Micromod Micro-PWC: 53PW6000 MicroPWC Configuration Guide - Manual (Page 253)

Micro-PWC CONFIGURATION GUIDE
Historical Database 233
5.2.4.4 Return to Default Settings
Click Default to change all parameters to their default settings. Default settings are illustrated in
Figure 5-12 .
5.2.5 Historical Database Configuration and Trend Compression
When configuring historical database points which will later be viewed in compressed form on a trend dis-
play, it is important to remember that the primary factor associated with the length of time it takes to display
a compressed trend is the amount of data which must be processed. When the Micro-PWC that is control-
ling the Operator Window which contains the trend display is different from the Micro-PWC on which the
data is stored, then data must be transferred across the system network, which increases the length of
time needed to compress the trend display. It can take over twice as long to compress a large trend under
these circumstances; thus, transferring less data across the network becomes even more important under
these circumstances.
The periodic collection rate, collection option and storage rate of historical database points can be config-
ured so that data compression can be performed in the historical database as a background task, rather
than as a function of the trend display. This can reduce the length of time required to display the com-
pressed data.
For instance, an initial compression ratio of 10 to one can be achieved within the historical database by
storing a value that is the average of 10 collection samples (collected at one second), and displayed 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 50:1 will be much faster, and will yield exactly the same trace as
that displayed when averaging of all collection samples (10 at a time, using the Seconds and Points
parameters) and compression (using a 50:1 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.
TC00590A
Figure 5-12. Historical Tag Configuration Window with Default Settings
✎ Note Compression of trend displays is discussed in detail in the
Micro-PWC Operator’s Manual.