The Max Time algorithm calculates the maximum value based on the good quality raw values in the sample. The highest value is the Max Time value. Where the Max Time algorithm differs to the other maximum algorithms is that its timestamp is not the start of the sample; instead, it uses the timestamp for the highest value in the sample.
The MaxTime algorithm is useful in situations where the maximum values are needed and the exact time at which they were reported is significant.
Example:
A point with historic enabled has the following values and time stamps:
| Timestamp | Raw Historic Value |
|---|---|
|
13:01:00 |
20.11 |
|
13:01:10 |
20.62 |
|
13:01:20 |
20.78 |
|
13:01:30 |
21.02 |
|
13:01:40 |
21.65 |
|
13:01:50 |
21.21 |
A Trend is configured to show the point’s historic data graphically. Rather than display each of the point’s raw historic data values, a processed historic trace is configured to use the Max Time algorithm. The trace has an Interval setting of 1M (1 minute), which means that at the start of every minute, ClearSCADA calculates the Max Time value using the raw historic values in the 1 minute sample (which starts from the beginning of the minute).
At 13:01, ClearSCADA has to calculate the Max Time value. To do this, it examines the raw historic values in the period 13:01:00 to 13:01:59. The highest value is the Max Time value, and so the result of the calculation is 21.65.
On the trace, the 21.65 value is plotted with the timestamp for the corresponding raw historic value. So, 21.65 is plotted at 13:01:40. Had any of the other maximum algorithms been used, the 21.65 value would have been plotted at 13:01:00 as the other maximum algorithms timestamp their results with the start time of the sample.
Further Information