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JohnBee

Discovery 2 scope confusion...

Question

Hello I'm happy to report that we've received our Discovery 2 education package and are looking forward to using it in our upcoming labs. 
That said, I'm a little confused as to how to use the device based on my limited experience with Analog Oscilloscopes. ie, I connected the device (power supply) and USB cable to the PC and the software detects the device and press select. - the loading bar loads, and presents me with a menu. 

In the next step, I attempt to measure a 5hz signal coming from a LM358 circuit running on 30v. 
After loading the scope, I attached a probe /lead to the CH1 and attach the probe clip and ground to the output connectors of the circuit but saw nothing. There is no activity line whatsoever. 

Can anyone help identify why I'm not getting a waveform (reading) with my current setup?

PS. I Have CH1 selected in the interface and the Discovery 2 device is showing a flashing green LED on it. 

Thanks for your help with this. 

Sincerely,
John

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Hello,

For 5Hz you probably have to increase the timebase at least to 20ms/div, and for 30V signal increase the channel range and adjust the offset.

Could you sent a screenshot from your application (to see the settings and acquisition data) ?

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The same thing happened to me when I first connected to a circuit that I had previously analyzes with a Tektronix scope.  I saw no change in the display levels of either probes.  So I connected a probe to a NiMH battery, still no change.  SO I looked at the BNC connector and saw that the jumpers are set to a default of AC, I switched them both to DC.  Now I was able to see the voltage change when I probed a battery.  When I went back to my circuit that I wished to analyze, still nothing.  After much fussing around trying to figure out how to use this thing, I set the V/div on the channel that I was using for a trigger to 2s per Div, set the trigger to rising edge/trigger at 2V, then set the Run to "Repeated" and hit the "Single" button.  The I quickly applied power to my circuit, knowing that it 'should' cross the trigger level right after power up, then I waited about 10 seconds for the "single" event to elapse.  Sure enough, there was my rising event, small and hard to analyze, but definitely there.  I bet if you do this, you will see you 5Hz waveform happily displaying its waveform. So now the (our) question becomes "How might we capture/stop the 'single event' when the specified trigger parameters are met, and display it on the screen"?

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Got it, if the Run mode is set to "repeated" then the box next to it (unlabeled) is changed from the default of 'Auto' to 'Normal' now the screen will capture the single event when the trigger conditions are met.  IMO this should be the default, Normal.  This is how a normal scope behaves when a Single sequence is to be captured upon trigger.

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aaaaaannnddd, now its back to not functioning correctly, wheeee.... (some time passes...)  It turns out that in the process of trying to figure this unbelievably unfriendly environment out, I had hit the "Auto Set" button.  The effect of auto set was to completely randomize all settings, so that I had to then manually try to re-establish all my previous settings.  Included among this randomization process was a change in the setting for 'Hyst:" to 'Auto'.  Hyst is presumably Hysteresis but could just as easily be for Hysteria because that is the effect either way.  In any case, the Hyst was set to a non-zero value, and so the effect was to 'freeze' the screen and not change anything, no matter what happened.  Nice feature, this Hyst, second only to 'Auto Set'.  When I manually change the Hyst to 0V then the scope's 'Single' once again captures when the trigger conditions are met.

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Hi dasboos,

Are you still experiencing problems with your Analog Discovery 2 or did you resolve your issue? If you are still experiencing problems I would like to help you get them resolved.

thank you,

Jon

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