User`s guide

1-2
enclosure is capable of withstanding extremes in temperature and humidity. Standard
units come equipped with an internal antenna that conceals the wireless nature of the
product, thereby serving as a passive deterrent against theft. The enclosure door can
be locked to prevent vandalism, and there is a sensor to detect when the door has been
opened.
Communications with the electric meter is conducted over an RS-232 serial interface.
The meter itself must be equipped with a similar interface.
Metretek has developed a powerful data collection software package called DC-2000,
which runs on the central computer and can process calls from thousands of devices.
Data from each device is stored in a database for later use.
1.2 Communications Options
Remote data collection is essentially comprised of three basic components:
1) A data collector instrument that takes measurements and stores them into
memory. For this application, the data collector consists of an ANSI C12-
complient electric meter, such as the Elster Alpha series.
2) A communications path that permits the transfer of information from the data
collector in the field to a computer site at the corporate office. It is possible for
the communications path to range from wired telephone lines to advanced
satellite transmitters. Trade-offs based on performance, economics, and the
existing communications infrastructure point to the wireless cellular phone as
being the best overall solution.
3) A central computer data collection / processing site is required for retention
and analysis of the data acquired from field units. Specialized software is
necessary for the user interface and data collection functions. After
processing has been completed, the data is stored using a database
application program. Metretek’s DC-2000 system provides all of these
functions.
Selecting a communications network to reliably transfer the collected data poses the
greatest challenge. Economic factors come into play where the initial product cost must
be weighed against monthly network service charges. This is further complicated when
considering the rapid pace with which communications systems are evolving.
Some points to consider when selecting a network are:
- Satellite or microwave data links have a high initial cost and a high ongoing cost to
maintain the service. Advantages include high reliability and high bandwidth (fast data
transfers).
- Wired telephone line connections with a modem circuit are the most common for cost-
sensitive applications. Installation and operation costs depend upon how accessible a
phone line is at the site, whether the line is dedicated or shared, and whether the calls
are local or long distance.