Instrumentation Vocab

Question 1

The science of automated measurement and control.

Answer 1

Instrumentation:

Question 2

The physical system we are attempting to control or measure. Examples: water filtration system, molten metal casting system, steam boiler, oil refinery unit, power generation unit.

Answer 2

Process:

Question 3

The specific quantity we are measuring in a process. Examples: pressure, level, temperature, flow, electrical conductivity, pH, position, speed, vibration.

Answer 3

Process Variable (PV):

Question 4

The value at which we desire the process variable to be maintained at. In other words, the “target” value for the process variable.

Answer 4

Setpoint (SP):

Question 5

A device directly sensing the process variable and translating that sensed quantity into an analog representation (electrical voltage, current, resistance; mechanical force, motion, etc.).

Answer 5

Primary Sensing Element (PSE):

Question 6

A device converting one standardized instrumentation signal into another standardized instrumentation signal, and/or performing some sort of processing on that signal.

Answer 6

Transducer:

Question 7

A device translating the signal produced by a primary sensing element (PSE) into a standardized instrumentation signal, which may then be conveyed to an indicating device, a controlling device, or both.

Answer 7

Transmitter:

Question 8

The values of process measurement deemed to be 0% and 100% of a transmitter’s calibrated range.

Answer 8

Lower- and Upper-range values (LRV and URV):

Question 9

The alternative descriptions to LRV and URV for the 0% and 100% points of an instrument’s calibrated range. “Zero” refers to the beginning-point of an instrument’s range (equivalent to LRV), while “span” refers to the width of its range (URV − LRV).

Answer 9

Zero and Span:

Question 10

A device receiving a process variable signal from a primary sensing element or transmitter, comparing that signal to the desired value for that process variable, and calculating an appropriate output signal value to be sent to a final control element.

Answer 10

Controller:

Question 11

A device receiving the signal output by a controller to directly influence the process. Examples: variable-speed electric motor, control valve, electric heater.

Answer 11

Final Control Element (FCE):

Question 12

The quantity in a process we adjust or otherwise manipulate in order to influence the process variable (PV). Also used to describe the output signal generated by a controller.

Answer 12

Manipulated Variable (MV):

Question 13

When the controller generates an output signal based on the relationship of process variable (PV) to the setpoint (SP).

Answer 13

Automatic mode:

Question 14

When the controller’s decision-making ability is bypassed to let a human operator directly determine the output signal sent to the final control element.

Answer 14

Manual mode:

Question 15

Instrumentation Documents

The proper form of diagram to represent the “big picture” of a process.

Answer 15

Process flow diagram (PFD):

Question 16

Shows the layout of all relevant process vessels, pipes, and machinery, but with instruments superimposed on the diagram showing what gets measured and what gets controlled.

Answer 16

Process and instrument diagrams (P&IDs):

Question 17

Show the interconnections of individual instruments, including all the wire numbers, terminal numbers, cable types, instrument calibration ranges, etc.

Answer 17

Loop diagrams (“loop sheets”):

Question 18

Diagrams used to document the strategy of a control system. In these diagrams, emphasis is placed on the algorithms used to control a process, as opposed to piping, wiring, or instrument connections.

Answer 18

Functional diagrams:

Question 19

Instrumentation, Systems, and Automation society. Instrument Connections

Answer 19

ISA:

Question 20

A hollow structure designed to provide an enclosed pathway for fluids to flow.

Answer 20

Pipe:

Question 21

A ring of metal, usually welded to the end of a pipe, with holes drilled in it parallel to the pipe centerline to accept several bolts

American National Standards Institute.

Answer 21

A pipe “flange”:

ANSI:

Question 22

The technique of alternating the torque sequence between four quadrants of the flange, ensuring the flanges are evenly compressed together as all bolts are gradually tightened.

Answer 22

Cross-torquing:

Question 23

Special wrenches that exist for the purpose of measuring applied torque during the tightening process.

Answer 23

Torque wrenches:

Question 24

A blank metal plate comprised of a regular blind plate attached to an equal diameter ring by a short tab, the outline of which resembles a pair of spectacles.

Answer 24

Spectacle blind:

Question 25

A device used to couple a section of tube to another tube, or to a section of pipe, or to a piece of equipment (such as an instrument).

Answer 25

Tube fitting:

Question 26

The tube used as the connecting units between an instrument and a process pipe or vessel.

Answer 26

Impulse tube or impulse line:

Question 27

A piece designed to seal off the open end of a tube fitting.

Answer 27

Plug:

Question 28

A piece designed to seal off the end of an open tube.

Answer 28

Cap:

Question 29

A narrow channel of metal – made of bent sheet steel or extruded aluminum – with edges designed for plastic components to “clip” on.

Answer 29

DIN rail:

Question 30

Refers to installing cable into an electrical conduit- something of an art.

It is a technique for cable routing.

Answer 30

Cable pulling:

Cable tray:

Question 31

A special form of wiring often seen in industrial facilities for power distribution.

Answer 31

Busway or bus duct: