Siemens MS Series, Инструкция по эксплуатации, Страница: 84 / 130

SITRANS P, MS series
84
C79000-B5674-C40-04
On-site Operation and Display
Explanations to example (Figure 9, p. 84):
A: We have a transmitter with a measuring span of 0 to 16 bar. It should be set to a
measuring span of 2 to 14 bar.
B: Two bar process pressure are set. The start of scale is set to the value by press-
ing the [Z/
↓
] button. 4 mA output current are generated at 2 bar input pressure.
C: 14 bar process pressure are applied. The full scale is set to the value by pressing
[S/
↑
]. 20 mA output current are generated at 14 bar input pressure.
D: The output current can be calculated according to the specified formula (Figure
8, p. 83) for any input pressure at all.
The start of scale and full scale can each be assigned to a desired current value us-
ing one reference pressure when
adjusting . This function is particularly suitable in
the event that the necessary pressures for start of scale and full scale are not avail-
able. After adjusting, the measuring range specified on the measuring point plate
may not match the adjustment you have made.
Conditions: Applied pressure (reference pressure), the adjusted start of scale and full
scale are known.
Using the formula in Figure 10, p. 85 the current to be adjusted can be calculated for
the desired start of scale and full scale by adjusting the start of scale.
A
Output simulation
B
Set start of scale
C
Set end of scale
D
Calculate output current
Figure 9 Example: setting start of scale and full scale, calculate output current
NOTE
The measuring span is not altered by setting the start of scale.
The start of scale remains unchanged when the start of scale is set.
0
4
0 2
4
0 2
4 16 20 mA
16 bar
20 mA
20 mA
16 bar
18
16 bar
11 14
I = * 16 mA + 4 mA = 16 mA
11 bar - 2 bar
14 bar - 2 bar