Definations

Question 1

Accuracy

Answer 1

Accuracy is the degree to which the output of an instrument approaches an accepted standard or true value.

Question 2

Actuator

Answer 2

The device which applies the controller output to the correcting element

Question 3

Calibration

Answer 3

The comparison of a device with unknown accuracy to a device with a known, accurate standard to eliminate variation in the device being checked

Question 4

Closed loop

Answer 4

A control loop in which feedback is used to modify the behaviour of the controller

Question 5

Cascade

Answer 5

With 2 or more controllers the output of the master is the set point for the slave controller

Question 6

Controlled variable

Answer 6

The physical property of the system which is being controlled

Question 7

Controller

Answer 7

The device which compares the value of the controlled condition with the desired value and if there is any difference will produce an output which cause the regulating unit to be adjusted to reduce the deviation

Question 8

Correcting element

Answer 8

The device in the process which produces the change required to control the process

Question 9

Deadband

Answer 9

Is the range through which the input of a device can be varied with out causing an observable response

Question 10

Dead Time

Answer 10

Is the amount of time that it takes for your process variable to start changing after your value changes

Question 11

Derivative

Answer 11

The D of PID with derivative action the controller output is proportional to to the rate of change of deviation between the desired value and the measured value

Question 12

Deviation

Answer 12

The difference between the desired value and the measured value

Question 13

Display element

Answer 13

The device which indicates the magnitude of the measured variable

Question 14

Drift

Answer 14

The actual change in measurement value when the same characteristic is measured under the same conditions at different points in time

Question 15

Error

Answer 15

The difference between the true and indicated value often expressed as a percentage

Question 16

Feedback

Answer 16

The signal returning to the controller from the process

Question 17

Gain

Answer 17

A way of expressing the P part of PID the more gain a controller has the faster the loop response and more oscillatory the process

Question 18

Hunting

Answer 18

A continuous oscillation about the desired value

Question 19

Hysteresis

Answer 19

The maximum difference between readings for the same input when approached from opposite directions

Question 20

Integral action

Answer 20

The I in PID output that varies at the rate that is proportional to the deviation between the desired value and the measured value can be shown as the area between DV and MV when shown graphically

Question 21

Linearity

Answer 21

A measure of the maximum deviation from a linear relationship usually expressed as a percentage of full scale

Question 22

Load Upset

Answer 22

An upset to the process that is not from changing the set point

Question 23

Lag time

Answer 23

The amount of time after the dead time that the process variable take a to move 62.3% of its value after a step change in valve position

Question 24

Manipulated variable

Answer 24

The property in a control system that is being changed to maintain the controlled variable at the desired value

Question 25

Offset

Answer 25

A permanent difference between the measured value and the desired value in a control system

Question 26

Open loop control

Answer 26

A control system in which no feedback of the process variable is present

Question 27

Precision

Answer 27

If a measuring instrument is subjected to the same input on a number of occasions and the output results are together then the instrument is precise

Question 28

Range

Answer 28

The region between the limits within which a quantity is measured

Question 29

Regulator

Answer 29

When a controller changes a process variable to move the process variable back to the set point

Question 30

Repeatability

Answer 30

An indication of the precision of an instrument and provides a measure of the closeness of the readings for a repeated input value when the element is remains connected to its input

Question 31

Reproducibility

Answer 31

An indication of the precision of an instrument and provides a measure of the closeness of the readings for a given constant input when the element is disconnected from its input then reinstalled

Question 32

Resolution

Answer 32

Resolution is defined as the smallest interval between two adjacent and discrete details that can be distinguished from each other

Question 33

Sample Interval

Answer 33

The rate at which a controller samples the process variable

Question 34

Sensitivity

Answer 34

The ratio of a change in output magnitude to the change of input that causes it

Question 35

Time Constant

Answer 35

A calculated figure given in seconds used as the indication of the speed of a system