Mutiple readings from Express DAQ Assistant VI

Hello All!
First I'm a fresh noob to LabView and although I understand most of the basic concepts, I'm also new to programming in general. I'm working on a project to remotely monitor several different parameters of a system. Right now I'm working on a test program to monitor three parameters in my shop across the street. I'm using a NI USB-6008 as a DAQ device, DAQmx 8.0 and LabView 8.0. All of my input signals are 4-20 mA signals coming from my three sensing devices.
Here's my problem; I need to monitor all three signals on digital displays. I can accomplish this by using three different instances of the express DAQ assistant but then I get the dreaded "50103 error" unless I wire the stopped output of one assistant to the stop input of the next in a feedback loop and even then I get the 50103 error on the first iteration of the loop. From my research I understand that this isn't the correct way to program this. I should use one DAQ assistant with multiple channels assigned to each one of my parameters. I've did this but now how do I make each one read out on an individual digital display? I only have one output from my DAQ assistant.

Hi George,
Use split signal in the signal manipulation functions menu to get your 3 individual singals on respective indicators
Regards
Dev
Attachments:
SPLIT.vi ‏85 KB

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Thanks for quick reply.
However, I did try it (see the picture) but I still have a problem: I only get 100 samples / channel during the test sequence (all from the first seconds of the sequence) in total even though I've set the data aqcuiring DAQ-assistant as "continous" and "samples to read = 95k" and rate is 1000Hz.
Edit.
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Attachments:
is_this_what_you_meant.jpg ‏212 KB

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Attachments:
TEST STAND STATE MACHINE 2-28-07.vi ‏288 KB

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Hello bentnail,
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How can I programmatically change the voltage range settings in a DAQ Assistant

Hi,
First post here.
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Ruby K
Solved!
Go to Solution.
Attachments:
Labview_question.PNG ‏14 KB
Sample_AIV.vi ‏91 KB

First, if you want to start getting beyond the basics with DAQ, you are going to have to stop using the DAQ assistant and do it with lower level DAQmx VI's. There are hundreds of examples in the example finder. You can even right click on the DAQ assistant and select open front panel. That will create a subVI that you can open and see what is going on behind the scenes. Do it. I think you'll find the DAQ task is being recreated on each (though I'm not 100% of how the settings are established or maintained in each section of that subVI).
The second problem is you have a bit of a race condition on iteration 0. Those two DAQ property nodes are running at the same time. So when you read the AI.Max, it may be happening before or after the AI.Max is set in your case structure.
Third, make sure you wire up your error wires.

Tare function DAQ assist and restart function for the vi program

Hi!
I have a program that aquiers a signal from the DAQ assist. I have searched here on the forum and on the web, but I can't find a way to implement a tare function. The signal is from a loadcell and therby it would be good if Icould tare the signal to value zero. In the DAQ assist I can calibrate it manually, but i would like to wire this function to a button.
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I have attached my code below.
Best Regards Maurlind
Solved!
Go to Solution.
Attachments:
Tare function and restart.vi ‏365 KB

I solved my problem with the tare function, i used a case structure and shift register to store values in it. se picture below.
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Attachments:
tare function.png ‏25 KB
restart vi.vi ‏488 KB

Error with 2 Daq assistant

Hello
Another noob joining the community. Here is my question.
What am i doing wrong? I use 2 Daq assistants on the NI9401 module this is for digital input and output. I use it for generating 2 signals. If i test it with 1 it works but if i go to 2 or more it fails. This is the error i get . I have also added the program as an attachment.
Thanks in advance.
Solved!
Go to Solution.

Hello,
That error means that the DIO task is reserved and cannot be obtained by one of the DAQ assistants. There is actually a nice example program on what you want to do. It can be found here:
https://decibel.ni.com/content/docs/DOC-11632
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regards,
Rik Prins, CLD
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Attachments:
2 Daq assistant generating error (3).vi ‏169 KB

DAQ Assistant to typedef data cluster

Hi All,
I was hoping someone could be able to shed some light on an issue I have been pulling my hair on for a week now. I am recently new to LabView (less than 6 months), and up until I have been able to locate/research any issues I had ran into. The problem I'm having is as follows:
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Breakdown: I have 41 thermistors being generated from the DAQ Assistant. I need to somehow convert this data into a form where it will be able to be constantly updated and read from a typedef/global/something. I have taken a screenshot of what I was working on when I decided to post here. There are broken wires atm, because I was trying everything I could think of. Signal Manipulation/From DDT, Array to Cluster, Build Cluster by Name, Build Array, numerous things. I basically want all 41 thermistors to leave the DAQ Assistant, be split by channel name/value, and input into an array or cluster that can become global. I have broken it down to 4 channels in my screenshot for simplicity's sake.
My apologies for repeating myself or running on, I'm working on very little sleep at the moment
I appreciate any help anyone can shed on the situation. Thank you!
-Justin
Attachments:
DAQ_Cluster.png ‏17 KB

I didn't have it connected in that particular screenshot but I have tried that before. I just redid that scenario and took another screenshot. Bringing a cluster typedef and dropping it in, switching to indicator so it will allow an input, and changing the Original Cluster Visible property to FALSE (just so two clusters of 4 Numeric Indicators are not visible). Using the attached screenshot, the numeric values do update (on the front panel of this VI), but as soon as I connect that typedef to another VI and unbundle, those values do not populate on the subVI. I changed the DAQ Assistant in this current example (to test) as I am at home and do not have the 1581/1102B hardware here with me.
I will note that I do have this functionality working on another section of the GUI I am working on. This working portion has 8 Boolean values in a typedef cluster and is exported and unbundled in the same manner as I am trying to get working with these data values on the subVI. The way that the values get sent to the typedef is different but overall the same way that I would like to aim for on the DAQ_Cluster2 image. Two screenshots enclosed this time. I can go into much further detail if necessary. Thanks again for the feedback. I'm going to knock out some more of the pages involved for now, if anyone has any more feedback that would be fantastic.
Also aeastet thank you for your reply as well. I started reading through your link to Ben's nugget but my brain is mush right now and I am not too familiar at all with some of that functionality. I will look back at it more soon.
Thanks again!
Attachments:
DAQ_Cluster2.png ‏27 KB
FCV_Cluster.png ‏8 KB

DAQ Assist Reading Wrong Voltage

Hello,
I'm using the DAQ Assistant VI to read an analog input voltage from a National Instruments PCI-6221 card. I'm reading the voltage from pin AI0. I supply a voltage directly to this pin from a DC power supply, but the voltage measurement obtained from the DAQ Assistant is incorrect - it seems to be scaled by a factor of about 1/3. For example, if I supply 4 Volts to pin AI0, the DAQ Assist reads 1.43 Volts. I used a multimeter to confirm that the voltage at pin AI0 is in fact 4 Volts, and so I know the problem is with my LabVIEW program and not my power supply.
Here are the steps that lead to my problem:
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Does anyone have an idea why this may be occuring. I've spent a good 4 hours trying to diagnose this and haven't found anything.
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Abed Alnaif
Solved!
Go to Solution.

Thanks so much for your help. I used MAX, and found out that the issue
is that I had specified differential voltage, but I should have
specified RSE voltage.
However, now I have a different issue: When I apply a voltage to one pin, MAX also shows a voltage on other pins.
For example:
1. I apply a DC voltage of 4V to analog input pin ai0.
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3. I click Start, and the chart shows the correct voltage (4V)
4. I change the Channel Name to Dev1/ai1and Input Configuration = RSE
5. The chart shows a noisy voltage reading between 1.45 and 1.5 V, even though no voltage is applied to pin ai1
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Plot from two DAQ readings on opposing axis

I have a DAQ system taking two different readings. I want to plot them both on the same graph with one reading, say temperature, on the X-axis and the other, say humidity, on the Y-axis. How do I do this?

Hi mbooker,
you should write "DAQ Assistent Express VI" whenever you mention "DAQ system"!
If you would use "plain" DAQmx functions you wouldn't have to go all the way through datatype conversion from DDT to meaningful representation...
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Hi!
I am a new user of Labview 8.5 and I am working with a USB-6210. I have two different instruments connected to the same USB device, half of the channels are being used for pressure transducers where I only need to reed and save the data, while the other half are associated to TCD detectors where I need to perform some analysis to the signal to obtain and save the data. I am in the first step of building the block diagram, After I define each of the signals which its corresponding channel using the DAQ assistant, I need to select and separate the signals coming from the pressure transducers from those coming from the TCD detectors, before I can continue drawing the block diagram. I am trying to use the Select Signal function but I am not sure how to do this. Can anyone please let me know at least in which manual can I find a good explanation? I have been reading the Getting Started and the User Manual for LabView but they have not been very useful so far.
Thanks!
Solved!
Go to Solution.

Wire the Select Signals express VI to your DAQ Assistant and run the VI once (this allows the signal names to propegate). Then when you open the Select Signals configuration you'll be able to pick out the channels you want by name instead of just "Signal 1" etc.
It sounds like you'll probably want two Select Signal Express VIs, one for the TCD detectors and one for the pressure transducers. Something like this:
If you right click on the VI and select Help or click on the Help button within the configuration dialog you will bring up the LabVIEW help page for this (or any other) VI. Are you looking for some other information that isn't documented in the help file?
Hope this helps,
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Mutiple readings from Express DAQ Assistant VI

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