Poor results when cascading SCXI 1141 with SCXI 1140.

[Jennifer Rice]

I am using an SCXI-1001 chassis with a DAQpad 6052E ADC for dynamic testing.  I'm trying to use an SCXI 1140 cascaded with an SCXI 1141 filter.  My goal is to acheive low-noise, filtered data with a negligable phase delay between channels.  I configure my hardware so that the data goes into the 1141 which is operating in parallel mode and then into the 1140 which is operating in multiplex mode.  My results are not good.  The 1140 is sucessful in eliminating (or mostlly eliminating) the phase delay between my channels however the data is very noisy.  When I use the 1141 alone, the phase repsonse is poor but the data is much cleaner.  So, somehow noise is being introduced to the data when it goes through the 1140.  I don't know if I have a problem in my configuration.  My channels are set up as Traditional DAQ - could that be a problem?

[Logan_K]

Have you considered replacing the 6052E and SCXI-1140 with a single S-series board (such as the PCI-6143) in order to eliminate the phase delay? The catch to this configuration is that you would need to be in parallel mode, so you would need a 6143 for every SCXI-1141. The SCXI-1140 is going to introduce quite a bit of additional error into your measurements that could be eliminated by sending the signal straight to a simultaneous DAQ board. I would recommend looking at the amplitude of your noise and comparing it to the specs of both modules (keep in mind that the noise from the 1141 will be amplified through the 1140 depending on how you have the jumpers set) - this will tell you if your noise levels match the specifications.

Regards,
Logan K

Message Edited by Logan K on 10-13-2006 08:51 AM