Process variable

How it is used

Common in process automation, PID controllers and trend screens. Usually shortened to PV, as in 'SP 80, PV 78'. The difference between the setpoint and the process variable is the error. Machine builders often say 'actual value' instead.

Example sentences

1. Put the setpoint and the process variable on the same trend so we can see how fast it responds.

2. The process variable is stuck at 0 °C; the temperature sensor is probably disconnected.

Common collocations

• setpoint and process variable
• PV value
• trend the process variable
• actual value

Related terms

• setpointThe target value a control system tries to reach and hold, such as a temperature of 60 °C, a speed of 1,500 rpm or a pressure of 6 bar.
• PID controlA common feedback control method that calculates its output from three terms: proportional (the present error), integral (the error built up over time) and derivative (how fast the error is changing).
• feedbackInformation about the actual output of a system, such as the measured position or speed, that is sent back to the controller so it can correct any difference from the target.
• analog signalA signal that can take any value within a range, such as 4–20 mA or 0–10 V, used to represent quantities like pressure, temperature or speed.
• overshootThe amount by which a controlled value goes past its setpoint before settling, for example a temperature rising to 85 °C when the target is 80 °C. It is often given as a percentage.

More terms: Control Systems

• controller
• closed-loop control
• open-loop control
• tune