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Does S Series support digital filtering?
JSInc
Member
08-09-2007 12:03 AM
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I am using a S series DAQ card (PXI 6123) in a project. The analog data acquisition is triggered by digital start falling edge at PFI0 pin. The problem is false triggering happens very often. I have added RC filter, pull up resistor, triggering isolation curcuit. These really help a lot. But I still get one or two false triggerings per day.
I look around and find an article on digital filtering with M Series cards.
I download the example vi and modify to run on my PXI 6123. It runs. When I increase the min Pulse Width to more than 10 seconds, a very short pulse can still trigger the vi.
My question is:
Does S Series multifunction DAQ card support digital filtering?
08-09-2007 12:06 AM
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I just realize that this post should be posted in Multifunction DAQ card board.
Can board admin move it to the right place?
Thanks a lot.
JSI
Matthew_W
NI Employee (retired)
08-11-2007 03:08 PM
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Hi JSI,
The PXI-6123 does not have the programmable input filters like the M-series boards do. What you can do is implement the same thing using the counters as a debounce circuit. Here is a knowledgebase article that gives more details on how to do this.
What will happen is the counter will be configured to output a single pulse when a rising (or falling) edge is detected on the gate. This single pulse will be configured to have a width such that a subsequent rising (or falling) edge on the gate will be ignored. The counter will re-arm when the single pulse is completed. The pulse width should be chosen to be short enough that the counter will re-arm in time for the next input to the counter, but long enough to ignore switch bouncing or other accidental duplicate inputs.
Look at the shipping example for LabVIEW: Gen Dig Pulse - Retriggerable. Search for Pulse in the Example Finder or browse to the Counter Generation examples.
Your digital input will then be configured to read from the PFI line that represents the Counter output.
Have a great afternoon!
Best regards,
MatthewW
Applications Engineer
National Instruments
The PXI-6123 does not have the programmable input filters like the M-series boards do. What you can do is implement the same thing using the counters as a debounce circuit. Here is a knowledgebase article that gives more details on how to do this.
What will happen is the counter will be configured to output a single pulse when a rising (or falling) edge is detected on the gate. This single pulse will be configured to have a width such that a subsequent rising (or falling) edge on the gate will be ignored. The counter will re-arm when the single pulse is completed. The pulse width should be chosen to be short enough that the counter will re-arm in time for the next input to the counter, but long enough to ignore switch bouncing or other accidental duplicate inputs.
Look at the shipping example for LabVIEW: Gen Dig Pulse - Retriggerable. Search for Pulse in the Example Finder or browse to the Counter Generation examples.
Your digital input will then be configured to read from the PFI line that represents the Counter output.
Have a great afternoon!
Best regards,
MatthewW
Applications Engineer
National Instruments
