Kipp&Zonen BSRN Scientific Solar Monitoring System - Manual (Page 34)

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power available. This can be accom plished by obtaining inform ation on the power supply from the
local power authority.
The m inim um suggested protection on all crucial equipm ent (e.g., com puters, trackers, line
powered data acquisition system s) is an uninterruptible power supply (UPS) capable of
m aintaining the system during outages caused by electrical storm s, increased com m ercial
dem and (brownouts) and autom atic switching of grid loads due to equipm ent failures. Most of
these outages only require that the system m aintain the equipm ent for less than 10 - 15 m inutes;
often the interruption is for less than one or two seconds. Nevertheless surges or failures, even of
this short duration, will cause the resetting and/or failure of equipm ent with an inherent loss of
data.
W ithin the observatory, the com plete power requirem ents, including design for future expansion,
m ust also be considered. Transform ers, fusing and wiring m ust be capable of bearing the load
required to m aintain the instrum entation. This problem is of particular concern when (1) individual
circuits are overloaded with com puting and data acquisition equipm ent or (2) long line lengths are
required to conduct electrical power to distant field sites from a m ain panel.
3.4.3 Com m unication
At stations rem ote from network infrastructures, consideration m ust be given to transferring
inform ation from the observation platform to the laboratory where data analyses are perform ed.
W hile form erly such data transfer took place by m ailing inform ation to the central processing
facility, first on paper and later on diskettes, today a plethora of options is available. The intent of
this section is to m ake the user aware of som e of the possibilities available to transfer the
collected m easurem ents to the platform (s) on which the analyses occur. Expertise on the
installation and operation of m any of these m ethods should be available either from within national
m eteorological services or through private-sector consultants.
For data transport within a com plex between two com puters, a sim ple m ethod is through direct
serial or parallel com m unication. Many software operating system s now include built-in m ethods
to allow easy com m unications between two com puters without the com plexity of local area
networking.
Long-distance file transfer can be accom plished using norm al telephone lines and high-speed
m odem s for direct com m unication between com puters. The frequency of the data transfer and the
am ount of data being transferred using this m ethod will dictate both the tem poral efficiency and
overall cost of this data transfer m ethod. Most high-speed digital serial m odem s are capable of
transm itting data at about 40 kbs (kilobits per second). At this rate one Mb (m egabyte) of data
could be transferred in just less than 3.5 m inutes.
The rapid advancem ent of the internet and world-wide web have m ade transfer of data over long
distances m uch less expensive than using direct-dial telephone com m unications. Local internet
service providers, which can be accessed through telephone, digital m odem or through local area
network connections provide a reliable and inexpensive m eans of delivering data over great
distances. The m ore norm al m eans of connecting to the internet are now being supplem ented
with direct line-of-site wireless and cellular telephone connectivity. Depending on the am ount of
data to be transferred several different options can be selected, varying from real-tim e constant
connections to daily or less frequent data downloads.
W hen m ore than two com puters are required to com m unicate, a sim ple Local Area Network (LAN)
can be easily established. Using standard protocols (often sold as part of the com puter operating
system ) and inexpensive adapters, several to hundreds of com puters can com m unicate together,
sharing resources, at far greater data transfer rates than serial com m unications. For exam ple,
data can be downloaded from a data acquisition system (e.g., Cam pbell Scientific CR7) using
serial protocols (either locally or through rem ote com m unication m ethods) onto a single com puter
which is part of a network. This com puter can then be accessed by m any authorized users
through a LAN. Data can be downloaded from the com puter com m unicating with the data
acquisition system through the network, or users can sim ply access the data from storage that
resides at the site of the observations.