Capture digital signal with DAQ 6015

I am wondering what is the best way I can capture a digital event accurately using my DAQ 6015 Pad. It seems as though I can only capture it using (on demand) timing which I'm assuming means it will only capture it as fast as the loop iteration. I'm looking to monitor this signal with accuracy down to about 10 ms. Are there any good digital examples i can goto that you can vary how fast you can capture an event using the 6015?

Hi caunchman,
In this card, the digital lines are static so you will have to provide the timing through software, which might not be too accurate. I would suggest using one of the counters of this card to count the digital event. I don’t know what programming language you are using, but if you are using LabVIEW you can find good examples in the NI Example Finder. You can go to Help > Find Example > Hardware Input and Output > DAQmx > Counter Measurements > Count Digital Events. If you are using Visual Studio, C or DotNet you can find the Counter examples here: \All Users\Documents\National Instruments\NI-DAQ\Examples. I hope this is helpful,
Ana P
National Instruments
Applications Engineer

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Measure Frequency of Digital Signal from DAQ-Board

I'm using a National Instruments DAQ board and I need to measure the
frequency of a digital signal from my data acquisition board.
I know the measure frequency.vi (In diagram - data acquisition -
counter), but i don´t understand yours implementation mainly in input
"counter". Because i don't understand the relationship of board channel (for
signal acquiring ) and the measure frequency.vi.
Thanks in advance,
[email protected]

Hi,
Attached is a vi which models your signal, and provides a way to measure the average frequency over a window of time. It converts the signal to a sequence of periods. I usually start with this approach because you can save the data in a much more compact form if your sampling rate is high. Obviously over a specified period of time, if there are no zero crossings the frequency is zero, so I was a little incoherent before. The real issue is the latency caused by averaging. Your frequency measurement is most accurate half your window size before the current time, so smaller windows give you more up to date measurements, but also more noisy. If you need the most up to date measurement, then you have to use the time since the last crossing which is the case where the frequency never goes to zero. That's probably not a realistic situation. If you needed less latency, you could use a prediction algorithm.
Also, there are a number of signal measuring and processing vi's that LV gives you, for instance pulse measurements that could be used to partially implement this or other approaches, but I normally steer clear of them unless they fit exactly due to having to convert back and forth to the waveform data type.
Have fun!
Attachments:
DigRandFreq.png ‏62 KB
DigitalRandomFreq.vi ‏34 KB

Sequence 1create output digtal signal- 2 make microseconds delay or less- 3 measure digital signal with board 6023e

hello
I need creat a digital signal and for this i use a counter output and then i need creat a delay after a signal measurment and for this i use again a couter. My problem is how i can make this delay betwen create and measure a signal. this delay must to bethe shortest possible and precise. une of my attemps was make a sequence and for make the delay i create a task for une virtual output with max frequency 5000000hz and just une pulse but i dont know how many time the labview get to go by the first task ( creat a output pulse and ent it) to make tis task before discribed to the last task (measure a digital sinal). Another thing that i dont know is how many time the libview get to create and eliminate une task. Une information beyond the kind of board (6023E) that can be useful to help me with this problem is the information about my pc in this case i use a pentium4 3Ghz.
thanks

...My problem is how i can make this delay betwen create and measure a signal.
...how many time the labview get to end one task and start another one.
What I tried to say is, that even if you use the counter of the 6023e-Board
to create the delay and trigger the measure via LabView under Windows,
you leave the realtime-path. Executiontime of LabView-code is then not
determinated.
One way to solve this, is triggering measurement via hardware and use LabView to read Data from the Buffer of the DAQ-card.
You can find more info about DAQ in the "measurements manuall" of NI, delivered with your LabView Software.
Lorand

Acquire 2 digital signal with custom scaling (Engg Units)

I am a newbie to DIO world.
I have write a VI to acquire 2 digital signals. one from a load cell and other for motor rpm (pulses). I need to acquire these two signals and then convert them into engg units using custom scaling and write them to a txt file with time stamp.
Please suggest best ways to accomplish this task.
Thanks
DAQG
Solved!
Go to Solution.

Look at the examples on DAQmx in the example finder.
You wouldn't actually be acquiring 2 digital signals. You would be acquiring an analog signal from the load cell. A digital or counter acquisition is what you would acquire from the motor. Search for analog measurements and counter measurements in the example finder. Some of the example should show you how to apply the custom scaling.

Generate complementary digital signals with dead time between each pulse and controlled by duty ratio

I am to generate two complementary digital signals using NI 9606 conected by RIO Mezannine Card to NI 9683 (Half Bridge DO).
I am able to generate the signals but I am not able to put dead time between high and low signal and also, low and high signal.
Requirement:
(1) When the first signal goes high and the second signal goes low, there should be a controllable dead time.
(2) Also when the second signal goes high and the first signal goes low, there should be a controllable dead time.
I am able to do requirement 1, but I am unable to fulfill requirement 2.
Please have a look at my VI and let me know how to go about satisfying requirement 2.
Attachments:
complementary test 2.vi ‏69 KB

Hi Frank ,
I have already taken note of the example Tannerite has provided and have built my vi ( attached in previous post) surrounding that example.
Now I require to control the PWM duty cycle as you can see from the vi using a knob and that control refers to both the signal 1 and 2.
Now the signal 1 end and signal 2 generation requires a controllable dead time. Similarly, signal 2 end and signal 1 geneeration also requires another controllable dead time.
I am able to do either one dead time at a time using delay but not two dead time simultaneously.
I feel that I have two put the delays at the appropriate data flow point. I am working on that.
I would really appreciate if you could give some insight on how to solve this dead time issue and generate two complementary waveform with dead times whose duty cycle can be controlled by a knob controller in fronty panel .
I have also posted the required timing diagram for reference as suggested by Tannerite.
Best regards.

Interrupt signal with DAQ-STC

I want to use an interrupt service routine with a PCI6025E using the DAQ-STC.
On which pin can I input my signal (perhaps on Gate0) and which registers
must be configured. I'm not interested about how to create an ISR, just the
register value to generate an IRQ on the PCI-Bus.

The DAQ-STC Technical Reference Manual (downloadable) may help you. A quick flick through my copy suggests the section you want is 8.4.1.3 Pass-Through Interrupt and it looks like input pins IRQ_IN<0..1> are what you need, assuming your card supports this functionality.
Jamie Fraser

Measuring digital signals coming from the HSDIO (PXI-6542) with the DMM (PXI-4070)

Hello,
in attachment you can find the program I'm using for my measurement: I'm generating and acquiring digital signals with the PXI-6542 and at some trigger point of one of those digital signals I'd like to capture the measured values on a plot with the Digital MultiMeter (PXI-4070).
It does work if you configure the generation repeat mode as continuous, but if you do have a finite repetition (repeat count is 1) it doesn't react on the trigger, as if it can't find a trigger. On the other hand, if you have a finite repeat count of 30 or more it does react and triggers correctly again.
First I though it had something to do with autocalibration before the measurement takes place, but If you do a highlight execution (stepping through the program) it looks like it measures before the generation session is initialized.
Is there a way to measure correctly when the repeat count is only 1?
Thanks in advance,
Jürgen

Hey Jürgen. I apologize that you haven't gotten an answer yet to your post. I looked at your code and had some questions. What is the source of your trigger to your DMM? I see that you're exporting the data active event to PFI1, and your comments indicate that PFI1 and PFI2 are connected to give you a start trigger for your digital acquisition. Exporting the data active event with a finite or continuous pulse should only give you a single edge per run, though - you wouldn't get a pulse each time. Is your trigger coming from a data line? I didn't see any line in your included data that would indicate a single pulse.
The other thing that I noticed is that you've got no timing dependency between your HSDIO code and your DMM code - they're in parallel with each other. Thus you could get different results run-to-run, since it's not deterministic as to which parallel "thread" that LV will start on first. LV may switch back and forth several times, but let's say that LV reaches the HSDIO Start command before reaching the DMM Start command - in that case, the HSDIO device may finish it's entire operation before the DMM ever starts looking for a trigger, and thus never get the trigger at all. I'm not sure why this would explain why you're seeing the finite case work and the continuous case not, but I wanted to point it out because it could bite you down the road.
I hope some of this this helps get you going in the right direction. I'd also suggest posting HW-centric questions in the appropriate form. There are Digital forums and DMM forums that might help you reach people that will be more familiar with your particular hardware.
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Data acquisition with daq card 6533

Hi all,
i need to develop a c++ (visual studio .net, no measurement studio)
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The program must sample 8 digital signals. Each signal has a limited
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cdio folder. It seems to me they almost do what i actually need.
Unfortunately, many of the functions used there are not supported by
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I'm a beginner in this field, so i don't know what are possible alternative solution to my problem (if any).
Thanks for any help.
walter

Thanks for your reply.
I don't know actually whether i need to use counter-related functions. My problem is the following:
I need to sample 8 digital signals with a frequency of 10khz. Every signal have a duration of a few seconds in time, and they come from sensors attached to a train's railway. Acquisition begins on the first rising edge of a signal (which coincide with the passage of the train), and end with user input (which should be after the train has passed).
It would be of great help if you can point me to a relevant example, or give me some basic guidelines on our to proceed. If you need more information, please just ask.
thank you very much.
walter

Read encoder signal with 9201

Hi
I have a quite uncommon problem. I need to acquire the encoder signal with a NI-9201 (analogue module).
Is this even possible? Of course I saw I that I should use a NI-9401 but my chassis is full...
I already tryed to acquire impulse signals with such a module but they were slower.
Thanks for any help.
Yves

Hi Yves,
when you acquire data from an encoder, do you mean a quadrature encoder or rotary encoder?
This encoder generates a binary or digital signal.
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When there is no free slot you can think about an expension chassis or a single carrier. This depense on your application.
How did you acquired the slower signal until now?
Kind Regards,
Philipp K. | NI-Germany

Capturing digital audio

i need to be able to capture digital audio via my m-audio delta 2496; audio only no pic obviously; mostly without TC but sometimes with.
FCP is pretty poor at dealing with this sort of thing but it used to manage ... now in FCP 5 it is broken; waited a while for new drivers from m-audio but they are now installed and do not help.
wondering if anyone else out there uses other software to capture digital audio with and without TC ....
R.

hello X,
thanks for the offering but i was looking for someone with experience ...
fwiw, my experience with final cut and audio-only/TC sources is that it is unreliable at best.
perhaps you could be more detailed (if you have experience with this), i don't see how providing a video source will allow capture of DAT TC, for instance; and Soundtrack Pro (which certainly falls into the category of "any audio editing software") sees the M-Audio card but gives me errors when i try to access it. last i recall, however, Soundtrack Pro was only able to capture mono audio, and no TC, and therefor is pretty useless right now.
without TC seems like i my copy of ableton will work; with TC, i'm still looking for someone who has experience problem solving FCP 5 (since there were work arounds in FCP 4) or other ideas for software.
thanks.
R.

MyDAQ - Generating a digital signal and displaying it on an analog waveform graph

Hi,
I am using the NI MyDAQ to generate a digital waveform with an adjustable frequnecy. This is being implemented into a program I have already written which generates a TTL "like" pulse out of the sound card. I am displaying the output on an analog waveform graph, and I'd like to be able to display the digital waveform generated by the myDAQ on the same graph. (Not at the same time, either one or the other, toggled by a button). I've been messing with arrays and conversions but I cant seem to really get anywhere with it all.
This is the vi I have made to generate the adjustable frequency digital signal with MyDAQ. Any suggestions on the proper way to do this if the following is wrong would be great too as I just got the MyDAQ a few days ago. I would think there must be a better way but this is the best I could come up with so far.
Solved!
Go to Solution.

Hi Jonny,
The general logic you are using to create a digital pulse train is fine. This VI you've written should work and will create the pulse train based on software timing (which is fine because you don't have hardware-timed DIO on the myDAQ anyway). However, it is usually good practice to start the DAQmx task just before your while loop and then clear the task after the while loop when you press stop.
For reference, there are some pretty good LV examples that I recommend looking at for this application too. If you are just trying to create a digital pulse train, the example Gen Dig Pulse Train-Continuous.vi is a good example that uses a counter to create a digital pulse train of your desired frequency. This is generally the prefered method to create a pulse train if you have the hardware available to do so (the myDAQ does have a counter). Alternatively, there are some DIO examples that continuously write to a digital line/port.
If you're not familiar, you can find the examples by going to Help >> Find Examples... in LV. Then, navigate to Hardware Input and Output >> DAQmx >> Generating Digital Pulses or Digital Generation.
Also, here is some additional information about the myDAQ and its counters:
myDAQ Counters
myDAQ Manual
Hopefully this helps.
Chris G
Applications Engineer
National Instruments

Digital mixed with analog signals

I tried several ways to capture analog and digital signals. I would need more than the standard two allowed on the NI-9174, so I came up with this using digital lines on the NI-9401 cDAQ. What do you think about this method?
Attachments:
Cont Read and record Dig Freq2.vi ‏50 KB

Hello Bassinbc,
After looking over your post and your code, it looks like you want to take a frequency measurement with a NI 9401 in a cDAQ-9174. Currently you are using a Digital Input task to perform this measurement. I was suggest though to use counters to implement this measurement. I have added an example to this post that will help you get started with this. I am assuming that you are working with low Frequency digital signals.
As for the hardware configuration, the 9401 doesn't have to be placed in any particular slot for the NI-9174 but if you have a NI-9172, then you would have to place this module in slot 5 or 6. Finally, you are look at the device pinout in MAX to find out where to connect your sensor to it.
I hope this information helps but if you have any more questions, feel free to post.
Jim St
National Instruments
RF Product Support Engineer
Attachments:
Implicit Frequency Measurement.vi ‏22 KB

Can i convert a wav file to a digital signal without using DAQ?

i tried the coversion of a sine wave to digital signal, ofcourse it doesnt work on converting wav file to a digital signal. i am also new in labview. i tried to explore it but there are many functions that i can't use.
so my these are my questions.
1) is a .wav file is an analog signal?
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tnx guys! i'll post the programs that uses quantization of a simple sine wave. i tried it to .wav file but it didnt work.
Attachments:
act04-02.vi ‏41 KB

.WAV is a digital "signal". It uses Pulse Code Modulation to encode analog signal. You don't need a DAQ device to "convert" it to analog. Any computer with a sound card, and media player can "convert" a .wav file to the analog audio signal it represents
Wan L
Applications Engineer
National Instruments
http://www.ni.com/support

Vb6,card: pci6111,daq box:bnc2110,receive digital signal+react on it,how?

want to send a digital signal from a function-generator into the daq-box (e.g. into ACH 2) and to react in my program on it, when the dig.signal makes the first step from 0 to 5 V e.g.must i change anything else on hw than connecting the function-generator to ACH 2? How can I react on it with my created CWDI1-Objekt. It doesn't work! Thnx a lot! p.s. other ideas are also wellcomed!

Hi,
I'm not understand the relationship between the components of your system (or even what they are!). You'll have to clear your system description a little bit.
1.- You have a DAQ board, what model?. This is important since it will determine what VIs you can use. Are you using the board for Analog input, anolog output ...?
2.- "The DAQ card relays the information to a digital oscilloscope", What do you mean by this?. Is the digital scope a hardware device or some sort of software component?.
3.- ActiveX is used to communicate different software components, not to communicate with external instruments. Again, what is the o-scope?.
4.- Initially you say that Win600 is a machine and then a program. Which one is it?.
I think once this quest
ions are cleared up we can start thinking of solutions.
DiegoF
National Instruments.

How to check 6 digital signals change value at the same time with PCI-6229??

I am using DAQ card PCI-6229.
Channel 1 generate a digital signal.
Channel 2,3,4,5,6,7 acquire digital signals.
I want to check:
1. Whether the rising edge of Channel 2,3,4,5,6,7 occures at the same time;
2. The time delay from the rising edge of Channel 1 to the rising edge of Channel 2,3,4,5,6,7 is within a certain range.
I know I can use counter to get the two edge seperation time delay. But I only have two counter, it is two time-consuming if I check one by one.
I don't know how to check the rising edge of 6 different channels occure at the same time.
Does anyone has any suggestions?
Thanks

Hello,
You can use the DAQ card's digital input change detection circuitry to detect changes in the input, you can then use a counter to measure the relative time between samples. Please read Page 6-9 DI Change Detection Applications for more information. Let me know if this helps
Christian A
National Instruments
Applications Engineer

Capture digital signal with DAQ 6015

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