Scan Engine period

[Snamprogetti]

In a Labview project, Scan Engine period can be set to up to 1 μs, but the document at http://zone.ni.com/devzone/cda/tut/p/id/7338 says that the Scan Engine updates the I/O variables at up to 1 KHz. This is not clear to me. Is the 1 μs period meant only for counters, PWM etc? For normal I/O what's the point in scanning faster than 1 ms if variables are updated at up to 1 KHz anyway?

[jkurtw]

1ms is the fastest scan rate you can set. once you click ok, it will coerce the value. the usec units are there for resolution. for example, you could set it to 2500usec. hope this helps.

[AdnanZ]

If I change the units to usec, and put in 1, shouldn't it coerce it to 1000?

[jkurtw · Accepted solution]

I was wrong. When you deploy, you get an error. 

"LabVIEW:  The scan engine period you specified is too short for this platform.

Deployment completed with errors"

This is most likely because  you can have a higher scan rate on PXI with the 9144 expansion chassis. 

[AdnanZ]

Don't want to be a bother but shouldn't this be mentioned in the documentation somewhere? And, I still think it should coerce to the minimum value (whatever that value is) since it does coerce to 1 when you enter a 0.

[jkurtw]

I agree. I will file a CAR.

[Donovan_B]

This was reported to R&D (# 147351) for further investigation.  Thanks for the feedback!

[Bastauss]

Hello,

I unearth this topic because I don't find any information about the minimum scan engine period on a RT PXI controller (LabVIEW RT). All topic are about scan engine period on a PXI with VeriStand.

In my case I want to develop a real time application on a PXI which is used Ethercat which means scan engine Loop. I just need to know if the minimum period is the same as on a cRIO ( 1ms) and have some bechmark about reading and writing variables.

Thanks for your answer,