I'm using CVI 6.0 and NI DAQCard-AI-16XE-50, I have a circuit that give me a pulse each 1 ms, And I need to set my DAQ board to acquire an analog signal on a rising edge of the 1 ms pulse. Is there a special easy way to do such thing ?
It sounds like you wish to perform a triggered acquisition. When the rising edge of your signal crosses a certian voltage level you will begin acquiring the entire waveform. This would be extremely easy with analog hardware triggers; however, your particular board only has digital triggers. This means that you will have to analyze each datapoint and make a decision whether or not to keep the data in software. Another option would be to use the digital triggers that your board has. Perhaps you could leverage some external circuitry to determine when your waveform crosses the trigger boundry and then this external hardware outputs a digital pulse which your DAQCard can detect.
Check out examples on our Development Library at www.ni.com/devzone.
S ingle Buffered Analog Input with External Start Trigger (LabWindows/CVI) http://venus.ni.com/stage/we/niepd_web_display.DISPLAY_EPD4?p_guid=B45EACE3EF8356A4E034080020E74861&p_node=200081&p_submitted=N&p_rank=&p_answer=&p_source=Internal
Analog Triggering in CVI http://venus.ni.com/stage/we/niepd_web_display.DISPLAY_EPD4?p_guid=B45EACE3E72956A4E034080020E74861&p_node=DZ52308&p_submitted=N&p_rank=&p_answer=&p_source=Internal
Justin's answer is great. I would add that if you do the analog trigger emulation he describes, you may wich to use a pretrigger as well. This way even though the analysis takes some time, you can sample the signal prior to the decision to trigger the acquisition. You will not lose any information this way.
To understand how this works you can search the knowledge base on "pre-trigger" and "circular buffer" that will bring up instructive information.
