Letter
Category
Processing function
A
Analysis
Alarm, message
B
Optical measurement (e.g. flame monitoring)
Limitation
C
–
Control
D
Density
Differential
E
Electrical voltage
– (must not be used)
F
Flow rate
Ratio
G
Distance, length, position
H
aManual entry, manual intervention
Upper limit, on, open
I
Current
Analogue display
J
Electrical output
K
Time-based function
Temporal rate of change, e.g. for acceleration or calculation of a deduction
L
Filling level
Lower limit, off, closed
M
Moisture
N
Electrical actuation (all electronic consumers, e.g. motor, heating)
O
Local or PCS status display of binary signals
P
Pressure
Point (test) connection
Q
Quantity or number, material characteristics*, quality factors*, analysis* (apart from D, M, V)
Integral, quantity or sum
R
Radiation variables
Value recorded
S
Speed or frequency (including acceleration)
Binary control function or switching function (not safety relevant)
T
Temperature
U
V
Vibration, mechanical analysis, torque
W
Weight, mass, force
X
– (for meanings not listed)
Y
Hydraulic or pneumatic actuation (switching, change, restriction by servovalve for example)
Computing function
Z
Binary control function or switching function (safety relevant)
The code letters for EMC technology according to EN 62424:2014-05 are used. * the meaning for Q is taken from the predecessor DIN 19227-1 1993-10.
Example of application of nomenclature to steam boiler equipment:
Example 1:
Example 2: