DSO Shell frequency issues

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eysi
Posts: 3
Joined: Mon Oct 02, 2017 8:54 pm

DSO Shell frequency issues

Post by eysi »

Hi

I am not an electrical engineer but like tinkering around with electronics and microprocessors etc. So I thought it would be a good thing to get a cheap "oscilloscope" to learn something before throwing in a few hundreds of $/€ for a decent one.

I got myself a DSO150 (DSO Shell) from banggood. The problem I seem to be having is that the frequency jumps around quite a lot if I change the timebase. Is it supposed to do that? For the built-in 1kHz pulse wave generator I get following readings:
internal 1kHz
internal 1kHz
2017-10-03 22_25_00-dso shell.xlsx - Excel.png (11.59 KiB) Viewed 3391 times
The board seems to be the most recent revision, and runs the 113-15001-064 firmware (which was preinstalled). The C5 calibration capacitor didn't change a thing, unlike the C3 one.

I also did a few more measurements, now with the signal output from my AN8008 multimeter set to 4kHz. Remarkably the detected frequency at 5ms and 10ms is 4 times less than what's actually generated by the multimeter. At 20ms, it shows the same 250Hz as in the 1kHz internal signal generator.
AN8008 4kHz signal
AN8008 4kHz signal
Is there something wrong with my oscilloscope or is this standard behaviour?

PS: I had also posted this question on the EEVBlog forums as my account was not activated here.
I'm here to learn, I'm just an electronics enthusiast
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