Hi
I'm a long time EEVBlog follower, first time on the forums though.
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:
sec/div Freq cycl (ms) PW (ms) duty
10us --- --- --- ---
20us 1,258 kHz 0,794 0,296 37,0%
50us 1 kHz 0,999 0,500 50,0%
0,1ms 1,127 kHz 0,887 0,386 43,6%
0,2ms 1,112 kHz 0,898 0,446 50,3%
0,5ms 1,026 kHz 0,974 0,487 50,0%
1ms 1,001 kHz 0,998 0,479 51,0%
2ms 1 kHz 0,999 0,519 51,9%
5ms 1 kHz 0,999 0,399 40,0%
10ms 999,020 Hz 0,999 0,399 40,0%
20ms 250,245 Hz 3,996 2,396 59,90%
50ms --- --- --- ---
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.
Could someone with a similar DSO check if theirs is detecting the same values?
Thanks!