Campbell Scientific CR6 CR6 Measurement and Control System - Page 196

Section 7. Installation For individual measurements to affect summary data, output processing instructions such as Average() must be executed whenever the data table is called from the program - normally once each Scan. For example, for an average to be calculated for the hour, each measurement must be added to a total over the hour. This accumulation of data is not affected by TrigVar. TrigVar controls only the moment when the final calculation is performed and the processed data (the average) are written to the data table. For this summary moment to occur, TrigVar and all other conditions (such as DataInterval() and DataEvent()) must be true. Expressed another way, when TrigVar is false, output processing instructions (for example, Average()) perform intermediate processing but not the final process, and a new record will not be created. Note In many applications, output records are solely interval based and TrigVar is always set to TRUE (-1). In such applications, DataInterval() is the sole specifier of the output trigger condition. Figure Data from TrigVar Program (p. 196) shows data produced by CRBasic example Using TrigVar to Trigger Data Storage (p. 196), which uses TrigVar rather than DataInterval() to trigger data storage. Figure 56. Data from TrigVar Program CRBasic Example 30. Using TrigVar to Trigger Data Storage ' the use of the TrigVar parameter in the DataTable() 'instruction to trigger data storage. In this example, the variable Counter is 'incremented by 1 at each scan. The data table, which includes the Sample(), Average(), and 'Totalize() instructions, is called every scan. Data are stored when TrigVar is true, and 'TrigVar is True when Counter = 2 or Counter = 3. Data stored are the sample, average, 'and total of the variable Counter, which is equal to 0, 1, 2, 3, or 4 when the data table 'is called. 196