Micromod Micro-PWC: 53PW6000 MicroPWC Operators Manual - Manual (Page 79)

Micro-PWC OPERATOR’S MANUAL
Trend Displays 65
6.1.12.1 Trend Compression Speed Factors
There are several factors which affect the amount of time necessary to perform trend compression. The
most important factor is the amount of data to be processed. To a lesser extent, both the location of the
data with respect to the location of processing, and the speed of the Micro-PWC performing the process-
ing, have a measurable influence.
Trend compression time is based on the amount of data that is processed. If all points on the trend display
contain the same amount of data to be compressed, each will take the same time to compress. However, it
is possible to have points with different densities displayed on the same trend (e.g., the trace from Pen 1
reflects data collected at 1 second intervals, while the trace from Pen 2 reflects data collected at 5 minute
intervals). When this situation exists, extra care is needed when comparing compression times.
Where trend compression is a common operation, it is better to do the compression in the Historical Data-
base, in which case it is done as a background task. This is done via the configuration of the Historical
Database points, where the periodic collection rate (1 second, 2 seconds, etc.), the storage rate option
(1, 2, 5, etc.), and the collection option (minimum, maximum, average, or instantaneous value) are config-
ured. (Historical Database configuration is discussed in the Micro-PWC Configuration Guide.)
Briefly, these configuration options make it possible to do much of the compression within the Historical
Database. For instance, an initial compression ratio of 10 to 1 can be achieved within the Historical Data-
base by storing a value that is the average of 10 collection samples (collected at one second), and dis-
played on a Trend Display so that one value is displayed for each point on the plot. Subsequent
compression of the Trend Display using a compression ratio of 1:50 will be much faster, and will yield
exactly the same trace as that displayed when averaging of all collection samples and compression (using
a 1:50 compression ratio) are performed via the Trend Display. By storing a value that is the average of 10
samples, the total amount of data extracted from the Historical Database and averaged is one tenth of
what would be required if every sample were stored and averaged on the Trend Display.
When the Micro-PWC on which the Historical Database data is stored is different from the Micro-PWC that
is controlling the Operator Window which contains the Trend Display, the data must travel across the sys-
tem (ethernet) network in order to be displayed. This can cause a noticeable delay when there is a large
amount of data to be transferred. It can take more than twice as long to compress a large trend under
these circumstances. Using the Historical Database configuration to perform data compression as
described above and thus transferring less data across the network becomes even more important under
these circumstances.
The speed with which trend compression is performed is also affected by the speed of the Micro-PWC
computer being used to view the Trend Display. The processing speed of the Micro-PWC computer is
affected both by the load placed on the CPU and the type of hardware in which the Micro-PWC software is
installed. Consult your system administrator if you have any questions about the hardware platform in use
at your site.
6.1.13 Zoom/Unzoom Button
Use the Zoom/Unzoom button to enlarge a portion of the Trend Graph by choosing two opposing corners
of a rectangular area which is to be enlarged. The chosen section will then be resized to fill the entire area
of the Trend Graph.
To use this feature, click the Zoom button. A prompt appears above the upper left corner of theTrend
Graph:
Select the first zoom point: