Radar level gauges-Intermittant comm failures in loop
Radar level gauges-Intermittant comm failures in loop
(OP)
All,
We recently installed a number of radar level gauges and we have the problem of ~3 units per loop (7-8 devices per loop) intermittantly dropping communication for short periods of time. They are placed in a sort of 'star' setup, and they come through a DIGI card at our input. Feel there is probably noise problems and I would welcome any ideas (hopefully from someone who has seen a similar problem) on methods of improving the integrity of this system. Thanks in advance.
We recently installed a number of radar level gauges and we have the problem of ~3 units per loop (7-8 devices per loop) intermittantly dropping communication for short periods of time. They are placed in a sort of 'star' setup, and they come through a DIGI card at our input. Feel there is probably noise problems and I would welcome any ideas (hopefully from someone who has seen a similar problem) on methods of improving the integrity of this system. Thanks in advance.





RE: Radar level gauges-Intermittant comm failures in loop
John
RE: Radar level gauges-Intermittant comm failures in loop
RE: Radar level gauges-Intermittant comm failures in loop
Mark Hutton
hutton4eng@picknowl.com.au
RE: Radar level gauges-Intermittant comm failures in loop
RE: Radar level gauges-Intermittant comm failures in loop
I realize everything was spec'd well but what about the cable length? Are we talking a few hundred feet or a couple thousand?
RE: Radar level gauges-Intermittant comm failures in loop
What kind of distributed control system are you using? (Siemens, ABB (taylor), Delta V, etc.)
Is it block programming or ladder logic?
And what protocol for sending the signal are you using?
(Foundation Fieldbus, Profibus, Analog (4-20ma), Asibus)
These are the kind of questions needed to determine a helpful solution. Also what kind of radar unit are you using? Manufacturer and cone setup.
Good Luck
Quote: "Its not what you know, its who you know" - anybody trying to find a decent job
RE: Radar level gauges-Intermittant comm failures in loop
RS-485 devices should be connected in a daisy chain fashion, not star. However this is really dependent on the transmission speed and cable lengths.
The problem with star connected networks is that there is no way to properly terminate the network. An unterminated network will have reflections which show up as noise. As the transmission rate increases, these reflections contribuite more noise.
RE: Radar level gauges-Intermittant comm failures in loop