Blind Zero Point/Limit Point; Difference Between Set/Adjust And Blind Set/Adjust - Siemens SITRANS P300 Operating Instructions Manual

6.5.6

Blind zero point/limit point

6.5.6.1

Difference between set/adjust and blind set/adjust.

Difference
In contrast to setting/adjusting with a reference pressure, you do not need a reference
pressure for blind setting/adjusting. Furthermore, you adjust a value in the physical variable
"pressure" without a reference pressure, and an output current with a reference pressure.
Adjusting blind
First select the desired physical unit. Then use the <UP> and <DOWN> keys to adjust two
pressure values and save them in the device. These theoretical pressure values are
allocated to the standard current values 4 mA and 20 mA.
Depending on the model and measuring range, a maximum downscaling of 1:100 can be
achieved (span ratio = r, turn down).
The correlation between the measured pressure and the output current generated is linear.
Example of adjusting blind
A
B
C Blind adjusting limit point
I
MA
ME
Explanations for the blind adjusting example
A
SITRANS P300 with HART communication
Operating Instructions, 06/2005, A5E00359579-02
Initial situation
Blind adjusting zero point
Output current
Old zero point
actual
Old limit point
actual
The measuring range is from 0 to 16 bar. You are changing the zero point from 0 to 2 bar and the
limit point from 16 to 14 bar. The span is then 12 bar.
p Pressure
MA New zero point
target
ME New limit point
target
Operation
6.5 Local operation
6-21