SCXI 1142's cascaded to 1140's

[Kingsbury]

We would like to obtain simultaneous, filtered voltage data using an E series DAQ card and SCXI modules for our machine vibration tests. Is it possible to use three 1142 modules cascaded to three SCXI 1140 modules in a chassis, and run the chassis in multiplexed mode. Will the data (all 24 channels) be synchronized (i.e in phase), and do the 1142 modules introduce any phase error between channels? Our application is primarily measuring bearing and shaft vibration at frequencies below the running speed of our shaft (about 300 Hz or 14000 RPM), thus we would like to attenuate frequencies above at least 600 Hz without significant phase lag. Bottom line is, will this configuration provide simultaneous, filtered data at a sampling rate of at least 600 S/s per channel? Thanks.

Neil Jenkins

[LA 75]

Hello Neil,

Below are the answers to your questions:

1. Is it possible to use three 1142 modules cascaded to three SCXI 1140 modules in a chassis, and run the chassis in multiplexed mode.?

Yes

2. Will the data (all 24 channels) be synchronized (i.e in phase), and do the 1142 modules introduce any phase error between channels?

The data will be synchronized because of the simultaneous-sample-and-hold feature of the SCXI-1140. You can sample muiltiple signals with negligible skew time between the channels. No phase error will be introduced between the channels.

3. Will this configuration provide simultaneous, filtered data at a sampling rate of at least 600 S/s per channel?

The maximum scanning rate of a system is limited by the slowest component on the system. In a setup consisting of a data acquisition (DAQ) board and simultaneous sampling SCXI modules, the maximum scan rate that can be achieved is a function of the acquisition time of the track-and-hold circuitry and the safe interchannel period of both the SCXI module and the DAQ board. The following knowledge base will provide you with some equations to help you calculate the maximum sampling rate of your system.

For more information on how to configure your SCXI-1140 and SCXI-1142 in Cascaded mode, refer to this knowledgebase

Finally, for information on "Cascading Configurations with SCXI Modules and Example Programs", refer to this knowledgebase

Hope this helps!

LA