DSO203 GCC APP - Community Edition (2.51+SmTech1.8+Fixes)

[us9igy]

With 5.1 no problems whatsoever.
Wildcat, thanks once again!
Tested with size optimisation - no noticeable difference...

[borland]

What I would be curious to know though, is the difference, if any, between the ADC versions used in the 2 devices you tested. The schematic for HW 2.81 specifies a HWD9288 from Chengdu Sino (CSMT), which is what I had in my device. Another, earlier HW V2.70 device I have might also have had one of these or possibly something from another source, can't remember, while the early V2.60 versions have Analog Devices chips.

I replaced the ADC chip on my DSO which was showing abnormal CH(A) traces. Used an Analog Devices AD9288-80 chip which I purchased from Digikey.com.

The old ADC chip was the same as yours; markings were difficult to read, but appeared to be HWD9288BSTZ-40.

Attached, are screenshots of BEFORE and AFTER ADC chip upgrade with WC5.1 and FPGA V1.1 installed. Screenshots for "full speed oversampling" and "normal buffer" modes.

[Wildcat]

Thanks again for the feedback. I think the results speak for themselves.

For those with issues with their DAC using V5.1 and it's FPGA with HW 2.81 an alternative would be to use the FPGA supplied with V5.0 . This should work fine with V5.1 and HW 2.81 with the problem DAC's, and while it would not have full speed sampling, it would provide improved level based triggering accuracy and overall triggering stability at the fastest timebases over the factory FPGA. It would also provide auto mode freerun behavior selection.

[frater]

A few days ago I ordered a DSO202, but something went wrong with the order. This will be fixed soon, but I'm now thinking of cancelling the order to get this DSO203 instead.

Its price is a bit higher, but I think it might be worth it.
I haven't owned an oscilloscope for 30 years now, but would like to have one again. If I'm getting much more "bang for the buck" with this one I will cancel that order of the DSO202.

I didn't know anything about a custom firmware like this one.
Is there one for the DSO202....

I would love to get some input before that order goes through....

Thanks

[Jerson]

Frater,

DSO203 has many custom firmwares to try out. 4 channels to work with. Bandwidth is much better.
My choice is DSO203.

Jerson

[frater]

I appreciate your reply and I know it's somewhat off-topic, but I had no time to research it.
It seems my order for the Nano is now cancelled and I can order this DSO203.
The order needed cancelling anyhow, even if I still took that DSO202

It does seem to be a much newer device (the touch), but I think

Another question.
They speak of 2 analog channels and 2 digital channels on this one.
The dso202 has 2 analog channels, does it?

[Jerson]

The touch 202 is a newer device and has good eyecandy but less analog bandwidth. However, I can swear by the DSO203 I own for a some time now. If you need more info, please open another thread so as not to divert this thread topic.

[indman]

Hi, WildCat! I want to thank you for excellent operation and to wish a good health!
I updated the DSO203(HW 2.81 SYS1.64 DCU 3.43) on version 5.1 and used FPGA 1.1. I checked operation of an oscillograph in the mode of the complete buffer. Results are visible on a photo. Problems begin in the AC1V,AC2V,AC5V mode. In channel B there are no such problems.

[Wildcat]

Hi, WildCat! I want to thank you for excellent operation and to wish a good health!
I updated the DSO203(HW 2.81 SYS1.64 DCU 3.43) on version 5.1 and used FPGA 1.1. I checked operation of an oscillograph in the mode of the complete buffer. Results are visible on a photo. Problems begin in the AC1V,AC2V,AC5V mode. In channel B there are no such problems.

Thanks for the feedback.

This is not an issue with the ADC. This is noise picked up by the preamp. Noise from the ADC would show up the same on the screen regardless of the vertical range used.

I had a similar problem with my unit, causing thickening of the trace on ChA in full speed mode similar to yours. Turned out to be a bad ground. The metal frame that holds the LCD is grounded by a stick-on metalized tape to one of the input or generator output jacks and it was making an intermittent connection. You could move the plugs around when inserted into the jacks and the noise would cut in and out.

In any case, this is definitively noise picked up by the front end in the input section. The device switches in a different op-amp when set to ranges of 1V/div and above. Looks to me like noise from the rest of the circuitry is being leaked into that section, possibly from a bad ground, capacitive coupling, power supply issues, etc... ChA seems more susceptible to this for some reason, probably because of the location of the circuit traces on the board. The LCD is also a prime cause of radiation into the circuitry if it's frame is not properly grounded, since it covers the entire board. The grounding method is rather poor, relying on simple pressure of part of the frame onto the metalized stick-on tape.

As I mentioned previously, the full speed mode will, by it's more sensitive nature more readily reveal any noise, whether generated by the circuit you are monitoring or generated inside the scope itself. This is in fact part of what makes it useful. Also, loose or defective probe plugs making a poor ground connection where inserted into the input jacks can cause problems like this.

You could try reverting to an earlier FPGA, it's possible the extra circuitry for the full speed mode is causing an increase of noise on the supply lines, and an increase in this noise, but since it's only appearing on some of the ranges, I suspect that some hardware issue in the preamp is causing this, and that it would also show up with earlier FPGA's, though possibly to a lesser extent. Notice that the "spike" part of the noise shows up in your screenshots even when not in full speed mode.

[indman]

Hi, Wildcat! Thanks for the detailed answer, I have understood you. It is interesting whether other owners of this version have such effect?
Prompt how you have solved a problem with grounding of LCD?