Error -201314 whenever engine killed

[rehelmin]

Hi Guys,

I am building a test stand that takes some measurements of smaller size engines. I am using the 9188 cDAQ platform and a 9401 C-Series module to obtain the signal from an encoder that is mounted to the engine. Whenever I go to kill the engine I get error code -201314 saying the following:

DAQmx Error: Multiple Sample Clock pulses were detected within one period of the
 input signal. Use a Sample Clock rate that is slower than the input signal. If
you are using an external Sample Clock, ensure that clock signal is within the j
itter and voltage level specifications and without glitches.

The way I have the task setup is the tach pulses act as an external sample clock, and the counter counts the 20MHz clock edges, so I find it hard to believe that I'm getting any kind of engine speeds faster than the 20MHz clock. Does anybody have any idea what this message means? I'm kind of wondering if I need to be more careful about how my grounds are connected.

Thanks for the help,

Ryan

[John_P1 · Accepted solution]

Hi Ryan,

Small glitches on the rising or falling edge of your tachometer signal could be picked up as additional edges.  I suspect that the act of powering down the engine is introducing noise onto the line, which the counter is picking up as duplicate edges during the transitions.

The 9188 does have support for digital filtering on the counter inputs--the feature was introduced in DAQmx 9.4 for the 9188.  You can use digital filtering to reject any pulses below a certain duration.  From your description, it sounds like this would be a likely fix to the problem.

In LabVIEW, you can set digital filtering of the sample clock signal with a DAQmx Timing Property Node:

If you're using a different API and have trouble finding the equivalent property be sure to let me know.  Keep in mind that if you are using a version of DAQmx prior to 9.4 you will have to upgrade your driver to have the feature available for your 9188.

Best Regards,

[rehelmin]

Thank You! I was on DAQmx 9.3, which doesn't support digital filtering for Counter Input tasks. I had an idea that it was noise related, and was starting to wonder what I could even do about it.

Is there a good way to keep up to date with new releases of software and what new capabilities they add?

Best Regards,

Ryan

[John_P1]

Hi Ryan,

NI Update Service should inform you of any driver updates, but I don't think it gives a comprehensive list of new features.  The major features of every driver release should be listed in the corresponding readme however, so this is probably the best way to go about finding this information.

Best Regards,