K-System – Isolated Barriers
Operation
20
20
-1
2
39
5.3
Current and Voltage Standard Signals
The following signals have established themselves as the standard:
•
the 0/4 mA to 20 mA current signal
•
the 0/2 V to 10 V voltage signal
•
the 0/1 V to 5 V voltage signal
Analog sensor signals and digital frequency signals are converted into one of the two standard
signals for processing in a wide variety of measurement, regulatory and control tasks.
This offers the measurement and control technician an easy-to-measure standard signal
common to all manufacturers. Sensor signals are converted into standard signals via signal
converters.
For more diagnostic options, the NAMUR organization published NAMUR recommendation
NE43, dividing the value range of the signal (e. g. current signal) into several areas.
Valid, defined measurement value information is transferred within the range
from 3.8 mA to 20.5 mA. Failure information is available when the signal current is < 3.6 mA
or > 21 mA i. e. outside of the range for measured value information. The same applies
to the voltage signal.
Figure 5.5 Signal ranges according to NAMUR NE43 (e. g. current signal)
1
Failure information
2
Measuring information
I [mA]
4
20
21
0 %
100 %
20.5
3.6 3.8
1
1
2
