AnsweredAssumed Answered

problem with MSO6012A trigger

Question asked by fanfan006 on May 19, 2009
Latest reply on May 19, 2009 by fanfan006
I had one problem and could not solve it by myself. I am just wondering if anyone here can help me.

I attached one bmp file of the screen to describe the problem I met. Basically I want to know what happens to a trigger signal. I am using two probes. Probe 1 is connected between channel 1 and the trigger source. Probe 2 is connected between the “ext trigger” channel and the trigger source. In another word, both probes are connected to the trigger signal. I want to detect the trigger signal and capture the waveform. The power supply is 5v. So you assume the trigger signal is 5v which can be verified by the later bmp files.

In print_002.bmp, I set the trigger level to 2.5v. The figure makes sense to me. The scope detects the trigger signal and start to write the post-trigger buffer. And finally shows the wave form.
Image

However, in print_000.bmp, I set the trigger level to 3.4v. The trigger signal starts around at the time point t= -50ms. But the scope starts to capture the trigger signal at the time point t=0. Why there’s such a big delay between the trigger signal itself and the signal that the scope is really triggered?
Image

For more details, I attached two other pictures to show the triggers in the above two settings. The major difference is the delay. In print_001.bmp, the huge delay seems very strange to me. I have been confused by this problem for a couple of days. Could you do me a favor and give me some thoughts?

Terry.  

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