Thanks you Carisa for fast response, but that not the right answer I am looking for.
May be I did not make myself clear. I attached two screenshots for example: On one screenshot, you will see bri00, bri01, bri02, bri03, bri04, bri05, bri06, bri07, bri08, bri50 on the virtual channel tab, however you won't see them display under NI-DAQmx Global Virtual Channel (second screenshot). On the second screenshot, you only see bri00, bri01, bri02, bri03, bri04, the rest of bris do not display on here like they display on the virtual channel tab.
Now I can't create the new global virtual channel under NI-DAQmx Global Virtual Channel with the name bri05, bri06, bri07, bri08, because I will get the conflict name error pop up on the screen. How can I delete those bris in the virtual channel tab?
Thanks again for your time, Dylan
Attachments:
virtual-1.png ‏45 KB
virtual-2.png ‏226 KB

Similar Messages

Troubles with virtual channels

I programm my applications on an PC without any NI-Hardware. My problem ist, that I need virtual channels from the Measurement&Automation-Explorer.
My first attempt was, to configure some channels without settings for hardware. Normally when I use an DAQ-Constant in my application, I could select the configured channels. In this case I couldn´t.
My second attempt was, to use two PCI-DIO96 cards. I configured also some channels, but I get the same result. I couldn´t select the configured channels in LabView(6.1)
Did I need the complete extern hardware, or is there another reason for my problem?
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Robert;
Virtual Channels only make sense when used in conjunction with a DAQ device. If you don't have a DAQ device, Labview won't recognize that Virtual Channel as a valid one.
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Regards
Filipe A.
Applications Engineer
National Instruments

Podcast channel with multiple channels inside?

Hi all,
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Just to be clear about terminology: a podcast is the overall wrapper for a number of episodes. People often refer to episodes as podcasts, and that way lies confusion.
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AI Group Config Error 10001 using Virtual Channels

In my LabVIEW block diagram, I usually enter in numbers, e.g. 0,1,2 for the channel string input of AI Config. When I try to use a virtual channel, I simply type in the virtual channel, e.g. 0,K Thermocouple,2. However, this causes AI Group Config Error 10001, which applies to an invalid channel string. What is the correct way to enter a virtual channel into the channel string?

Do you have channels with virtual names of "0", and "2"?
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Is there anyway to read the unscaled voltage from a scaled virtual channel?

I am using DAQmx to read voltage from a SCXI chassis. Programmically in Labview I created a task with virtual channels and custom scales. Later in the program, I wish to view the scaled volatge and the raw voltage at the same time. Is there a property node which will allow me to do so?

Hi Fergusonhd -- yes, there is a way to do this --> Look in DAQmx-> DAQmxAdvanced-> Scale -> Scale Property node.
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Why is the input mode greyed out when I try to create a virtual channel for my 1102?

I have set up a virtual channel for my SCXI-1102, and the input mode is greyed out with it set to "differential". I have already skimmed this forum for answers, and I have checked to verify that the mode slot under the AI tab for my MIO-E series card is set to nonreferenced single-ended mode. I then created a virtual channel with the device slot under the hardware column set to Dev1_SC1_MD1CXI-1102. At this point, as already stated, the input mode goes grey while set to differential. What's going on?

Hello,
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Is CJC compensation automatically applied to Virtual Channels created with MAX?

I have a SCXI 1000 chassis, a SCXI 1102 module and a TC 2095 terminal block. I am configuring virtual channels with the names TC(n) where n is the channel number. When I configure the virtual channel, I am selecting 'built-in' CJC. The question I have is:
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Wes;
You are right. That is the way it works. If you specify the CJC compensation in MAX when creating a Virtual channel, to be the built in CJC, the data you get is going to be CJCed already.
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Virtual channels with 6602 counters

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Virtual Channel with RT system

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Yes, I would have the same virtual channel configuration on the Windows machine as on the remote RT Engine.
With the virtual channel configuration on the Windows machine, I can use the "Test" button (from MAX) which is an easy and very quick way to verify that the channel is working.
In fact, as you mentionned in your answer, I just need to create a RDA device in the "Device and Interface" folder, and automatically all the virtual channels configured on this remote device are "imported" under the "Data Neigborhood" folder.
I didn't see this functionnality in my first test because I had created the Remote Device entry before I created the virtual channel on this device.

Single virtual channel with multiple digital ports

Hi all,
I have created a program that creates a task to read continuously from 3 digital port lines from the same device (PXI-6133). I am trying to figure out how I can retrieve the data from each port line to put into a waveform graph. Currently, I am using the DAQmx Read instance with "1 Channel N Samples" but I get a waveform with all values at the same time or a waveform graph with all three lines transposed.
I am using Windows XP and LabVIEW 8.6.
Appreciate any help!
Solved!
Go to Solution.

Hi Matt,
Thanks for your reply. Unfortunately thats not quite I am looking for. I am sending the DAQmx task the 3 port lines that I want therefore as I have read it bundles them all into one channel by default. What I want to do is take that one channel and parse out the data of each of the 3 port lines to create 3 new waveforms to work with individually.
After fumbling around a little bit, I was able to sort of get what I wanted. I've attached a screen shot of that portion of the program. The red circle in the bottom right hand corner is how I want to end up. I only did it for one of the pieces of data just to try it out and the conversion to string is just for me to print out what I'm working with. Unfortunately, when I look at the waveform it seems like maybe some extra 0's are being thrown in because its not the same graph that appears from the beginning (when all 3 pieces of data are transposed on each other). Let me know what you think.
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Attachments:
LabVIEW-ss1.JPG ‏57 KB

How can I get properties of global virtual channels using DAQmx?

I'm using DAQmx with VB6. In my app, I would like to be able to present the user with a list of available predefined channels to select from. I can use DAQmxGetSysGlobalChans to get a list of the channels, but I need a way to sort out which of these channels are defined as inputs, and which are outputs. It would also be nice to be able to query other properties of the virtual channel (for example, the device and physical channel being used). These all seem very simple things, but I haven't found anything like this in the documentation so far.
Thanks.

Try using DAQmxGetChanType(TaskHandle taskHandle, const char channel[ ], int32 *data)DAQmxGetChanType(TaskHandle taskHandle, const char channel[ ], int32 *data). This will return one of the following types:
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Duplicating a CTR Global Virtual Channel in MAX does not update the CO.Pulse.Term setting

Hi,
Here is the issue description:
MAX version: 4.6.2f1
daqmx: 9.0.2
Hardware: cDAQ-9178 , NI-9474 Digital output.
For this module one has:
crt 0 out <--> PFI3
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ctr 3 out <--> PFI5
1. In MAX create a Global Virtual Channel as a CTR output on ctr0.
2. use the Duplicate in the menu to create a second counter output. Change its name, and change it ctr output to ctr 1 OUT.
3. In MAX, the Pulse Output Setup pane should reflect the change by showing the ouput terminal pointing to the proper PFIi
4. Export the settings to an INI file, and look at the CO.Pulse.Term settings for both CTR channels: they will both appear with the SAME PFIi !
5. Using LabVIEW Write a vi that generate pulses on these 2 channels , you will get Error -89137 saying a PFIi resource is already used. If you look at the Task property CO.Pulse.Terminal, it returns the same for both tas, which is the same error seen in the ini file.
Can someone at NI check this? Thx.
Laurent
PS: I posted this message in the LabVIEW board as I did not find one for MAX
Solved!
Go to Solution.

Hi Laurent,
I verified this behavior with DAQmx 9.1 and a simulated device. I will file this as a Corrective Action Request (CAR). Creating the channels manually works correctly and produces the correct .ini file. Sorry for any inconvenience this may cause.
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Digital Multimeter Resources

About virtual channel in different device and/or different type channel

Hi all,
I am looking for a way to write to several analog channels at the same time. In my code, I didnt' pay much attention to that, I just have them placed in the the same frame in the flat sequence such that they might be started to write simultaneously. However, sometimes they might not working perfectly. I am reading something on DAQmx and I found that there is something call virtual channel so I have put more than 1 channel into a unit (called virtual cahnnel), so I can write something to it at the same time. Here are my question
1) what's the different between virtual channel and channel group? If I write a array of 3 elements to a channel group (consists of dev1/ao1, dev1/ao2 and dev1/ao5), am I writing to channel group or virtual channel?
2) can I bind different channels from different devices to form a virtual channel, e.g. dev0/ao0 dev1/ao0 dev2/ao0?
3) can I bind different type of channel to form a virtual channel, e.g. dev0/ao0, dev0/port0/line0?
4) last question is about synchronization on writing to a virtual channel (or channel group?) Last say I have a pulse train each pulse is separated in time by 1.2ms and total time is 122.4ms. The pulse train will be sent to dev0/ao3, and at 12ms after start send very first pulse of the train, I need to write two analog signal to dev1/ao1 and dev1/ao5. In my current code, create a flat sequence, start the task for sending the train in the first frame, put delay in second frame and delay for 12ms, write dev1/ao1 and dev1/ao5 in the third frame. For some times, this gives me acceptable timing but not always. I wonder how does it help to use virtual channel?
In the similar situtation, what about if instead of writing to two analog channel, I write to one analog channel and one digital channel?
Thanks.

1) virtual channel is created per task and contains a collection of settings such as a name, a physical channel, input terminal connections, the type of measurement or generation, and can include scaling information.. A virtual group is specific to digital IO and has to deal with the way you read/write data off/to the port
2) yes you can create a task with physical channels from multiple devices assuming they are comparable writes (ie all analog or all analog read, or all digital) but they will have the same channel characteristics (see answer above)
3) no you cannot create a task that handle an AO and a DO from with in the same task
4) if you created a task you are using a virtual channel. The only way to ensure timing is to use hardware timing (ie onboard sample clock of you DAQ card) otherwise the reads/writes are basically interrupts and you are at the mercy of the OS to service the interrupt request
if you need more information please repost with more questions, include your DAQ hardware, and any code pictures to give us a better idea of what you are trying to accomplish and how you are going about it
Applications/Systems/Test
National Instruments | AWR Group

Thermocouple reading has offset when I choose a large range on virtual channel?

I am using SCXI 1102 with 1303 terminal block. I create a virtual channel for a type J thermocouple using CJC built-in. I set the range of the measurement to 0 to 500C. At ambient temperature (22C) I read 10C. If I change the range to 0 to 100C the reading is correct. How can I fix this problem?

Well, you already tried the obvious. The less obvious might include NI-DAQ driver problems. It has happened before.
On a SCXI-1126 frequency module, back in the 1998-2000 time frame, the underlying code within NIDAQ had a problem where when you picked a channel scaling that was EXACTLY within the boards ranges, such as 1k, 2k, 4k, 8k, etc., the board read back frequencies correctly. However, when you used a virtual channel to set up scaling to something like, say, 0-2200hz, the algorithm to span that wrange worked incorrectly. It evidenced itself as a drop off followed by a peak rather than a gradual ramp up in readings as the frequency increased. I eventually created a program that plotted the problem and showed it to our local
rep, who got it fixed back at NI.
The point is, the problem didn't show up in NI's production testing because they always used exact ranges in tests, while virtual channels allowed more flexibility. Somehow you need to be able to get NI to duplicate the behavior.
- You could try using other ranges in your scaling that still have your necessary ranges as a subset.
- You could try using DAQ MX if you are using traditional DAQ, or vice versa.
- You could send someone at NI your NICONFIG.DAQ file and have them try it there, with whatever version of LV and DAQ you are using.
Another thing that could have happened is that you may have a group of boards with a bad lot of chips. Check to see if all the boards you are swapping during troubleshooting have the same lot numbers on the chips. If possible, try to find at least one board that is much older or much newer when you are swapping. We resolved a 4 year problem when we finally realized 56 solid state relays on 14 different S
CXI-1321 front end modules all had the same exact thermal problems, and were all from the same manufacturer lot. Swapping with a different module 2 years older confirmed what we had been missing for years!
Tim Jones

Use virtual channel name as input to DAQmx Write? LV8 and DAQmx

I've created a task for digital output that contains 8 named channels using the DAQmx Create Channel VI in Labview. Is it possible to use the channel name as an input to the DAQmx Write VI to reference the desired channel? I tried wiring a string with the channel name to the "task/channels in" input but I get a -200428 error that says the Value passed to the Task/Channels In control is invalid.
The help "name to assign" input for the DAQmx Create Channel VI says
If you use this input to provide your own names for the virtual channels, you must use the names when you refer to these channels
in other NI-DAQmx VIs and Property Nodes
OK, so how do you use the name assigned in other VIs?
George

George,
I think that there may be some confusion here about the difference between local and global virtual channels. First of all, please take a look at the following knowledge base:
Physical Channels, Virtual Channels, and Tasks in NI-DAQmx
As discussed in this KB, local global channels are created inside a task, and they only apply to that task. In the help file for the DAQmx Write VI, the "task/channels in" description says "if you provide a list of virtual channels, NI-DAQmx creates a task automatically." When you wire a string to this input, a new task is being created, and unless the channel name that you wire in is a global virtual channel (listed in MAX), you will get the error 200428 that you mentioned. This is because that virtual channel that you are specifying is local to another task and is not associated with this new task.
One solution to this issue is to use the DAQmx Save Global Channel VI to save your local virtual channel as a global virtual channel before calling DAQmx Write. Once this is done, you can then wire the same string constant to the "task/channels in" input of DAQmx Write or other DAQmx VI's.
The help text is still correct, but is only applicable in certain situations. For example, if you create and name an analog input local virtual channel with DAQmx Create Channel, you could then use this channel name as the source input to a DAQmx Trigger VI configured for an analog edge start trigger. You could also use that channel name as the input to the "ActiveChans" DAQmx Channel Property, which would enable you to modify the properties of that particular channel.
Hopefully this information is helpful to you.

Duplicate physical channel with virtual channel

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