The Max Time algorithm calculates the maximum value based on the 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 results returned by the algorithm do not depend on the quality of the data. You can choose to filter the data on quality using the Qualities combo box in the Edit Source window (see Configure a Trace)
The MaxTime algorithm is useful in situations where the maximum values are needed and the exact time at which they were reported is significant.
If the same maximum exists at more than one timestamp, the oldest value is used, although the quality of the data also affects which value is used.
Example:
A point with historic enabled has the following values and time stamps:
| Timestamp | Raw Historic Value |
|---|---|
|
13:01:05 |
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, Geo SCADA Expert 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, Geo SCADA Expert 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