GE PQMII, Инструкция по эксплуатации

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CHAPTER 7: APPLICATIONS
PQMII POWER QUALITY METER – INSTRUCTION MANUAL 7–19
Total Space = (196224 / Record Size) – 1
As in the example, the total space calculated would be 196224 / 26 – 1 = 7546.07. This
equates to 7546 records with 28 bytes of unused memory at the end of Block 1536. The
total amount of space used in the structure can also be found in the Log Header in the Log
Total Records field.
Address 1270h in the PQMII Memory Map is the Holding Register for the first available
parameter for use by the Data Logs. The Data Logs will place the user-selected
parameters into their respective Record structures based upon their respective order in the
PQMII Memory Map.
For example, if Positive kWh, Frequency and Current Unbalance were selected as
measured parameters, they would be placed into the Record structure in the following
order: Unbalance (2 bytes, 16-bit value), Frequency (2 bytes, 16-bit value), and Positive kWh
(4 bytes, 32-bit value). The Data Log Parameters table on the following page illustrates the
order of parameters and their size.
Therefore, the Record size would be 8 bytes. To put a time value associated with each
Record, you must read the Log Time and Date from the Header. This is the time of the most
recent Record in the Log. To time stamp the first Record used, multiply the Log Time
Interval by the Log Records Used and subtract this number from the time associated with
the last Record. To determine the time associated with any Record, add the Log Time
Interval times the Record to be read to the time associated with the first Record in the Log.
For example:
Log Time Interval:3600
Log Time, Hours/Minutes:02 30
Log Time, Seconds:30300
Log Date, Month:06 15
Log Date, Year:1997
Log Records Used:1600
The last Record entry time is interpreted as 2:30 AM, 30.300 seconds, June 15, 1997. The
Log Time Interval is 3600 seconds, or 1 hour. Taking the Log Records Used (1600) and
multiplying this by the Log Time Interval (3600) gives 5760000 seconds. This translates into
66 days and 16 hours. Subtracting backwards on a calendar from the time for the last
Record gives a time and date of 10:30:30.000 AM, April 9, 1997. This is the time stamp for
the first Record. In the PQMII, the sampling time (log time interval) accuracy for the data
logger is 0.15%. This could result in a different time stamp for the first record if the data
logger is retrieved at a different time with a different number of records in the data logger.
Time stamping the remaining Records requires adding 3600 seconds for each Record
starting from the time associated with the first Record. It is important to note that when in
the Circulate mode, and the Data Log fills the available memory, the Log wraps around the
first available Register of the memory structure and the Log Pointer to First Item of First
Record will float along in time with each additional entry into the Log. For example, if the
Data Log has wrapped around the available memory more than once, the Log Pointer to
First Item of First Record will always be preceded in memory by the Log Pointer to First
Item of Record After Last. As each new entry is written into the Log, these two pointers
move down to the next record space in memory, overwriting the first entry into the log as
of the Present Log Time and Date.