VPFlowScope M
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© 2016 Van Putten Instruments BV | MAN-VP-MPRO-UK | Revision:1602 | Date:20-10-2016
10.3
Alarm
The alarm output is an active non potential free current output.This means that the + wire is shared
between power supply and the alarm output. The idle current will be 0mA. When an alarm is
triggered, the alarm output will go to 20mA. The alarm output can be wired into a central data
acquisition / building management system as signal. An external control current relay is required to
switch on lamps or buzzers. When selecting a relay, make sure that the input can be controlled by
a current signal.
Cabling
The electrical specifications are identical to the 4..20mA output. Therefore the suggested cabling is
identical.
Electrical scheme
10.4
RS485
Installing a RS485 network require specific knowledge. Not following the
specifications strictly might result in in-correct communications and equipment
damage. Please leave installation up to professional contractors. Make sure that
they read this chapter carefully and follow up all RS485 guidelines.
RS485 is a differential balanced line over twisted pair. It can span relatively large distances up to
1200 meter | 4000 feet. The wires should be connected as a point-to-point configuration, or also
called daisy chain. Do not install as star or ring network! The trunk line goes from the master to all
devices making a drop down to each device. The cable length from the trunk line to the Modbus
device needs to be as small as possible. Junction boxes are used to make the T junction.
Shielded twisted pair should be used. Connection of a third wire between the master and slave
should be done to limit the common mode voltage that can be impressed on the slaves inputs. The
