In “SDS13781-5 Z-Wave Application Command Class Specification.pdf”, of April 10, 2018, table 67, p251, there is reference to several measure that are described as ‘Instant’. I know from work on smart metering that such measures are open to all sorts of interpretation, since there is often no consistent description of when an instant occurs, or how the value should be calculated. I’d expect the situation for ZWave to be particularly bad as the sampling periods can be quite lengthy.
From a signal analysis pov, the issue is that the sampling period is nowhere near the Nyquist frequency. If there is no standardised specification for Instant values, the actual measures can be very variable. It is rare for the sum of Instant values to match corresponding accumulated measurements, where they could reasonably be expected to do so (eg Instant Power, Accumulated Energy).
This issue is not as significant for accumulated values.
Is there any standardisation of the measurement of Instant values, requirements that they should sum to Accumulated values, where appropriate, or even that both Instant and Accumulated values (with the relevant dimensions) should all be available so that the application can have some reconciliation of the reported data?