Outref pin on SCXI-1540

[FRG]

Hi All,

According to the manual on the rear connector of the SCXI-1540 is a pin (19) described as OUTREF.

This connects directly to the AISENSE pin of E series daq cards.

But there is no mention of this pin in the manual. 

Is it possible to generate a ref voltage in the scxi 1540 and thereby do a NRSE measurement on the daq?

Are there any detailed circuit diagrams of the scxi-1540 so that I can see whats up with this outref pin?

cheers

Frank Greenslade

Christchurch

New Zealand 

[mr_]

Hey Frank--

Let me know if this is not what you were talking about.  I found the reference to the OUT REF on pin 19 in the manual.  I believe this is what you were seeing.

This pin's usage is discussed on page 2-7 and I believe it answers your question directly.  

Does this answer your question about the pin being referenced in the manual?  Do you see how you can use this to take added measurements?  The Rear Signal Connector is used with the SCXI-1180 to provide these channels as noted in the above image.

SCXI-1180/1181 User Manual

Please let me know if you have questions about this.

Have a great weekend! Cheers!

Message Edited by Tyler C on 05-15-2009 02:51 PM

[FRG]

hi Tyler, thanks for your reply. I missed that reference in the manual. I had an older version.

I guess what i really want to be sure is that if  I output a voltage from  Aout (on the daq) and connect that to Outref (AIsense on daq). Then this will not do any damage to the scxi1540. 

This will allow me to acheive an NRSE measurement on the LVDT channels. Then i can increase the gain and measure extremely small displacements.

And then I thought maybe the scxi1540 can generate its own 'outref' internally. The name of the pin sort of implies that but i've found no info about this.

cheers

Frank

[mr_ · Accepted solution]

Hello Frank,

So first off, you can certainly use the Out Ref as your floating ground for an NRSE measurement.  If we look at the Field Wiring Considerations tutorial, it talks about these configurations a little further.  I am having trouble understanding what you are trying to acheive outside of this. 

[FRG]

Hi Tyler,

I have tried doing the NRSE measurement and it works fine. Thankyou.  I use the Aout from the Daq card and feed it back to the AISense on the Daq card.

I guess I was just being a bit inquisitive about why the terminal is called 'outref' on the scxi-1540. The name implied to me that a reference voltage could be generated inside the scxi-1540 and it would be directly connected to AISense on the daq. And I was also concerned that there might be something  inside the scxi1540 that might sink some current if I drove the outref pin from the Aout on the daq.  Probably not making myself clear here. Do you follow me?

Another thing that I'm not sure about is the parallel/multiplexed modes of operation. The manual says that Traditional NiDaq could only read the SCXI-1540 in multiplexed mode. Nidaqmx can read in both parallel and multiplexed mode. 

But , I can't see where or how in Nidaqmx to switch modes. Is there a property somewhere to do this?

Thanks for your help.

cheers

Frank

[mr_]

Hello Frank,

Yeah I think I understand where you were coming from.  As for the parallel or multiplexed mode, I simulated a SCXI-1000 chassis in my MAX.  If you right-click on the chassis an choose properties, you will get a screen that looks like the following:

Click on the details button and notice the following:

I hope this answers your questions.  There is also this great document for common questions (SCXI Troubleshooting Resource (FAQ)). 

Cheers!

Message Edited by Tyler C on 05-20-2009 03:42 PM

[FRG]

Hi Tyler, thanks for that.

I was looking everywhere else except MAX.

cheers

[mr_]

That's good to hear Frank.  Glad I could help.

Cheers!