Rievtech x-Messenger Series - Page 218

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analog input into digital values from 0 to 1000. A voltage of 0 to 10 V (or current signal 0/4…20mA) at input
AI is transformed internally into range of values from 0 to 1000. An input voltage exceeding 10 V is shown as
internal value 1000.
Because you cannot always process the range of values from 0 to 1000 as predetermined by x-Messenger,
you can multiply the digital values by a gain factor and then shift the zero of the range of values (offset). This
allows you to output an analog value to the x-Messenger display, which is proportional to the actual process
variable.
Parameter
Minimum
Maximum
Input voltage (in V)
0
≥ 10
Input current(in mA)
0/4
≥20
Internal value
0
1000
Gain
–10.00
+10.00
Offset
–10000
+10000
Mathematical rule
Actual value Ax =
(internal value at input Ax∙gain) + offset
Gain and offset calculation
The gain and offset is calculated based on the relevant high
and low values of the function.
Example 1:
The available thermocouples have the following technical
data: –30 to +70℃, 0 to 10 V DC (i.e. 0 to 1000 in x-Messenger).
Actual value = (internal value ∙gain) + offset, thus
–30 = (0 ∙A) + B, i.e. offset B = –30
+70 = (1000 ∙A) –30, i.e. gain A = 0.1
Example 2:
A pressure sensor converts a pressure of 1000 mbar into a voltage of 0 V, and a pressure of 5000 mbar into a
voltage of 10 V.
Actual value = (internal value. gain) + offset, thus
= (0·A) + B, i.e. offset B = 1000
=（1000 ∙A) +1000, i.e. gain A = 4