Control Instruments

Question 1

Def : feedback control

Answer 1

When an “error” ( difference between desired and actual value) occurs, the control system reacts to reduce the magnitude of the error by changing the manipated variable

Question 2

Def : feed forward control

Answer 2

Disturbances are measured 1st, calculations if any, then change the manipulated variable

Question 3

Closed loop difference from open loop

Answer 3

An open loop has no feedback , ie no self correction

Question 4

Def : measured variable

Answer 4

A quantity , property or condition that is measured also called measurand

Question 5

Def : setpoint (SP)

Answer 5

An input variable that sets the desired value of the controlled variable

Question 6

Def : process variable (PV)

Answer 6

Any variable property of a process

Question 7

Def : error

Answer 7

Algebraic difference between the indication and ideal value of the measured signal

Question 8

Def : manipulated variable (MV)

Answer 8

The quantity or condition that is varied to correct error ie opening a valve more

Question 9

Def : controlled variable (CV)

Answer 9

In a contol loop the variable that is sensed so as to originate a feedback signal ie temp of the pipe after the ajax

Question 10

Def : transmitter

Answer 10

A transducer that senses a measured variable and converts that state to a standardized signal

Question 11

Def : controller

Answer 11

A device or program that operates automatically to regulate a controlled variable

Question 12

Def final control element (FCE)

Answer 12

The device that directly controls the manipulated variable. Ie the valve itself

Question 13

Def : disturbance

Answer 13

An undesirable change in a variable applied to a system which tends to adversely affect the value of the controlled variable

Question 14

This indicates

Answer 14

Located in the feild
Visible at feild location
Normally operator accessible

Question 15

This indicates

Answer 15

Located on front of Central consol or main panel
Visible on front of panel / hmi
Normally operator accessible

Question 16

This indicates

Answer 16

Located in rear of Central consol or main panel
Not visible on front / hmi
Not normally accessible to operator

Question 17

This indicates

Answer 17

Located on front of secondary or local panels
Visible on front of panel or hmi
Normally operator accessible

Question 18

This indicates

Answer 18

Located in rear of secondary or local panel
Located in feild cabinet
Not visible on front panel/ hmi
Not normally operator accessible

Question 19

This indicates

Answer 19

Instrument connection to process and equipment, impulse lines and analyzer sample lines

Question 20

This indicates

Answer 20

Electrical or electronic signal

Question 21

This indicates

Answer 21

Pneumatic signal

Question 22

This indicates

Answer 22

Communication link or bus connecting 2 or more independent microprocessor or computer based systems

Question 23

This indicates

Answer 23

Filled thermal element capillary tube, filled sensing line between pressure seal and instrument

Question 24

This indicates

Answer 24

Hydraulic signal

Question 25

A controller is direct acting if

Answer 25

Its output (CO) increases in response to an increasing measured signal (PV)

Question 26

This means ? DA or RA ?

Answer 26

Valve fails closed DA

Question 27

Controller is reverse or direct

Answer 27

Question 28

When a controller is in auto mode the operator only controller the

Answer 28

SP - set point

Question 29

Bumpless transfer is

Answer 29

A smooth transition from auto to manual and back

Question 30

A direct acting controller calculates error as ___ - ____

Answer 30

PV - SP

Question 31

A reverse acting controller calculates error as ____ - ____

Answer 31

SP - PV

Question 32

With an on/off controller If the error is positive the CO is ___% If the error is negative the CO is __% If the error is 0 the CO :

Answer 32

+ = 100% - = 0 % 0 = CO stays in last position

Question 33

A transmitter is almost always ____ acting

Answer 33

Direct

Question 34

____ = e (error) = sp - pv is for

Answer 34

Reverse acting

Question 35

_____ = e (error) = pv - sp is for

Answer 35

Direct acting

Question 36

This is? And works?

Answer 36

Forward hysteresis It changes stat at PV and will not change back till below SP

Question 37

This is? And works?

Answer 37

Reverse hysteresis. The controller changes state at SP and doesn't change again till below PV

Question 38

This is? And works?

Answer 38

Reverse hysteresis. The controller changes state at SP and doesn't change again till below PV

Question 39

This is? And works?

Answer 39

Changes state at PV1 and doesn't change again till below PV2. Both PV are equal from SP

Question 40

If SP is 40 degrees and PV is 30 degrees calculate pressure

Answer 40

Or (.8 degrees per kpg) +20 kpg

Question 41

If a tank has a set point of 3 meters ad is using a differential gap of 1.5m what is the UTP and LTP

Answer 41

UTP : 3.75 LTP : 2.25

Question 42

Explain how this works

Answer 42

When PV is below SP the relay R is closed sending the signal to the FCE. When the PV overcomes the SP it opens the nozzle and therefore the relay cutting off the signal to the FCE

Question 43

FCE stands for

Answer 43

Final control element

Question 44

Pid DA : sp __ co __ mv __ RA

Answer 44

DA : up down up RA : down up down

Question 45

This is an _____ response

Answer 45

Underdamped

Question 46

This is an ______ response

Answer 46

Overdamped

Question 47

This is a _____ response

Answer 47

Critically damped response

Question 48

This is an _____ response

Answer 48

Marginally stable , aka sustained oscillatons

Question 49

This is a _____ response

Answer 49

Unstable response

Question 50

Ramp calc P only

Answer 50

Question 51

This is

Answer 51

Pulse / response tho pulse

Question 52

What effect can proportional gain have

Answer 52

Smaller offset , but still takes as long to get to steady state

Question 53

A FC valve is ___ acting? Why?

Answer 53

Direct Increase in signal increases opening

Question 54

A FO valve is ___ acting? Why?

Answer 54

RA Increase in signal decreases opening

Question 55

PID P is and does?

Answer 55

Proportional - creates an output signal to the magnitude of the error

Question 56

PID I is and does?

Answer 56

Integral - creates a signal proportional to duration and magnitude - eliminates offset

Question 57

PID D is does?

Answer 57

Derivative Output signal proportional to rate of change of error

Question 58

PID formula?

Answer 58

Co = P + I + D

Question 59

PID prop calc

Answer 59

P

Question 60

PID I calc?

Answer 60

I

Question 61

PID D calc

Answer 61

D

Question 62

HUH?