Electro Industries Nexus 1262, Installation & Operation Manual

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Electro Industries/Gauge Tech Doc # E151701 Glossary-4
Master Device: In Modbus communication, a Master Device initiates and controls all
information transfer in the form of a Request Packet to a Slave Device. The
Slave reponds to each request.
Maximum Demand: The largest demand calculated during any interval over a billing period.
Modbus ASCII: Alternate version of the Modbus protocol that utilizes a different data transfer
format. This version is not dependent upon strict timing, as is the RTU version.
This is the best choice for telecommunications applications (via modems).
Modbus RTU: The most common form of Modbus protocol. Modbus RTU is an open protocol
spoken by many field devices to enable devices from multiple vendors to
communicate in a common language. Data is transmitted in a timed binary
format, providing increased throughput and therefore, increased performance.
Network: A communications connection between two or more devices to enable those
devices to send and receive data to one another. In most applications, the
network will be either a serial type or a LAN type.
NVRAM: Nonvolatile Random Access Memory is able to keep the stored values in
memory even during the loss of circuit or control power. High speed NVRAM
is used in the Nexus® meter to gather measured information and to insure that no
information is lost.
Optical Port: A port that facilitates infrared communication with a (1260/1262 or 1270/1272)
meter. Using an ANSI C12.13 Type II magnetic optical communications
coupler and an RS232 cable from the coupler to a PC, the meter can be
programmed with Communicator EXT software.
Packet: A short fixed-length section of data that is transmitted as a unit. Example: a
serial string of 8-bit bytes.
Percent (%) THD: Percent Total Harmonic Distortion.
Protocol: A language that will be spoken between two or more devices connected on a
network.
PT Ratio: Potential Transformer Ratio used to scale the value of the voltage to the primary
side of an instrument transformer. Also referred to as VT Ratio.
Pulse: The closing and opening of the circuit of a two-wire pulse system or the
alternate closing and opening of one side and then the other of a three-wire
system (which is equal to two pulses).
Q Readings: Q is the quantity obtained by lagging the applied voltage to a wattmeter by 60
degrees. Values are displayed on the Uncompensated Power & Q Readings
screen.