04-19-2008 07:30 PM
04-19-2008 08:00 PM
04-19-2008 08:24 PM
04-19-2008 11:58 PM
04-20-2008 11:14 AM
04-20-2008 11:21 AM - edited 04-20-2008 11:24 AM
Hi andrikos,
use the "convert from dynamic data" function from the express palette and select "1D Array of Waveform", you can index the array and then you can use the "Get Waveform Components" function.
Or you can use the index array function directly after your waveform variable.
I would prefer a direct wire instead of the local valriable.
Mike
04-20-2008 12:01 PM
04-20-2008 04:01 PM
04-21-2008 12:25 AM
andrikoscy wrote:
hi,
...
because if i try to execute the 2 analog with the same task, the two analog will work with the same sample rate..
04-21-2008 01:17 PM
Hello Andrikoscy,
For most multi-function DAQ boards what you're trying to do is not possible. If you want each analog input to run on a different sample clock then you'll need to look into a NI R Series Intelligent Data Acquisition Device. These DAQ boards have a built in FPGA and allow for more customization than M Series boards, including independent sample clocks.
To address your questions:
1. On a non-intelligent DAQ board all analog input channels must share the same sample clock--if you need two different rates I would suggest sampling both channels at the faster of the two frequencies and then just ignore some of the data points on the slower channel.
2. In order to find out the exact time between samples from an external trigger (instead of the constant dt inserted by the waveform acquisition), you will need to take a period or frequency measurement of your signal using a counter on your card. By taking a buffered period measurement you will get an array of the times between samples and with that you can graph your samples on a precise x-axis. Normal analog input tasks that use an external clock do not associate any exact timing information with when a trigger was received.
I hope this helps, and if you'd like more information on the R Series Intelligent Data Acquisition Devices please feel free to contact National Instruments directly at www.ni.com/contact.
Have a great day!