Static Performance Characteristics

Question 1

Range or span

Answer 1

Minimum and maximum values of a quantity that the instrument is designed to measure.

Question 2

What is instrumentation?

Answer 2

Application of instruments for monitoring,sensing and measurement

Question 3

Static performance characteristics

Answer 3

Part of the data specification for a particular instrument

Question 4

Repeatability

Answer 4

Display the same reading on a number of occasions when input is applied at short intervals of time

Question 5

Stability

Answer 5

Display the same reading on a number of occasions when input is applied over a long period of time

Question 6

Accuracy and precision

Answer 6

Accuracy is stated in terms of errors introduced

Precision is a measure of how close together the results lie

Question 7

Resolution

Answer 7

Measure of the smallest detectable change in the instrument output

Question 8

Non linearity

Answer 8

Measure of the maximum deviation from a linear input/output relationship

Question 9

Tolerance

Answer 9

Measure of the maximum allowable error

Question 10

Threshold

Answer 10

Measure of the minimum level of input required to produce an observable change in the instrument output

Question 11

Zero drift

Answer 11

Where the zero reading is altered by a change in ambient conditions.
Normally removable be re-calibration

Question 12

Sensitivity equation

Answer 12

Change in output/change in input

Question 13

Measuring system

Answer 13

Primary quantity – transducer -(transducer signal)-signal conditioner -(conditioned signal)-display or recorder

Question 14

Transducer

Answer 14

Is an energy converter which receives the physical quantity being measured and converts it into some other physical variable

Question 15

Signal conditioner

Answer 15

Rearranged the signal into a form which can be readily recorded or monitored

Question 16

Main features of an open loop system

Answer 16

1-no comparison between actual and set values

2-each input setting determines a fixed operation condition

Question 17

Main features of a closed loop system

Answer 17

1-output is fed back so that comparisons can be made with the set point

2- closed loop systems have a self regulating property since any external disturbance will change the output , resulting in an error signal being generated by the comparison element

Question 18

Open loop system basic elements diagram

Answer 18

Input
Control element
Actuator
Process or plant
Output

Question 19

Control element

Answer 19

Determines action to be taken with reference to input to the control system

Question 20

Actuator

Answer 20

Responds to input from control element and initiates action to change the variable to the required value

Question 21

Process or Plant

Answer 21

Is the system of which a variable is being controlled

Question 22

Closed loop control system basic element

Answer 22

Input
Control element 
Actuator
Process or plant
Measurement element

Question 23

Comparison element

Answer 23

Compares reference and actual output variable elements and produces error signal

Question 24

Control element

Answer 24

Decides on action when receives error signal

Question 25

Actuator

Answer 25

Produces change in process to remove error

Question 26

Process or plant

Answer 26

Is the system in which a variable is being controlled

Question 27

Basic forms of mechanical system building blocks

Answer 27

Spring - associated with stiffness of the system Damper- exhibits force which opposes motion Mass- offers inertia / resistance to acceleration.

Question 28

What are the specific tasks a mass,Spring and damper perform in a mechanical system

Answer 28

Spring - energy storage device Mass- energy storage device Damper - energy dissipation device

Question 29

What is a hydraulic and pneumatic fluid system

Answer 29

Hydraulic - liquid is deemed incompressible Pneumatic - gas which is compressible and exhibited a change in density

Question 30

Hydraulic resistance

Answer 30

Due to resistance of flow through valves or change in pipe diameter

Question 31

Hydraulic capacitance

Answer 31

Associated with energy storage of a liquid in the form of PE

Question 32

Hydraulic inertia

Answer 32

Equivalent to a Spring in a mechanical system

Question 33

Transient response

Answer 33

Occurs as a result of change in the system input and dies away after a short interval of time

Question 34

Steady state response

Answer 34

Remains after all transient responses have died down completely

Question 35

``` Draw the graph for the typical input signals to a control system Step Impulse Ramp input Sinusoidal ```

Answer 35

-------- | / Sin wave

Question 36

Draw the graph for a first order system subject to a step input

Answer 36

Slow increase in cure which levels out

Question 37

``` Draw the graphs for the response of second order systems to a step input Step input No damping Some damping High camping ```

Answer 37

Look at notes

Question 38

What is rise time (performance measures for second order systems )

Answer 38

The time taken for the response @0 to rise from 0 to the the steady state value and is a measure of how fast a system responds to an input.

Question 39

What is peak time (performance measures for second order systems )

Answer 39

Is the time taken for the response to rise from 0 to the first peak value Time taken for the oscillatory response to complete a half cycle

Question 40

What is overshoot (performance measures for second order systems )

Answer 40

The maximum amount by which the response overshoot @ss

Question 41

What is Settling time (performance measures for second order systems )

Answer 41

A measure of time taken for the oscillations to die away

Question 42

Open loop (control strategies)

Answer 42

On-off switching or timed switching sequence or action

Question 43

Closed loop (control strategies)

Answer 43

Often a two step mode control, proportional control or proportional combined with other features

Question 44

Two step mode control

Answer 44

The error input signal to the control element results in on/off output which is used to switch the correct element on or off

Question 45

Proportional control

Answer 45

Output from the control element is a signal which is proportional to the error

Question 46

Derivative control

Answer 46

The output is proportional to the rate of change of the error signal

Question 47

Integral control

Answer 47

The output at time t is proportional to the integral of the error signal

Question 48

Three term controller

Answer 48

A proportional plus integral plus derivative