User Manual, Firmware rev. 3.0 or LATER Owner's manual

172 Publication 1404-UM001F-EN-P - November 2009
Chapter 8 Advanced Features
Readback Mode
The data client uses the indexed read method to read harmonic
analysis and individual harmonic data. The options include the
following:
• Auto-increment (0): increments the channel after each read of
the Harmonic Results; THD, Crest Factor, and More
table. This
also controls the read-back channel for individual harmonics
results tables. If you use the auto-increment mode, read any
desired individual harmonic data for the current channel before
the next read of the Harmonic Results; THD, Crest Factor, and
More table.
• Manual-increment (1): successive reads of the Harmonic Results;
THD, Crest Factor, and More table return harmonic results from
the current channel.
As with other indexed reads, DeviceNet and Ethernet networks
optional communication support only manual increment read-back
mode so that the client must write a read-back select message to
change the channel returned in the results table. For all other
communication options, auto-increment Read-back mode provides the
highest communication throughput.
Reading Harmonic Analysis Data
The power monitor presents harmonic analysis results in the
Harmonic Results; THD, Crest Factor, and More
table. This read-only
table contains 9 floating-point elements in the M4 and M5 models and
10 floating-point elements in the M6 and M8 models. The table
contains the following parameters.
• Channel number: the voltage or current channel being returned.
See above
• % IEEE THD: Total harmonic distortion in per cent based on the
IEEE definition. Range 0.0…1000.0
• % IEC THD (DIN): Total harmonic distortion in per cent based
on the IEC definition. Range 0.0…1000.0
• Crest factor: Range 0…10
• THD & Crest iteration: each new calculation increments by one
from 0…32,767 and rolls back to 0
TIP
The remaining elements are reserved in the M4 and M5 models and
return values of 0.