Counting falling edge on pci 6281

I have an analogue signal consisting of pulses of 5V (reference level 5V, pulses to 0V) which occur randomly.
I read this signal in using a pci 6281 NI card. This works fine.
Now I would like to count the number of pulses for a given time (e.g. number of falling edges). According to what I read in the manual it should be possible to configure the system such that one can start a counter (arm it) and then ask the counter from time to time what the current number of pulses is.
So the question is rather simple: what is the best configuration to do this? Should I use a different input (instead of analoge input)? Can I use the simple 'count events or time.vi' or should I use more advanced counter vi's?
Thanks for any suggestion.

Dear Steven,
The best way to count events (falling or rising edge), it is to use the counter
functionality. The device NI-6281 provides two counters.
That means
for the Software: see the examples under. Find Examples
-> Hardware Input and Ouput -> DAQmx -> Counter Measurements ->
Count Digital Events
for the Hardware: you need to connect you signal to the
input ctr0/source
PS: Counter level is based on the TTL technologies
Best regards
Nick_CH
www.ni.com/gettingstarted

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Attachments:
DAQ_appln.doc ‏70 KB

Hello MWallace,
Is it triggering properly the first time? Since you have the timing VI outside of the while loop, it should only read in 4000 samples total, not 4000 each time you hit start. It is probably just reading the same data in the PC Buffer over and over, not getting new data every time. To prevent this, pull the timing VI into the while loop and clear the task every time (DAQmx Clear Task.vi).
If it is not triggering even the first time, take a closer look at signal on the PFI line. Is it actually starting at 5 V and going down to 0 V? Instead of using a PFI line, use the same setup on a counter source line. Open a test panel in the Measurement and Automation Explorer. On the Counter I/O tab change the mode to edge counting and see if it detects the falling edge.
Please let me know if you have any questions. Have a great day!
Sincerely,
Marni S.

Is it possible to start one counter on the rising edge of its gate and the second counter on the falling edge of the gate of the first counter?

Hello,
for my application I want to perform a buffered semi-period measurement with three counters.
Therefore the first one have to start on a rising edge of its GATE and stop on the next rising edge. This is not a problem.
But the second one should start on the falling edge (that immediately follows the rising edge) of counter 1 and stop the same time counter 1 will do.
The third one should start after the falling edge of counter 2.
Is this actually possible?
Thanks in advance.
Regards Thomas

I think I may be a bit confused on exactly what you are trying to accomplish, so if my answer does not
help, I apologize.
Anyways, the way to do it (from what I gather) is to set the gate of the third counter to start on the falling edge of counter 1 and start on the next falling edge of counter 1.
A little more clarity in how the counters are intended to start/stop may be helpful in getting a better answer.
Derek

Two Edge Seperation / PCI-6238 / Error -200140

Trying to use a PCI-6238 card to measure the time between Digital Inputs rising or falling. From what I was directed, this should be able to be done via the Two Edge Seperation Task... However, when I configure the task it seems that no matter what the Min. and Max Time I set, I get the error:
<<<<
Error -200140 occured at MyTwoEdgeSeperationTask - DAQ Assistant
Possible Reason(s):
Two consecutive active edges of the input signal occurred without a counter timebase edge.
Use a faster counter timebase.
>>>>
I can I change the Counter Timebase?? I thought the system selected the optimum counter timebase based on the Min and Max value entered in..
Thanks for any help.

Not at hw to test, but here are some brief thoughts anyway:
1. Error message sounds a little odd to me, almost like it's only looking at 1 input signal rather than 2. Could simply be poor choice of error text though...
2. There's a property called "Duplicate Count Prevention" that is frequently relevant to situations where the signals to be timed are faster than the timebase used to time them. If you search the forums for that term, you'll find more detailed info. The summary is that it can either be enabled or disabled and the behavior when the inputs are too fast are either to produce an error like yours or to return a measurement of 0. (I honestly don't know which setting does which -- it's easy enough to experiment and find out though).
3. The timebase can be chosen explicitly, though DAQmx should indeed have picked the appropriate one for your specified Min / Max. You'd probably want a Min of 0 and a Max that's less than about 50 seconds. My guess: DAQmx *did* pick the appropriate timebase, and the error text suggesting you use a faster one is just generic advice that doesn't actually apply to your case.
4. Two Edge Separation requires you to know which signal will come first. If you don't know which one will come first, you may still be able to accomplish your goal by setting up a "change-detection" DI task and then measuring the period of the change detection pulse signal with a counter. I know this would work on the 5V DIO versions of the M-series, but I'm not so familiar with your particular board.
-Kevin P.

Falling edge to trigger event case

I'm collecting voltage measurements from a photodiode using a NI PCI-6229. I'm thresholding this signal and converting it to digital with a simple comperator. Currently, I'm using some boolean gates to detect a falling edge on this signal. However this gives me a boolean array which I can't wire to a case structure. How can I trigger an event when a falling edge is detected?
I've searched through the forums and looked through some examples and it seems like I have to create my own user event, but even with the help documentation, I have no idea how to actually implement this. Am I even on the right track? Is there a simpler way to go about this?

The loop for data acquistion is set to 100 samples. The iteration count of the for loop around the booleancrossing also says 100. I also checked the array size and that's 100 as well.
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How to do a digital output triggered by the falling edge of a clock?

Hello !
I would like to do a digital output (on a given line of a pci 6602 card) triggered by the falling edge of a clock.
More precisely, a pulse train is generated. I have to output each bit of a variable (first, the LSB ; then, the others bits, until the MSB), each bit being transfered on a falling edge of the pulse train. How could I do that, please ?
Thank you for helping me.
Julian.

see the following link (other forum same subject)
http://forums.ni.com/ni/board/message?board.id=40&message.id=1634

求助PCI-6281

利用新装的PCI-6281采集卡/CB－68LP。配置一切顺利。可是采集数据的时候，无法进行，显示错误为
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That makes sense. So, here's my issue...
I need to sample at least 6 channels at 10kHz (For my DEI MotionPak accelerometer). There's no doubt I will have to incorporate anti-aliasing filters as the 40kHz filter won't be adequate. I don't have the option of spending any more $ on something fancier like a dynamic signal analyzer so I need to try to get the 6281 to work for my DEI MotionPak accelerometer.
I have an SCB-68A so my plan is to put the filters there using the built in RC filter pads.
With the lowpass filter disabled, the settling time is stated to be 8us per channel.
10kHz * 6 channels equates to about 20us of potential settling time per challel. So it seems like this should be more than adequate.
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DAQmx is version 8.7.2. Also, I installed the card prior to the drivers, I will try removing the card and replacing it. I seem to have isolated the problem - my old computer had the card showing up under the heading NI-DAQmx devices, where on the new computer it shows up under in the PXI heading in the measurement and automation explorer. I'm still not sure how to fix it though.

Counting rising edge during 50ms for a TTL signal

Hello, I'm using Labwindows 6 and a traditionnal DAQ. I've injected a TTL signal on my card and I would like to count the number of rising edge each 50 ms without using an internal timer in labwindows so that the counting pace cannot be disturbed by Windows.
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Hi it's still me with still some troubles
I've generated with my counter0 a square wave of 50 ms pulse width from an internal source but then, I don't know how to specify that this signal will also be the pin gate (ND_PFI_4) of my counter1 which will count the rising edge.
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And the value of compteur is not the value expected at all.
thanks.
(ps : can you speak french?)

Thinkcentre-edge-72 PCI communication PCI simple

thinkcentre-edge-72 PCI communication PCI simple where find this driver?
Solved!
Go to Solution.

Good day and welcome to the community.
I believe that device is supported via the Intel AMT and Management Engine Interface packages, which can be found on your support site: http://support.lenovo.com/us/en/products/desktops-and-all-in-ones/thinkcentre-edge-desktops/thinkcen... in the Chipset section.
The AMT / MEI feature set is generally only useful for machines in an enterprise environment facilitating out-of-band remote management.
Hope this helps.
Regards.
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Compatibilité carte PCI-6281 et DAQmx 8.1

Bonjour, voici mon problème : je possède une carte d'acquisition NI PCI-6281 que j'aimerais utiliser avec le logiciel Labview 7.0. Avant d'installer la carte j'avais Daqmx 7.1 (fourni avec labview 7.0) mais cette version du driver n'a pas reconnu la carte. Du coup j'ai installé le driver fourni avec la carte : daqmx 8.7.1 mais ce driver n'est pas supporté par ma version 7.0 de labview... Donc j'ai téléchargé daqmx 8.1 la version la plus récente compatible avec labview 7.0. Le driver a bien reconnu ma carte et l'a installé mais il s'avère qu'aucune voie physique n'apparait dans le MAX... Pensez vous que le driver n'est pas compatible avec ma carte? Avez vous de ssolutions à me proposer? Car là je commence à desespérer! Merci d'avance.

Bonjour aurelieB,
Labview 7.0 et votre carte PCI-6281 sont bien compatibles avec le driver NI-DAQmx 8.1. Voir le readme du driver 8.1 sur le site ni.com:
http://joule.ni.com/nidu/cds/view/p/id/319/lang/fr.
Pour visualiser les voies physiques de votre périphérique depuis MAX utilisez le panneau de Test, ou créer une tâche. Ce faisant vous aurez accès à vos différentes entrées sorties.
Cordialement,
Rémi D.
National Instruments France
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PCI-6281 How to use80 mHZ timebase for A/d and D/A sample clocks

Does anyone know how to use the 80 mHZ internal clock as the timebase for my A/D and D/A sample clocks rather than the default 20 mHZ timebase?
I am using straight NI-DAQmx version 8.3 with C code. No Lab View, no Measurement Studio.
I have an application which uses the D/A to generate a sequence that is collected by the A/D. The D/A is clocked out at an integral multiple of the A/D clock. In order to maintain this integral relationship I can only use a limited set of Sample Clock Timebase Divisor pairs (as returned by DAQmxGetSampClkTimebaseDiv). This means that am further from my desired base frequency than normal. For example, using the degault 20 mHZ timebase, if I want a 2000 hz center fequency, the closest I can get is 2003.205 hz.
I cannot find anyway to use the 80 mHZ internal clock as the timebase for my A/D and D/A sample clocks. If I could, it would be possible to get closer to my desired center frequency.

Post is responded to in the multifunction DAQ forumn.
PCI-6281 How to use80 mHZ timebase for A/d and D/A sample clocks
Have a good one.
Michael D
Applications Engineering
National Instruments

How to trigger on Falling Edge?

Hello,
I could not find any example on Falling Edge trigger Acq. for 6534 or 6110. Can anybody tell me how to trigger on falling edge, or for that matter even specify which edge to trigger on?
Dhruvish

There are some great NI-DAQmx triggering examples that install into LabVIEW 7.0 or newer when NI-DAQ is installed (as long as you include support for your LabVIEW version when installing NI-DAQ). With the release of NI-DAQ 7.4, both of your devices are supported by NI-DAQmx, so I would definately recommend using the DAQmx API. In LabVIEW, go to Help>>Find Examples. For your analog board (6110), navigate to Hardware Input and Output>>DAQmx>>Analog Measurements and maybe take a look at Acq&Graph Voltage-Int Clk-Dig Start.vi. For your digital I/O board (6534), go to Hardware Input and Ouput>>DAQmx>>Digital Measurements and try Read Dig Chan-Int Clk-Dig Ref.vi. Both of those examples has a control on the front panel that allows the user to select whether he/she wants to trigger on the rising or falling edge of a digital signal. Hope this helps!
-Alan A.

Counter Output Pin on PCI-6229

I am using NI-DAQmx 7.3 C API with (among others) a PCI-6229.
I have used DAQmxSetCOPulseTerm() to connect a counter output to a terminal other than the default. It seems to work- the output pulses do, in fact, appear at PFI 6 (the terminal I'm using for testing). But the pulses continue to appear at the default output pin as well.
Is that expected?
In order to reverse the situation, I used DAQmxResetCOPulseTerm() just before calling DAQmxClearTask(). The function returns zero, but if I subsequently make a new task to do pulse output from the same counter, pulses appear at both PFI 6 and at the default pin.
Am I missing something?
John Weeks
WaveMetrics, Inc.
Phone (503) 620-3001
Fax (503) 620-6754
www.wavemetrics.com

Salvador Santolucito wrote:
Hi John,
I would suggest using the DAQmxTristateOutputTerminal. I have tried what you are doing in LabVIEW and I'm seeing the exact same results. When I set the default pin to tristate, the counter output does not show up on it.
-Sal
Thanks for trying it and confirming what I saw, and thanks for the pointer to DAQmxTristateOutputTerminal.
John Weeks
WaveMetrics, Inc.
Phone (503) 620-3001
Fax (503) 620-6754
www.wavemetrics.com

How can I make an analogue falling edge trigger

I'm using a Labjack DAQ board which doesn't support the DAQ-NI VIs. I Need to make a trigger which will stop the acquisition when it detects a significant voltage drop from the peak current. Any advice would be grateful.
Thank you.

Hello Pelle,
I've never used a Labjack DAQ board before so I'm not sure how you
would setup an acquisition that stops on an analog edge. However,
I know that it is very easy to setup a continuous acquisition that
stops on an analog edge using our DAQ board and NI-DAQmx driver.
One thing that you might want to check is to make sure that the Labjack
board actually supports analog "stop" triggering. I know that
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triggering, perhaps the Labjack driver installs examples as well?
Eric
DE For Life!

Counting falling edge on pci 6281

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