Veris Industries H8126-CB Install - Manual (Page 10)

VERIS INDUSTRIES
™
H8126-CB
INSTALLATION GUIDE
Z203167-0A PAGE 10 ©2009 Veris Industries USA 800.354.8556 or +1(0)503.598.4564 / [email protected] 10092
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demand comPutatIon, Internal
algorIthm
The H8163 energy meter records every kW/kVAR reading, as well as a count of the
number of these readings. These readings are recorded every 200 msec (5 Hz). The
meter then computes the present subinterval demand as:
Average kW/kVAR = accumulated kW/kVAR / number of readings
This present subinterval demand can be read at registers AI 25 (kW) and AI 28 (kVAR).
A subinterval may be terminated in three ways:
Write to BO. 1.
Detection of the hardware signal (interval reset). 2.
Set the subinterval length (register ADI 16) to a nonzero value. The subinterval 3.
will end if the count of the number of kW readings equals or exceeds the nonzero
subinterval length.
While there are three ways to end a subinterval, it is expected that applications will
use only one of them.
The maximum valid subinterval length is 65535 readings, which corresponds to 3
hours, 38 minutes, 27.2 seconds. When the device records the 65536th reading, the
subinterval reading counter will roll over. This condition is detected and causes the
subinterval to end. The next subinterval will begin on the next reading. In normal
operation, a subinterval should not last longer than 1 hour.
When a subinterval ends, the average kW/kVAR during that subinterval (accumulated
kW/kVAR readings divided by the number of readings) is added to a 6 value fifo list
of the 6 most recent subintervals. The kW/kVAR accumulator and count of kW/kVAR
readings are cleared to zero, a new subinterval begins, and the count of subintervals
(ADI 14) increments. The present demand is recomputed by averaging the first
N elements of the fifo, where N is the value in register ADI 17. If the new present
demand is higher than the stored peak demand, then the peak demand is updated to
the new present demand.