Process Measurement

Question 1

the process variable is directly measured in units that represent the basic nature of that variable

Answer 1

Direct Method

Question 2

the measurement of a process variable indirectly by using another variable

Answer 2

Inferential Method

Question 3

*TYPES OF MEASUREMENT

Answer 3

• Single Point Type

* Continuous Type

Question 4

• the measurement depends on a fixed value of the process variable
• the reading is indicated either as high or low

Answer 4

SINGLE POINT TYPE

Question 5

the measurement indicates the actual value of the process variable

Answer 5

CONTINUOUS TYPE

Question 6

refers to the capability of the instrument to measure a variable

Answer 6

INSTRUMENT RANGE

Question 7

refers to the set of values within the instrument measuring range where the scaled output; 4-20 mA, 3-15 psi or 1-5 V is set during calibration

Answer 7

CALIBRATION RANGE

Question 8

it is the distance (or difference) between the upper range value (URV) and lower range value (LRV)

Answer 8

INSTRUMENT SPAN

Question 9

the highest value of the measured process variable that the output of a transmitter is currently configured to measure

Answer 9

UPPER RANGE VALUE

Question 10

the lowest value of the measured process variable that the analog output of a transmitter is currently configured to measure

Answer 10

LOWER RANGE VALUE

Question 11

refers to a true-or-false condition

Answer 11

“discrete” variable or measurement

Question 12

one that is only able to indicate whether the measured variable is above or below a specified setpoint

Answer 12

DISCRETE SENSOR

Question 13

• typically take the form of “switches”, built to trip when the measured quantity either exceeds or falls below a specified value
• these devices are less sophisticated than so-called continuous sensors capable of reporting an analog value, but they are quite useful in industry

Answer 13

DISCRETE SENSORS

Question 14

are sometimes referred to in the electrical industry as form-A contacts

Answer 14

Normally-Open Switch

Question 15

sometimes referred to in the electrical industry as form-B contacts

Answer 15

Normally-Close Switch

Question 16

• an electrical switch actuated by a person’s hand motion.

- this may take the form of toggle, pushbutton or rotary

Answer 16

HAND SWITCHES

Question 17

• detects the physical motion of an object by direct contact with that object.
• a limit switch will be in its “normal” status when it is not in contact with anything

Answer 17

LIMIT SWITCH

Question 18

• detects the proximity (closeness) of an object.

- these switches are non-contact sensors, using magnetic, electric or optical means to sense the proximity of objects

Answer 18

PROXIMITY SWITCHES

Question 19

• detects the presence of fluid pressure

- use diaphragms or bellows as the pressure sensing elements, the motion of which actuates one or more switch contacts

Answer 19

PRESSURE SWITCH

Question 20

• detects the level of liquid or solid (granules or powder) in a vessel.
• often use floats as the level-sensing element, the motion of which actuates one or more switch contacts

Answer 20

LEVEL SWITCH

Question 21

• detects the temperature of an object

- often use bimetallic strips as the temperature-sensing element

Answer 21

TEMPERATURE SWITCH

Question 22

• detects the flow of some fluid through pipe

- use “paddles” as the flow-sensing element, the motion of which actuates one or more switch contacts

Answer 22

FLOW SWITCH

Question 23

-the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or acts to prevent flow altogether

Answer 23

ON/OFF VALVE

Question 24

-a voltage or current whose magnitude represents some physical measurement or control quantity

Answer 24

ANALOG ELECTRONIC SIGNAL

Question 25

to calculate the equivalent milliamp value for any given percentage of signal range, the equation takes the form of the _________________

Answer 25

STANDARD SLOPE-INTERCEPT LINE EQUATION y=mx + b