DSO firmware version 3.2

Mine varies quite a bit between ranges. If I zero it on the 1V range, I get a 400mV offset on the 2V range for example. My experience with analog electronics makes me think it is unlikely to drift much with temperature, particularly over the ‘operating range’ of a human being, who must be operating it! Although the TL082 doesn’t have the best characteristics… Drift with time may be experienced, but this is likely to be over a very long period (years).

I would personally be very happy to calibrate the necessary points - particularly if I only had to do it once. What may be worthwhile would be to use an average of calibrated ranges for the cal of any range the user neglects to do.

I personally think it IS worth the effort. I hope you will consider it further!

But I can’t use it as Ref , may be add function to load xml as Ref? or Load Buf as “Virtual 2-nd chanal”?


My DSO Nano arrived today. After a quick check to verify that the hardware was fine, I upgraded to 3.21.

Dude it rocks!

My one request is that I do a lot of work on 125KHz RFID tags. As you may know, that’s a pretty standard speed for LF tags and the Nano has just enough bandwidth to work at that frequency.

Is there any chance that you could add 125KHz to the list of output frequencies from the PWM? It would allow me to insert a signal into a tag to test resonance.

Apart from my eternal gratitude, I’ll buy you a beer next time you’re in Western Australia. :slight_smile:

…and if you can’t or don’t want to…it’s all good. You still have my thanks for what you’ve done so far.

Assuming this is offset – what about range. Any qualified guesses on whether we’re good with one only, or better yet can someone share actual calibration data?

Developing for embedded devices isn’t quite like Windows. As an example, the buffer file is an image that would occupy more than 150kB of RAM, which is far more than we have to work with altogether.

You also have the option to capture settings in files and one approach could be to always do both and use the same file sequence number (e.g. load profile 100 and reference 100).

Look for the next update, there should be something for you here. (I’ tempted to stop by and collect that beer – right now it’s freezing cold where I alive).

Ok. Here is some calibration data. I did the calibration on the x1 1V range, where it needed an offset of -40mV and gain of -1.5%.

x1 attenuation:
Range Zero Vin Reading
0.1V 0mv 0.30V 304mV
0.2V 40mV 0.60V 640mV
0.5V 20mV 1.50V 1.52V
1V 0mV 3.00V 3.00V (cal range)
2V 400mV 3.00V 3.44V
5V 200mV 15.0V 15.2V
10V 0mV 25.0V 25.2V

x10 attenuation:
Range Zero Vin Reading
0.2V 48mV 0.60V 664mV
0.5V 40mV 1.50V 1.56V
1V 0mV 3.00V 3.08V
2V 400mV 6.00V 6.32V
5V 200mV 15.0V 15.2V
10V 0mV 25.0V 25.2V
20V 3.2V 25.0V 28.8V
50V 2.0V 25.0V 26.0V
100V 0mV 25.0V 24.0V

That didn’t format too well! It seems to have compressed multiple spaces into single ones. Oh well… Just copy/paste then replace spaces with tabs.
Basically it looks to me as if zero calibration is needed for each range, but we only need a single gain cal for each attenuation setting? I used a Fluke 8840A meter so the Vin readings are known to be accurate.

Thanks for sharing the calibration data.

To get a better handle on the deviations, I converted the data to relative values and compensated for offset before calculating range errors.

There appears to be some correlation across ranges for offset errors, but less so for range. Still there is sufficient variation to suggest that handling each range separately is better than trying to device some common scheme. I will consider this for a future update.

[code]Offset Range
0 % 1,3 %
7 % 0,0 %
1 % 0,0 %
0 % 0,0 %
13 % 1,3 %
1 % 0,0 %
0 % 0,8 %

8 % 2,7 %
3 % 1,3 %
0 % 2,7 %
7 % -1,3 %
1 % 0,0 %
0 % 0,8 %
13 % 2,4 %
8 % -4,0 %
0 % -4,0 %[/code]

Just installed this on one of the first batch dso nano’s ( yep i have had it that long)

Thanks ben I love it.