ISA INSTRUMENTATION CODES IN
PROCESS CONTROL SYSTEMS
The ISA standards and symbols are important for
the P&IDs and documents describing the process control system
Process Variable
|
Symbol
|
Type of Instrument
|
Symbol
|
Analyses
|
A
|
Alarm
|
A
|
Burner
|
B
|
Users Choice
|
B
|
Combustion
|
B
|
Controller
|
C
|
Users Choice
|
C
|
Control valve
|
CV
|
Users Choice
|
D
|
Trap
|
CV
|
Voltage
|
V
|
Sensor (primary element)
|
E
|
Flow Rate
|
F
|
Rupture disc
|
E
|
Users Choice
|
G
|
Sight or gage glass
|
G
|
Current (electric)
|
I
|
Monitor
|
G
|
Power
|
J
|
Indicator
|
I
|
Time
|
K
|
Control Station
|
K
|
Level
|
L
|
Light (pilot/operation)
|
L
|
Users Choice
|
M
|
Users Choice
|
N
|
Users Choice
|
N
|
Flow
Resistance Orifice
|
O
|
Users
Choice
|
O
|
Test
point (sample point)
|
P
|
Pressure
/ Vacuum
|
P
|
Recorder
|
R
|
Radiation
|
R
|
Switch
|
S
|
Speed
(or Frequency)
|
S
|
Transmitter
|
T
|
Temperature
|
T
|
Multifunction
|
U
|
Multivariable
|
U
|
Valve/Damper
|
V
|
Vibration
|
V
|
Well
|
W
|
Weight
(force)
|
W
|
Unclassified
|
X
|
Unclassified
|
X
|
Relay
|
Y
|
Event
|
Y
|
Driver
|
Z
|
Position,
dimension
|
Z
|
Actuator
|
Z
|
A level indicator will
receive the symbol "L" for the process variable "Level",
and "I" for the "Indicator" type of instrument. Both
combines to:
LI
|
For unique
identification it is common to add a number to the ISA code, by example the
code for level indicator no. eight may be:
LI 08
|
