Triggering on Rigol scope

[Marty_MC]

Hello freaks,

first of all, I know this board is discussing about sniffing on the I2C bus then rather of using the DSO. However so many people are there who are using the DSO. So I believe someone can answer my question very quick. I am adding a big sorry to write an off-topic question there.
My question is very simple: It is triggering problem
I am struggling with a measurement problem: I have a big power Generator who is generating 400Volts AC. The armature coil is driven by 15V DC.
Unfortunately sometimes the 400V is going to zero for 10 Seconds. After that, everything is OK for hours or days. I am trying to figure out the reason. For that I am monitoring on channel A the one 230V AC phase and on channel B the 15 DC. However how can I parametrize a trigger?  I want to store the "event" of the two Voltages. At the moment I do not what the reason for the problem is. I do  not know if the 15DC is going to zero or the 400V before.
My idea is to store the event of the power drop-out. The DSO should stop after that event the acquisition.
i can not sit hours or days on the DSO to wait for the drop-out event. The problem is the event is very short, only 10 Sec. It can happen in the middle of the night. 

Thank you so much for our help. Any sorry again for the off-topic story.
 MartyMC

[marmad]

Welcome, Marty!

Some (or all) of this may be obvious, but I'll write it anyway (in case there are others who can benefit):

You'll want to use either Single Shot mode or Frame (Segment) Recording - either one will store the event.
If you use the full 56 M sample size @ 1s/div - you'll get a reasonably detailed view of 14 seconds (7s pre/post trigger). Don't forget to adjust the horizontal trigger position if you want a different division between pre/post-trigger information (e.g. if you only want 1 second pre-trigger, adjust the h.trigger position 6 divs left).
As far as your trigger goes, I assume if the AC goes out, the 15V will go out as well (or vice-versa)? If so, for capture purposes, it doesn't really matter which one initiates the event - as long as you capture enough pre-trigger data to include it. So as long as you calculate the maximum amount of time it takes for an AC dropout to drop the 15V, you can just trigger using a Falling Edge trigger on the 15V. Correct me if I'm wrong with my assumptions - otherwise another option is to use one of the pattern triggers with both channels as sources.

I hope some of this is helpful for you.

(I also answered your question over in the other main DS2000 thread.)

[Marty_MC]

Dear Marmad,

thank you for the warm welcome.
The generator has a over voltage protection. So I do not know what the reason for the power-drop-out is. The 15V DC could also increase and the over voltage protection is cutting the line for the event. That is the reason why I want to monitor the event.
A trigger could be the output socket of the 230V. Once the 230V drops out, I want to see what kind of driver signal is putted on the armature coil of the Generator. I have to find out whether the voltage regulator has damage (like it is oscillating). Interesting is this event happened also when the generator is load with 2kw only. It is 34 kW Generator. 2kW is the lowest load.
14 sec is enough I guess. I have 56 M sample size.
How can I generate a "shot" with some seconds pre-trigger once the 230V is gone for let me say 1 sec?
I am really struggling with the manual because this is not a usual use I guess.
Thank you so much for your help.
Marty

 

[marmad]

14 sec is enough I guess. I have 56 M sample size.

Of course, it can always be longer - it just depends on where you set the time base. If you set the horizontal scale to 1.43 seconds a division, then you will capture 20.02 seconds (but with less detail than 14 seconds). You should just decide what is the minimum amount of time you want to capture, and then set the time base accordingly. The standard trigger horizontal position is the center of the screen (D 0.00000000ps) - which gives you exactly the same amount of data captured before and after the trigger. Moving that left or right will increase/decrease the amount of pre/post trigger information captured.

How can I generate a "shot" with some seconds pre-trigger once the 230V is gone for let me say 1 sec?

You can set the channel monitoring the 230V to a TimeOut trigger - triggering on both edges (up and down arrow) with a time out period of 1 second. If the 50Hz AC waveform does not continue to cross the trigger level after one second, the trigger will happen. By changing the time out period, you can set at exactly what lower frequency the AC line will trigger the capture.

Thank you so much for your help.

No problem - that's why we're all here.

[AndersAnd]

(I also answered your question over in the other main DS2000 thread.)

His post in that topic has been deleted again, so it's probably best you delete your reply in that topic too and keep the discussion here.
He also made the same post in the IIC topic which was moved here because it was off topic in that topic.

[marmad]

Here's a Single Shot image I just made using a 50Hz sine wave to simulate the AC line - and a 1 second TimeOut trigger. Note the 1 sec period before the center line which is the 1 second delay. Once the trigger has happened, it doesn't matter what the two channels do during the subsequent capture period.