PCI-6070E : Maximum number of ( analog in ) samples per Hz ?

[reteb1]

In MAX and in LV8.6 I can have 1kS converted ( analog in ) at a rate of 1kHz ( the 6070E is rated at 1,25 MS/s  ), so, looks OK.

However, why does conversions fail at 10kS at 100 Hz, just being the same 1 MS/s ?

Something to do with an internal 6070E's maximum buffer size ?

If so, is Labview 8.6 fast enough to read and store 1 MS/s contiguously off the 6070E although the 6070E DAQ presents the data to Labview in 1000 chunks/s.

I run an AMD64 x 2 @ 6 GHz @ 4 GB RAM @ 2 TB HDD,  must be fast enough.

I certainly do miss something, but what ?

In the DAQ manuals I couldn't find enlightement on this subject.

Thanks for any explanation.

[Dennis_Knutson · Accepted solution]

I'm having a hard time understanding what you are doing. You say 'conversions fail at 10kS at 100 Hz, just being the same 1 MS/s'. What is the actual sample rate you are using? Is it 100 samples/sec? And are you requesting 10k samples? If so, why are you doing it that way? If you want 10k samples at that rate, you should probably request 100 samples and do multiple reads. To get 10k samples at a 100 hz rate, that would take 100 seconds, you would not get anything until the 100 seconds is up, and probably overflow the buffer. Take 100 samples at a time and repeat 100 times would give you the same number of samples but you would get data every second and not need such a large buffer.

[ninlmartijn]

Hello Reteb1,

which error do you get? I suspect you get the error -200248, which is a timout error.

The rate you are setting is the actual sample rate. You can specify how many samples you want to (internal memory of your computer) buffer before the task will read those samples (because reading samples through a driver takes a lot of time). If you specify a rate of 100 Hz and samples to read at 10 kS; the task will read every 10 kS the samples out of the buffer; filling a 10 k buffer with a rate of 100 Hz takes 100 seconds.

The default time out of a task (can be found on advanced timing in the task configuration or on DAQmx read VI within Labview) is 10 seconds.

I hope this will clarify the usage of a task, please don't hesitate to contact me if there are any further questions.

Best regards,

[reteb1]

Thanks to both of you.

Indeed, I must have been way off beam.

In the past I worked with the 16 bit 100 kS/s and 250 kS/s NI DAQ cards.

So I should have known better, but apparently I recalled erroneously and mistook ( confused  ) the " samplerate " and the " samples to read ".

Right now I do understand the card 6070E works flawlessly, in DAQ Assistant.vi as well as in LV8.6's other .vi's.

Again, thanks !

Peter.