OPC-UA sampling times

Just wondering about the sampling times on the drivers from the OPC-UA server…

These aren’t really clearly stated anywhere (from what I can find), but from what I understand, the sampling rate is generally matched against the polling rate you set in your scan class. Is this correct? My question then would be what is the sampling rate of leased and driven scan classes? Is it equivalent to the fast rate at all times?

My second related question is when using the system.opc.* library, that accesses the driver directly right? As in, no sampling rate or polling rate involved, just a straight request to the device itself?


Leased: it switches between slow rate and fast rate, depending on whether the lease is active.
Driven: it’s subscribed at the fast rate or not at all, depending on whether it’s currently driven.

They issue read or write requests to the OPC server, which then presumably goes straight to the driver, but it depends on the server I guess. In ours that would be the case. There’s no sampling or polling involved since it’s just read or write requests.