Serial output meter come with one of two protocols, Modbus or EZ Plus. Modbus is a commonly used protocol for all types of industrial control equipment. EZ Plus is a protocol developed by Davidge Controls for calibrating and communicating with EZ Meters.
All serial meters use 2-wire RS-485. With low impedance drivers, up to 255 meters can be installed on a single RS-485 wired network. By using repeaters or wireless links, there is no upper limit. CAT5 or CAT6 cable is normally used to connect to the meters. Two pairs of the cable are used, one for communication and one to power the isolated communication circuit on the meter. It needs to be isolated because the meter is not grounded. The cable can extend up to 4000 feet (1219 meters) before it connects to a PC or other device. That other device could be:
- a USB to RS-485 adapter such as the FTDIChip USB-RS485-WE-1800-BT which connects to a computer
- an RS-485 to Ethernet adapter such as the NET485 which allows the meters to be read over a LAN or the internet
- a radio bridge such as one from Digi or SnapLink. One radio at the computer can communicate with other radios all over a campus.
- a cellular modem such as the CloudLogger from 38 Zeros.
Modbus and EZ Plus meters report not only KWH but watts, volts, amps, power factor, hertz and polarity. With the exception of KWH and watts, these values are calculated by averaging the values of the voltage and current inputs over the last 64 cycles (1.07 seconds) and are not RMS values. Their accuracy depends on the distortion of the wave form.
Our sales staff can advise you one these products. We also can purchase them and pre-wire them before shipping your meters to you.