Setting both a time and value deadband for retrieval
- Last UpdatedMar 19, 2025
- 2 minute read
If both time and value deadbands are specified, then every sample is checked for both deadbands, against the current basis value (the last sample returned).
If it passes both tests, then it is returned and acts as the basis for checking the next sample.
For example:
SELECT DateTime, TagName, Value
FROM History
WHERE TagName = 'ReactTemp'
AND DateTime >= '2002-03-13 10:08'
AND DateTime <= '2002-03-13 10:28'
AND wwRetrievalMode = 'Delta'
AND wwTimeDeadband = 5000
AND wwValueDeadband = 5
The tag selected, ReactTemp, has a MinEU value of 0 and a MaxEU value of 220. Thus, the value deadband will be 5 percent of (220 - 0), which equals 11. ReactTemp changes rapidly between its extreme values, but the value remains constant for short periods near the high and low temperature limits. Therefore, when changes are rapid, the value deadband condition is satisfied first, then the time deadband is satisfied. In this region, the behavior is dominated by the time deadband, and the returned rows are spaced at 5 second intervals. Where the temperature is more constant (particularly at the low temperature end), the time deadband is satisfied first, followed by the value deadband. Both deadbands are satisfied only when the value of a row is more than 11 degrees different from the previous row. Thus, the effect of value deadband can be seen to dominate near the low and high temperature extremes of the tag.
The results are:
|
DateTime |
TagName |
Value |
|---|---|---|
|
2002-03-13 10:08:00.000 |
ReactTemp |
121.0 |
|
2002-03-13 10:08:10.000 |
ReactTemp |
189.10000610351562 |
|
2002-03-13 10:08:20.000 |
ReactTemp |
147.69999694824219 |
|
2002-03-13 10:08:30.000 |
ReactTemp |
106.30000305175781 |
|
2002-03-13 10:08:40.000 |
ReactTemp |
30.100000381469727 |
|
2002-03-13 10:08:50.000 |
ReactTemp |
16.399999618530273 |
|
2002-03-13 10:09:00.000 |
ReactTemp |
61.0 |
|
2002-03-13 10:09:10.000 |
ReactTemp |
151.0 |
|
2002-03-13 10:09:20.000 |
ReactTemp |
173.0 |
|
2002-03-13 10:09:30.000 |
ReactTemp |
131.60000610351562 |
|
2002-03-13 10:09:40.000 |
ReactTemp |
57.700000762939453 |
|
2002-03-13 10:09:50.000 |
ReactTemp |
16.299999237060547 |
|
2002-03-13 10:10:10.000 |
ReactTemp |
96.0 |
|
2002-03-13 10:10:20.000 |
ReactTemp |
186.0 |
|
2002-03-13 10:10:30.000 |
ReactTemp |
156.89999389648437 |
|
2002-03-13 10:10:40.000 |
ReactTemp |
115.5 |
|
2002-03-13 10:10:50.000 |
ReactTemp |
41.599998474121094 |
|
2002-03-13 10:11:00.000 |
ReactTemp |
21.0 |
|
2002-03-13 10:11:10.000 |
ReactTemp |
41.0 |
|
2002-03-13 10:11:20.000 |
ReactTemp |
131.0 |
|
2002-03-13 10:11:30.000 |
ReactTemp |
184.5 |
|
2002-03-13 10:11:40.000 |
ReactTemp |
140.80000305175781 |
|
2002-03-13 10:11:50.000 |
ReactTemp |
99.400001525878906 |
|
2002-03-13 10:12:00.000 |
ReactTemp |
25.5 |
|
2002-03-13 10:12:20.000 |
ReactTemp |
76.0 |
|
2002-03-13 10:12:30.000 |
ReactTemp |
166.0 |
|
2002-03-13 10:12:50.000 |
ReactTemp |
124.69999694824219 |
|
2002-03-13 10:13:00.000 |
ReactTemp |
50.799999237060547 |
|
2002-03-13 10:13:10.000 |
ReactTemp |
16.399999618530273 |
|
2002-03-13 10:13:30.000 |
ReactTemp |
111.0 |
|
2002-03-13 10:13:40.000 |
ReactTemp |
193.69999694824219 |
|
2002-03-13 10:13:50.000 |
ReactTemp |
152.30000305175781 |
|
2002-03-13 10:14:00.000 |
ReactTemp |
108.59999847412109 |
|
2002-03-13 10:14:10.000 |
ReactTemp |
34.700000762939453 |
|
2002-03-13 10:14:20.000 |
ReactTemp |
21.0 |
|
2002-03-13 10:14:30.000 |
ReactTemp |
51.0 |
|
2002-03-13 10:14:40.000 |
ReactTemp |
146.0 |
|
2002-03-13 10:14:50.000 |
ReactTemp |
177.60000610351562 |
|
2002-03-13 10:15:00.000 |
ReactTemp |
136.19999694824219 |
|
2002-03-13 10:15:10.000 |
ReactTemp |
92.5 |
|
2002-03-13 10:15:20.000 |
ReactTemp |
18.600000381469727 |
|
2002-03-13 10:15:40.000 |
ReactTemp |
86.0 |
|
2002-03-13 10:15:50.000 |
ReactTemp |
181.0 |
|
2002-03-13 10:16:00.000 |
ReactTemp |
161.5 |
|
2002-03-13 10:16:10.000 |
ReactTemp |
120.09999847412109 |
|
2002-03-13 10:16:20.000 |
ReactTemp |
76.400001525878906 |
|
2002-03-13 10:16:30.000 |
ReactTemp |
20.899999618530273 |
|
2002-03-13 10:16:50.000 |
ReactTemp |
81.0 |
|
2002-03-13 10:17:00.000 |
ReactTemp |
176.0 |
|
2002-03-13 10:17:10.000 |
ReactTemp |
163.80000305175781 |
|
2002-03-13 10:17:20.000 |
ReactTemp |
122.40000152587891 |
|
2002-03-13 10:17:30.000 |
ReactTemp |
46.200000762939453 |
|
2002-03-13 10:17:40.000 |
ReactTemp |
18.700000762939453 |
|
2002-03-13 10:18:00.000 |
ReactTemp |
116.0 |
|
2002-03-13 10:18:10.000 |
ReactTemp |
189.10000610351562 |
|
2002-03-13 10:18:20.000 |
ReactTemp |
147.69999694824219 |
|
... |