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Signal processing
7.2 Universal input evaluation
SITRANS DA400 for material flow monitoring with protection against explosion
64
Operating Instructions, 09/2007, A5E00841152-01
7.2.3
Evaluation of 24 V digital signals
Relates to following parameters
Parameter no.
Parameter name
Adjustment/display
range
Remark
P.26 to P.29
"INP1" to "INP4"
"24V" and
"¬24V"
24 V-Digital signal >7 V -> High
¬24 V-Digital signal <4.5 V -> High
Evaluation
The electrical (voltage) signal is converted into a current by a multiplier and measured. This
is described in the "Evaluation of analog current signals" section. A comparator then uses
this value to determine the Low or High level for the signal. The threshold value is set so that
a normally open contact also generates a High signal via the 8.2 V source. With the
parameter setting "¬24 V", the digital signal is inverted.
GR,
GR,
GR,
GR,
0HDVXUHG
YDOXH
,Q
,Q
,Q
)LOWHU
9
3,13
3,13
3,13
3,13
9
3,13
3,13
3,13
3,13
Figure 7-4
24 V digital signal function diagram
See also