Tracking where I am in between TTL pulses

Greetings. I have a little Labview experience but very little with counters. I have a PCI-6602 card with a CB-68LP connector block. I have used up 7 of the 8 channels counting events so I have one channel left.
What I have is a Z pulse that is followed be four events and then another Z pulse. I know the point in the cycle at which each of these events occurs. I need to write in my program which event is occuring.
I apologize for the confusion. It's difficult to explain.
The ideal situation for me is that if the Z pulse is a 360 degree cycle I could track in my program if I am in the first, second, third, or fourth quarter of the cycle between Z pulses. I know that sounds almost impossible since my Z pulse can change.
For what it's worth, I CAN run one of the events in a separate TTL input if that helps me.
I have been trying to just reference the Z pulse to a timebase, then a little math would get it done for me but I don't have a full knowledge of counter/timers.
Any help would be appreciated. Sorry for the confusing post.
Dave B
www.signalg.com

I am measuring the speed of an event. To keep it simple, I am measuring the edge separation between TTL pulses. As the event moves through a cylinder it sets off probes that will send my system a 5 volt, TTL pulse. Knowing the time between the event passing probe 1 and probe 2 will tell me the speed of the wave. I have 7 probes in each of 4 tubes. Because we are running at 40 hz or less my boss would like to run all seven probes for each tube together. This way we are writing a smaller amount of data and only using a 7 channels of a counter card rather than 28.
So probe 1 in each tube will generate a pulse to the same channel.
To determine which tube I'm in I am referencing the spark for each tube. My plan is that when the spark for tube 1 occurs it initiates case #1. Spark 2 will make case 2 true, etc for 3 and 4. Each case performs the exact same reading on the exact same channels. Since not all tubes are exactly the same, each case will have custom formatting for that tube.
In each of these cases I am measuring the time between probes to figure speed. We can run one tube up to all four. My program should work for all without any intervention from the user since unused tubes will never send their corresponding case structures to true.
Using the 90 degrees per was when I was considering using the Z (timing) pulse to determine which tube is active. Now that I'm using sparks for each tube that is much simpler (I hope). The sparks coming into the DIO (adjusted to give me a clean TTL) will activate the case for their corresponding tube.
The 6221 is pretty affordable but I think this should work with what I have. If it doesn't I could sell them on another piece of hardware.
Do you think this will work?
Thanks
Dave
www.signalg.com

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From your description it seems to me that the best option is to use two-edge separation measurement. I am not on a PC with CVI installed so I cannot point you to a specific example but this tutorial gives you a brief explanation and some guidance on examples to look at.
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Counting TTL pulses at high speed

Hi all,
I am using PCI-6221 board with DAQmx to count the number of TTL pulses (which varies in its frequency between 0Hz to 10MHz) at a high speed (200,000 samples/sec.) and I am having a problem when the TTL pulse frequency drops below a certain level.
I am using CTR0 to generate continuous pulse train at 200kHz frequency to feed to CTR1 Gate input. I verified that the pulse train is being generated fine.
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CTR1 Gate is coming from CTR0 Out, which is 200kHz pulse train with 50% duty cycle, and CTR1 Source is the TTL signal that I am trying to count. At first, I thought that everything was working fine with the Source signal being at around 5MHz. Then, when I had the Source signal down below about 300kHz, I noticed that the program is taking longer than 1 sec. to collect the same 200k samples. Then, when I got the Source signal down to 0Hz, the program timed out.
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One thing you can try is to set the counter input CI.DupCounterPrevention property, this setting will filter the input, it is possible that when the ctr 0 is slow then many of the values you are counting become zero as well and are filtered out, since they are nolonger points, the counter will not collect enough points before the time-out occurs and the counter input read times out. I am not sure if this is your issue but I found out the hard way that this occurs when I switched to daqMX where this feature was added. Let me know if it worked,
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Counting TTL pulses within specified integration time

Dear all,
I have a PCI-6014 board, and I use Labview 7.1 and would like to do the following task with DAQmx7.4:
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Signal: photon signals from a photomultiplier (random TTL pulses)
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I used to do this with the traditional DAQ and connected the analog source to the "GATE" pin of the counter , so i could count "while gate is high" ( or while gate low, or count on rising edge/ falling edge. ) However I found some problems and I think my counter wasn't counting correctly, and I would like to rewrite the task with DAQmx anyway. Ideally I would like to separate the signals that occur in the first 1/2 and the second 1/2 of each analog cycle. But if that is not quite achievable, I can do the separation later when I process the data, provided that I know each 10 data points from the counter correspond to each analog cycle.
I have read several threads on the discussion board, but I still couldn't configure my applications using those examples.
Also I wonder if the "Arm Start Trigger" function is not available on my PCI-6014 card ? Because I can not find it in the Start Trigger property node.
Thank you very much for your reply. Any hint or advice would be greatly appreciated.
Joyce

...(Continued from prev post due to 500-char limit)
Now, here's a proposal for a method that should be able to work, though it'll require more data and more processing. One key area to watch out for under DAQmx is the property node for "Duplicate Count Prevention." The behavior changed between 7.1 and 7.3 (on E and/or M series, but not on TIO-based counters), then the defaults changed in 7.4, and something changed yet again in 7.5
Bottom line: you can set it to True or False. One setting will allow you to buffer up 0 values for intervals where there are no Source signals (photon events) within a sampling period (10 Hz hw clock). The other setting will not record anything in the buffer for those intervals. Clearly, you need the former setting, so you can always experiment to see how it behaves. I kinda gave up on trying to interpret it, understand it, or keep up with the differences by DAQmx version and DAQ board.
Ok, here goes: I'm going to propose that you actually oversample by about 10x and that you capture the Analog square wave in sync with your photon counts. Then your post-processing can determine for sure which samples correspond to Analog Square High and which to Low. You'll also be able to adjust for times when you get 1 too many or one too few samples in a square wave cycle, due to having independent un-sync'ed timebases.
So on one counter you generate a 100 Hz clock. The other one is programmed for buffered period measurement using the 100 Hz clock as a SampleClock and the photon pulses as the Source signal (this must be set up using a DAQmx Channel property node I believe). Remeber to be careful also about the DuplicateCountPrevention property.
You would further setup an AI task using the same 100 Hz clock as a Sample clock. Be sure that the 100 Hz clock task is started after starting both the other tasks. Also, be sure to always read the same # of samples from both tasks to keep the counter period and AI data in sync.
Voila! You now generate a data record of # of photon pulses for each 10 msec interval along with the voltage of the analog square wave at the end of that interval. A bit of post-processing and you're covered. If you're not required to manipulate data while the acq tasks are running, you can surely afford to bump up the oversampling rate considerably. The main advantage is to gain resolution on the time of transition of the analog square wave. For any interval ending with a TTL state change, you won't know where within that interval the transition occurred.
-Kevin P.

I want to create a TTL pulse. The stepper motor I'm trying to control responds to a high to low edge, when the low pulse width is greater than 0.5 microseconds. What is the best way to go about creating a pulse like this?

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My first attempt has yielded some surprising results.
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The first frame sets the line in wire to false.
The second frame sets the line in wire to true.
The device channel on both frames has been set to my user defined channel nam
e -> clock.
clock --> sets the DIO0 channel to be digital write out.
Using an oscilloscope and some wires I hook ground to the SCB-100's digital ground and I hook the probe to the DIO0 channel. What I see are two different pulses alternating between one another. One has a pulse width of 5ms and the other has a pulse width of about 50ms. You seem to get a grouping of one type of pulse followed by a grouping of the other type of pulse.
Obviously this is very strange and not what I want. It is also far too slow. So I'd like to know if anyone knows how to do this properly. Remember I only need a low pulse width of 0.5 microseconds.
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Scott

Scott,
You don't need to use a digital line to create a TTL pulse. The PCI-6025E has two onboard general purpose counters. You can use one of these counters to create a single pulse of the desired pulse width. For an example of how to program the counters on your board, refer to LabVIEW's Search Examples>>I/O Interfaces>>Counters>>Pulse Generation>>DAQ-STC based.
The advantage of using a counter over the digital line is that it allows you to control the timing of the pulse through hardware and not software. Thus, it is inherently faster, and the timing resolution is more accurate. The counter will count down an internal 20 MHz timebase to create the pulse delay and the pulse width.
For more information on the hardware capabilities of your board, you can refe
r to the User Manual online at www.ni.com/manuals.
Hope this helps.
Regards,
Erin

How do I get the difference in time using 2 ttl pulses

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Hideya

Hi Hideya,
As is the case with many programming questions, there are several ways to go about solving this one. The solution I have in mind is to poll the digital input line for a transition from low to high. The simplest way to do this would be to use a loop with a shift register to store the previous digital input value. When the current digital input value is greater than the previous value, you can get the tick count (microsecond resolution sounds like it would be sufficient). You can then do that sequence of operations a second time. The difference between these two tick counts can be used as the input to the wait (microsecond) function. After that you can send your digital output pulse.
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Need to generate a TTL pulse of 3 ms using USB Daq 6361

Hi all,
I need to generate a TTL pulse of 3 ~ 5 ms to trigger my external device. I am using USB daq 6361 with BNC connectors. I tried to use this examples(attached) but was not succesfull , can any one help me out in this, I just want a TTL pulse out to trigger my device. I tried to modify the example to see the wave form out but all it shows is a straight line. I want to generate a TTL pulse as soon as my program starts.
Am I using wrong example? should I use somethis else to generate the pulse. please let me know.
Thanks,
Attachments:
Capture.PNG ‏76 KB
Digital - Continuous Output_ttl.vi ‏65 KB

AnkitG wrote:
Jeff·Þ·Bohrer wrote:
Why would you create an Task with an analog output? its a Digital line you want to drive! and, just create it in the project.
Hi Jeff,
thanks but I couldnt understand , what you meant by create in project? Can you please explain. should I create digital line but I am still getting the same error.
Creating DAQmx items in Project Explorer saves the DAQmx object properties as part of the *.lvproj file. This can be very useful when the Task configuration does not change in the built application and you seldom want to use the task elsewhere. If you want to make minor tweaks to configuration of the run-time app there is even a human readable text file in the build output where properties like scale offsets, timing rates or ranges can be modified without redeploying a new app.
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Counting ttl pulses

Hello Everyone,
I am attempting to continuously record (i.e. time stamp) only positive (i.e. 'Logic High' event) TTL pulses from a PMT using a PCI-6602 board via a BNC-2121.
From reading the LabVIEW tutorials/examples it seems that I should be able to get very high precision (15 digits) from the "Get Date/Time In Seconds" VI. I need to be able to record times to the microsecond (at least). Yet when I look at the data it appears that for every digit less than a millisecond either a 9 or a 0 is recorded, which leads me to believe that I can't get better time resolution than a millisecond. Is there anything I can do to change this?
Assuming that I can get this to work I would also like to simultaneously monitor and record a second PMT channel. Any hints or tips would be great!
I've attached my very basic VI below.
Cheers,
CJ
Message Edited by CJKS on 05-22-2006 11:53 AM
Attachments:
PMTcounter.vi ‏126 KB

Yes the simpliest way to do what you want is to count the time between rising edges using a counter (the 6602 has 8 80 Mhz 32-bit counters). Yo will not use digital io but time counting. The gate of your counter will be the TTL/Cmos pulse from your PMT and the source of the counter will be the 6602 master clock 80Mhz, so you can count clock ticks between photons, now you have a 12.5ns time resolution. You can use the system clock to get a time zero if you would like to use absolute time. The olny thing to keep in mind is that you will be limited to a maximum time between pulses of 2^32/80M or 53 seconds, you will get an overflow of your counter but usually this is not a problem with photon counting. You will be also limited to a maximum photon rate of about 20Mphoton events.sec this is also not a problem since the interesting photon events seem to happen between these time scales. if you want a longer time scale you cvan always casceds 2 counters to get 64bit resolution but this is probablu not necessary. Look at the buffered period measurment examples. You can easily scale this to 8 counters with 8 PMTs if desired with your curent hardware but this gets expensive. Goodluck.
Paul
Paul Falkenstein
Coleman Technologies Inc.
CLA, CPI, AIA-Vision
Labview 4.0- 2013, RT, Vision, FPGA

Count ttl pulse only over 2 V

Hi I have a problem while I was trying to count a ttl pulse by using the DAQ Assistant. The problem may be simple but I just cannot solve that since I am new to LabView.
There is a TTL pulse generated from our APD which is about 30 ns width, 5V. I want to use LabView to do the photon counting. However due to the noise, I would like to set a count limit of 2V, so the software only count the TTL pulse which is greater than 2V. But I cannot do that. There is no option to set the limit.
And our hardware is BNC-2110 and PCIe-6323.
Can someone help me with this? Thanks.
Solved!
Go to Solution.

Okay so perform a finite or continous read of your analog input. Then you can perform a threshold, where all values below 2 become 0. This can be done many ways but I'd suggest an auto indexing for loop and using a select function in the for loop. Then you can perform any normal edge detection you normally would to count pulses.
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Hi,
Have things changed over the years?
I need to syncronise a digital output (Modul NI9474) and an analoge input (AI-Modul NI9203) module. I need to measure time intervals from a flank in signal A to a flank in signal B. I would like accuracies of the order of 1 ms. Currently, the signals are not synchronised, with errors of the order of 2 times the block length (block size x sample rate), sometimes much higher. The best I got so far was a block size of around 20 with a sample rate of 1 kHz.
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Tracking where I am in between TTL pulses

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