3. The Field Wireless Network
Issue 06/15 Publication PUB059-002-00 27 of 136
3. THE FIELD WIRELESS NETWORK
A Pakscan wireless network will contain a master station with a PS721 module fitted to its back plane
(2 for hot standby). Each of these will connect to a PS722 P3W coordinator module. The P3W
coordinator module is the device that controls and organises the wireless network. For an actuator to
be connected on the network it must have a wireless actuator module. The IQ and IQT range of
actuators fully integrate into the wireless system. Other devices can be integrated into the system
using a Wireless to Modbus adaptor (P3W WMA). The P3W WMA can be attached to any device that
has a Modbus interface on it. The host then uses the master station and the wireless network as a
transport layer only to send Modbus messages that are directed to a Modbus device.
A network may also require a number of P3W repeaters to overcome wireless dead spots or to ensure
a redundant path to all devices.
Fig 23: A typical P3 wireless network
Up to 60 devices can be connected in a wireless network. The distances between each node in the
network is recommended to be no more than:
Indoors: 30 metres
Outside: 100 metres
In practice, it has been found that these distances can be extended, but a site survey is required to
confirm this. Each device is able to route messages onto the next device. By this method, the range
of the network is increased. It is recommended to have no more than 7 ‘hops’ from the master station
to the final device. A ‘hop’ is where a message routes through a wireless device to get to the
destination device.
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