Trek Oscilloscope 2012C trigger problem

[Helenz]

Hi everyone,

I have probelemswith Trek Oscil. I have a Lab program to Charge/Discharge a battery. For Discharge part, I use a 2012C to catch the discharging curve of the battery. Most time I get the correct discharging curve. But sometime it seems the Oscilloscope didn't get triggered and sometimes the Oscil got triggered a little late and I could not get correct curve.   But for the same running program and hardware, the oscilloscope is supposed get the same triggered curve at the same time.   I have two questions to ask. First why could I not get the same time trigger for the same condition? Second how could I get the correct triggered curve? 

Could anyboday help me out? Thank you.

[crossrulz]

Triggering a scope can potentially be tricky.  What settings are you using?  What voltages are you using with the capacitor?  How quickly are you charging/discharging?  How noisy is the signal?

[Helenz]

The Charging voltage is pretty high (up to 1000V). The dischargeing time is around from 25ns-10ms.  The noisy is low and doesn't affect the result. Most time I can get correct curve. But sometimes I saw the trggered curve on the Oscil but the curve was not fetched by labview program. Do you think the problem related with system grounding ? Thank you.

[crossrulz]

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@Helenz wrote:

But sometimes I saw the trggered curve on the Oscil but the curve was not fetched by labview program.

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Wait, the scope has the right waveform but when you try to read the waveform using LabVIEW it is the wrong waveform?  That sounds like a timing issue.  I often find that the Tektronix scopes need time to put stuff in buffers before you can read it properly over GPIB or Ethernet.  Add in something like 500ms to 1 second wait to make sure the oscilloscope has the waveform captured before you try to read it.

[Helenz]

The unnormal triggered waveform on Oscil is sometimes " later" than the regular one.  The oscil has been set up the time base is 1ms, time position 3ms.  Some waveform has out of the frame.  How can I read those correctly?  Also like I said before, the Osil is not triggered at all sometimes.   Thank you.