Dräger PIR 3000 Instructions For Use Manual page 9

— The leads between central device and gas transmitter must have a sufficiently low
resistance to ensure the correct supply voltage at the gas transmitter. The maxi-
mum resistance per core is calculated as follows:
R = 2.5 x U – 25
C
with R: maximum resistance per core
U : voltage supplied by central device in volts (usually depends on the
C
supply voltage of the central device)
= 24 V, the result is a maximum resistance per core of R = 35 Ω .
Example: With U
C
With cable lengths per core of 1000 m, the resistance per unit length
R' = 35 Ω /1000 m = 35 Ω /km may not be exceeded.
NOTICE:
Cable resistance deviations caused by temperature influences, transition
resistances of terminals, etc. can also contribute to the fact that the calcu-
lated cable length can not be fully used.
— The maximum resistance of the loop R
tral device and of the cable resistance of the signal line) depends on the transmit-
ter supply voltage as described below:
Supply voltage at
the transmitter
10 V
12 V
14 V
16 V
(sum of the internal resistance of the cen-
I
maximum resistance of
the loop R
200 Ω
300 Ω
390 Ω
480 Ω
I
Installing the Gas Transmitter
9