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Trigger delay has no impact on acquisition-PXIe-5122

Hi,

 

I'm using a PXIe-5122 to sample a signal generated by a balanced detector. The sample rate is provided by a photodiode signal feeded into the CLK_IN pin, which is taken from the monitor output of the laser, which is generating the measured signal too. Moreover, this monitor signal is used as a trigger signal, so that all three signals (acquired signal, trigger signal, sample clock signal) are synchronised. The frequency is 80 MHz. 

 

Since the signal of the balanced detector is not perfectly balanced, even when the incoming beam intensities are equal, I have to sample this periodic signal at different points of the residual curve to find the ideal spot for my measurements. My idea was to simply set different trigger delays to "walk through" the signal curve. However, no set delay value seems to have an impact on the acquisition. The program samples the same position all the time. Even if I use different trigger sources, which should have a random phase with respect to the laser signal and therefore different positions should be sampled, I receive the same result all the time. 

 

Does anyone could help me out with this?

 

I have attached my used code.

 

Kind regards,

 

Michael 

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Message 1 of 4
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Hi,

 

I coudn't find any definition of 'TRIG' in trigger edge configuration.

 

session.configure_trigger_edge('TRIG', trigger_coupling=niscope.TriggerCoupling.DC,

slope=niscope.TriggerSlope.POSITIVE, level=1, holdoff=0.0, delay=0.0)

 

I think that you should change the value of property trigger_source. 

https://nimi-python.readthedocs.io/en/master/niscope/class.html#configure-trigger-edge

http://zone.ni.com/reference/en-XX/help/370592AB-01/scopepropref/pniscope_triggersource/

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Message 2 of 4
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Hi,

 

thank you for your answer. The problem is, even when I use '0' or '1'  as a trigger source, where both channels are receiving the exact same signal from one function generator output, the measurement is just random (which should not be the case, because it should measure the same spot for each measurement as the trigger event should occur at the same position on the sine for each measurement)

 

Any ideas?

 

Sincerely,

Michael

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Message 3 of 4
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Maybe try to use built-in PXIe oscillator timebase and check if the behavior is the same (there's a set delay after trigger observed).

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Message 4 of 4
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