Larry,
There are some PID benchmarks available in the Knowledge Base:
PID Loop Performance Guidelines for LabVIEW Real-Time on a PXI-8156B Target
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/fac66608b1af9ea586256a320052d47f?OpenDocument
PID Loop Performance Guidelines for LabVIEW Real-Time on a PXI-8170 Target:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/b7bc0a08c95d505286256a32005488ce?OpenDocument
PID Loop Performance Guidelines for LabVIEW Real-Time on a PCI/PXI7030/60XX Target:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/43d60aeb2c24d43a86256a32004f419a?OpenDocument
If you are unfamiliar with a PID loop, it is essentially a single scan from a DAQ board, calculations on that scan (a separate PID cal
culation for each channel), and a single update. The simple PID calculation consists of approximately 4 additions, 4 multiplicaitons, 5 subtractions, 2 divisions, and 7 comparisons.
Besides these benchmarks, the only way to know how the VI will perform is to actually build and run it. Performance depends on factors such as processor speed, hardware used, VI priority, and good programming techniques that avoid poor memory management and shared resources.
Chad H.
Applications Engineering
National Instruments
http://www.ni.com/ask
