I have recently been testing the performance of the Siemens Enhanced Driver versus the Siemens Legacy Driver. One useful addition in version 8.3.9 is the Sampling Rates performance page, which provides visibility into how the drivers are performing at different sampling intervals.
During testing, I noticed that the Siemens Enhanced Driver does not appear to provide sampling detail information for rates below 100 ms. For example, if I create a Tag Group with a 50 ms sampling rate and assign tags to it, no corresponding 50 ms sampling information is displayed on the driver's "View Details" page. However, if I create a Tag Group with a sampling rate above 100 ms, such as 110 ms, the sampling details are displayed correctly.
In comparison, the Siemens Legacy Driver does display sampling information below 100 ms in its "View Details" performance page.
This raises a concern that the Siemens Enhanced Driver may effectively be limited to a minimum sampling interval of 100 ms, regardless of how low the Tag Group rate is configured. If this is the case, it could also limit applications that require data acquisition or historian collection at intervals faster than 100 ms.
I don't know why you see this specific behavior, but polling protocols struggle with fast acquisition rates. 100ms is a problem for most non-trivial applications. IA, or the maker of the S7+ library being used, might just not want to deal with users abusing the protocol for a task it cannot do well.
You need an I/O protocol to go really fast, and typically need a PLC-side ring buffer to deal with hiccups. (Especially GC stalls in java.) Or use a PLC-side OPC server that can poll extra fast internally, but deliver batches.
In other words, don't hold your breath waiting for this to be "fixed".
There is not a major use case for sub-100 ms sampling at the moment. My main objective is to understand the practical limits, stability, and performance differences between the Siemens Enhanced and Siemens Legacy drivers before we standardize on one for an upcoming project.
If we move forward with the Siemens Enhanced Driver, we could potentially need more than 100 licenses. Because of that scale, I want to identify any limitations, performance concerns, or edge cases as early as possible. If we discover a critical limitation later in the project, rolling back or changing the driver across a large number of systems could become difficult.
So, at this stage, I am mainly trying to evaluate the drivers thoroughly and identify any potential concerns that could affect us in future use cases.
The Siemens Enhanced driver currently sets a minimum sampling interval of 100ms. We could lower this, the limit is arbitrary, but it doesn't mean you'd actually be able to achieve it, especially for any appreciable quantity of tags.
I’ll keep an eye out for a potential use case, although I expect sub-100 ms sampling would be fairly rare and would likely involve only a very small number of tags.