Was wondering if anyone could confirm this bug aswell:
If i use the test signal as input (1.000kHz) and change my timebase using fine adjust, the measurement go all weird (while they dont have to)
- attach channel 2 (f.e.) to the test signal
- press auto
- you should now have a timebase of 200us
- active frequency measurement (2nd in left menu)
- it should read 1.000kHz
- change timebase to 500us -> it still reads 1.000kHz
- change timebase to 1ms -> it still reads 1.000kHz
- change timebase to 2ms -> it still reads 1.000kHz
- change timebase to 5ms -> it still reads 1.000kHz
- change timebase to 10ms -> it still reads 1.000kHz
- now, change the scale adjust from coarse to fine
- change timebase to 9.350ms -> frequency reads 891.3Hz!!!
now, this is way off (more than 10%) and doesnt have to be. on the screen, there's 14*9.35ms=130.9ms of data. In that time, there have been 130.9 oscillations. Maybe it's possible the scope is reading one oscillation more or less, but imo the max error should be /130.9 * 100% = 0.76% = (9.9924Hz to 1.0076kHz), not more than 10%! Using a slightly smarter algorithm, the error should be even smaller..
This is with the latest firmware. Can anyone confirm this?
if i set the timescale one higher (9.4ms), the scope reads 1.064Khz, one lower (9.3ms) and it reads 1.075Khz, which is about the error I'd expect.
Same thing happens on other timebases, f.e. on 5.450ms the reading is >8% off!
Update :
It also seems to depend on the numer op points being taken.
on the 5.45ms timescale, the auto mem depth is set at 7.63Mpts when using only one channel. The reading is 917.4Hz
When changing the mem depth manually, you get :
14kpts - 1.019khz
140kpts - 1.019khz
1.4mpts - 1.019khz
14mpts - 1.019khz
56mpts - 1.019khz
so only the auto setting for the mem depth is way off.. isnt that weird?
At a timescale of 7.05ms/division, I'm even getting a reading of 886.5Hz, which is more than 11% off.. this is at a mem depth of 9.87Mpts. Any other manual mem depth gives a reading of 1.013kHz..