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Glossary
74
Siemens Industry, Inc.
125-201
09/30/2019
Word
Description
Net
When a register/object has the word “net” in its description, the net equals the
sum of all individual signed measurements.
Object
A BACnet object is a standard data structure that on the MD Model Power
Meter represents electrical measurements.
Power Factor
The power factor of the AC electric power system is defined as the ratio of the
real power flowing to the load to the apparent power, and is a number between
0 and 1 (frequently expressed as a percentage, for example, 0.5 = 50% pf).
Real power is the capacity of the circuit for performing work in a particular time.
Apparent power is the product of the root mean squared current and root mean
squared voltage of the circuit. Due to energy stored in the load and returned to
the source, or due to a non-linear load that distorts the wave shape of the
current drawn from the source, the apparent power can be greater than the real
power.
Pulse Input
Used for counting, accumulating, and scaling pulses received from non-DENT
external pulse initiating meters such as gas, water, or other electrical meters.
Pulse Output
Pulse output is used to generate pulses for external devices such as data
loggers that can accept pulses. The MD-P1 and MD-P1D Power Meters can
generate pulses based on accumulated value(s) such as system kWh, system
kVARh, and system kVAh.
Rising edge
Transition of the input signal from low to high.
RMS
Root-Mean-Square. True RMS is the AC voltage/current that produces the
equivalent amount of heat in a resistor as a DC voltage/current, whether
sinusoidal or not. The MD Model Power Meter measures true RMS.
RS-485
EIA-485 is used as the physical layer underlying many standard and proprietary
automation protocols used to implement Industrial Control Systems, including
BACnet/Modbus/P1.
RTU
A Remote Terminal Unit (RTU) is a microprocessor controlled electronic device
which interfaces objects in the physical world to a distributed control system, or
a SCADA system by transmitting telemetry data to the system and/or altering
the state of connected objects based on control messages received from the
system.
SCADA
Supervisory Control And Data Acquisition. It generally refers to an industrial
control system: a computer system monitoring and controlling a process.
Service
A BACnet service is a message that the MD-P1 and MD-P1D Power Meters
must respond to. In BACnet these include WhoIs, I-Am, and ReadProperty.
Volts Multiplier
A multiplier that changes voltage so that a meter can read measurements
higher than 600V.