Bronkhorst EX-FLOW Mass Flow - Manual (Page 19)

BRONKHORST HIGH-TECH B.V.
4 Cables
4.1 Introduction
An average two-wire cable has a capacity of 120 pF per meter and an inductivity of 0.67 µH/m.
For 100 m cable this results into:
C
cable
= 12 nF
L
cable
= 67 µH
4.2 Control system with XC coil
For the XC coil the capacity and inductivity is not important, but the voltage loss is the limiting factor.
The maximum voltage output of the controller is 14 Vdc.
14Vdc
65 Ohm
XC
Control
circuit
Rk
For a two-wire shielded cable we don't want to allow more than 1 Volt loss.
So, on the coil V
max
will be 13 Volt.
for XC
I = V
R
= =
13
65
200 mA
The cable resistance may be R = U
I
= 1
0 2 ,
= = 5 Ω
A 0,25 mm 2 cable has a loop resistance of 1,6 Ω per 10 meter.
In other words: the maximum length is:
m 30 10 x
1,6
5
≈
cable dia max. length
0,25 mm 2 30 m
0,50 mm 2 60 m
0,75 mm 2 90 m
9.17.028 page 19