Installation guide – Veris Industries H8163-CB Install User Manual

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Z202879-0D

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H8163-CB

INSTALLATION GUIDE

NOTES

Integer format registers represent the data as 16-bit integer values. Float format
registers represent the same data, as 32-bit floating point values.

For measured data, the float format registers are recommended. The integer format
registers are difficult to use for the measured data, as a multiplier must be employed
for each to calculate the correct value. Most of the multipliers change, depending on
the CT size. Reading the float format registers avoids the need to use multipliers.

Modbus Block Reads

There is no maximum block size restriction, as with the 80xx Series power meters, as
the entire Modbus response is fully buffered. However, the total number of registers
requested may not exceed 125, as the Modbus protocol only allows up to 256 bytes.

125 registers * 2 bytes per register + 5 bytes overhead = 255 bytes.

Demand Computation, Internal Algorithm

The meter computes average kW/kVAR, by accumulating every kW/kVAR reading
and keeping a count of the number of kW/kVAR readings accumulated. This occurs
every 200 msec (5 Hz). The accumulated value, divided by the number of kW/kVAR
readings, is the present sub-interval demand (kW/kVAR), which is read at registers 25
(kW) and 28 (kVAR).

A sub-interval may be terminated in three ways.

1. If a write to the command register has bit #0 set.

2. If the hardware signal (interval reset) is detected.

3. If the sub-interval length (register 36) is set to a nonzero level and the count of the

number of kW readings equals or exceeds the nonzero sub-interval length.

Although there are three ways to end a sub-interval, it is assumed that applications
will use only one of them.

The maximum legal sub-interval length is 65535 readings, which corresponds to 3
hours, 38 minutes, 27.2 seconds. When the 65535th reading is taken, the sub-interval
reading counter overflows. The H8163-CB detects this and ends the sub-interval. The
next sub-interval begins on the next reading. In normal operation, it is expected that
a sub-interval will not last longer than 1 hour.

When a sub-interval ends, the average kW/kVAR during that sub-interval (the
accumulated kW/kVAR readings divided by the number of readings) is added to a
six-value FIFO (first in, first out) that stores the six most recent sub-intervals. The kW/
kVAR accumulator and count of kW/kVAR readings are cleared to zero to begin a new
sub-interval. The count of sub-intervals (register 34) is incremented. The present
demand is recomputed by averaging the first N elements of the FIFO, where N is
the value in register 37. If the new present demand is higher than the stored peak
demand, then the peak demand is updated to the new present demand.

Miscellaneous

Some registers list a model suffix. These registers apply only to those models.
Registers that are not available for the particular model will read “0xFFFF” for integer
points and “NaN” for floating point registers.

The kW accumulator is reset by writing to the command register with bit #1 set. This
clears the kWh accumulator to zero. Any writes to the kWh points are ignored.

Floating Point Registers

All floating point values are compatible with the “32 bit IEEE real” format. All floating
point variables are read-only. All read/write points must be written to their integer
registers.