Historical data reads
- Last UpdatedMar 27, 2026
- 1 minute read
- Developer
OPC UA provides a standardized way to access historical (time-series) data stored by a server. Unlike subscriptions, which deliver live updates, historical reads enable a client to query past values, trends, and aggregates over a specified time range.
The following table summarizes supported historical aggregates.
|
Aggregate |
Description |
|---|---|
|
Interpolative |
Returns an estimated value at a specific point in time by interpolating between recorded historical values |
|
Average |
Computes the arithmetic mean of all values in the interval |
|
TimeAverage |
Computes a time-weighted average, useful for irregularly sampled data |
|
Total |
Computes the sum of all values, typically used for cumulative quantities |
|
Count |
Counts the number of values in the interval |
|
Minimum |
Returns the smallest value in the interval |
|
MinimumActualTime |
Returns the minimum value in the interval and the timestamp at which that minimum occurred |
|
Maximum |
Returns the largest value in the interval |
|
MaximumActualTime |
Returns the maximum value in the interval and the timestamp at which that maximum occurred |
|
Start |
The first value in the interval |
|
End |
The last value in the interval |
|
Range |
Returns both the minimum and maximum values over a time interval |
|
PercentGood |
Percentage of interval duration that values were Good |
|
PercentBad |
Percentage of interval duration that values were Bad |
Please consult the documentation for your OPC UA client to configure and execute OPC UA history reads.