Dear All,
reading the manual is not clear to me if the maximum distance of 1200 meters must be calculated between two devices or between devices further away, having to monitor a 4 km long tunnel with 10 measuring points, about every 400 meters (MD485 + AVW200 in each point)
Many thanks
Smile
The MD485 uses standard low power RS485 drivers which have a cable length limit of 1200 m (4000 ft). This is the total cable length.
To stretch the connection out further you would need to add several repeaters. You can form a repeater at a logger using two MD485s (with different SDC addresses) but this does not form an isolated bridge.
Alternatively you can buy commercial RS485 repeaters. One company we have recommended in the past for a source of isolated repeaters is:
These are isolated repeaters which can help avoid ground loop and some noise issues on very long cable runs. Such problems would not be uncommon in long underground tunnels, especially if electric trains are involved.
If there are safety or access issues to the tunnel I would however advise you to seek the advice of an industrial comms specialist as extending MD485 networks have been problematic in the past and can take a while to get right.
thanks for the reply.
Despite your valuable suggestions and assumptions, could be a solution use of mod. AVW216?
Thanks
Smile