ARS31(Pro)-UMB
Operating Manual V9/03.2017
G. Lufft Mess- und Regeltechnik GmbH, Fellbach, Germany
13
The power consumption changes with change in the cable length:
The sensor will have a capacity of max. P = 30W needed.
R1 + R2 = loop resistance
U =
Voltage in the cabinet at the end of the cable
(24V)
U
S
= voltage at the sensor
I = supply current
I is calculated with the equation
𝐼² − 𝐼
U
(R1+R2)
+
𝑃
(R1+R2)
= 0
or
𝐼 =
U
(R1+R2)
−√(
U
(R1+R2)
)
2
−4∗
P
(R1+R2)
2
For the calculated case with loop resistance
1,83 Ω:
24
(1,83) −
√( 24
(1,83))
2
− 4 ∗
30
(1,83)
2
= 1,4 𝐴
Not considered here is the short piece of the standard cable
!
