A–16 PQM POWER QUALITY METER – INSTRUCTION MANUAL
DATA LOGGER IMPLEMENTATION APPENDIX A: APPLICATION NOTES
• Log Time Remaining Until Next Reading: This is a counter showing how much time
remains until the next record is to be written into the Data Log
The Data Logger has 2 modes of operation, Run to Fill and Circulate. In the Run to Fill
mode, the Data Log will stop writing records into the memory structure when there is not
enough memory to add another record. Depending on the size of each record, the Data
Log may not necessarily use the entire 65536 bytes of storage available. In the Circulate
mode, the Data Log will continue to write new Records into the Log beyond the last
available Record space. The Log will overwrite the first Record after the Header and
continue to overwrite the Records to follow until the user wishes to stop logging data. The
Log will act as a rolling window of data in time, going back in time as far as the amount of
records times the Log Time Interval will allow in the total space of memory available.
ACCESSING THE DATA LOG INFORMATION
The Data Log can be accessed in two ways: using EnerVista PQM Setup via the serial port.
Access via EnerVista PQM Setup is as described in Chapter 6: SOFTWARE. Access is
manually via the serial port as follows:
• Set the Block of data you wish to access at 1268h in the PQM Memory Map
• Read the required amount of data from the 64 Registers in the Block
Accessing the Data Log in this manner assumes that the user knows which Block they wish
to access, and knows the size of each Record based upon the parameters they have
selected to log.
The easiest way to access the data in the Data Log is to read the entire log and export this
data into a spreadsheet for analysis (this is the method incorporated by EnerVista PQM
Setup). This requires defining the Block to be read, starting at Block 0, and reading all 128
bytes of data in each of the 64 Registers within the Block. You would then define Blocks
1,2,3 etc. and repeat the reading of the 64 Registers for each block, until Block 511. This
requires 512 reads of 128 bytes each. The data can then be interpreted based upon the
parameter configuration.
INTERPRETING THE DATA LOG INFORMATION
Using 2 Data Logs in the Run to Fill mode, the Data Log is configured as follows:
FIGURE A–3: Data Log Configuration
BLOCK 3
FIRST RECORD OF DATA
32
LOG 1 HEADER
RESERVED
RESERVED
LOG 2 HEADER
33
Courtesy of NationalSwitchgear.com
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