EZMeters are available with three types of Automatic Meter Reading (AMR): Pulse Output, Serial Communication, or None.
Serial Communication (Wired and Wireless)
Using serial communication allows the meter to report kilowatt hours (KWH) as well as volts, amps, watts, power factor, phase angle, hertz and polarity. The meters can be connected together either by a wired network, a wireless network, or very commonly, a combination of both. The meter network itself can be connected either to a local computer, to a local ethernet network (LAN), or to the internet.
Each meter has an RS-485 port which can be connected either to a wired or wireless network. Because the meter is not grounded, these ports are optically and electrically isolated from the electronics on the meter. They require a separate low-voltage power supply to power the isolated side of the communications port.
See the Meter Selection Guide, User and Installation Manual for more details.
RS-485 uses a twisted pair of wires for communication plus another pair of wires for the isolated power. A wired network can be up to 4000 feet (1.2 km) and contain over 200 meters. The cost of running long wires frequently dictate systems where several meters near each other are wired together then connected to a radio for long distance. Davidge Controls can provide a system engineered to work with either SnapLink or Digi radios that can range up to 7 miles (11 km) or you can put together your own system using any radios capable of acting as an RS-485 modem.
An ethernet to RS-485 adapter can extend a meter reading network around the world via the internet. Several companies make devices of this type. The NET485 is a popular choice as it is easier to set up than most. USB to RS-485 adapters are also available from Davidge and others to connect a local computer directly to the meter network.
EZ Plus Protocol
A communication protocol defines how the messages sent between a computer and a meter are structured. The EZ Plus protocol addresses each meter by the serial number printed on the meter case. Its data messages are very short with the data compressed into binary bytes.
For users wanting to use their own software for reading the meters, Modbus is their most likely choice. This protocol has been around since the 1980s and is one of the most common protocols for industrial controls. It requires a separate Modbus address be assigned to each meter, and the meter data is retrieved from numbered registers. When ordering a meter, choose this option only if you have Modbus compliant software such as Davidge’s EZ Meter Power Suite. EZMeters support Modbus RTU.
Davidge is happy to provide a free Windows utility program for setting up a Modbus system. Setup instructions are in the Modbus Installation Guide
Modbus or EZ Plus?
|Max meters in network||246||Unlimited|
|Software Options||Many||Davidge Controls or write it yourself|
|Supported by EZMeter Power Suite||Yes||Yes|
|Supported by EZMeter Reader||No||Yes|
|Ease of programming||Good if you know Modbus||Easier if don’t already know Modbus|
While pulse output meters only report KWH, water and gas meters can also output pulses that can be read by the same system that reads the electric meters. There are several companies that make pulse counting systems, usually with small battery powered radios although some use hard wired data loggers. One such pulse counting system is the Inovonics TapWatch product line. The meter briefly closes a dry-contact switch every time it registers a kilowatt hour and the pulse counting system detects the switch closure, records it and transmits the total count by radio to a data accumulator. Because of the cost of the data accumulator, these systems are rarely installed with fewer than 100 meters. Submeter Solutions offers some reasonably priced alternatives with systems for as few as four meters.
The downside to this type of AMR is that KWH is all you get. The upside is that it can be installed as part of a system that includes water and gas meters
The most popular type of AMR is none. Its cheap. It rarely breaks. It requires that someone manually records the meter readings each billing period and figure out how many KWH were used. The EZMeterReader billing software supports manual entry of meter readings.