© 2017 Van Putten Instruments BV | MAN-VP-SINL-UK | Revision:1701 | Date:22-03-2017
25
Available write operations
Option
Data
Description
4..20mA unit
0
1
2
3
4
5
6
7
8
9
Other
m
n
/sec
m
3
n
/hr
l
n
/min
SCFM
m
3
n
/min
sfps
bar
psi
°C
°F
m
n
/sec
4..20mA min
Decimal value
4..20mA max
Decimal value
Totalizer
Integer or floating point type
depending on register type
Will reset the totalizer to zero
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
required cable quality depends on the total cable distance, the number of nodes and the
environmental influences. A local contractor can help you select the right cable for your application.
