furnace. The current temperature is the process variable, while the desired temperature is known as the set-point (SP). [1]
Control system use
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Set-point_control.png/220px-Set-point_control.png)
Measurement of process variables is essential in control systems to controlling a process. The value of the process variable is continuously monitored so that control may be exerted.
Four commonly measured variables that affect chemical and physical processes are: pressure , temperature , level and flow. [ citation needed ] but there are in fact a large number of measurement quantities which for international purposes use the International System of Units (SI)
The SP-PV error is used to exert control on a process so that the value of PV equals the value of the SP. A classic use of this is in the PID controller .
References
- ↑ B. Wayne Bequette (2003). Process Control: Modeling, Design, and Simulation . Prentice Hall Professional. p. 5. ISBN 9780133536409 .
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