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Signal generator inverted output?! (trigger, ps3404A)

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Signal generator inverted output?! (trigger, ps3404A)

Postby Rastko » Thu Sep 10, 2015 9:25 am

Hello world, I need your help.

My problem is annotated in the image in the attachment. I am using a ps3404A as a pulse generator. I want to detect a trigger event (no problem here) and send out a single pulse upon the event. Here I have two problems:

  • the pulse is inverted by default ---_---, and I cannot change it to __-__, (no Arbitrary pg on ps3404A)
  • I cannot send the pulse out with a certain delay after the trigger event is detected (the trigger delay button)

Application note: I'm trying to use the the signal generator to modulate a the gain of a PMT detector with some precision. For this I need to send out a positive pulse with pulse duration of about 100us, that occurs upon a trigger event, with a tunable delay (trigger->delay->pulse).

P.S. If MATLAB or LabView can solve this, do tell how.
Attachments
Modulation.JPG
Problem description
Rastko
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Re: Signal generator inverted output?! (trigger, ps3404A)

Postby Martyn » Mon Sep 14, 2015 1:17 pm

It may look like a negative pulse, however it is actually one full cycle of a square wave, negative then positive, starting from the previous level of the signal generator.

Using your settings the first time you run this after starting the scope, it will go from 0V (the starting voltage of the generator) to 0V (the first part of the square wave), then to 1.6V (the second half of the square wave) and then remains at 1.6V . If you trigger again it will go from 1.6V to 0V to 1.6V

Unfortunately without the use of the AWG, available with the B models, it is not possible to generate the pulse you require.
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Re: Signal generator inverted output?! (trigger, ps3404A)

Postby Rastko » Mon Sep 14, 2015 3:26 pm

Thank you for the explanation Martin :) now I know what not to try.

There is one more thing that I would like to try before I quit my ps3404A altogether. Since I don't have to have a pulse, a step function might do. I can easily generate the desired DC value on trigger with the signal generator like so: ____trigger------------.

What i don't know how to do is how to save the exact buffer where the level goes from ___ to ----. Do you have an idea how might I do this?

I have tried letting the signal generator be its own trigger and then activate an alarm -> save buffer on capture, but did not succeed.
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Re: Signal generator inverted output?! (trigger, ps3404A)

Postby Martyn » Fri Sep 18, 2015 7:15 am

If the scope is waiting for a trigger then it can't change the signal generator, so using the generator to cause the trigger to change the generator is not possible.

I have tried letting the signal generator be its own trigger and then activate an alarm -> save buffer on capture, but did not succeed.

Can you post a psdata file with the setup you tried and we can take a look.

Making use of the external input to trigger the generator may be an option.
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