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Pulse width depends on the number of pulses (pci 6602)

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Hello,

i have just updated ni daqmx, now i have daqmx 9.3

Problem is not solved Smiley Sad

 

I test timers with Rubidium precise oscillator and PPS output:

1st counter source: 1 MHz from rubidium

1st counter trigger: pause when counter 2 is low

2nd counter source: 1 PPS

 

Multiple pulse generation works fine! if i configure one counter to generate two  50-second pulses and trigger other counter with it, the last one indicates exactly 100.000.000 loops (1 MHz source * 100s)

 

but the problem with 1 pulse generation is still actual:

high ticks=5   =>  4.008.011 pulses counted

high ticks=100 =>99.007.899 pulses counted

 

i post the test program which i used

 

i will try to control 1st timer with start trigger and stop it with connecting gate input to ctr2output, trigger pause function may be bugged.

 

Probably it is the software bug, unfortunately i cannot update labview 8.5 right now, it would be very nice if some one test the attached application with the labview 2011, 2012

 

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Regards,

Alexander

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Hey Alexander,

 

I got a PXI version of this 6602 and have hooked it up. I was having some issues with the code you provided, so I switched to purely using some of the examples inside of LabVIEW. I think these examples are available still in LabVIEW 8.5, but I'm not sure. I used the Generate Dig Pulse - Dig Start vi. Basically this configures a counter ouput instead of ticks to use pulse time. I'm not seeing any problems with it. 

 

Are you able to try out the pulse time instead of ticks? Although if it's a software bug, this could still be part of the bug. I didn't notice any unexpected behavior over here though using Daqmx 9.3.5 with LabVIEW 2010. I have been looking over your screenshots though, and things appear to be configured correctly, and I see the behavior on your screenshots. 

 

 

Lea D.
Applications Engineering
National Instruments
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Hello, thanx for the reply, i have tested program without ticks option, it works fine! but i need high accuracy signal with stabilized phase, so i have to use external oscillator. I have found a solution for me: 1. generate finite number of pulses. 2. use generated pulses to trigger new pulses istead of gating. but it will be more appropriate to use gating, i will try to update software soon 🙂
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Alexander,

 

I'm glad to hear that things are working with the time option. If you have any issues with this with the upgraded software, please post again. Have a good day!

Lea D.
Applications Engineering
National Instruments
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Solution
Accepted by topic author AlexanderRyabov

Hi All, The solution was found!

now i can generate any number of pulses,

the problem was with generating pulse from PPS timebase.

 

Experiment 1:

   ctr0 [Source of ticks = PPS signal, high ticks = 10] => ctr0out-ctr2gate => ctr2 [Source 5 MHz rubidium]

   Result: 45 038 014 counted

Experiment 2:

   ctr0 [Source of ticks = 1 MHz rubidium, high ticks = 10 000 000] => ctr0out-ctr2gate => ctr2 [Source 5 MHz rubidium]

   result: 50 000 000 counted

 

The same program was used for both experiments.

I dont know why, but pci-6602 cannot works properly with low frequency timebase (source ticks), but it counts PPS pulses perfectly.

I will use PPS signal for starting counters only, using PPS for puls generating results an error!

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Alexander.


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