Rockwell Automation 1425 PowerMonitor Wireless 250 - Manual (Page 42)

42 Rockwell Automation Publication 1425-UM001A-EN-P - January 2012
Chapter 3 Software Interface
The start of such an interval is at the hour + n* interval.
When writing a value other than the ones listed to this parameter, it will be
discarded and the PowerMonitor W250 unit will continue to use the previous set
value.
Note that the PC Receiver will respond with an ‘ACK’ to a write of a valid or
non-valid value as it does not check the contents of the message sent to the
PowerMonitor W250 unit.
Zero Power Detection (register 70)
This register defines a Zero Power Multiplier integer value between 0…10, with a
default value of 3. The formula below utilizes this value to define a Zero Power
Threshold, below which the power monitor will consider the value as zero. A
value of less than 3 for the multiplier is not recommended.
The Zero Power Threshold level expressed in watts, is then:
(Zero Power Multiplier * 8.8) / Interval Energy Scaling Factor.
For instance, considering a PowerMonitor W250-100 device.
Zero power threshold = 3 * 8.8 / 3.2 = 8.25 watts.
When the measured value of power is less than the zero power threshold, Real,
Reactive, and Apparent Energy registers do not increment, and the Maximum
Current registers are set to 0.
IMPORTANT When changing the interval time, the PowerMonitor W250 unit will calculate
the end of the next recording interval time while keeping the current interval
measurements. This means that at the end of the recording interval, the
timestamp will be correct with respect to the new setting, but the first interval
values are not guaranteed to be integrated over the set interval time and thus
should be discarded by the master application software.