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Troubleshooting 6602 counter for LV 7.1 DAQmx 7.3 question

Hey all,

 

TL, DR; My 6602's channel 2 counter is dropping my signal sporadically.  Any thoughts as to why?

 

Background:

I have an embedded machine running LV 7.1 with DAQmx 7.3 and MAX 4.0.  I have been running into a problem with one of the counters on my 6602 card that is in the chassis.  The basics of my problem is that I'm reading in a PWM signal from a motor.  The signal goes from the motor, to a back panel connection, to a line driver, to a TB 2715 connector, then to a PXI 6602 card.  The PWM signal goes to the gate of my counters and I'm using the high time read function (assuming my signal to be a perfect 1 kHz signal).  I have 8 separate stations that follow this same set up.  I was running into some noise issues early on, so I set the channel property to enable filtering on the 6602 counter and am ignoring any signal that is less than 10 ms, my lowest signal coming back to me will have a high time of 50 ms.

 

Problem:

One of my counters (counter channel 2) is having an issue where it is "dropping the signal".  It will read fine correctly for 5-50 reads, then drop to 0 for a read, then pick back up for a few reads, then drop back to 0.  All my other channels work as I expect and can run my code fine.

 

What I've tried:

At first I thought my line drivers were bad, so I made sure everything was wired securely.  I then made sure that the connection at the back panel and the TB 2715 were secure and I had continuity where I expected it to be (IE, back panel to line driver, line driver to TB 2715).  I swapped line drivers for channel 1 (works) and channel 2 (doesnt work) to determine if it was a driver issue.  Channel 1 still worked fine but channel 2 was still dropping the signal when I was expecting channel 1 to drop due to a bad line driver.  I then tied both channel 1 and 2's counters together and connected them to channel 1's line driver - thought is that they should both be bad or both be good.  Channel 1 was fine, channel 2 was not.  I then tried using a different TB 2715 terminal block to make sure the terminal block was working as expected in my original configuration.  Channel 1 works, channel 2 does not.  I then swapped 6602 cards from a different tower with the original and new terminal block.  Channel 1 works, channel 2 does not.  I then went into my code and verified that I set the filter to ignore signals lower than 10 ms by setting the filter, then reading back the physical channel, filter enable state, and filter time from the set (a node for writing, followed by a node for reading).  Channel 1 works, channel 2 does not.  I then hooked up a function generator to my channel 2 input.  Finally, I see a clean signal.  Replace it with the original PWM connection, and it goes back to dropping the signal.  I have monitored both sides of my line driver with an oscope to verify that they have the same frequency and high time at channel 2 along with looking at the noise on my signal (there is some noise at 0V and 5V, but the rise and fall times looks fine and I dont see the signal dropping back to 0 during a high time).

 

What I'm looking for:

Basically what to do next.  At this point I'm not sure what is wrong with my system.  I have verified that the connection between my back panel and my 6602 card exisits.  I have ruled out the possability of a bad line drive (swapped line drivers with a good signal, channel 2 still drops, I have tied my channel 2 counter to a "good" counter pin to see if they both fail or not, and I have put channel 2's signal through channel 1's line driver and read the high time fine).  I have ruled out the 2715 terminal block by using a different one.  I have ruled out my 6602 card by using a different one (granted, it COULD be possible that both cards some how suffer from the same bad channel).  The only thing I can see is signal fidelity being an issue.  That being said, when I tied channel 2 to channel 1, channel 2 was dropping while channel 1 was reading fine.  I have verified that my filter settings for the channel are set correctly by writing then reading.  The only thing that has worked has been the function generator.  At this point, I'm thinking its a bad back plane in the chassis and I'm not going to be able to run channel 2.  I guess it could be that the filter for channel 2 is getting over written somehow, but I dont use any channel property nodes in my code outside of the initialization VIs, so I don't see how it could be over written. 

 

Anyone got any tips or advice for troubleshooting or what to do next?  I'm open to anything sans sacraficing a baby to get it to work 😄  I can attach code but I'm not sure what part you guys would want and I feel strange just dumping the entire project.  Basic set up is a "make the tasks" VI, then a "start the tasks" VI which includes setting the filter, then run the test VI (several state machines), then once the test is done, close the tasks.

 

Matt

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Hi Matt,

 

Could you generate a MAX technical report so that we can see your system? Here's a link that explains how to do so.

 

Also, can you remove all other cards from you PXI chassis connect your signal to the Count Edges example program in LabVIEW? It can be found under Help >> Find Examples >> Hardware Input and Output >> DAQmx >> Counter Input >> Count Edges.vi. Try running this program using both counter channel 1 and counter channel 2 on your card and attach screenshots of your signal. Then, switch the card to a different slot in your chassis and run the program again on both channels and attach screenshots. Using the example program will remove you program from the equation and the four screenshots will help us understand what is happening on each channel and across different slots. 

Adena L.
Technical Support Engineer
National Instruments
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Adena,

 

I can not make a technical report through MAX.  When creating a report, the two options I have are "Simple" or "Custom".  I created a custom report and believe I have selected all the options available to me.  

 

Would I have to install a newer version of NI MAX to make the technical report?  I know my group has been hesitant with upgrading NI MAX/DAQmx because they've seen issues where scales/tasks/cards wont appear on NI MAX. 

 

I'm about to start getting the screenshots now.  I just wanted to give an update in regards to the technical report.  

 

Thanks for the response,

Matt

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Hi Matt -

 

The MAX technical report would confirm what hardware and software you have installed, and this would have been the easiest way to do so. The latest version of DAQmx that is compatible with LabVIEW 7.1 is DAQmx 8.9. I would recommend upgrading to this version if possible.

 

For now if you can generate those screenshots they should help determine if the problem is slot dependent!

Adena L.
Technical Support Engineer
National Instruments
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Adena,

 

The custom report that I have shows all the cards and software installed, so thats good at least.  Is there a way I can back up my NI MAX data?  I know I've backed up/restored a system before and it seems that not all the scales/tasks/channels seem to get stored in the backfile.  I ask because coworkers have upgrade DAQmx/NI MAX in the past with mixed results - some had everything run smoothly, others have lost their NI MAX databases.

 

I'm running into a bit of a headache with removing all the cards - the system is in the tower and it's a massive pain to take cards in/out because we've got lots of wires everywhere.  Basically, it's kind of a rats nest in the tower and its super hard to work on the chassis.  Each card has a front panel terminal block associated with it.  Would removing those terminal blocks be sufficient for the request or do I have to physically remove the cards from the slots? 

 

Additionally, we have one of the PXI/SCXI chassis, should I be removing the SCXI cards too?  Assuming yes, but figured I'd ask.

 

Matt

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Matt,

 

Fortunately, there is a way to back up your MAX data. This link should describe that process--you'll just need to make sure you select all that you want to save when exporting. 

 

As for emptying out the cards from the chassis, we'll probably want to take the cards themselves out. I'm interested if moving just the card that's dropping connection to counter two to a different slot will change anything.

 

Let us know how the DAQmx upgrade goes!

Claire M.
Technical Support
National Instruments
Certified LabVIEW Developer
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Bad news fancy folk,

 

I didn't have time to go through and troubleshoot anything.  I was on a pretty tight timeline and had to get a test running (only needed 6 of the 8 channels for my test so it was "good enough" since I had 6 working channels).  I don't think I'll be able to get to the system anytime soon, so it looks like this is a dead end until we will need to run that tower again.  Fingers crossed I'll have more time then to figure out whats wrong next time.

 

Matt

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