Taking Counter Input samples at 500kHz

[tmaul]

I've got a Counter module hooked up to my compactDaq Chassis and I am attempting to read samples at a rate of 500k samples/second. I believe that the DAQ comes with internal clock capabilities of 100k, 20M and 80M Hz. Is there a way that I can adjust the configuration to take samples at 500k? I've attempted to find a pulse generator or external clock that will give me this capability but I have had no luck, and I really don't know where to look. I've got a few DI/O, AI/O modules, but nothing capable of pulse generation.

Thanks for your time everyone.

[Dayna]

Hey tmaul,

What chassis and module are you using?  Are you using LabVIEW?

This would be applicable if you are using LabVIEW with the DAQmx driver:

Use the DAQmx Timing.vi to specify the sample clock and rate.  If it is not possible for the clock to tick you specify, the clock will round up to the next possible rate it can tick at.  In order to find out the rate it is ticking at, you can use a DAQmx Timing Property node for the sample clock rate property.  This will tell you whether the clock rate was rounded or not.

Hope this helps!

Regards,

Dayna P.

Applications Engineer

National Instruments

[tmaul]

Dayna,

I am using the NI cDAQ-9178 chassis and NI 9411 counter module with labview. I tried setting up the task to count at 500k Hz through the Daqmx timing .vi but I received an error that said the sample rate must match the clock rate. Is there any sort of external clock I can get that would allow me to count at 500k Hz?

Thanks for the reply.

[Dayna]

Hi tmaul,

Page 5-2 of the manual for the chassis is very helpful for your application: http://www.ni.com/pdf/manuals/372838c.pdf  In order to count at 500k hz, you must use an external source. You have many options for the source, but this may require additional hardware.

If you look at the shipping examples provided in the example finder in LabVIEW (Help > Find Examples), there is an example that uses an external timing source for the counter.  If you are using LabVIEW 2012, you can browse to Hardware Input and Output > DAQmx > Counter Input > Couter - Count Edges (Continuous Clock).vi .  If you are using LabVIEW 2011, 2010, and 2009, you can browse to DAQmx > Counter Measurements > Count Digital Events .

Hope this helps!

Dayna P.

Applications Engineer

National Instruments 

[John_P1]

The counters on the cDAQ chassis backplane may be used to generate signals for internal routing without the use of any modules.  The way I read your post you are probably looking for something along the lines of this (i.e. generate a 500 kHz signal to be counted):

One could also interpret your question as if you were asking to sample the count register at 500 kHz (i.e. using 500 kHz as the sample clock rather than the source of edges to be counted).  This route would also be possible (although if you are on the older 9172 chassis I don't believe that the 2 sample FIFO will allow you to sustain transfers at 500 kHz--the newer chassis should work for this if this is what you actually want to do).

Best Regards,