Canton’s existing fixed-based AMR system consists of a Meter Transmitting Unit (MTU) that is wired directly to each water meter register. In most cases, these MTUs were installed inside the home or business near the meter. The MTU transmits meter readings two-times per day via radio signal to a nearby Data Collection Unit (DCU). These DCUs, 43 in all, are located on area commercial rooftops or telephone poles to improve reception. They collect and relay meter readings via a cell phone signal to the central server located at the Utility Billing building. Once uploaded, the meter readings are used to generate monthly or bi-monthly utility bills.
Battery Failures in MTUs Detected
After installation and debugging, Canton’s original AMR system worked well. With an anticipated life cycle of 20 years, the system was expected to be relatively trouble free until 2017. In 2009, however, it was brought to the attention of Superintendent Tyler Converse that 1,974 MTUs had stopped transmitting due to premature battery failure. The lithium batteries are both permanently sealed and hardwired in place, and could not be replaced. The only practical option was to install a new unit.
In 2010, approximately 1,500 additional MTUs stopped transmitting and were replaced. In 2011, the number jumped to 4,291 failures. It was theorized that the failure curve would be “bell shaped”, making the large increase in failures in 2011 an ominous sign of things to come.
In 2011, CWD staff met with ACLARA and decided to go forward with the new 3320 series MTUs that were not only less expensive than the old units, but also offered 2-way communication. The new MTUs operate on a different radio frequency than the older units, which meant the 43 Data Collection Units that accept their transmissions would have to be upgraded to read “dual frequencies.” This would allow both the old and new MTU models to be read simultaneously as both would exist in the system during the transition. The central server and AMR software package would also need to be upgraded to accommodate the new 3320 series MTUs.
In 2012, CWD purchased 8,000 new MTUs and upgraded the DCUs, servers and software. The upgrade took 9-10 months as various technical obstacles were identified and resolved. The new MTUs could not be read until the upgrade was complete.