MSA Senscient ELDS 1000 series, Руководство по эксплуатации

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Installation & Commissioning
104
Senscient ELDS™
Rev 15
GB
Bluetooth™ Absorption by Water – Microwave radiation at around 2.44GHz is very strongly
absorbed by water molecules. The human body comprises approximately 90% water and
consequently Bluetooth™ radiation can be strongly absorbed by the presence of people or their
limbs in the direct path of a Bluetooth™ link.
Bluetooth™ Directionality – Bluetooth™ radiation has a relatively short wavelength of just 12cm,
which makes it much more directional than the longer wavelengths typically used for radio
communications. This directionality makes the radiation patterns of Bluetooth™ devices narrower;
and less likely to propagate around corners or behind obstructions than longer radio wavelengths.
Bluetooth™ ‘Patchiness’ – Bluetooth™ wireless radiation interacts with the physical environment
in a manner that can produce a patchy distribution of ‘zones’ from which reliable Bluetooth™
communications are possible. This ‘patchiness’ means that relatively small changes in the location
of one or other of the ends of a Bluetooth™ link can produce significant changes in the
performance / reliability of a Bluetooth™ link.
4.6.2 Bluetooth™ Communications: - Notes and Guidance
In summary, when used correctly the Bluetooth™ communications link will often provide a quicker
and simpler means of communicating with ELDS units than the hard-wired RS485 communications
link. The following notes and guidance should help the user to get the best out of the Bluetooth™
communications link in different installations and environments:-
Proximity:
Remember that Bluetooth™ is a short-range wireless communications link. In general,
the closer you are to the ELDS unit you want to communicate with, the easier it will be to make a
Bluetooth™ connection to it.
Use One Bluetooth™ Connection at a Time: There are no SITE functions requiring
simultaneous connections to both ends of an ELDS system. Every SITE function can either be
performed from just one end of an ELDS system, or at one end followed by the other. Since, in the
majority of field installations it will not be possible to make reliable, simultaneous Bluetooth™
connections to both the RX and TX of an ELDS system, avoid problems by only using Bluetooth™
to connect to one end of the system at a time.
To the Fore Often Works Best: Since Bluetooth™ is directional and the antenna is on the lens-
window at the front of ELDS units, you will often get a better connection somewhere to the fore of
an ELDS unit than to the rear. If you can see the lens-window of the unit with which you wish to
connect and you are not blocking the system’s beam-path, you are probably in a good location for
making a Bluetooth™ connection.
Keep Industrial Computer Stationary Once Connected: Since the strength of Bluetooth™
signals vary significantly with location, once you have made a Bluetooth™ connection it is best to
keep the industrial computer stationary whilst using this connection. Moving the industrial
computer introduces the possibility of the connection being lost.
Keep Out of the Bluetooth™ Path: The water in your body and limbs strongly absorbs
Bluetooth™ signals, so try to keep them out of the path between the industrial computer and the
ELDS unit. (NB: Bluetooth™ signals are completely harmless and present no risk to health.)
Always Give Discovery a Retry: On occasion, the Bluetooth™ device discovery process will fail
to discover the device that you are trying to connect to. It is always worth giving Bluetooth™
device discovery a second try before doing anything else.
Can’t Connect – Try Another Location: Since in some environments Bluetooth™ can become
patchy, if you can’t make a connection to a particular ELDS unit from one location, try moving to
somewhere else. Even a small change in location can enable a Bluetooth™ connection to be
made that was not possible in the original location.