Deadband (absolute)
An absolute deadband suppresses a data change unless the new value differs from the last reported one by at least DeadbandValue, expressed in the value's own engineering units. It is configured in the DataChangeFilter with DeadbandType Absolute, and it is the cheapest way to stop sensor noise from flooding a subscription.
The comparison is against the last reported value
Not the previous sample. That matters: a value drifting by less than the deadband per sample still reports eventually, once the accumulated difference crosses the threshold, so slow trends are not lost. What is lost is the fine structure of the movement, which is exactly the intent. Status changes are reported regardless of the deadband - the filter only suppresses value changes.
Choosing the number
Set it above the noise band and below the smallest change you care about. A thermocouple reading with plus or minus 0.2 degrees of noise takes a 0.5 degree deadband and stops chattering while still resolving a real process change. If the noise band and the significant change are the same size, no deadband will help - fix the instrument or filter in the device.
Where it does not apply
A deadband is meaningful only for numeric scalar values. Booleans, strings, enumerations and structures have no distance function, and a server may reject the filter with BadDeadbandFilterInvalid or ignore it. On arrays, servers vary in whether the deadband is evaluated element-wise, so verify behaviour before relying on it for array-valued tags.
Example
A 0.5 unit absolute deadband against a noisy signal
last reported 20.0
sample value |diff to last reported| reported? new reference
1 20.1 0.1 no 20.0
2 19.9 0.1 no 20.0
3 20.4 0.4 no 20.0
4 20.6 0.6 YES 20.6
5 20.9 0.3 no 20.6
6 21.2 0.6 YES 21.2
Six samples, two notifications. The drift still gets through; the jitter does not.Defined in: Part 4 - Services, DataChangeFilter; Part 8 - Data Access for engineering units and ranges.
Last verified 7 September 2026 against OPC UA 1.05.07. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.