Have a 6211 and need to trigger a digital output from a analog input using edge detection

[Pinton]

Hey All

    I have a USB 6211 and I am trying to use my position feedback to trigger a relay. I want to fire the relay as the position is rising past the trigger point. Then turn off the relay when the position is falling past the trigger position.

The rising and falling edge is greyed out in the window measurement of an analog channel  Thanks in advance

[Brandon_B]

Hello Pinton,

Thank you for using NI forums.  It sounds like you are trying to do analog level triggering where you specify a certain voltage level and if your analog input exceeds this level then you send a trigger.  Unfortunately, the USB-6211 doesn't support analog triggering (you can find this on the specifications tab under the triggering section of the 6211 Product Page).  You can, however, use a case structure in your program (assuming you are using LabVIEW) to compare the analog in voltage and perform an operation based on the level of the input.  There could be some slight delay with this method because the triggering is dependent on software, but it is a way to get the job done if you don't have an analog trigger.  Please let me know if I misunderstood your application.

Regards,

[ewv2104]

Hello -

I am trying to do a similar project with a PCIe-6351 DAQ card. I have had issues making the digital signal wait for the analog trigger to actually occur (as soon as I press run, the digital output jumps to high state right away).  Do you have any ideas for that? I have attached my code to this post.

- Eddie

[Courtney_L]

Hi ewv2104,

A noisy signal could cause the analog trigger to mistakenly fire. I would recommend looking into an analog hysteresis trigger if you're not using that already. 

I hope this helps make the trigger a bit more accurate. More info on analog hysteresis triggering can be found here.

Best,

[ewv2104]

Courtney -

It doesn't make sense though because the analog data acquisition is supposed to wait for the same trigger and it does.  So, I feel like the error has something to do with the the code structure itself.  Is it possible for me to use case structure or some other kind of programming loop to ensure the digital output waits until the analog data acquisition is triggered?

- Eddie