DS0138 Output Looks Inverted

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dobbiem
Posts: 2
Joined: Wed Dec 13, 2017 9:23 am

DS0138 Output Looks Inverted

Post by dobbiem »

Hi,

I purchased this kit so that I can get to grips using an oscilloscope as I've never used one before.

Everything appears to be working but it looks like the output is inverted.

I've attached a picture while reading the test signal and to me it looks like it is reading -3.3V rather than +3.3V. I've also tried reading the signal from my laptops serial port when I send a character and the same thing happens, the shape appears correct but its the opposite of what I expect to see.

I'm not sure if I'm just reading it wrong or somehow I've managed to solder something incorrectly.

Any ideas would be appreciated.
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IMG_0050.jpg
MNTech
Posts: 59
Joined: Wed Sep 13, 2017 2:23 pm

Re: DS0138 Output Looks Inverted

Post by MNTech »

I suspect the zero volt position of the trace is not correct

Verify that the the voltages at AV-, AV+, +3.3V and +5V are correct.
A low battery will let the -AV drop causing the trace to be offset.

With no input and the trigger mode set at auto you should see the trace in the middle of the screen.
If it's not, do the Vpos alignment.

Version -66 of the firmware is available, it's worth upgrading
dobbiem
Posts: 2
Joined: Wed Dec 13, 2017 9:23 am

Re: DS0138 Output Looks Inverted

Post by dobbiem »

Hi,

Thanks for your reply, it looks like it was the Vpos alignment that wasn't correct.
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