Individual Tags vs Arrays (Crimson 3.0)

[ais]

This question being asked on the basis of using Crimson 3.0 but probably applies to all similar software.

Does the number of tags used in the HMI impact performance?
If so, how many tags are too many?

Is there any gain to be had by reading (by the HMI) data from the PLC or any other device as an array and referencing the individual bits as opposed to reading indidual tags.

If there some sort of guideline that determines when using an array is better than using individual tags?

 

[RMA]

Does the number of tags used in the HMI impact performance?

Yes!

If so, how many tags are too many?

This will be dependant on the Performance of both the HMI HW & S/W as well as the performance of the PPLC's CPU (and maybe also of its communication processor )

Is there any gain to be had by reading (by the HMI) data from the PLC or any other device as an array and referencing the individual bits as opposed to reading indidual tags.

All the HMI S/W that I know works best if the data is organised in contiguous blocks. This need not necessarily be an array though, simply arranging individual BOOLS sucessively in a BYTE (or better DWORD since most Systems I know communicate using DWORDS) would suffice.

If there some sort of guideline that determines when using an array is better than using individual tags?

Probably not because data organised in a contiguous fashion will always be transmitted faster than a load of BOOLS spread around here, there and everywhere!

 

[OkiePC]

Tag arrays in Crimson:
Pros:
Array tags can be set up to very quickly access many PLC tags in a contiguous block.

Cons:
You only get one label for all of them, so if they're used in a trend viewer, for example, you will be looking at "Tag1[0], Tag1[1]" etc, or your one label followed by the index.

You are limited to 32000 tags, if I recall correctly. The update rate is variable, but the Crimson drivers and the update rates are generally very quick.