Multiple channels, labview 6

Dear All,
I am using labview 6 with SCXI-1122/1322 to acquire voltages from ch5 for strain gage and ch7 for load cell.
The problem is no matter what I do, I always got the same voltage input for both channels.
I've been talking to tech support for a long time, and they have no idea.
If necessary, I will post my code.
Thank you

Hsin wrote:
The MAX showed me the correct data.
This problem only show up if I input two channels, either the string or the virtual channel name.
Here is my channel string : OB0!SC1!MD2!5............then I got the reading is -0.082
OB0!SC1!MD2!7............reading is 0.0005
Once I put.........................OB0!SC1!MD2!5:7.........the reading either both the same value or one of them won't be the reading I mentioned above.
If anyone know what happened, please let me know.....Thanks
If memory serves me the "5:7" specifies channles 5-7 which includes channel 6 in between. An open channel will often (if not tied to ground) reflect tha value of the previous channel.
I think I used to use an array for the channel list (try it it may take an array) since (for most widgets) it let gather data in an order other than the hardware order.
So try an array.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

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Acquiring Analog Input from Multiple Channels in Labview

Hello,
i am working on a VI where i need to acquire signals from multiple channels in Labview using NI-9129.Initially i want to acquire contineous input signals (voltage and current) and display it on the graph.
Having looked at forum and Labview examples i tried to make an initail VI but i am not sure if the setup i made needs any modification to serve my purpose.I am fairly new to Labview software.
All i want is
1.To acquire conteneously current and voltage
2.Display current and voltage individually on the graph.
3.Perform some basic calculations like MAXIMUM,MINIMUM and AVERAGE values of voltage and current.
4.Log the data into excel file
I have attached the VI i made so far.i need abit of advice if i am moving in the right direction or not.
Thank You for having a look at my question.
Attachments:
Voltage-Current VI.vi ‏81 KB

Engr_tech wrote:
i think i already have the tdms for data logging.as far as the tdms data logging is concerned,when i enable the logging mode to "read and log" the data logged inside the excel sheet would be seperate for current and voltage.?
Is it practically possible to acquire data from 4 different channels and plot them.if yes,then am i right to assume that all i need is to modify the current VI for four channels having all of them in parallel.
Yes, you are logging directly to a TDMS file. This is definately the best route for data logging from a DAQ. The currents and voltages will show up as different channels in the same group.
To add more channels, just add them to your DAQmx task. The logging will handle it with no issue. Your calculations will also a little work to add the extra channels. Same for the graphs, since you are using seperate charts.
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How do I read multiple channels at one time using labview with the Fluke Hydra Data Bucket 2620a using serial port?

I need to take a reading of 15 channels about once a second. I can read one value at a time using the monitor function on the read values.vi driver, but this takes forever to read all the channels.

I don't have this instrument but I took a look at the instrument driver and it appears that you can only configure one channel at a time to read from. You might want to take a look at the command set for this instrument and see if it allows for configuration of multiple channels. It could be that the instrument driver just doesn't have that built in.
J.R. Allen

Data acquisition from multiple channels.

Hello
Right now, I am able to acquire the signal from a single load cell and display it.But I would like to know of how to acquire acquire signals from two load cells simultaneously.I am using Labview 6i and I am using AI S-Scan with AI config to acquire the waveform.It would be of great help if you could suggest a simple method to acquire the signals.
PS: Please find the attached file used for acquisition from a single load cell.
Looking forward for your reply.
Manasa
Attachments:
test 4.vi ‏102 KB

Hi Manasa,
If I understand what you are trying to do, it is relatively
straightforward to configure your application to acquire data on two channels.
I was unable to run your vi as it was missing some of the subVI’s
from your application. However, your
attachment was sufficient to see what you are trying to do.
Here is how to add channels:
1.
In the I/O Channel Constant, you can add
additional channels by using a comma or a semi-colon. For example, to scan the first four channels
you would put 0:3 in the constant (see attached screenshot ChannelConfig.jpg). To scan the first and third channel you would
put 0,2.
2.
The AI Single Scan VI will now read from
multiple channels. Often it easiest to
configure the output of this VI for viewing by first putting the data into an
array using the Build Array VI. It can
then be plotted in a waveform graph. (see attached screenshot ReadtoGraph.jpg
and WaveFormGraph.jpg)
Just a few notes about “simultaneous” sampling:
Most of the NI data acquisition cards have a multiplexer
between the various input channels and the Analog to Digital (A/D) converter
creating a very small delay between each channel (usually ms range or
smaller). NI does make several data acquisition
cards that can perform true simultaneous sampling, meaning that there is an A/D
converter for each channel.
For the large majority of applications, the small delay
between channels is negligible.
Jared T.
Attachments:
ReadtoGraph.JPG ‏21 KB
ChannelConfig.JPG ‏288 KB
WaveFromChart.JPG ‏61 KB

Multiple channels acquisition and Number of samples per channel

Hi,
I'm a new labview user and I need some help in trasposing an old traditional NI-DAQ acquisition software in a NI-DAQ-mx one.
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Is that a normal behaviour?
Thank you
Daniele

This is my code. The problem is the same with or without the code for the scan backlog indexing.
Tomorrow I will try with the code from the example.
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Daniele
Attachments:
acq code.jpg ‏119 KB

DAQmx multichannel read error. DAQmx believes there are multiple channels in my task.

Hello,
I recieve the appended error message when attempting to use DAQmx Read in my VI. LabVIEW is telling me that I am attempting to read a single channel when my task is configured for multiple channels. However, as you can see in the task configuration pane, that is not the case! If I attempt to use DAQmx Read to generate a waveform with multiple channels, the VI executes without error but I do not want a 1D waveform array.. Any tips?
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Steve
Solved!
Go to Solution.
Attachments:
multi_chan_errr.JPG ‏42 KB
channel_Vin.JPG ‏108 KB

This is exactly why I ALLWAYS hide my DAQ Tasks inside a "Resource Module"
As I use the term a "Resource Module" is a special case Action Engine tha exposes only that subset of functionality that a specific project needs to take on a given resource external to LabVIEW. And, it provides a single point of entry to access that resource by keeping private data private. Had you used the technique here you would have had one vi to look at. and, there likely would have been no "Reconfigure to add channel" method available to cause trouble.
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Steps to create a VI to read multiple channels

This is the first time I've used LabView. I want to create a VI to be able to read viltages from multiple channels and output the value of each channel to individual numeric indicators in the VI. I know how to read a single channel and I've created a task in DAQmax with multiple channels but how would I put that into a VI that will do what I need.
Thanks,
Albert

Assuming you are using the DAQ Assistant and getting one sample per scan, then you just use the Split Signal and wire the outputs to your indicators.
Message Edited by Dennis Knutson on 04-30-2007 09:49 PM
Attachments:
Split Signals.PNG ‏4 KB

Is there a way to acquire a set number of points from multiple channels?

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Hello,
Thank you for contacting National Instruments.
As Dennis had mentioned, there are many example programs that ship with LabVIEW that demonstrate how to take measurements from multiple channels with either a finite or continuous amount of data to be acquired. In LabVIEW 6.1 you can find these examples by going to Help >> Find Examples >> Hardware Input and Output >> DAQ >> Analog Input >> General.
In these examples, if you would like to sample multiple channels, you simply need to add the physical channels separated by a comma for example: 1,3,5 would sample channels one, three, and five. You can also use a colon to sample a sequence of channels for example: 4:6 would sample channels four, five, and six. This makes it easy for you to choose the chann
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Save multiple channels to binary?

I am trying to save multiple channels of analog signals measured using DAQ express. I want to save the waveforms to binary and be able to read them back to re-create the waveforms at a later time. I have tried writing the waveforms to binary as dynamic data and as arrays. Neither seems to work. I am not sure if my problem is how I am saving/writing the data or how I am trying to read it back. What is the best form to use to write the data and how should I read it back?

Hi VCUBME,
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Measuring Multiple channels at a time

Hello All,
I am new to Labview trying to measure voltages and currents from a
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Anyone please look into my file and modify it for multiple channels.
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Let me explain. Your board has a single A/D. There is a mux that rapidly switches between channels. It will take a sample from channel 0, then channel 1, then channel 2, and then start all over again. It will repeat until the total number of samples that you requested have been taken. The switching is very fast - on the order of usec, so you can take the 3 measurements but it is not truly simultaneous. Depending on the frequency and the accuracy of the phase difference you're looking for, this may not make a difference. You can also get the inter-channel delay and compensate for it.

Agilent 548xx multiple channels

I downloaded the driver off Ni's site and am able to configure scaling and trigger and read from one channel. Problem is my client's testing requires sometimes reading 2 and sometimes reading 3 channels also. The configuration sub-palette has a VI for configuring 2 channel mode or 4 channel mode, but I can't get this working. Tried changing the order that I configure things in, no help there. Anyone using an old Agilent scope and reading multiple channels, or know of an example along these lines?
Thanks,
lmd2
Lawrence M. David Jr.
Certified LabVIEW Architect
cell: 516.819.9711
http://www.aleconsultants.com
[email protected]
Solved!
Go to Solution.

Thanks Rob, yes I am using a 54825A which is supported by that driver, but the Configure Multiple Channels function is only valid for the 54845A. Found the work around though, in the Action-Status subPalette is a function called hp548xx Actn On Off.vi
I used this to force three channels to be enabled, and was then able to configure them and retrieve the waveforms from all three channels.
Thanx for the reply, weird that the one function is limited to a single model while the rest of the functions are valid for the entire family, but at least there is a simple work-around.
Thanks again
lmd2
Lawrence M. David Jr.
Certified LabVIEW Architect
cell: 516.819.9711
http://www.aleconsultants.com
[email protected]

Multiple channels definitions for AI

All examples for analog input use one channel only. I would like to see and example using multiple channel inputs.

Hi rlbrehm,
If you have already created Global Virtual Channels in MAX, you can use the DAQmx Create Task vi to create the task from those in LabVIEW.
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Using a DAQmx Task in LabVIEW
If you want to define the channels in LabVIEW with multiple characteristics, you can also use the DAQmx Create Channel multiple times in your code to define channels with different characteristics (scales, ranges, etc.). The following code shows how this can be done, although a more elegant solution would use an array of channel configurations in conjunction with a for loop.
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Help! data manipulation for high speed streaming to disk from multiple boards and multiple channels

I am using Labview 7.1 and have been trying to capture data from 12 channels simutaneously sampled at 2MS/s each and streaming to disk for up to a minute or more. The hardware I am using is 2 x PXI 6133 S series boards with a MXI4 link to a Pentium D 2.8 Ghz machine with 2Gb ram. I have 2 sata drives set up in a raid 0 configuration which should give me hard disk write speed faster or equal to the MXI-4 transfer speed.
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Is there a cleaner way of streaming this data to disk and keeping the channel data separated from each other?, and/or is there a better way to capture and handle the data I need?
I have attached the vi which I have got to consistantly work streaming to disk using the raw 1D I16 format.
Thanks in advance to anyone who can help.
Attachments:
multidevicesync_analoginput_streamtodisk.vi ‏197 KB

Hi,
i can suggest following
Refer to an example VI called as "High speed data logger.VI" in conjunction with "High Speed data logger reader.vi" in Labview examples. Alhrough the logger might be in Tradiditional Daq format, it can be quite easily converted to Daq Mx format to store data in Binary (I32 format) . I have used this for many of my applications and i have found that the data retrieved does not have any "messups".
Why not keep a seperate file for each card? This way, you do not have to load your application with extra process. You only have to acquire and save. After saving in Binbary format, you can retrive it offline, convert it to ascii format and merge the data files of various cards to get one consolidated ascii data file.
hope this helps
Regards
Dev

Reading multiple channels for multiple graphs

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I know I can use the Express> DAQ Assistant, however that outputs "Data" and I was hoping to use this in an Array. So I used the DDT to Array to convert it to the Array format that I needed (thanks to the forums for the help there). My only problem is that I don't know how to do this with multiple channels at the same time. But I have possibly been going about this all wrong.
So I just wanted to know if I could get some help on how to read multiple channels and write to them to three different graphs in real time that would be of great help.

Whether or not you use the Convert From Dynamic Data or the Split Signal, your data should be shown as soon as the DAQ Assistant returns. How you format the data is irrelevant. If the number of samples you request is greater than the sample rate, then it will take longer to acquire the data and there is nothing you can do about that except reduce the number of samples and acquire in a loop. You can append new data to old and display everything in a graph if you want.

Displaying real-time data using gui meter from multiple channels.

I am using DAQ USB-6009 for my assignment. Part of my task is to display real-data from multiple channels in the form of gui meters. eg. irradiance and voltage...
I used a split signal to separate the signals from different channels coming out of the data output terminal of the DAQ assistant. The problem is that I do not know which vi to connect in between the split signal and the gui meter. I am looking for one vi that is capable of handling signals (measurement) and outputting the data to the gui meters simultaneously and individually based on the channel they are coming from.

Thnx for your tip, Dennis.
However, I have another problem that just occurred to me when my VI manages to execute as I wanted.
I noticed that the needle on my gui meter will only "appears" to be responding to every changes to its input when I have set it to run continuously and the only way to stop it is via abortion which might leave the resources (eg. external hardware) in unknown state. Is there any safer and workable ways to organise the VIs using while loop?
I have placed my DAQ assistant, write to measurement file (vi), add function, split signal and gui meters all in 1 single while loop.
    DAQ-------> write to measurement file
             |
             |                                                                    |--------------------------------> add function----> gui meters
             ---------------------------------------------> split signals ---|--------------------------------> add function----> gui meters
                                                                                  |--------------------------------> add function----> gui meters
If I do the following steps,
1. press run continuously to start the VI
2. click the same button to disable continuous run when the VI has completed its task.
3. click the stop button in the front panel to stop the while loop
Does doing these steps ensure that I will not leave resources in unknown state? Is it a safer way to stop a VI which is running continuously?
Pardon me for I am new to LabView. Even though, I have read the user's
manual and tried out all the execises, there are some concepts that I
need clarification on and mistakes that I need to discover through more hands-on.

Multiple channels, labview 6

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