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| Titel |
The Telemetric System of Zante station for measuring the Electromagnetic Variations. |
| VerfasserIn |
Manolis Kefalas, John Kopanas, George Antonopoulos, Gregory Koulouras, Dionisis Cavouras, Constantinos Eftaxias, George Minadakis, Constantinos Nomicos |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049467
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| Zusammenfassung |
| Nowadays, one of the most important applications of digital communications is digital
Telemetry. Telemetry is the science that deals with the remote data collection of either
environmental or other kind of signals from field stations to a central one. The purpose
of this project is to study and implement a telemetric system based on the recent
technology regarding remote instrumentation devices and high level programming
languages. In this project the Central station is located at the Physics Department of the
University of Athens, while the remote electromagnetic field station is located at Zante
Island, and specifically, at Agios Leontas vicinity, 35 km far away from Zakynthos
town.
The communication between the field station and the Central station has been established
via dial up modems. ADSL was not utilised because such facility is not available at the
location of the field station, which is quite remote (and thus clear of electrical noise), and
GPRS Technology could produce noise at the electromagnetic measurements. The alternative
of using dedicated digital leased lines was considered extremely expensive. The
system adopted for measuring and recording electromagnetic variations (EMV
signals) in the field station is the datalogging technique. A Powerful Server has been
installed in the Central station, in order to collect the appropriate data from the field
station.
The data of the measurements collected at the field station through the datalogger system
is first stored in ASCII format, in files of one-hour duration. Then the files are packed as zip
files and moved into a directory, ready to be sent to the Central station. The transfer procedure
is implemented via special commercial backup software which is ideal for synchronizing files
in almost any possible way. In our configuration, the backup software has been
scripted to transfer the files to the Central station using dial-up connection. The
backup software establishes the connection to the Central station with the use of a
command line scripting and then it recognizes the Central station as a local network
computer.
As soon as the connection is active, the computer’s clock is synchronized with the clock
of the Central station, which is constantly synchronized over the internet. The next step
following the time synchronization is the transfer of the data. The data is sent as files - with
different filenames from the originals- to a shared directory of the Central station. If each
transfer is successful, the files on the Central station are renamed back to their original name
and are deleted from their source at the field station. If a data file name already exists on the
Central station, the backup software renames the older files accordingly, so that all versions
are stored. The transfer is implemented using shares, but ftp could also be used
for this purpose. When the transfer has been completed, the modem connection is
terminated.
This circle of data transfer is repeated every hour. This means that the field station clock
is also synchronised every hour. Just after midnight, the datalogger clock is checked against
the computer clock. If a time shift of 2 or more seconds is observed, then the datalogger clock
is automatically adjusted.
If a transfer fails for any reason - most probably due to an unsuccessful modem
connection- the full procedure is retried for several times, every few minutes. The exact hour
and minute of each successful file transfer to the Central station is an indicator of the quality
of the line that affects the communication.
After a transfer is completed (or not) and the modem is disconnected, the modem is
automatically set to auto answer mode, thus allowing for the administrator to dial- up and
connect to the field station for maintenance or change of configuration. The screen of the field
station can be remotely observed. |
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