DAQ assistant block

Hi, in my block diagram (labview), i cannot see DAQ assistant block. i check it by going express- input. But i donot see DAQ assistan block. if you please tell me.

Did you install DAQmx after installing LabVIEW?
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PCI-6251 into LABVIEW DAQ Assist block interruptions and resets

Signals being received from PCI-6251 into a LABVIEW DAQ Assist block interrupts and resets every 10 seconds after 1 minute of data acquisition. Would this be a memory buffer problem or is it something related to the hardware? I am using a BNC-2110 hardware connector. Please view the attached image.
Attachments:
Interuption1a.GIF ‏4 KB

Hey Peter,
Ahh, I understand the graph now! Hmm, this is very strange behavior. Instead of using the DAQ Assistant, try to use the explicit DAQmx VIs (see picture). You have more explicit control over what is going on with the DAQmx VIs and keep as much as you can out of the loop.
Regards,
Erik
Attachments:
analoginput.JPG ‏23 KB

DAQ Assistant: How Can I Control this at the lowest Level?

DAQ Assistant:
I have the PCI slot version of this which I use to generate specific signatures. However I would like to get down to the very low level of this block to see what makes it tick if only to add some other features such as have it dynamically change high and low times after "N" number of pluses/bursts.
At the current state I can't seem to get any further than the GUI that I work with right now. I can give you a VI upon request however this VI is included with labview from what I understand I have version 8.2. If anyone wants a copy of the vi which contains the DAQ Assistant block I will be more than happy to include.
DAQ Assistant Location: Right click on the block diagram of a VI --> Measurement I/O --> NI-DAQmx --> DAQ Assist (This is an icon in itself)
I see the read,write nodes however I have played and tried to see what they do but I have had no such luck. If anyone can point me in the right direction I would be grateful.
Thank You.
Solved!
Go to Solution.

You've got a couple of misconceptions about the DAQ Assistant. First, there is no such thing as a pci version. There are some slight differences between versions of the DAQmx driver. Second, the DAQ Assistant is a code generator. When you start it up, it will create custom code for the type of task you want (digital i/o, analaog i/o, etc.) so the VI you eventually have on the block diagram is not included in any version of LabVIEW.
Once you have configured the assistant, you can right click on it and select 'Open Front Panel' this will convert the assistant task to a normal subVI that you can opne and view the block diagram. You can also right click and select 'Create DAQmx Code'. This will place the low level DAQmx functions on your block diagram. You could also skip the whole assistant and just start with the low level DAQmx functions in the first place. There is help associated with each and you have all of the shipping examples to look at. There is also the Getting Started with NI-DAQmx page.

DAQ Assistant with multichannels causing Simulation Loop slow?

Hi, another LabView newbie here.
I have in a Real Time Target (NI 9132) a Control & Simulation Loop with DAQ Assistant block inside, whose signals are fed into a Discrete State Space block. The discrete state space model has 1 second time step. I have set the Simulation Loop parameters so that it executes every 1 second as well (see Fig. A below). *sorry for the big white gap under the figures..
The DAQ assistant acquisition mode is set as "1 Sampe (On Demand)".
However, when I run the VI, the plot seemed to be updated much slower than 1 second rate. To confirm this, I put an "Elapsed Time" block inside the Simulation Loop. The "elapsed time" shows the actual time in seconds while the simulation plot show slower time (see Fig. B below).
I tried to isolate the problem by removing the block one by one. Finally, I found out that this problem was caused by (at least) the DAQ Assistant which acquires multichannels data of NI 9214. When I remove some channels and leave one or two channels, the VI runs at the actual time (see Fig. C below). But when I added more channels reading, it became slower again.
Here is the snippet of the block diagram (after all other blocks were removed):
What am I doing wrong here? I'm going to use all of NI 9214 channels so how not to have similar problem like this?
I look forward to hearing any relevant comments from the members. Thanks in advance.
Tian

Hi Tian,
why do you need a Sim loop anyway?
- When it comes to speed you shouldn't use the DAQAssistent. Use basic DAQmx functions…
- Use parallel running loops for each task. Put DAQmx functions in their own loop, running in parallel to your Sim loop…
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

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:
1. In the block diagram, I insert a DAQ Assistant block.
2. In the Properies of the DAQ Assistant, I select Analog Input->Voltage
3. I select channel ai0
4. I click "test" in order to test the channel
5. The voltage is shown to be 1.43 Volts, even though 4 Volts is being supplied to the pin (this is confirmed with a multimeter).
6. To ensureI click OK to finish configuring the DAQ Assistant. I run the program and plot the voltage. The plot also shows 1.43 Volts.
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.
Thanks,
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.
2. In MAX->Text Panels..., I select Channel Name = Dev1/ai0 and Input Configuration = RSE
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
6. When I change the voltage on pin ai0 to 2V, the voltage reading on pin ai1 changes to 0.63V
7. Using my multimeter, I confirm that there is in fact 2V on pin ai0 and 0V on pin ai1
Does anyone know why applying a voltage to pin ai0 causes a voltage reading on pin ai1?

DAQ Assistant verses DAQmx

Whats the advantages of acquiring data from the DAQmx block rather than using the DAQ assistant block? Are there pro's and con's to each? What is normally used in industry?
I've also noticed there are multiple methods for writing data to file and wondered what the proper method or pros and cons for this are?

Dawud-Beale wrote:
Whats the advantages of acquiring data from the DAQmx block rather than using the DAQ assistant block? Are there pro's and con's to each? What is normally used in industry?
You have A LOT more control over the acquisition with the DAQmx API over the DAQ Assistant. You can also make the code more efficient with the API. Normal in industry to to avoid the DAQ Assistant
The only real advantage of the DAQ Assistant is that it is easier to set up your task.
Dawud-Beale wrote:
I've also noticed there are multiple methods for writing data to file and wondered what the proper method or pros and cons for this are?
Well, that just depends on your requirements.
Need human readable? Go with a tab delimited text file or CSV.
Need to log a lot of data quickly? Use a TDMS or binary file. I tend to use the TDMS since it is well put together for DAQ and waveforms.

DAQmx driver for DAQ 6009? Need DAQ Assistant in Block Panel palette.

Do I understand things right? The Ni USB DAQ 6009 is supported in DAQmx base and not DAQmx, or is this only true for the 6008? I need the DAQ Assistant in my LV 2009 Block Panel palette. Do I go to my Ni-DAQmx 8.8 CDs, or do I download something. Maybe I have the DAQmx base already? I'm going to search my palette and NI Max. I am also going to look at http://www.ni.com/support/daq/version_portable.htm#du. If I'm going about this all wrong, please help.
Thanks
Norm

Hi Dennis
My DAQmx Cds are 8.8. I don't have a selection for the DAQ Assistant on my block panel palette, so I'm looking to get an update for my DAQmx driver for my USB 6009 DAQ that I'll be using with my student software for LabVIEW 2009 version 9.0. I've looked at a NI document "NI-DAQmx and NI-DAQ Driver Support: Portable Devices" that was published on Jan 17, 2013. It says for Windows 7 I should be using 9.6mx, but this document make no reference to a version of LabVIEW. The date of the document is 1/17/13; maybe it is refering to only to version LabVIEW 2013. Can you help?
From what I've read I believe I need to use DAQmx and not DAQmx base, but I can't help wondering if the DAQmx base has something to do with the "NI DAQmx Device Basics" that I see on the right side of the screen when I'm in NI MAX getting ready to run the test panels. ?????
Thank you for your time
N.D.

DAQ Assist to block diagram code

Hi,
I am fairly new to NI Signal Express.
I am using the NI 9214 for thermocouples and I have sucessfully communicated with the NI using DAQ assistant.
It generated the code below.
How can i have more control of my VI?
I want to be able to turn on and off my CHANNELS
i want to have graphs, etc.
can i expland the DAQ ASSISTANT ICON to something with more control?
thanks in advance.
Solved!
Go to Solution.
Attachments:
TCs.vi ‏102 KB

Oh, you already opened it.
Well we don't know what you want to do. Since you have a real VI to work with YOU need to decide how you want to enhance it. I would start with changing some of the constants on the block diagrams to controls. You can drop a chart on your front panel and wire DAQ out data right to it. If you get stuck, be specific about your goals and post your newly opened VI.
EDIT: BTW, if you want more help I suggest you use File > Save for Previous Version... and make it a 2013 or 2012. Many of us who could help out still haven't upgraded to 2014. I saw that you wanted channel control and graphs but I can't open your code.
Using LabVIEW: 7.1.1, 8.5.1 & 2013

How to select signals from the output of a DAQ assistant

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,
Simon

How to properly read data from one DAQ-assistant and write simultaneously with another DAQ-assistant (which is inside a loop)

Hello.
I'm a newbie working on my Master's thesis conserning a project that is based on old G-code made by another newbie so bear with me.
I need to create a sequance of output controls. For this I'm using a for loop that eventually creates two triangular ramps during a period of 90 seconds. I've confirmed that this function works properly by measuring the actual output of the DAQ-decice (NI USB 6353).
The problem is the following: During this controll-cycle I need to simultanously collect data from the same DAQ-device. At this point there is only one DAQ-assistant output-block in the main loop of the program and all the signals are derived from it to where they are needed.There is a case-structure (the bottom case structure in the picture) that contains the functions needed to collect the data during the test cycle. However these two actions, outputting data and inputting data, are not synchronized in any way which may be the reason why I get the 200279 error or alternatively the 200284 error during the test cycle. I've tried changing the sample rate, buffer size and the timeout time as adviced but nothing seems to help.
What would be the simplest way to solve this problem?
Help is greatly appreciated!
Attachments:
problem.jpg ‏206 KB

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.
And lastly, I have trouble adding this "extra" DAQ-assistant to the vi. because I get an error about a resource (The 6353) being reserved, even though I connected a false constant to the "STOP" -input of the main DAQ-assistant.
Attachments:
is_this_what_you_meant.jpg ‏212 KB

NI-DAQmx task works in MAX or DAQ Assistant test panel but not in LabVIEW

I am attempting to read a single AI channel from a PCI-6024E card via an SCB-68. I have created a NI-DAQmx Analog Input Voltage Task in MAX for this channel, sampling in contiuous aquisition mode at 100 kHz, 10000 samples at a time, with RSE terminal config. If I use the Test feature from MAX, the channel acquires data as expected.
In LabVIEW, I call this task using an DAQmx Task Name Constant. If I right-click this constant and select "Edit Task", the Daq Assistant opens and I can use the Test feature from the DAQ Assistant to see that the data is still being acquired as expected.
However, when I try to programmatically read this channel in LabVIEW using the VI "DAQmx Read (Analog Wfm 1Chan NSamp).vi", the VI returns a constant DC value of 500 mV, which I know is incorrect (I can monitor the signal across the two terminals in the SCB-68 with a DMM to know that the signal coming in varies as expected, and as I read using the test panels). This erroneous reading occurs even if I make a new VI, drop the task name constant on the diagram, right-click the task name constant and select "Generate Code - Example" and let LabVIEW create its own acquisition loop (which is very similar to what I already set up, using the "DAQmx Read" VI).
Any ideas why the Test Panels work correctly but the LabVIEW code does not?

Hello bentnail,
I'm not sure why the test panels are readin the value correcly but the LabVIEW code does not, but there are a couple of things we can try.
1) What happens if you just use the DAQ Assistant and place it on the block diagram? Does it read out the correct values?
2) Try running a shipping example that comes with LabVIEW. "Acq&Graph Voltage-Int Clk.vi" should work well.
3) What kind of signal are you expecting to read (peak to peak voltage, freqeuncy, etc.)?
Thanks,
E.Lee
Eric
DE For Life!

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

Hi,
First post here.
I need to be able to change the voltage range properties of a daqmx DAQ Assistant based on user input. My hardware, an SCXI-1102C does not allow changing this property on a running task, so I'd like to either set the analog input voltage range before the DAQ Assistant activates, or pause the DAQ Assistant immediately after it starts, set the values and then resume.
I don't know how to edit the task ahead of time because the DAQ assistant creates the task when it runs, and there is no task before that.
In the attached picture, I have a conditional section, set to run only if the while loop iteration is 0. I take the task from the Daq assistant, send it to a stop task vi, set the property, and then send the task on to the start task vi. I can watch it run with the debug light on, and everything seems to work correctly, but on the second (and all the other) iteration of the loop, I read out AI.Max and it seems like the DAQ Assistant has re set it back to 5V. Can anyone see what is going wrong here?
BTW, this is continuous acquisition and the code does not produce error messages when it runs.
I did come across a similar question that someone posted here back in 2006, but his question was specifically aimed at a Labview API (VB, I think), and not an actual G solution.
Attached are the actual vi in question and a png image of the block diagram.
Thanks!
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.

I do not see the DAQ Assistant Express on Functions Input palette.

Software config: Windows XP machine, Traditional NI-DAQ 7.4.4 for PCI 6602. I do not see the DAQ Assistant express on Functions>>Input palette. I get error message when I place the Instrument I/O assistant on the block diagram:-" Measurement and Automation Explorer or Instrument I/O Assistant not installed correctly. Please install from LabVIEW CD". I've tried uninstalling, re-installing driver and rebooting my computer several times.

Hello PJ-SJM,
The DAQ Assistant Express VI installs with the NI-DAQmx Driver and not Traditional NI-DAQ. The good news is that the PCI-6602 is supported in both Traditional NI-DAQ and NI-DAQmx. Check this KnowlegeBase article to find out what version of NI-DAQmx you need and then search the Drivers and Updates page for to find the version you need. Once you download and install the driver you should see the DAQ Assistant Express VI on your functions pallet.
The Instrument I/O Assistant is not for use with DAQ cards, it is for using other communication protocol like serial or GPIB. However, if you need this you can install the Device Driver CD and it should work after that. Note: The device driver CD that came with LabVIEW should also contain the correct version of NI-DAQmx.
I hope this helps, and have a great Friday!
Brooks

Why can I only open DAQ assistant properties using the windiws profile I registered labview on?

I have Labview 7.1 installed on Windows 2000. When generating block diagrams for codes, the properties dialog box for the daq assistant can only be opened when logged into our system on the profile originally used to install the software or when logged in as administrator. All other properties dialog boxes open under any user profile.

I do not use Windows 2000, but I expect that the folder in which this function is held does not have a 'Full Control' access setting for all users.
See if you can change the folder profile to allow access and full control to all users.
Hope this helps.

Missing wire connectors on DAQ Assistant express VI's

I'm seeing some strange behavior on one specific computer running LabVIEW. The problem is that DAQ Assistant VI's have no connector points. I have nine other identical computers (used in a classroom setting) but I don't see this behavior on the others (I haven't tested them all).
I've removed LabVIEW (and all other NI software) and re-installed it (LabVIEW v 8.6.1). I also tried a more recent version of LabVIEW (2010?). Same behavior, no connector dots on DAQ Assistant VI's.
The computers use DAQmx with USB hardware (cDAQ).
I guess my next step is to format the hard drive and re-install everything. My theory is there's some kind of driver corruption. What do you think?

Allie,
Here are the steps I use to create the Express VI using the DAQ Assistant:
* On the block diagram:
Right click -> Measurement I/O -> MX -> DAQ Assistant
* Drop Blue box on block diagram.
* Configuration Screen Appears
Aqcuire Signals -> Analog Input -> Voltage -> Dev1 (USB 9219) -> ai0 -> Finish
* Voltage Input Setup Appears
Accept default settings -> click OK
* Voltage Input screen disappears, a blue DAQ Assistant appears on block diagram. No connection points.
When I execute the exact same procedure on another computer I get a DAQ Assistant with connection points.
Weird eh?
thanks!

DAQ assistant block

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