Problems when using count digital events buffered continuously example

[qwang]

Hello,

I met two problems when using the count_digital_events_buffered_continuously_Ext_clk.vi

1. I have only one input channel.  I set the sample clock(external) frequence 1000HZ,   when my input signal frequency is larger than 1000HZ, everything goes on well, however, if my input signal frequency is lower than 1000HZ, something unexpected happened: the program will not record the counter data unless the next available signal is detected. That is to say, if my input signal is 10HZ,  only 10 numbers are read from the buffer(1,2,3,4,...) every second.   I expected to receive 1000 numbers per second (of course, there will be some same numbers. such as 1111112222223333333...) How can I modify the example to achieve this kind of data output?

2.  I am confused by the "sampling rate" property: what does the sampling rate mean in this example?  what will happen if the value is set too high or too low?

thanks for your attention.

[Kevin_Price]

Based on the terminology ("events" rather than "edges"), it sounds like you're using traditional NI-DAQ.   I think you should (need to?) switch to DAQmx and experiment with the "Duplicate Count Prevention" property.

For more info, look at the bottom of this thread where I just typed up a reply to a similar issue.

-Kevin P.

[falkpl]

Yes dup count protection strikes again, this is a common problem that keeps popping up.  NI should put a warning about this.  It had me stuck for a few days when I migrated from traditional DAQ to DAQMX, and it stumps just about everyone who encounters it for the first time.  To make things worse, it is a property that is very well hidden in the property hierarchy. 

Paul

[qwang]

Yes, Thank you guys so much. it was the "Duplicate Count Prevent" Problem. I have turned it off and now the counting works just at normal sense.