WX16 User Manual | 62
special configuration is required by the
master
or
slave,
since this is a standard
ModBus network. However, radios must have the same
Hop Channel
and
System ID
settings to communicate. Radio modules may only be configured when connected to
the WX16’s
master
port. If it is necessary to modify
Hop Channel
and
System ID
settings, the radio module may be temporarily connected to the WX16’s master port for
configuration then moved back to the
slave
port for operation.
The entire WX16 ModBus database, including registers and supported Function
Codes, is documented in section 5.1.
7.4
Wireless ModBus Master Mode
WX16 applications as a “Wireless ModBus master” are similar to the “Wireless
Receiver” mode described in section 7.2 and wiring to the radio modem is identical.
The radio setup menus described in section 7.1 may also be used for configuring hop
channel and system ID settings. The difference is each Channel’s
INPUT DATA
FROM
menu must be configured with the correct
MODBUS
values to match the slave
device instead of
Wireless RF900.
Wired and wireless inputs may be mixed between
the WX16’s sixteen channels so it is also possible to accept wired signals from analog
input option PCB’s described in section 3.1.
This is a popular application when the ModBus slave is another remote WX16 or
Oldham’s WX4 controller available with built in radio modem compatible with the WX16
Radio Kit. Other ModBus slave devices may also be converted to wireless by addition
of another Radio Kit at the slave’s location.
7.5 Antenna
Selection
7.5.1 Dipole And Collinear Antennas
These antennas are connected to the radio via a length of coax cable. If the cable is
larger than 6mm diameter (1/4 inch), do not connect the cable directly to the radio
connection on the WX16 enclosure. Thick cables have large bending radii and
sideways force on the connector can cause a poor connection. Use a short flexible
pigtail (such as our 1000-2308) between the thick cable and the radio.
The polarity of these antennas is the same as the main axis, and they are normally
installed vertically. They can be mounted horizontally (horizontal polarity), however the
antenna at the other end of the wireless link would need to be mounted perfectly
parallel for optimum performance. This is very difficult to achieve over distance. If the
antenna is mounted vertically, it is only necessary to mount the other antennas
vertically for optimum “coupling” – this is easy to achieve.
Dipole and collinear antennas provide best performance when installed with at least 1
to 2 “wavelengths” clearance of walls or steelwork. The wavelength is based on the
frequency:
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