Multichannel Frequency Response Function Block?

Question

We are currently using the FRF block to evaluate our DUT with two
channels (X and Y). However our DUT has 8 output channels. Ideally I
would like to be able to wire up the existing FRF block with
multi-channel support (ie 1x X Signal, n x Y Signal) and get the new
block to correctly perform averaging. Currently if I wire up the FRF
block in a loop it averages CH1, CH2, CH3 etc which obviously is the
wrong result.
One solution was to have 8 FRF blocks - but this seemed a bit of an
overkill. Is there a n Channel FRF block anywhere - or has someone
modified it for n Channels? (if not, I suppose I will have to do the
modifications!).
Many thanks,
Marc

Answer 1

Hi Marc,
You asked if there was an N channel FRF block anywhere.  LabVIEW 8.0 added multichannel support for the FRF.  Modes include 1xN,
Nx1, and NxM, where NxM can be interpreted as a pairwise FRF (first
element of X with first element of Y, ...) or as all the combinations
of X and Y array elements.
Barring an upgrade to LabVIEW 8.0, the simplest solution is
probably your
approach of placing N FRF VIs on a diagram.  This ensures that the averaging is the same as the 1x1 case with little programming effort. 
For the 1XN case it should be fairly simple to export the averaging
state and manage that yourself.  If you use one of the other
measurement VIs as a starting point (e.g. FFT Spectrum (mag-phase).vi)
please note that the state cluster that is used is intended to cover the
general case where each "channel" could have a different number of
points, different sampling rate,  different timestamp...  This is the
reason for the array-of-clusters-of-arrays approach.  If you make a
simplifying assumption that each channel will have the same number of
points, same timestamp, etc. then you could utilize a much simpler state cluster
that contains some 2-D arrays to hold the multi-channel averaging information. 
Hope this helps.
-Jim