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HRB1684301-01 109
Chapter 12 Measurements and calculations
This section describes how the power meter processes measured and calculated data.
Real-time readings
The power meter measures currents and voltages, and reports in real time the RMS
(Root Mean Squared) values for all three phases and neutral. The voltage and current
inputs are continuously monitored at a sampling rate of 128 points per cycle. This
amount of resolution helps enable the meter to provide reliable measurements and
calculated electrical values for various commercial, buildings and industrial
applications.
Related topics
• See “Introduction” on page 11 to learn about the meter’s capabilities.
• See “Viewing meter data” on page 61 to learn how to navigate the data screens
using the front panel.
• See “Using software to view meter data” on page 67 for information on energy
management software systems.
Energy
The power meter calculates and stores accumulated energy values for real, reactive,
and apparent energy.
You can view accumulated energy from the display. The energy value units
automatically change, based on the quantity of energy accumulated (e.g., from kWh to
MWh, then from MWh to TWh
).
Related topics
• See “Energy” on page 12 for a list of energy readings.
• See “Energy” on page 65 to view energy readings using the meter display.
• See “Using software to view meter data” on page 69 for information on energy
management software systems.
Min/max values
The meter’s real-time readings are updated once every 50 cycles for 50 Hz systems, or
once every 60 cycles for 60 Hz systems. When the readings reach their lowest or
highest value, the meter updates and saves these min/max (minimum and maximum)
quantities in non-volatile memory.
Power factor
Power factor (PF) is the ratio of real power (P) to apparent power (S), and is a number
between zero (0) and one (1). In a purely resistive circuit, PF is equal to 1 (unity PF).
Inductive or capacitive loads increase the reactive power (Q) component in the circuit
which causes the PF to become less than 1.
Power factor can have a positive or negative sign, depending on the type of load or
direction of power flow. See “Power factor sign convention” on page 110.