Multi channel continuous DAQ acquisition

Complete newbie question here. First time using Labview so I apologize for asking this question: Is it possible to have multi channel contiuous acquisition? If so, does this have to go through a circular buffer to prevent tying up all the computer memory? Can you vary the scan and read rates for each channel? Last question: If it is possible to do all of the above....how do you do it? I've attached a .pdf file with screen shots of my front panel and block diagram....it's extremely crude just trying to get some basic concepts down. Also if anyone can recommend some good books on actually doing the wiring and conditions of the various elements, I'd be extremely grateful. Currently I have "Labview for Everyone".
Attachments:
DAQ.pdf ‏33 KB

Hello,
It is possible to have a multi channel continuous acquisition and it does use a circular buffer. Please check out the Continuous Waveform Acquisition Tutorial for more information about how this is done. With our DAQ devices you can use different sampling frequencies as long as they have a common divisor and the sampling rates remain within the device specifications. There is an example of that called Multi-Rate Continuous Analog Input.
The example finder is always a useful place to look for ideas on how to make a VI. In LabVIEW, go to Help->Find Examples and you will open up a browser that will allow you to look through many examples. You can also check out the LabVIEW Zone Learning Center where you can find a book listing under the fundamentals section.
Hope this helps!
Laura F.

Similar Messages

Continuous multi channel voltage data acquisition

Trying to use a NI 9223 to continuously sample voltage data from three channels the code work for a singel channel but when I added the other two channel I started to get errors.
I have attached my code if anyone can give me some pointer i would appreciate it.
Thank you
Attachments:
Voltage.vi ‏218 KB

Hi,
Did you try doing a search on the forum for error code 50103? (Leave out the "-" sign.) This question has been asked many, many times before.
You need to put all of your analog input channels into a single task. You only have one clock to work with. You get error code -50103 because you are trying to use that clock for three separate tasks.
Looking at your VI, it seems obvious that's the error you're getting even though you don't specify. Searching the forum for that error code will yield plenty of information for you which should be helpful (although I already told you what the problem is and how to fix it -- some of the posts will go further in-depth for you...I just don't really feel like re-typing all of the information when it's already available).
For examples of how to properly perform a multichannel acquisition, look under "Help...Find Examples...Hardware Input and Output...DAQmx...Analog measurements..." You'll find a lot of example code there which should help you.

Multi Channel USB Data Acquisition

I am using the following VI for arduino HC-06 bluettoth data acquisition. I would like to acquire multicahnnel data
Could you suggest me how to acquire multichannel data from USB? To do this, in what way i have to program the arduino?

Thank you very much for your suggestions. its working.
But if i give input to channel 2 or 3 or 4, they are not responding. only channel 1 is responding irrespective of input pin. what could be the reason for this?
earlier, i was acquiring single channel data at 57600 baudrate, i was getting pure sine wave signal upto 90Hz, after that it was started distorting.
Now, it started distoring above 20Hz, i think i need to increase the baudrate to 230400 to get 4 channel undistorted signal upto 100Hz,
but arduino supports upto 115200 only, what shall i do??

NI RF Phase-Coherent Multi-Channel

Hello! I would just like to ask why I'm getting the results shown in the attached file in using the NI RF Phase-Coherent Multi-Channel.
For all frequencies, I'm using the same demo program (included in NI RF Phase-Coherent Mulit-Channel) for the generation and acquisiton.
Generation: NI-RFSG Phase-Coherent Multi-Channel Generation Example
Acquisition: NI-RFSA Phase-Coherent Multi-Channel Acquisition Example
The desired results are those under the 1GHz frequency. However, I'm working on 915MHz. Needless to say, I can't see any pattern in the behavior of the plots when increasing/decreasing the frequency. That's why I really can't understand the results I'm getting.
Please help me.
Thank you very much for your time!
Attachments:
results.pdf ‏24 KB

Hello!
Attached are pictures of the hardware set-up. It is identical to the typical 2-channel phase-coherent RF signal generation and acquisition set-up.
This thread is same as http://forums.ni.com/t5/RF-Measurement-Devices/RF-Synchronization-Suite/m-p/1893713#M1995.
The software I’m using is suggested by Andy on post no.2 in the link above. I’m trying to generate a CW with 915MHz carrier frequency. However, I get incorrect plots when I use 915MHz. Setting the frequency to 1GHz results to correct plots. This is without changing any setting in the front panel.
The main problem when I use 915MHz is that one channel moves faster compared to the other channel. For example, in the IQ plot, there would be 2 points representing the 2 channels. These points travel in circular path. If the slower channel travels 1 complete circle, the faster channel is able to travel more than 1 circle. Moreover, the phase delta is not constant since one channel moves faster than the other.
More on this in the link above.
Thank you very much for your time! I really appreciate it.
Attachments:
DSC03062.JPG ‏2182 KB
DSC03063.JPG ‏1991 KB
DSC03064.JPG ‏1934 KB

Important question: I have got a PXI-4472 and I am able to do single-channel acquisition. How does multi-channel acquisition work?

Look at the VI: it is quite eleborate, but the crucial point is Data Acquisition and Trigger&Gate (and, consequentely, Write to File operation).
I can add plot on the Waveform Graph DATA, this is rather easy, simply adding the channel numbers in the channel control (es. writing 0,3,7 will collect data from the three channels).
First question: is this operation of adding plots correct?
Second question: does the sampling rate dwindle when I consider multi-channel acquisition? I mean: 1 channel-->100KHz ; 2 channels-->50 KHz
More over, and MORE IMPORTANT: is it possible to set different trigger conditions for different channel
s? How can I control this operation?
Third: can you have a look at the VI as all (the appearence, the functionality, the logical sequence...). I am looking forward to get your advice. In particular:
Look at the frontal panel: what do you suggest to make it "smaller"? More tab controls?
Look at the Block Diagram: do I have to connect ERROR IN and ERROR OUT to every suVI or function that makes this connection possible (as Trigger&Gate and Write File)?
Attachments:
Start&StopTrig_SpectralMeas_style+image.vi ‏700 KB

First: yes, the operation is correct.
Second: yes again. When you consider a multi-channel acquisition, your sampling rate must be shared among the channels.
Third: when you specify a list of channels you want to acquire from, the channel considered for analog triggering is the first you put in the list.
Connect the error clusters whenever you can,in particular when you are dealing with I/O operations.
Bye!

An application for multi-channel measurements

Does NI have a software solution for multi-channel measurements? I mean systems for measurements, tests and monitoring which contain numerous DAQ devices with thousands of sensors.
I suppose the software for such system should have the following features:
Instrument control
Sensor management (type, s/n, accuracy, calibration data, next calibration date, measurement limits, etc.)
Data acquisition
Storing data in databases
Data visualisation and analysis
Report generation
Tools for creating custom user interfaces / data visualisations for monitoring
As far as I know the DIAdem is great for data analysis, visualisation and report generation but it's not suitable for other tasks. With LabVIEW you can do anything but it's not an "out-of-the-box" solution.
Just to clarify what I'm talking about, here's an application that seems to fit the description. It's the HBM catman. Maybe someone worked with it? Do you know any analogues for it?

Just to add to Hooovahh's comments.
NI has flat out stated that they do not want to make turn-key solutions. That would take away from them being able to make tools for people to create the solutions. That is why they have alliance partners. These partners take the tools made by NI and make really cool stuff. My latest project was a software package that helped a technician build a jet engine correctly so that the turbine blades do not come out and destroy the engine (just slightly important). I have also done some test systems for space craft avionics.
So if you are really serious about this, I highly recommend finding an Alliance Partner to help you out. If you want, give me a PM and I can work on getting you and a few people on my side to discuss your requirements and proceed from there.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Real-time PID control and continuous buffered acquisition. Does it work together?

I use the "real-time PID control.vi" that acquires single AI point and generate single AO point in every "while loop" iteration to control a piezo actuator motion. Simultaneously I need to do (in another loop) a continuous buffered acquisition of another two AI channels (in the same rate as first AI channel).
It does not work together.
Does anybody know how to fix it?
Platform: LabVIEW 6.1
Board: PCI-6024E

Hi,
I would try to avoid the idea of using a separate loop since the PID
loop is a continuous acquisition and will require un-interrupted access
to the Analog DAQ system of the board. The last thing it needs is for
you to attempt to start other AI functions at the same time.
Configure your AI in the PID loop to read in multiple channels (Just add
some more channels to the Input Channels Control. Separate the data as
it comes out of the AI single Scan function using Index Array or other
Array functions into that needed for the PID and that needed for your
other data (the example is already doing this to make sure it only gets
1 channel of data into the PID). If you don't need to sample all your
channels of data all the time you can throw some data away as
required.
Obviously your other channels are now arriving one sample at a time so
if you might need to build an array, insert into an array or use Auto
Index on the loop if you are data logging.
Regards,
Dave R.
varmih wrote:
> I use the "real-time PID control.vi" that acquires single AI point and
> generate single AO point in every "while loop" iteration to control a
> piezo actuator motion. Simultaneously I need to do (in another loop) a
> continuous buffered acquisition of another two AI channels (in the
> same rate as first AI channel).
> It does not work together.
> Does anybody know how to fix it?
>
> Platform: LabVIEW 6.1
> Board: PCI-6024E

Transferring DAQ acquisition data via TCP/IP

Hi all. I am trying to write a program which shares the raw data acquired from a DAQ acquisition device to several computers at the same time. I am using a NI-USB DAQ 6251 to acquire 2 channels of data at 200kS/s on each channel. I need to send this data to other computers in a network so that the each computer can perform different functions on the signal.
Anyone who has done something similar before? Can you help to advice on how I can go about doing this efficiently and reliabily? I cannot afford the data to be lost during the transfer. I did try using shared variables but it did not work well.
Thanks in advance.

Hi K.P,
I hope you are doing well today! The following links should help you get started. If you face any other issues, please be sure to let us know.
Using the LabVIEW Shared Variable and OPC With NI-DAQmx
Shared variable to grab data from remote PC with DAQMX
Message Edited by Adnan Z on 04-12-2007 10:29 AM
Adnan Zafar
Certified LabVIEW Architect
Coleman Technologies

How to input notes in a binary file used to save continuous DAQ?

Hello,
I have a continuous data acquisition vi with trigger. Data is saved in a binary file. I would like to save some comments or notes in this file; I want to be able to read the notes afterwards and the saved data that has to be displayed in charts. I got some examples from NI but they are simple and do not include the continuous data acquisition and reading both the notes and the (dynamic) data.
Does anyone have examples of binary files with notes and continuous DAQ write and read?
I've been working on this issue for quite a while and I got stuck...
Thanks...

Thank you Emilie.
I know these examples all right. Now try embedding this into a 'Cont Acq. and Chart - Int. Clk.vi' or any vi that does data acquisition and saves the data in the same file where you wrote the string of comments. And this is not all - how do you read them all back in the right order and right length...
I have inserted some examples to make you understand better what I am talking about.
'AcquirePFV_Header.vi' and 'Read_with Header.vi' are only some trials that do not really work correctly.
Could you or anybody else help me solve this problem?
Thank you.
Radu
Attachments:
ForNI03.zip ‏1170 KB

Multi channel multiple sample

Hi,
I am using USB6218 DAQ device and Labview 9. I have used DAQ assitant in my VI and my setting are RSE mode to sample 30 channels, continuous mode,20 samples,rate 100hz. This is what I had in mind from my programming background from C/C++ and I am new in using Labview. I was trying to get 20 samples from channel 1 in 10ms period and store in an array for eg channel_1_val[20] and switch to channel 2 and get 20 samples in 10ms time and store in channel_2_val[2] and so on for thirty channels. I figured timing should not be an issue as USB device has 250Ks/S for 32 channel which would approx 7ks/S for channel which is 120us roughly. So 20 samples in 10msec is plenty of time. Does the setting in DAQ assistant would do my above task as expected. Need help from experts.
Thanks

Hi Christian,
Just curious to know what I think is gonna happen to my attached VI. Please correct me if I am wrong. I am expecting, channel 1 sample 1 and a msec later channel 2 sample 1 and a msec later channel 3 sample 1 and so forth. And when all my 20 samples for 30 channels are acquired which would take roughly 600msec the while loop will wait for 500msec to start the next sampling. This is what I had in mind when I created the VI. I am also curious to know is there any buffer allocated or it just takes a sample from channel 1 writes in a register or memory and after a msec takes a sample from channel 2 and overwrites on the same register or memory. The reason I am asking that is I would like to write all my samples on an excel in a format given below and fill an array with 20 samples from each channel and take an average to determine the pressure leak
Timestamp | channel no | Voltage(v) | Pressure(psi)
and may be plot a graph based on how fast I get this done. Currently write to spreadsheet on my Vi is filled with rows equal to no of samples and just one column. I am guessing that I need a build an array with the value that I sample everytime after a msec and finaly write this array to excel. If that is the case how will I form the dynamic array. Thanks for your support.
Attachments:
analog_ip1.vi ‏78 KB

Multi-channel Sequential Controlling Pulse Generator Design

Hello, all,
I need to design a Labview problem as a Multi-channel Sequential Controlling Pulse Generator and output through DAQ card. The required digital pulses are showns in the attachment. Time scale values are shown on the top as an example. CLK's duty cycle is 0.5. x1 and x2's value need to be programable.
Could anyone give example codes? Or, give me any idea to program these pulses?
Attachments:
clock.png ‏22 KB

Duplicate
http://forums.ni.com/t5/Multifunction-DAQ/Multi-channel-Sequential-Controlling-Pulse-Generator-Desig...

Multi-Channel Sound Cards

Hi,
I was wondering if flash player had support for multi-channel
sound cards. Everytime I play a .swf with sound i only get audio
out of two channels.

The audio interfaces that I use are an EMU 1820 and a Tascam FW-1884 firewire device. Both are fine for what I do (broadcast quality material). I believe the EMU gives better audio quality and is certainly more robust, but the Tascam, being Firewire, is more easily movable between machines. I also like to work with real faders and it integrates well enough with Audition to be usable. The EMU has the incredibly flexible virtual mixer, but I find it hard work keeping my brain up to speed with this.
I also have other cards either inside machines or usb, but these are all just 2 channel.
I'd be surprised if anyone was using Audition for logging, as the requirements are rather specialised. I'm way out of touch with this field now, but the requirements used to be that the recorder could be left to run continuously, and users on the network should be able to pull material off at random while the recording continued. Recording is the fairly easy bit, management is the problem.
I'd have thought any computer based system ought to be capable of high quality. There are one or two low-cost or free loggers, I believe, but I've no idea how useful they are.

Multi-channel Scan

i am using PCI-6025E DAQ card. do Multi-channel Scan
,before signal input to analog input , i use a voltage follower ad623. sample frequency is 1k, is it safe ?
or how to reduce settling time effect ?

Hi Schmidt,
The input range for the 6025E board is +/- 10 V, so if your signal (going into the DAQ board) is within this range you are safe. In regards to reducing settling time, you are on the right track. The following link is a great resource when using a voltage follower to reduce the impedance of a transducer.
http://zone.ni.com/devzone/conceptd.nsf/webmain/CD57A73721E0612586256BAE0055CDD9?opendocument&node=dz00000_us
Have a great day!
Brooks W.
National Instruments

5122 and continuous triggered acquisition

I have a PCI-1522 and I want to do a continuous synchronous acquisition and have tried a number of things in NI-SCOPE without success. The signal I want to acquire is triggered (or to be more technically correct is synchronous with a second external signal) at 10 or 20 kHz and I want to sample at about 20 MS/s. Setting up the ext trigger is fairly straightforward if you put the initiate and fetch within a while loop. But then you have to loop on each trigger every 100 us (which the software is not fast enough to do even without the decimated processing I want to do) or acquire a larger chunk of data. This latter approach essentially initiates on one trigger pulse but acquires a large number (2M) of samples at 20 MS/s and therefore is subject to jitter if the samples acquired aren't exactly right. (I adjusted the sample size to correct within one sample and there is still persistent jitter so without triggering the accuracy required is less than one sample.) Bottom line is you aren't synchronous with either approach. With the fetch forever example, you move the initiate outside of the while loop which is great. But you have to use a software trigger in order to get it to work. All of the possible solutions essentially boil down to software triggering. I suffer either from jitter or drift.
I thought about using the video ref triggering schemes but then I have to configure my signal to fit into the pre-defined video formats which may not be possible. I haven't thought too much about a DAQmx solution. Are there any examples or solutions of a hardware-synchronous, continuous acquisition in NI-SCOPE or DAQmx?

Hi Dan,
You might want to take a look at the niScope EX Multi Record Fetch More Than Available Memory.vi shipping example. With this VI you can set up a multirecord acquisition and fetch records as they are being acquired. This allows you to acquire more records than will fit in the onboard memory. Currently, there are limitations in the driver which limit you to fetching about 2,000 to 3,000 records per second, so you will not be able to keep up with your 10 to 20 kHz trigger signal indefinitely. However, we are currently working on fetching optimizations which should bring this number up to the 10 kHz range in the future. We hope to release these optimizations in Q1 of 2007.
I hope this helps.
Regards,
Sean Close

Write 32 channels thermistor data (temp in degree vs date/time) into xls file for all channels continuously.

i am acquiring 32 channels thermistor data (temp in degree vs date/time) in waveform plot using array to cluster function ,
now my problem is how to write this data into xls file for all channels continuously.
please help me at the earliest & i am new to Labview.

Hi Priyanka,
Writing to excel file continuously is not a good idea, you can use ".CSV" or TDMS file format and once data acquisition is completed you can convert that to excel file using report generation toolkit.
With Regards
Miraz
Kudos is better option to thank somebody on this forum

Multi channel continuous DAQ acquisition

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