Afonso Teles

Hi Raj,

I would suggest following the troubleshooting tree on page 4-22 of the service manual.
If that doesn't resolve the issue, your next option would be to send it in for repair.

Hi Vikas,
 

Overshoot measurement 25% means signal must cross atleast 30V (6V more for 24V). From the waveform max. value is not crossing 26V.

I disagree with that conclusion and I gave my explanation in the previous reply. I would need you to share the waveform file for me to be able to confirm what's going on with that measurement.

Channel 4 is at 5V only still scope trigger the waveform and giving false result.

No, your trigger is operating just fine, the problem is your sample rate is too low so you're missing events. You should increase the sample rate by decreasing the time/div or increasing the record length (or both).
I'll also say that you probably don't want to have your channels be bandwidth limited for such fast events, so I'd suggest going into the channel menus and switching "Bandwidth" to "Full".

Hi Hans,

I agree with you that this is something which can be improved on the AFG1062 and I will be working with our product line towards that.
Thank you for bringing this to our attention and working with me to understand it!

Regards,
Afonso Teles

Hi Ralph,

I don't believe schematics for the TDS430A were ever published, but the service manual does include detailed block diagrams and a table of power rail voltages: https://w140.com/tekwiki/images/b/b2/070-9703-06.pdf

Hi Daniel,

You can manually synchronize 4 AFGs to, from my experiments, nanosecond precision by tying their triggers and ref clocks together but it's laborious and error prone. On an AFG31000 you have a "multi-unit sync" menu that will take you through synchronizing two AFG31000s, but the process is largely the same for more units, no mater if they're AFG3ks or AFG31ks.

For higher precision and much better ease of use I would suggest looking at our AWG5208 which has 8 output channels, all internally synchronized.

Hi Hans,

And how do you then explain that the output of CH2 changes when changing the startphase?  Shouldn't it be zero all the time until triggered??

This is a good question and it hints at the core reason behind this unexpected but correct behavior. When the AFG is waiting for a trigger, it holds the output at the last point of the waveform. When your angle is 0 degrees, this point is 0 V, but at 1 degree the waveform loops around and the last point actually becomes 3 V, this is what causes the apparent "inversion" of the pulse.

Also the signal on the display doesn't corespond the the sinal on the output, although this is the least of my problem.

This is because what the signal looks like on the oscilloscope depends on your external trigger, which the AFG doesn't know beforehand so it cannot possibly draw the signal correctly.

I think a good away to visualize this is if you vary the trigger frequency you will see the pulse shape change, which is an inevitable consequence of what I mentioned above.

Defining phase for an externally triggered pulse doesn't really make sense, which is why in our new AFG31000 we don't allow you to set the phase, instead you can set a delay, which is much more intuitive in how it works. So this isn't a bug in the AFG1000, it's working as intended, but it would be better if they allowed you set a delay instead of phase.

Hi Vikas,

That is certainly unexpected, I think the issue might be that the measurement is considering that first hump at around 22 V to be the start of the pulse.
Would it be possible to share a waveform file of your captured signal?

Hi,

It sounds like you aren't triggering on the pulses. What's your oscilloscope and how is its trigger configured (an image of the trigger menu would be helpful)?

Hi Lee,

Not sure what exactly you're asking for but I don't believe it's possible to get this information without polling, no.

Hi Hans,

To set a certain phase the AFG has to know your frequency, which it cannot possibly know when it's externally triggered, so it uses the pulse frequency. The problem is that this isn't the correct frequency and so when you increase your phase angle to such a point that the pulse overlaps the end of the period, you get a situation where the pulse looks stretched out as it stays high between triggers.
This is easy to test, if you set your external trigger frequency to the same as your pulse frequency, you will see it looks as you'd expect, but if you then change the external trigger frequency you will see the problem reappear.

So yes, this behavior is surprising, but not incorrect.
I will say that on the AFG31000, when generating an externally triggered pulse it doesn't allow you to set phase. Instead, you can set a delay and this delay is limited such that the pulse never overlaps the end of the waveform, avoiding this problem. The designers of the AFG1000 decided not to do it this way, which leads to some surprising behavior, but isn't exactly wrong.

This is a difficult issue to understand so I apologize if I haven't done the best job at explaining it.