Sandy City Utility wanted a proposal and bid to installing a
radio SCADA system to control their well sites and water tanks. We knew that
they were currently using telephone lines to achieve control now. In the RFP
Sandy was asking for a replacement of the existing system. We knew that a
standard radio system would meet their needs. So we proposed
Option 1 using the MDS
9710 which uses a licensed frequency. It included yagi antennas pointed at a
site on the Oquirrh Mountains which repeated the data signal back to the
Master Radio site. While this is a good system we knew that we needed a
competitive edge to beat out others who were going to bid the same system.
We decided to let Sandy City know that new options were now
available. So we also proposed Option 2. We
designed a system around the MDS iNET 900 Industrial Ethernet radio and the
MDS TransNET 900 radio with 'Store & Forward' and 'Alternate Path' features.
We used a combination of yagi and omni antennas. The iNET can reach
communications speed up to 512k allowing a relative inexpensive IP video
camera to be installed for remote security monitoring. With the iNET and its
use of wireless Ethernet it can become part of a larger communications
network. They can also be used in a mobile setting allowing a field operator
to be alerted directly and have access to network data as shown in the
Communications Block Diagram. The TransNET was used to allow for
redundant data paths from the wells that needed less security and to help
keep the costs down.
With this forward thinking technology we knew it might be
difficult to assure Sandy City that it was workable for them. We created a
working demonstration in two days to use in our oral presentation before the
decision making body. We mounted an antenna on our office and connected it
to a PLC and our local LAN. In the back of a truck we mounted an antenna and
radio and parked it beside their Utility Office. On the day of the
presentation we setup the antenna and radio on a tripod in the conference
room of the city building. We were able control a light in our office from
their conference room at the same time feeding them streaming video of the
light. We also presented a slide presentation using data files stored on our
local LAN and visited an internet site of their choosing.
Our Option 2 did have some cons. The radios use the 900 MHz
frequency and are acceptable to line of sight issues. Another con is price.
The iNET 900 radios are more expensive than the MDS 9710 radio. They include
so much more for the price but can make being competitive on a low-bid job
much more difficult.
The speed, flexibility, the use of an un-licensed frequency,
encryption, built in frequency hopping to minimize interference, future uses
and the ability to design a system that reduces the risk of 'whole system
failure' due to a failure of the repeater made Option 2 the a clear choice
even if it was not the least expensive option. |
Option 1 (.pdf 114k)
Option 2 (.pdf 138k)
Communications Block Diagram (.pdf 39k)
Roof Mock-up (.jpg 150k)
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