Siemens MS Series, Инструкция по эксплуатации, Страница: 85 / 130

SITRANS P, MS series
85
C79000-B5674-C40-04
On-site Operation and Display
Explanations to example (Figure 11, p. 85):
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. A reference pressure of 11 bar is available.
B: The current to be adjusted is first calculated for the desired start of scale (2 bar)
at the applied reference pressure using the formulae (Figure 10, p. 85). The cur-
rent to be adjusted is first calculated for the desired start of scale (2 bar) at the
applied reference pressure using the formulae.
C: The current to be adjusted is first calculated for the desired full scale (14 bar) at
the applied reference pressure using the formulae (Figure 10, p. 85) and then ad-
justed (16 mA).
Figure 10 Formula for calculating the current (start of scale, full scale)
A
Output simulation
B
Calculate start of scale
C
Calculate end of scale
Given: p
Ref
= 11 bar
The measuring span 2 - 14 bar is to be adjusted
Figure 11 Example: adjusting start of scale and full scale
Current to be ad-
justed at MA
Current to be ad-
justed at ME
I = output current
p = applied reference pressure
nom
Ref
I = * 16 mA + 4 mA
p - MA
ME - MA
Ref
nom
act
I = * 16 mA + 4 mA
p - MA
ME - MA
nom nom
nom
Ref
nom
act
ME
act
= old full scale
MA
act
= old start of scale
ME
nom
= new full scale
MA
nom
= new start of scale
p
16 20 mA 4 adjust
0 11 16 bar 14 2
MA ME MA
nom nom act
13 18 4 adjust
0 11 16 bar 2
MA MA ME
nom act act
4 15 20 mA
0 11 16 bar
Ref
Current to be ad-
justed at MA
current to be ad-
justed at ME
nom
nom
I = * 16 mA + 4 mA = 13 mA
11 bar - 2 bar
16 bar - 0 bar
p
Ref
I = * 16 mA + 4 mA = 16 mA
11 bar - 2 bar
14 bar - 2 bar
p
Ref