Control loop

This controller operates the heating system for a constant time regardless of the temperature of the building.

In the case of the boiler analogy, this would utilize a thermostat to monitor the building temperature, and feed back a signal to ensure the controller output maintains the building temperature close to that set on the thermostat.

In the case of the boiler analogy this would include a thermostat to monitor the building temperature, and thereby feed back a signal to ensure the controller maintains the building at the temperature set on the thermostat.

"[4] An example of a control system is a car's cruise control, which is a device designed to maintain vehicle speed at a constant desired or reference speed provided by the driver.

However, if the cruise control is engaged on a stretch of non-flat road, then the car will travel slower going uphill and faster when going downhill.

The difference, called the error, determines the throttle position (the control).

Now, when the car goes uphill, the difference between the input (the sensed speed) and the reference continuously determines the throttle position.

This greatly aids diagnostics and repair, as all the connections for a single control function are on one diagram.

[6] Based on the standards ANSI/ISA S5.1 and ISO 14617-6, the identifications consist of up to 5 letters.

This is also known as the "tag" identifier of the field device, which is normally given to the location and function of the instrument.

An electromechanical timer, normally used for open-loop control based purely on a timing sequence, with no feedback from the process
A block diagram of a negative feedback control system using a feedback loop to control the process variable by comparing it with a desired value, and applying the difference as an error signal to generate a control output to reduce or eliminate the error
Example of a single industrial control loop; showing continuously modulated control of process flow.