# MCQ on Building Controls III: Introduction to Control Loops | Primo Engineering

The value that the controller is aiming to achieve is called the:

• Set point
• Control point
• Offset
• Controlling variable

Floating control may be used to control an analog device. The process will increase or decrease the control signal to the device based on its current position and its operating range. When floating control is used to control an analog device, the signal will be a value within a range, for example, between 0% and 100%. "

• True
• False

Which of the following are digital responses?

• Proportional
• Proportional + Integral
• Proportional + Integral + Derivative
• All of the above
• None of the above

Two-position control always produces an analog response where the end device is either in an "on" state or â€œoffâ€ state. The controlled device is also analog.
• True
• False

What are the five control loop responses?

• Two-position response, floating response, proportional response, proportional plus integral, and proportional plus integral plus derivative response
• Two-position response, tri-state response, floating response, proportional response, and inverse response
• Tri-proportional response, integral response, derivative response, floating response and a programmed logic response
• None of the above

What is a differential and why are differentials needed in building controls?

• The differential is where the “deadband” or neutral zone occurs. It is needed to ensure the system differentiates between on and off.
• The differential is where the throttling range is maximized. Without a differential, the throttling range the actuator will hunt for the programmed logic, and not finding it, will eventually shut down.
• The differential is a characteristic of a two-position controller. It is the difference between the setting at which the controller operates at one position, and the setting at which it changes to the other position. This is needed to prevent the controller from rapidly cycling off and on, also known as “hunting”.
• None of the above

A tri-state device can accept one of three input signals. What are the possible responses?

• Clockwise rotation, counter-clockwise rotation, or remain stationary
• Open a contact, close a contact, or sound an alarm
• None of the above

The difference between the actual value and the value that the controller is aiming to achieve is called the.

• Error-Offset
• Differential
• Setpoint-Control point
• None of the above

What is the throttling range?

• The throttling range refers to the precision with which an actuator may be positioned, e.g. in increments of 10%
• The throttling range is the amount of change in the controlling variable required to run the actuator of the controlled device from one end of its stroke to the other end.
• The throttling range is the set of outputs that inversely correspond to the deadband of a floating response.
• None of the above

Stability is achieved when the controller has obtained the desired value with zero offset.

• True
• False

## Summary of Building Controls III: Introduction to Control Loops Course

controllers are the components of the system that take in the data from the input devices, such as sensors or pushbuttons, and process them using programmed logic. The method with which the controller interacts with the controlled device is called the control loop response. We then identified the five control loop responses, which are:
• A two-position response
• A floating response
• Proportional response (also called by its initial P)
• Proportional plus integral (or P.I.),
• Proportional plus integral plus derivative (also called P.I.D. response)

We also review the terms associated with control loop responses, which included:

• Set-point
• Offset or error—which is sometimes referred to as drift, deviation or control-point shift
• Stability
• Differential
• Neutral zone, and finally
• Throttling range

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