topic Re: Analog triggered counter in Counter/Timer

Analog triggered counter

Emach — Mon, 25 Jul 2016 16:12:55 GMT

Hello,

I am attempting to use analog edge detection to increment a counter, which I will then read from at a regular interval. I keep hitting brick walls when trying to run/adapt the examples on NI's site.

I'm using a cDAQ-9174 chassis and a NI9223 analog input card with LabVIEW 2014 SP1.

Any suggestions would be greatly appreciated.

Thanks,

Emach

Re: Analog triggered counter

David22JRA — Tue, 26 Jul 2016 15:30:20 GMT

Hello Emach

First of all I will share with you one link where you can see all the function each device can use so, see below:

http://zone.ni.com/reference/en-XX/help/370471Y-01/TOC40.htm

http://zone.ni.com/reference/en-XX/help/370471Y-01/cdaqmxsupp/ni_9223/ (For 9223)

On the other hand I was thinking you can create a VI where you acquire the analog signal and when that signal has a specific value you can increase a counter (by software).

Regards

Re: Analog triggered counter

Emach — Tue, 26 Jul 2016 19:21:12 GMT

David,

Thank you for posting the link to the reference documents. Too bad NI does not list the cards that have a specific property instead of properties by card.

So long story short the 9223 does not support analog edge triggering. My signal is a fast, 45 us long, pulse. I'm trying to catch the rising edge so I can count pulses. I really needed the 1MHz sample rate of the 9223 to ensure I always caught the rising edge of the pulse.

Re: Analog triggered counter

David22JRA — Wed, 27 Jul 2016 14:37:23 GMT

Hello Emach

I really apologize for that. I would like to know if you are able to read the signal every time. If the answer was yes you can create a counter by software.

On the other hand is that a TTL signal. Have you considered to use a counter module?

Re: Analog triggered counter

Emach — Wed, 27 Jul 2016 15:13:52 GMT

When sampling at 1MHz, I am able to reconstruct the pulse when viewing the TDMS data in Excel. The test in question is about a minute long, resulting in 180 MB TDMS files. I ended up using another VI to post process the data in chunks. According to my down sampled data I do not miss pulses.

It is not a TTL signal, the low voltage is ~1V and the high voltage is ~2.2V. I can always use a microcontroller to serve as an A/D and then feed that pulse data into a DI counter card.

Re: Analog triggered counter

David22JRA — Thu, 28 Jul 2016 20:15:02 GMT

Hi Emach

That might be a great workaround then use then a counter module. Another option it is use a module which support the analog trigger like: http://zone.ni.com/reference/en-XX/help/370471Y-01/cdaqmxsupp/ni_9205__dsub/

Regards