Simultaneous analog inputs on a 4472 with different settings

[UVA-BIER]

I am taking accelerometer data from different types of accelerometers.  One with an internal IEPE, and one with an external IEPE.  They also have different sensitivities.  What is the best way to set up controls to specify which input is using which accelerometer.  Is there any example code that I might be able to look at? 

Thanks!

[gaving]

Here's a quick response to get you going...

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000YH72CAG&l=en-US

Using the channel property node should get you what you want.  You can call the property node several times with a different "Active Channel" (meaning the channel you want to change settings for).

(see the picture below)

-gaving

[UVA-BIER]

How do you pass these values to the 'Create Channel'.  I can only get it to be 'Read' or 'Write' not both.  Once I have multiple channels coming in to the property node can I still use one 'Create Channel'.

Sorry I'm pretty new to the DAQmx world...

[gaving]

no prob

check out this (attached) and see if it helps...

-gaving

[UVA-BIER]

Thanks again for this help.  I thought I was getting somewhere until I added the while loop.  So I need to continuosly/simultaneously record data from up to 8 (different) accelerometers.  Is this possible?  Here's a screenshot with what I have using the method you suggested.  It either fails to access the data points, or runs out of memory.  I know I'm missing something simple, but it's hard to debug in strange territory!  Thanks!

[gaving]

Well,

First, I'd say use the "more common" way of saying "all eight channels" and put Dev2/ai0:7.

When you say it "runs out of memory", what actually happens?  Do you get an error in the error cluster?

-gaving

[UVA-BIER]

So I figured out my problems from last night, but I have run into new problems.  It appears that the property values make it into the for loop but to not get applied to the channel.   I inserted another property node in the for loop to read the values and it's not reading the values that are being passed to the 'write'  version of the node.  This is also consistent with the data that is being shown on my graph.  The inputs are displaying vibration data, but the scales are clearly wrong.  Any ideas?

Thanks again for all this help.

Also, what's the best way to specify inputs that might not be in order.  For instance  if we were using ports 0,1,5,8.   

[UVA-BIER]

It appears that the device has a constant +-10V scale, so some of the values are trumped by the sensitivity parameter.  It automatically changes the scale to fit that range so I guess even thought the transducer has a lower limit, the device could still read higher.  To make things more complicated the external amp. we're using for the excitation is amplifying the signal so the sensitivity is the device times the gain.  I think I've got it working now though.  Does any of that make sense? 

Thanks again!  Onto post processing the data, so I might be around with more questions....

[preston_johnson]

you might consider using the sound and vibration toolkit

https://www.ni.com/en-us/shop/product/labview-sound-and-vibration-toolkit.html

This tool has a feature called scale to engineering units and will account for units and pre-amplifiers.  Further, it carries the units all the way thru the analysis including power spectral density, fft, etc.  Saves a lot of time of pulling hare over scaling and units and provides ansi and iso standard sound and vib calcs

[Mark_E]

If you want to look at specific channels, try separating them with commas, like "Dev2/ai0, Dev2/ai2" etc.