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New 2ch pocket DSO+SG - Zeeweii DSO2512G

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Aldo22:

--- Quote from: timschuerewegen on October 22, 2023, 09:03:36 am ---V1.3.0C has the same "bug". I have the formula that calculates the "Mean" value from the raw FPGA data so I will check if it is a bug or a feature  :-DD

--- End quote ---
Thanks.
It is interesting that the line on the graticule seems to be more accurate than the number (Mean).

PS I came across this because I thought I had made a mistake with my screenshot analyzer tool, which I am currently fiddling with (last screenshot).  :palm:

timschuerewegen:

--- Quote from: Aldo22 on October 22, 2023, 09:29:16 am ---It is interesting that the line on the graticule seems to be more accurate than the number (Mean).
--- End quote ---

This is the formula that calculates the "Mean" value from the raw FPGA data.

Mean = (ChanGain * ((((ChanVolDiv / 25) * DataSum) / DataCount) - (ChanVolDiv * ChanPosZeroVolt / 25))) / 970

ChanGain is default 1000 and can be changed in steps of 2 by entering "Calib:AC gain" mode
ChanVolDiv is the vertical sensitivity
DataSum is the sum of all FPGA signed 8-bit values
DataCount is the number of FPGA values
ChanPosZeroVolt is the zero voltage position (can be adjusted by moving waveform up/down)
25, 2000 and 970 are fixed

Example:

(1000 * ((((50000 / 25) * 6583) / 1200) - (50000 * -56 / 25))) / 970 = 126774 µV

timschuerewegen:

--- Quote from: timschuerewegen on October 22, 2023, 10:22:17 am ---This is the formula that calculates the "Mean" value from the raw FPGA data.
--- End quote ---

That formula basically converts "screen y value" back to µV.

Test with +2V :
Mean = (1000 * ((((1000000 / 25) * 58269) / 1200) - (1000000 * 0 / 25))) / 970 = 2002371 µV

Test with -2V (swapped 2V and GND) :
Mean = (1000 * ((((1000000 / 25) * -62102) / 1200) - (1000000 * 0 / 25))) / 970 = -2134088 µV

Now I need to check if the values came directly from the FPGA or had some calibration applied to it.

(The .wav files attached to this post are the standard DSO2512G .wav blobs with extra data appended to it. The 1200 signed 8-bit values start at offset 0x116C)

ptluis:

--- Quote from: timschuerewegen on October 20, 2023, 03:40:15 pm ---what else can I add/change :)

--- End quote ---

About NORMAL trigger mode: if I set the scope to NORMAL TRIGGERING when Stop button is pressed, the trigger must change to STOP and KEEP the signal already acquired instead of going into a wait state that make me loose what's on screen.
If it STOP the trigger, the last signal recorded before the stop can be inspected with the cursors or zoom or even saved.

An option to enable/disable 20MHz bandwidth limit would be nice to have also. I know it's a hardware thing and we could build an external one, but maybe it could be done through software somehow.

Aldo22:

--- Quote from: ptluis on October 22, 2023, 12:53:28 pm ---An option to enable/disable 20MHz bandwidth limit would be nice to have also. I know it's a hardware thing and we could build an external one, but maybe it could be done through software somehow.

--- End quote ---
I think for the problem with the jittery signal with steep square wave sources (rise time) at higher frequencies, a 20MHz LPF is too much.
I have a 30MHz LPF from the "RF Demo Kit" and a homemade ~64MHz LPF with the parts I had on hand.
The signal is much smoother with the 64MHz LPF than without a filter, but you can still see a 12MHz square wave.
With the 3OMHz filter the same square wave is completely ironed out.

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