
Depending on the series and measuring range, a maximum downscaling of 1:100 can be
achieved (measuring span ratio = r, turn down).
The correlation between the measured pressure and the output current generated is linear.
The square root extracting characteristic curve for differential pressure transmitters is an
exception. Calculate the output current using the following formula.
,
S0
$
0(0$
P$P$
I Output current MA
actual
Old start of scale value
p Pressure ME
actual
Old full scale value
MA Start of scale value MA
target
New start of scale value
ME Full scale value ME
target
New full scale value
Figure 6-6 Current calculation formula for setting
Example of setting with reference pressure
A Initial situation
0$
DFWXDO
0$
WDUJHW
0(
DFWXDO
0$
DFWXDO
0$
WDUJHW
0(
WDUJHW
S>EDU@
,>P$@
S>EDU@
,>P$@
S>EDU@
,>P$@
B Setting start of scale value
C Setting full scale value
Explanations for the example of setting with reference pressure
A The measuring range is from 0 to 16 bar. You are changing the start of scale value from 0
to 2 bar and the full scale value from 16 to 14 bar. The measuring span is then 12 bar.
B 2 bar process pressure is created.
Use the [M] button to set the transmitter to mode 2. To set the start of scale value, press
the [↑] and [↓] buttons simultaneously for 2 seconds.
If there is 2 bar input pressure, the transmitter produces an output current of 4 mA.
Operation
6.5 Local operation
SITRANS P, DS III series with HART
76 Operating Instructions, 09/2012, A5E00047092-08
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