PCI-6133 always returns huge constant number of counts

[AndyAina]

Hi,

I am trying to use a PCI-6133 with a BNC-2110 adapter to counting leading edges of pulses.  Please excuse my high degree of ignorance of how to do this.  Anyway, I connected up my TTL input signal according to the BNC-2110 instructions (to PFI-8 via User-2). Whenever I run the DAQmx sample program Count Digital Events.vi, it recognizes the PCI-6133 OK, but always returns an absurdly high and constant number of counts, like 3.2e9.  The number doesn't change as I send test pulses into the input.  It also remains the same even if I disconnect the input line entirely and rerun the sample program.

Rebooting yields the same behavior.

Using DAQ assistant to generate my own code, instead of the sample program, produced exactly the same result.

Thanks for any help you can give me.  I don't even know where to start to debug this problem.

Thanks,

Andy

[BVeezy]

How/what exactly are you measureing from;? Are you wiring the digital signal directly into PFI 8? Have your tried using the other counter (CTR1) on the 6133? It should be PFI 3 (as indicated in the manual). You may also try generating a pulse signal from the 6133 and reading it with this VI to determine if your source may be the issue (you could use PFI 2 as a Digital Output for this). Finally, does it read the same value every time you run it (the reported 3.2e9)?

Regards,

Brandon V.

Applications Engineer

National Instruments

[John_P1]

What is your count direction and initial count set to?

Are you sure you are using a 6133?  It only has a 24-bit counter and therefore its max count should be 16,777,215 (~1.7e7).  Something seems off.  Could you post a snippet of code?

If you are only reading 2 digits of precision and getting a number like 3.2e9, you would only see the count increment every 100 million pulses.  Change the formatting of your reading and let us know the exact count you are seeing and whether or not it is changing.

Best Regards,

[AndyAina]

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@BVeezy wrote:

How/what exactly are you measureing from;? Are you wiring the digital signal directly into PFI 8? Have your tried using the other counter (CTR1) on the 6133? It should be PFI 3 (as indicated in the manual). You may also try generating a pulse signal from the 6133 and reading it with this VI to determine if your source may be the issue (you could use PFI 2 as a Digital Output for this). Finally, does it read the same value every time you run it (the reported 3.2e9)?

Regards,

Brandon V.

Applications Engineer

National Instruments

---

Thank you very much for your help.

How/what exactly are you measureing from;?

I am measuring (counting) TTL pulses coming from a TTL driver.  They are about 1 us long and nominal TTL high and low values.  The pulses look fine on a scope.  The rate is very low, typically a few Hz up to perhaps 200 Hz.  The behavior is the same regardless of whether I have the input signal connected to the BNC-2110, however.  The pulses are ultimately generated by a neutron detector, with a bunch of signal processing in between.

Are you wiring the digital signal directly into PFI 8?

The input signal is connected by BNC cable to the "User 2" port on the BNC-2110.  A jumper wire connects the "User2" PFI Terminal to the "PFI-8" PFI Terminal.  Again, the behavior is exactly the same regardless of whether these wires are installed or not.

Have your tried using the other counter (CTR1) on the 6133?

The behavior is exactly the same on ctr1, which has no wires connected to it.

You may also try generating a pulse signal from the 6133 and reading it with this VI to determine if your source may be the issue (you could use PFI 2 as a Digital Output for this).

I tried running a "test panel" in MAX to count the 20 MHz internally generated signal.  It gave the exact same results, on both ctr0 and ctr1.  It did not throw any error message.

Finally, does it read the same value every time you run it (the reported 3.2e9)?

It reads the same value every time I run the sample VI or test panel (3217997774) on both channels, except that the number changes to a different constant number (very close) when I reboot the computer.

I have been wondering if the problem might be associated with the configuration of the ports on the PCI-6133.  The manual repeatedly says that you can configure the ports to input or output, for example, but it is not clear to me how to do that.  When I right-click the device in MAX, "Configure" is not one of the choices, despite what it says in the "Getting Started" manual.

Again, thanks for your help. 

Take care,

Andyaina

[AndyAina]

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@John_P1 wrote:

What is your count direction and initial count set to?

Are you sure you are using a 6133?  It only has a 24-bit counter and therefore its max count should be 16,777,215 (~1.7e7).  Something seems off.  Could you post a snippet of code?

If you are only reading 2 digits of precision and getting a number like 3.2e9, you would only see the count increment every 100 million pulses.  Change the formatting of your reading and let us know the exact count you are seeing and whether or not it is changing.

Best Regards,

---

Thank you very much for your help.

1)  The initial count, count direction, and edge in the sample VI are set exactly as in your picture.

2) The device is detected as a PCI-6133 in MAX.  To that extent, I am sure.  The only code I am running is the sample VI included with labview called "Count Digital Events.vi" (unmodified by me) and the test panel generated by MAX.

3) The front panel in Count Digital Events.vi and also the "Counter value" output in the Test Panel both display the entire integer, so I would see if the least significant digit were changing.  The displayed number is constant at 3217997774.

Again, thanks for any help you can give me.

Take care,

Andyaina

[BVeezy]

A couple more questions:

Have you tried it on a different computer?

How slow of a Pulse rate have you attempted to measure? (try 1 Hz)

[AndyAina]

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@BVeezy wrote:

A couple more questions:

Have you tried it on a different computer?

How slow of a Pulse rate have you attempted to measure? (try 1 Hz)

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1) Not yet.  I will try this.

2) The typical pulse rate is about 0.3 Hz in the testing I have done so far.  (That is the background rate in our detector.)

Thanks,

Andyaina

[BVeezy]

Be sure to report back with your results from 1).