rajsiyer

How to create a trend - from a database-table in Citect Scada (v7.40)

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Hi friends, The scene is like this... I have some 200 energy meters whose readings are continuously logged at 15-min intervals into a logging table. The meter does not have any other value logged. Let's consider these readings as analog tags. However these tag values are continuously increasing to ever larger numbers. Thus we have a problem for display on trends. Customer now requires that the Citect shows usage trends for any meter for a specified period of the past. That is to say, the meter that he wishes to observe is selected - along with a period typically between 2 dates (perhaps also with a sampling period) - and the trend must appear. So in other words, given a single trend object, how do you make values appear for any selected tag on this trend. Perhaps this can be overcome by some genie/super-genie mechanism. My approach to this is...For the selected meter, I use SQL to query the 15 minute logged values (also taking into account the required sampling period) taking the reading on starting date as initial. All values thereafter are subtracted -within the SQL query- and the result of this query is kept in a 2 dimensional array(x for time, Y for value) or a new database table so that the trend displays values starting with zero. This much I can do with Cicode. After this, I need a method to display the values so obtained in a trend object. Essentially this is the same as feeding a trend object with a set of X & Y values that I have in the form of an array or in a database table. I shall greatly appreciate any help to meet the above objective. Thanks for looking in. With best wishes.

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