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sync AI with DO - M series PXI 6221

Hello everybody,

 I need to provide DO to the a multipexer (Pressure scanner with 16 Pressure lines , 1 AO and 4 DI) to select the desired pressure channel, give it time to settle before I sample the AI in my DAQ card. I have the following hardware :-

1.PXI Chassis 1052,

2. PXI 6221 DAQ card

3. Labview 7.1 with Win XP

Looking for valuable suggestions.

Thanks,

Surender Kumar

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Hi Surender,

The problem as I understand it is that you have a PXI-6221 DAQ card that you are trying to output a digital signal on and use to acquire an analog input. The DO will be controlling a multiplexer from which the analog signal is coming. You want the analog acquire to begin after the multiplexer has had some set amount of time to settle. I am assuming that the multiplexer is controlled by writing a static value to the digital inputs.

The best way to go about addressing this issue would be to combine two examples from the NI Example Finder, one for the Digital Generation and one for the Analog Measurement. You could then use the timing functions and/or a sequence structure to control the flow of the two. The attached image is a simplistic example to give you an idea of how you could wire the two tasks. There is a software timed wait before the analog read. However, you will need to configure the sample clocks, digital write, and analog read as are appropriate for your application.

The examples can be found by navigating to the Help Menu>> Find Examples>> expanding the Hardware Input and Output folder>>and then looking in the Digital Generation and Analog Measurements files.

Good luck and feel free to post back if you have any further questions.

Mallori M.



Message Edited by mallorim on 12-03-2007 12:45 PM
Mallori M
National Instruments
Sr Product Manager, Customer Proficiency

ni.com/training
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Hi Mallorim,

Thanks for your suggestion.

I can follow the suggested way but want to do it more precisely and at more frequency, 1khz or more.

I am looking for some counter clock sync with DO , DO maped with DI (read DI to know which pressure chaanel is selected) and AI read.

Best regards,

 

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