Signal Conditioning

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Often unable to get data from our pressure transducer using SCX1-1314 and SCXI-1520


I am using a SCXI-1314 with the SCXI-1520 for a pressure transducer to measure the load from a compression machine.  We thought the maximum load we would need for our research would be 50KN so that is all we had created in the Labview program.  We quickly discovered that we needed about 200KN.  Our machine can do more than that so we just needed to measure the voltage drop over the transducer ( between the S+  and S-) for the rest of the loads from 50KN to 200KN.  Before we did that, we wanted to run the test again and found that the load will only record for about 10% of the times we run the program.  As far as I can tell there has been no change- we have not even added the additional scaled values from 50KN to 200KN.   The fuses are fine and I am out of ideas.  Anything helps. 



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Message 1 of 7


I have a few questions to ask before we can start resolving this issue.

1. Have you ever been able to get all of the data points you are trying to record? It sounds like this might be
the first time you are trying to read this data in general, but I couldn't quite verify that in your post.

2. Also, can you explain how you are reading and recording this data in LabVIEW? I am not sure how you are
setting up your data acquisition to read and record your data and this will help in narrowing down the problem.

3. Can you provide your LabVIEW version, daqmx driver version and operating system? We want to make sure you aren't running into any compatibility issues.

I look forward to hearing back from you.

Tori W.

National Instruments
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Message 2 of 7

Hi Tori W,


It is always good to make sure thigs are clear. 


1.) I was actually able to get all of my data points- but only once. 


2.) We have a pressure transducer attached to out compression machine.  There is a voltage drop over the S+ and S- ports on that we can convert to load in KN.  We recrod the load twice a second. We have the relationship between voltage and load.


3.) I would hate to think it is a compatablily issue since it did work on Monday.  I am just trying to understand why it stopped working.

LabVIEW= LabVIEW 2010

daqmx driver=NI-DAQmx

Operating System= Windows XP Professional 


Hope that gives you a better picture.  I look forward to hearing back from you.






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Message 3 of 7


So if it was working at one point did anything change? Not necessarily just with your code, but did you
change anything in your computer or with your device? (ie, any software updates, adding/removing other
devices, etc) Sometimes even small things like computer anti-virus updates can be relevant. This is
probably not the case, but it's good to know for troubleshooting purposes.

How exactly are you recording your data? I would assume you are using something like a Waveform Chart or are
exporting your data to Excel in tables for example. Data reporting can behave differently depending on your
reporting method.

When you mentioned only recording data 10% of the time, do you mean you are only getting 10% of your data to
record in your program? Or do you mean that roughly every 10th time you run the program you get any data at all?
If the latter is the case, is the data good and what you would expect?

Feel free to attach a screen shot of your code if you need help explaining anything. Have a good afternoon.

Tori W.

National Instruments
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Message 4 of 7

Hi Tori H,


I did not notice anything change but there might have been some kins of update to the anti virus or something similar.  It happens so often I don't really take note of updates. 


There were no phyical or program changes when the problems started.


The data is being recorded using a waveform chart and then we take the data into excel.  


What I ment by the data is recored about 10% of the time is that about 1 in 10 test proformed will have a values for the load.  The other 9 time will have 0 listed for the duration of the test. When it works, that data looks good. 



Thanks again for your time. 



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Message 5 of 7

Hi Tori H,


It appears to be working now for the past 2 hours.  I just shut everything down and restarted and it appreas to be fine. 


I have a new problem.  The load maxes out a 50KN.  but I put in the scales values for voltage to KN up to 200KN into the program... 


Hopefully, I can figure out this new problem.  Thanks.



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Message 6 of 7


Unfortunately, I do not have enough information to figure out what could be happening with your code. Screen shots are always
encouraged and I think it would help in this case to see the exact behavior at 50KN. Specifically, it would help to know, at 50KN,
does your signal flatten out, stop displaying completely, give nonsense data, etc? Also, what signal shape are you expecting
from your devices? Does it ramp up/down, oscillate, etc? I look forward to hearing back. Have a good weekend.

Tori W.

National Instruments
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Message 7 of 7