6-3 SHORT-TERM TRENDING

The Real Time Plot program on the Mark V <I> processor shows the user a plot of data points versus time. Normally when a point is chosen for a Real Time Plot, it starts plotting at the current time. No point information is available before the point was chosen. Short-Term Trending, an optional product for the <I> processor, allows the user to specify up to 64 points to be collected all the time. If any of these points are plotted on the Real Time Plot, information on their short-term history is available. This means a point plotted will show a history of the point leading up to the present in addition to new data as the plot progresses. The rate of collection (in seconds) and the amount of time to hold the data can be specified for each point.

6-3.1. Theory of Operation

An IDOS background task (STTREND) is started as part of the normal RUN_IDP startup. This task collects and stores the data in memory. This short-term data memory area is organized in a set of data queues, one queue for each point being saved. Each queue has a period, which defines how often to write a data sample into the queue. The period is defined in seconds, and can range from 1 to 32767 seconds. Each queue also has a depth, which defines how many data samples are stored in the queue, and can range from 10 to 1800 samples. The queue is circular in nature, so once the queue is full the new value overwrites the oldest value in the queue. For example:

• If a queue has a period of 1, and a depth of 600, it will hold one point sample per second for 10 minutes. • If a queue has a period of 60, and a depth of 180, it will hold one point sample per minute for 3 hours.

The STTREND task reads a data file which defines the points, periods, and depths of the queues. STTREND creates the global section to hold this data and proceeds to collect and store the desired data. When a point is plotted on a Real Time Plot, the plotting program will look into the global section to see if the point was saved in short-term trending. If it was, the plot will show the values leading up to the current reading.

6-3.2. Adding Short-Term Trending

The first step is to enable the Short-Term Trending Option. The F:\CONFIG.DAT file defines what options are enabled at each site. Edit this file's options section to include the line:

ST_TREND = Yes

If this line is not included, a reduced size section of memory is reserved to hold just the information for the six points currently being displayed on the Real Time Plot. The second step is to reserve memory for holding the short-term trending queues. By default the <I> will reserve 1 MByte of memory for short-term trend data queues. Always use the default first, and only change the size if there is an insufficient memory error. If the <I> does not have 1 MByte of memory available, the size of the global section can be reduced by adding the option line:

ST_TREND_SIZE = 512

The size given is the number of KBytes of memory to reserve for the short-term trend data. The default value (used if this line does not appear) is 1024, which reserves 1 MByte of memory. Next, the points to be included in the short-term queues

need to be defined. The Short-Term Trend package uses the file F:\RUNTIME\ST_TREND.DAT to define which points

are to be included in the short-term data queues; up to 64 points can be included. The total size of all the data collected must fit within the memory allocated for the short-term trend data. Figure 6-8 contains a sample point definition file.

Once this file has been edited, a report can be generated on the points in the ST_TREND.DAT file. This report is generated by the trending administration (TADMIN) program; to generate a report, enter the command:

F:\RUNTIME> TADMIN /LIST

TADMIN will read the system options from F:\CONFIG.DAT and the point list definition from the

F:\RUNTIME\ST_TREND.DAT file and prepare a report similar to Figure 6-9.

If all the desired information has been received, the size of the reserved memory may be reduced as shown above. This will free up some memory for other IDOS functions.

NOTE

The six points available on the Real Time Plot program are NOT included in the count of the number of points used, but ARE included in the percent of the global section used. Even if a file is reduced to zero points, about 8 percent of the global section will be used.

; This file is used to define what points are to be ; included in the Short Term Trend data queues. ;

;Pointname Period Depth ;Comments ;--- --- --- FE:TNH 1 600 ;Every sec for 10 min FE:WATT 1 600 ; FE:DEAR 1 600 ; FE:TTXM 1 600 ; FE:B_MAX 5 120 ;Every 5 sec for 10 min FE:CSGV 10 360 ;Every 10 sec for 1 hour FE:TTWS1AO1 60 60 ;Every minute for 1 hour

Figure 6-8. F:\RUNTIME\ST_TREND.DAT

--- SHORT TERM TREND POINT AND QUEUE INFORMATION --- Pointname Period Depth Total time --- --- --- --- FE:TNH 1 600 0000 00:10:00 FE:DWATT 1 600 0000 00:10:00 FE:DVAR 1 600 0000 00:10:00 FE:TTXM 1 600 0000 00:10:00 FE:BB_MAX 5 120 0000 00:10:00 FE:CSGV 10 360 0000 01:00:00 FE:TTWS1AO1 60 60 0000 01:00:00 --- --- --- --- TADMIN-INFO, You have used 7 out of 64 possible points. TADMIN-INFO, You have used 11% of the global section space.