Our customer is a leading automated meter reading solution provider for commercial buildings and multifamily dwellings.

Energy Monitor is a member of a family of sensors, controllers and infrastructure that is used to transmit specific energy related information from multiple locations in factories / laboratories to a central point in the facility.

The energy monitor can be one of five different kinds of meters, depending on its configuration. The firmware of all the five meters will reside in one energy monitor. Based on configuration, it can be a Fan Coil Monitor or Heat Meter or Pulse Meter or Run Timer or Energy Meter. The data that will be transmitted will be different in different cases.

The data is then passed via commercial communications infrastructure to a central processing point where data is stored, processed and made available to customers. In addition to energy consumption, diagnostic information, unit health information and time information are stored and transmitted. The unit can be configured at the factory to measure one or more parameters necessary to accomplish energy monitoring. The scope of the project includes design and development of application for accurate collection and reliable transfer of utilities metering data. The hardware design consists of RF, baseband controller, utilities sensors, and power supply. Key design factors include:

	Data integrity and security of the data transfer
	Long term reliability
	Low power consumption
	Low cost
	Size

The Solution

Once the energy related information is calculated and stored internally in non-volatile storage, the water meter’s 2.4 GHz spread spectrum wireless data transceiver, periodically transmits information to the host computer. This component is designed utilizing the Direct Sequence Spread Spectrum modulation techniques, and is compliant with the IEEE-802.15.4 standard. The transmission mechanism utilizes Zigbee network architecture, where each energy monitor is configured as a mobile and sleepy reduced function device and the primary gateway as the coordinator. There are multiple other Gateways configured as routers. Commands can also be sent from the gateways to the energy monitor, based on which certain registers are updated at the monitors. The sleepy monitors poll for the commands from their parents when awake. The transmission from the energy monitor to gateway and vice versa makes use of intermediary routers/repeaters, in a secured manner. The coordinator, routers/repeaters and energy monitors are connected in a mesh network topology. The optimization of available bandwidth and minimization of the amount of network activity has been taken into consideration while forwarding the data. For the purpose of forwarding the data to the gateway and vice versa, the router maintains a list of best available routes in order of preference. The network re-establishes itself with a new Pan Id and un-used channel if the Link Quality and the Received Signal Strength of the monitors become gradually poor. In the monitors, the micro controller and the RF chip are put to sleep when not in use, in order to save battery consumption. However, the routers and the coordinators are mains powered and such considerations are not required for them.

A popular third-party ZigBee stack is used to implement the ZigBee architecture for transmission of data and for the remote server to remotely re-program one or all of the devices in the network over the air.

The RF communications using ZigBee networking in energy monitors is similar to water meters. The only difference is the data packet that is being transmitted.