Can't acquire continuous signal

Hi-
I am trying to acquire a continuous signal using the Daqmx acquire data
vi. I have the scan rate set for 100,000 (which is fine for one
channel) and the samples set to 10,000. The output on the graph
is the same no matter if I select "continuous" acquisition or "N
samples" in the Acquire Data.vi. The graph and chart seem to
update every few seconds as opposed to continuously. Also, I am
unable to stop running the program by pressing the "stop" button.
I have to abort the program. I've attached the program
below. If anyone has any thoughts, I would appreciate it-
Sherri
Attachments:
Datalog17122005.vi ‏450 KB

Your stop button has to be wired to something to actual stop and the normal thing is to wire it to the termination terminal of a while loop. Clicking the run continuous button on the toolbar is not the normal way to operate a VI. This should never be used except for occasional debug purposes. Put your code inside a while loop, wire the stop button and retry. There are numerous shipping examples on continuous data acquisition. Take a look at them to see what I mean. I've never really used the DAQ Assistant so I can't say whether you still won't have a discontinuity in your acquisition. If you do, using the DAQmx functions themselves instead of the assistant should solve your problems.

Similar Messages

How can i acquire analog signals from PXI 4472 card?

Regards
Aks
(Appreciate answers by giving KUDOS)
Hit the stars.............. sky is not the limit.

There are a lot of shipping examples for DAQmx. Once you open the example finder (Help>Find Examples), use the 'hardware' listbox at the bottom to find all of the examples that pertain to a 4472.
Message Edited by Dennis Knutson on 10-28-2008 07:30 AM

I need to acquire impulsive signal(s) and then write them to a file - but I need a good approach

Okay, I am pretty new to Lab View, and would appreciate suggestions of how to approach a problem.
My
only LabView experience has been writing a simple .vi to acquire
voltage signals in a loop at a certain sample rate, get 5 of them each
time the loop iterated (it did so every second), average the 5 samples,
and dump them into a file at every loop iteration.
That
was for continuous data acquisition while viewing/monitoring the data
at the same time, and was probably not the most efficient way (or even a
good way) to do it.
Now,
I am doing something different. I want to record voltage signals but
only after a trigger event has occured, and only until a certain time
window after the trigger event.
Should I use continuous data sampling?
Or should I sample "N" samples?
Should I use "producer / consumer" structure?
Should I continuously log to a TDMS file (I just started reading about that.... I used lvm files before....)?
I
am very confused. I have enough programming knowledge to be dangerous,
but am very new to Lab View. Any quick pointers to get me started?
This is sort of time-critical....
Thanks a lot
-Jay

Jay,
There are quite a few examples in the example finder of how to implement various types of triggers IIRC.
How long is your time window and how fast do you want to sample? That will probably determine whether you want to use N samples (for shorter time windows where all your samples will fit in the hardware buffer) or continuous (for when you will want to make several reads before you have enough data).
Producer/consumer is a very versatile design pattern. If you have a long running acquisition that you'd like to be able to cancel or update the UI mid run then you might want to use it. If, on the other hand you are doing a quick (in UI terms) acquistion then there may not be any need. Templates and design patterns also become more important the longer you plan to keep the code around -- the more you plan to maintain and add onto the VI the more thought should go into the design.
File format is often a personal preference. TDMS is a richer file format (faster, smaller, IMO normally better) than LVM (essentially just a text file). TDMS files can be opened in Excel with a plugin or natively in any NI tools (LabVIEW, DIAdem etc.) Text files such as LVM can be opened with just about anything. One thing that may force your decision is if you are acquiring large amounts of data quickly (too fast to buffer in RAM) then you'd definitely want to use TDMS as it is much faster and gives your hard drive a chance to keep up with the inflow of data.
Good luck, let us know how you get on.
~Simon

What is the maximum number of samples that can be acquired with a single trigger using PCI-6036E DAQ card?

1. My PCI-6036E card has a FIFO of 1024 bytes in AI. Maximum how many samples can be acquired with single trigger for digitizing a waveform?
2. PCI-6036E DAQ card has got a AO with 10ks/s update rate? Can I generate a pulsed output with the AO of this card? I need a pulse of, say, 5 V and 1 kHz frequency.

Giri,
1.The trigger is usually for enabling the acquisition. I mean, when it is logic zero, you acquire nothing; however, when it is logic one, you start acquiring your waveform,and you can acquire continuously without having to worry about how many samples, unless you want to set your program for doing so. You can acquire continuously by implementing buffer acquisition. Finally, the FIFO that is in the board will not affect the buffer acquisition.
2.Yes, you can do that! You can generate your 5V signal with that specific frequency, and you should not have any problems, because the freq fits in the update rate.
I hope this information is helpful.
L Aguila
Applications Engineer
National Instruments

Suggestions to improve the filter output of the acquired pulse signal

Hello,
I am working with acquiring the pulse signals form DAQ using a sample rate of 1k and number of samples as 1k for every 1sec signal using the DAQ.
I am using the smoothing type filter with Moving average->Rectangular->Halfwidth=3 and passing the smoothed signal to the butterworth filter with my requirements of 2.3hz and 0.7 with sample rate of 1000.
Problem:The filtered signal is always starting form 0 instead to start with the first value in the acquired pulse signal.For example, starting from 0 instead to start from around 0.057 as shown in the images.
How to make the filtered signal to start from the original pulse signal value.
Thanks in Advance.
Attachments:
improvementinfilter.jpg ‏164 KB

All filters have a transient response. A bandpass filter with a DC component at the input will have that transient strongly excited.
Some of the filter VIs have an Init? input. If the signal is continuous but is being filtered in segments, that input can help by retaining the previous state of the filter. The first transient will still be there, but later ones should be erduced or eliminated.
In the example VI attached you will find that there is a transient at the beginning of each segment. This is due to the sine signal not having an integer number of cycles.
The IIR Cascade Filter with I.C.vi and IIR Filter with I.C.vi in the Signal Processing >> Filters >> Advanced IIR Filtering palette have an initial state input.That might be helpful but calculating an appropriate set of initial conditions from the signal data may not be straightforward.
What do you want the output to look like? What are you doing with the filtered data? Perhaps there is a better approach than a filter.
Lynn
Attachments:
Filter transient.vi ‏19 KB

Basic question to continuous signals

Hello.
Unfortunately
I got no answers of my questions after reading in help documents and articles.
Technical
details: Labview version 7.1; we want to receive signals from different channels
of a lock-in amplifier. We have a PCI 6220 and a a/d converter.
First of
all I had the error -50103, but I could solve it, when I put the two signals
together in one task. All in one the program runs, but I have some questions in
basics.
For
example: When I choose a number of samples per channel of 100 with a rate of 50
Hz the signals run not continuously. I see some information in the chart, then
a few seconds there is nothing and after that the signals go on. With a number
of samples per channel of 1500 the curve gets worse. But I want a continuous signal,
whatever number of samples per channel I choose. Is it generally possible that my
signals will be continuously/directly run in my chart? Maybe with arrays, but
if yes how could it work? It really seems to me, that “DAQ read” saves some
information in for example buffers and then shows it in a chart, then saves and
show and so on. But that’s not what I want.
Please can
anybody answer my questions?
Thank you
very much.

It's basic arithmetic. If you specify a sample rate of 50 samples per second and request 100 samples, then it will take 2 seconds for the board to acquire that number of samples and return them (100/50). If you request 1500 samples, it will take 30 seconds to return that number (1500/50). The samples you see in the chart are continuous but the update rate of the chart is determined by the ratio of the number of samples and the sample rate. You can specify a higher sample rate or specify a lower number of samples.

How can I acquire data in a PCI DAQ board using a SCXI rack?

Hello.
I have an acquisition system that consists in:
· 3 PCI DAQ boards:
- PCI-MIO-16-E-1
- PCI-6052-E
- PCI-6034-E
· 3 cables to connect PCI boards and SCXI modules
· 1 SCXI chassis:
- SCXI-1001
· SCXI modules + terminal blocks:
- 4x SCXI_1121 + SCXI_1320 (for voltage analog inputs)
- 1x SCXI_1520 + SCXI_1314 (for strain gauges)
- 1x SCXI_1530 (for accelerometers)
I have been trying to acquire different signals (specially voltage signals that are easier to reproduce) but I haven't been able to do it. I can't read anything from MAX or LabView. I have tested the PCI boards with a SCB68 terminal block (without any SCXI component) and they work properly. Problems appear when I use the SCXI chassis and the SCXI modules. I don't know if there is a problem with the hardware or it is a wrong configuration.
I guess channels in the SCXI modules correspond to analog input channels in the PCI board they are connected to, but I don't know if I have to read data from analog input channels of the PCI boards or from SCXI channels that appear in MAX (I have tried both posibilities, but they don't seem to work).
I don't know if I have to use Differential, RSE or NRSE configuration. I have tried all of them. Sometimes I only read noise, sometimes signal is fixed in a limit value (maximum or minimum, it depends), sometimes it's fixed in a value near zero,... I have changed connections and configuration options so many times I can't exactly say when one thing or another happens.
I have tested only one PCI board with only a SCXI module in order to avoid interaction and confusion. Nothing.
I think I have tried changing almost every option in MAX, but it doesn't work.
I'm sure I'm missing something and solution is quite simple, but I can't find it.
Can anybody explain to me how to connect and configure my system to read any signal? I only need a few steps or highlights. Maybe some clues about what the problem can be.
Thanks!

I have several comments and suggestions:
A) Have you "added a device" in MAX and actually added the SCXI chassis? This step is necessary to get the chassis to work. Click on "add a device" and choose the 1001 chassis . Do this for one DAQ card and one module only initially. The Set Up wizard should walk you through the configuration. If you are unable to add a chassis within MAX, I suspect the chassis is not working correctly.
B) Once configured, you can examine the SCXI channels in MAX as follows:
1) Open the DAQ card in MAX and Open the Test Panels
2) For the SCXI channel to view, use the following convention OB0!sc(n)!md(m)!ch where the letter (n) corresponds to the chassis number in MAX (usually = 1), the letter (m) corresponds to the module number (slot) where the module is located in the chassis, and (ch) represents the channel(or channels) you wish to view. So presuming chassis ID=1, and a module in slot 1, and you wish to view channel 3, you would type the following in the channel field for the DAQ card channel to view:
OB0!sc1!md1!3 (note OB0!sc1!md1!3:6 will display channels 3 through 6)
All of the SCXI channels for a given DAQ card are multiplexed through channel 0 of the DAQ card, Channels 1 and up are not used, hence the initial three characters in the SCXI call refer to "On-Board Channel 0 (OB0)"
C) For the subsequent set up, it will be necessary to first add the additional modules to the chassis (when powered off). Then open MAX and update the chassis. (If you get an error then simply delete the chassis reference in MAX and add a new chassis). You will then be required to set the interface mode of each module as either parallel or multiplexed. In parallel mode, you associate a distinct module with a distinct DAQ card in the host PC. For those DAQ cards that will address multiple modules, you must first configure the modules to be in adjacent slots in the chassis and then assign the first module to the cabled DAQ card - then all of the modules assigned to that DAQ card should be configured in "multiplexed" mode.
D) Once the chassis has been properly configured, you can click on each module and set the gains, filters, and terminal block types.
I hope that this helps to get you started.

Can I acquire from more than one device at once using Labview?

I have two SC-2345 boxes. One is device 3 and one is device 4. Can I acquire from both of these boxes at once? I know for most of the AI functions you just put in one Device number. But what if I want to acquire from 32 channels at once? How would I do this? Your help and tips are appreciated.
ALSO- If you know about SC-2345 boxes, how many Analog input channels can I use? I see 8 slots for AI and the other 8 appear to be for signal conditioning. Can I still use these for AI? Could I have 16 thermocouple modules in one box?
THANKS!
Lauren

Lauren,
Yes, you can simultaneously acquire from both devices. However, each device will require its own analog input task. Furthermore, if you want to synchronize the acquisitions, you will need to connect the DAQ devices that are cabled to the SC-2345s with a RTSI cable. Below, I have included a link to a KnowledgeBase detailing RTSI:
KnowledgeBase: What is RTSI?
In order to understand the required programming structure, you may want to examine the following examples that are available in LabVIEW (one uses NI-DAQmx and the other uses Traditional NI-DAQ):
NI-DAQmx
Multi-Device Synch-Shared Timebase-Cont Acquisition.vi
Tradi
tional NI-DAQ
Two E-Series Shared ScanClk.vi
With regards to your second question, the SC-2345 provides access to 16 analog input channels through 8 modules. Most analog input modules have two channels. However, both of the SCC-TC series thermocouple input modules only have one channel because the other is used for the built-in CJC sensor. Thus, using the SCC-TC series modules, you will only be able to acquire from eight thermocouples with a single SC-2345.
Good luck with your application.
Spencer S.

How to control two 6011e daq card to acquire eight signals simultaneously.

I use two 6011e daq card to acquire eight signals simultaneously .I use labview function to realize it,but the data graph show that the signals aren't acquired simultaneously,why?how to do it?

Hello;
You need to use the RTSI bus to route one board's clock signal to be the second board's clock signal. By doing that, you will have the same signal clock timing both boards, which will make the synchronization hardware timed.
You will need to have a RTSI cable connecting both boards together also.
The best way to go about this is to open the Labview examples that show how to synchronize multiple devices. You can apply the same idea to your board.
The examples can be found at Search Examples->I/O Interfaces->Data Acquisition->Multiple Device DAQ Examples.
Hope this helps.
Filipe

Acquiring analog signal from PC mic

Hi Guys,
Is it possible to acquire a signal (audio) from a laptop mic and display it in Labview? I know this can be done with a DAQ card but I was curious if I could bypass that and just use the mic in my laptop.
Thanks.

Here is a higher level example, for LabVIEW FDS:
http://decibel.ni.com/content/docs/DOC-4834
-AK2DM
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~

Can we demodulate the signal recieved at DAQ card without using any hardware interface(by only using labview)?

Hi all,
Can we demodulate the signal recieved at DAQ card without using any hardware interface(by only using labview)? if yes then how? please give brief idea.
Regards,
Amit

There is probably a way to do it, but it it may be easier to use an X-series board for the job. They support a new counter capability for count reset on a digital edge without needing to be configured in encoder position mode. I am not sure exactly how that feature's been implemented however, so maybe it won't make things easier after all.
The plan based on the hoped-for behavior:
1. Configure an X-series counter for pulse generation based on "ticks" of your clock channel.
2. Set both initial delay and low time to the critical # of ticks.
3. Configure for count reset on a digital edge (if possible in pulse generation mode)
4. Configure the count reset value to be the critical # (or possibly 1 less, if possible in pulse generation mode)
5. If you want the output to remain high indefinitely, configure the counter task to use its own output as a
pause trigger, and pause while high.
The way pulse generation works is to preload a # of "low time" ticks into the count register. Then every source edge will decrement the count. When the count reaches terminal count (0), the counter's output is toggled (or can be configured to pulse). The register is then loaded with the # of "high time" ticks and the process continues.
You would be perpetually interrupting the count-down process as long as you got your triggers in time. The count would keep getting reset to the # of low counts, keep decrementing toward 0 without reaching it, and so on. If ever you did reach 0, the output state would toggle high, then the high state would prevent subsequent clock signals from decrementing the count.
You can conceivably do a similar thing with a 6601, but I'm pretty sure you'd need 2 counters working together to get it working.
-Kevin P

Acquire a signal with mac osX

Hello.
I am a very beginner with LabView.
I would like to acquire a signal with a NI-USB 6009. I have LabView 10 on osX 10.8. I already installed the daqmx base driver.
Could you explain me how to acquire a signal which come from the NI USB 6009 and export it as a list of numbers (the amplitude and the time).
Thanks!

Hello matttgic,
What kind of signal do you want to acquire/generate?
For exemple, if you want to acquire an analog input, you should use the architecture use in the file "Analog_input attach to this email.
As Johnsold told you, you can find some code for your device in the "find exemple" section of LabVIEW.
Hope this help
Sabri
Attachments:
Analog_input.PNG ‏13 KB

Is it possible to multiplexe 8 analog sensors output into one PXI4472 channel?? can PXI4472 recognize those signals??

I have around 64 analog sensors to connect to PXI4472. Instead of buying 8 PXI4472, is it possible to multiplexe 8 analog sensors output into one PXI4472 channel?? can PXI4472 recognize those signals??

Such a set up is not recommended. Some of the drawbacks are:
Depending on how you plan to multiplex the signals together (SCXI/PXI switch, 3rd party mux), you could very easily be introducing noise to your system.
Multiplexing the signals together into one line limits your sampling rate to the switching speed of you multiplexer device.
You will probably need to spend more time developing handshaking schemes in order for switching and acquisition to occur in such a way that you don't miss signals that you want to acquire.
These are only some of the drawbacks to this setup. All in all, the only functionality of the 4472 board that you would be left with is it's ability to sample all eight channels at the same time. So, you could multi
plex all the signals together, but doing so is not recommended.
However, I have a couple of questions. Do you want to sample all 64 sensors at the same time? Assuming that you are not, how are you planning on multiplexing the signals together? What kind of a chassis are you working with? Please let me know.
Logan S.

Continuous signal to discrete

Hi everyone,
I'm supposed to do a discrete time fourier transform (DTFT) for my input signal.
I got the input signal from "Basic Function Generator.vi" which is suppose to be a continuous and periodic signal. With respect to DTFT function, the signal has to be discrete and non periodic.
Now the question is, how to I convert the continuous signal to be discrete, and how can I make the signal non-periodic?
Thanks a lot in advance.
Solved!
Go to Solution.

Hi,
When you generate the waveform with the vi, it is already a discrete and non-periodic signal.
It is a discrete signal because the function is not defined for all time, but only at the multiple of your sampling period, i.e. you only have data point at the sampling period intervals. If you have a sampling rate of 0.1ms with initial time =0, you would have a point at 0, at 0.1ms, at 0.2ms, at 0.3ms, etc, and you will not have any data point at 0.05ms, 0.25ms, etc.
It is a non-periodic signal, because at any given time, you would only have a waveform from a particular time instance to another particular time instance, and you will never have a waveform form from -inf to +inf, which is part of the definition of being periodic. Let me know if this is clear or not.
Yik
Kudos and Accepted as Solution are welcome!

Acquire continuous waveforms from two channels on a scope

Hello,
I want to acquire a continuous waveform on each separate channel on my scope, and to see each waveform on it's own graph.
I tried to do it, you can see the VI that I uploaded...
The problem is whan I run the VI - it works, but each graph refreshs in it's time and it doesn't happen simultaneously.
It's a problem because it creates a situation that I can loose a waveform because while one graph is refreshing the other one is not refreshing.
What can I do?
Attachments:
Tektronix TDS 200 1000 2000 Series Acquire Continuous Waveform 2 Channel.vi ‏35 KB

You are using serial communication. This sort of communication is very slow. So I doubt you will not get much data in real time. You are probably only getting segments of the realtime curve.
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

Can't acquire continuous signal

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