Measure frequency by singalExpress V2.0

[MYWONG]

I am trying to use 6602 to measure frequency   (  2 Counters mode), but i get an error

"Sample period too Short" even i increase the Measurement Time....

Attached the Screen Capture, could anyone help me?

[MYWONG]

I try to set to continuous mode and i get a 1D array output. However, i can't plot it into a graph....

What i am going to do is monitor the Frequency against Time.....So , do you guy have any solution to me??

[MYWONG]

anyone can give me your hands?

[sensei]

In the next version of SignalExpress and NI-DAQ, you will be able to plot N Sample and Continuous counter measurements to a graph.  The data will be plotted vs. "sample number", not vs. time because in counter measurements, the signal is determining the sample period.  For example, if your signal is varying between 1 kHz and 5 kHz, your sample period would vary between 1 ms and 200 us.

In your current version of SignalExpress and NI-DAQ, counter data can only be viewed in a table.

Sensei

[MYWONG]

Thanks, may i know when will the new version of SE lanuch?

I have an idea, i am trying now, but don't know is it possible.

Can i use a VI to cal the mean of the array of the captured frequency, and plot the mean to graph? I have tried it, and is it possible, however, i failed to log this data, it seems to me that , there is lack of time stamp of the data, because the X-axis (time) keeps unchange, even the graph is updated...

I am afraid i can't wait for the new version of SE...so i hope i can slove this problem asap. Thanks...

[--Chris]

If your calculated Mean is a double it should display as a chart (X Axis will be iteration) and it should be loggable.

[MYWONG]

Dear all, i try to set using 2 counter to measure single point frequency...but why the program SE warm me that the " Sample period too short" , How can i solve this problems??

[sensei]

There was a bug in NI-DAQ 8.5 that defaulted a "sample period" of 100 ms (and you couldn't change it).  This occurred only in SignalExpress, not in MAX or LabVIEW.  Therefore, if your signal is slower than 10 Hz, SignalExpress would error.

In the next version of NI-DAQ (due out on the August 2007 Driver CD), this issue has been fixed.

sensei

[MYWONG]

What does you mean the defaulted sample period? is it similar to the measuremnt period???My input signal is around 1Mhz, but i still get this error message??

What can i solve it? by DAQmx 8.2?? But i know SE 2.0 support to DAQmx 8.5 only....

If i change it to other mode " N sample" or continuous mode, the error gone away, but i failed to plot it into a chart or graph...any method??

Thus, i write a VI to calculate the sum from the array of data (get from continuous mode) and try to plot into a graph. It works, but didn't show me the time base.

How can i include the time base into the graph???

[--Chris]

The sample period is the time between calls to the DAQmx Acquire step.  It is a bug that you get the error.  Installing the August 2007 Driver CD will fix it.

Graphing the N sample or continuous mode output of the DAQmx step has been added to SignalExpress 2.5 which is also included in the August 2007 Driver CD.

SignalExpress does not currently support timed single point output from a User VI.