Testing a Fixed Network RF AMR System
By Bob Sirkle, Michigan Consolidated Gas Co.
Michigan Consolidated Gas Co. (MichCon) believes, as many utilities do, that the need for more frequent meter reads is now a necessity and that an AMR system is required to cost-effectively obtain these readings. Alternative concepts for achieving centralized AMR were evaluated, including a pilot installation of a telephone-based system. A decision was made, however, not to pursue this particular technology because of installation costs and several other concerns. Other approaches to centralized meter reading, such as low power radio frequency (RF) systems, were also evaluated; they were eliminated from consideration because of the excessive number of data collectors required by these systems.
MichCon decided to commence a pilot evaluation of Hexagram`s STAR fixed network RF AMR system. The chosen test site was Skideway Lake, Mich., located north of Bay City, where MichCon had recently brought gas service to about 800 new residents. This area was chosen for a number of reasons, but primarily because winter conditions make it difficult to read existing gas meters on a regular basis. Either meters are read at an extremely high cost or they are not read at all, in which case residents complain about estimated gas bills. The battery-operated STAR meter modules were easy to install and contained a microprocessor and a high power, narrow band transmitter. The microprocessor stores a programmable I.D. number, monitors usage and senses tampering. At periodic intervals, the radio transmitter sends meter data to the data collectors on a licensed UHF channel which is not subject to interference.
The system provides “one-way” data transmission so that the meter module doesn`t require a receiver to “listen” for wake-up signals. Eliminating the receiver reduces the cost and enables the battery to provide a calculated life of 20 years. Data collectors, containing a receiver and a small computer, receive meter transmissions, decode and error-check data, and store it in memory. Redundancy is inherent because several data collectors receive each meter`s data.
At the Skideway Lake pilot site, two data collectors are located one mile apart. Since field testing determined that transmission range was as great as two miles, MichCon felt that these two collectors would provide reliable coverage over the pilot area.
The data collectors are solar-powered and do not require connection to power or telephone lines. This greatly simplified the siting and installation of the collectors. For purposes of the pilot, meter data is being locally downloaded from the pole-top data collectors by means of a laptop computer. In full-scale operation, however, the data collectors would transfer data to the central computer via cellular phone.
As of June 1996, 125 meter modules have been installed and the system is meeting all of MichCon`s expectations. As time passes, the utility will continue to monitor system performance under various field conditions. Future installations at other sites will be added as the system expands to meet utility requirements.