Evaluation Of Analog Current Signals - Siemens SITRANS DA400 Operating Instructions Manual

7.2.2

Evaluation of analog current signals

Relates to parameters
Parameter no.
P.26 to P.29
P.30 to P.33
Procedure
The analog current signal is changed by internal measurement resistance into a voltage that
is strengthened, filtered, and changed via an analog-digital exchanger into a digital signal.
This measured value passes through a low pass filter with a fixed time constant. The
measured value is then monitored for under and overflow, which is used to derive a fault
message if appropriate. The following standardization is performed depending on the setting
for the selected parameter:
P.*
0 to 20
4 to 20
20 to 0
20 to 4
The percentage value obtained can then be displayed. It is then monitored to see if it
exceeds the associated alarm "P.30/ALI*" to "P.33/ALI*". The digital signal "dol*" is then
obtained. If the state is "0", the
"1", the
SITRANS DA400 with protection against explosion
Operating Instructions, 02/2006, A5E00684661-01
Parameter name
"INP1" to "INP4"
"ALI1" to "ALI4"
0 %
0 mA
4 mA
20 mA
20 mA
symbol (alarm received).
Adjustment/display Comment
range
0-20 Analog signal 0 to 20 mA->0 to 100%
4-20 Analog signal 4 to 20 mA->0 to 100%
20-0 Analog signal 20 to 0 mA->0 to 100%
20-4 Analog signal 20 to 4 mA->0 to 100%
-5.0% to 105.0% Alarm for universal inputs 1 to 4
symbol (alarm not received) is displayed, if the state is
Evaluating and processing signals
7.2 Evaluation of universal inputs
100%
20 mA
20 mA
0 mA
4 mA
7-3