Wrong gain settings for SainSmart DDS120

[Ho-Ro]

This report from eevblog tells us:

Have problem with DDS120 and OpenHantek6022 (b188)
I try use my DDS120 again, find new software OpenHantek6022 (b188) and try configure all again.
I see that OpenHantek6022 not read calibration data from DDS120 and zero is not in zero and gain wrong.

Proposed solution: Change these lines:

OpenHantek6022/openhantek/src/hantekdso/models/modelDDS120.cpp

Line 34 in c365d9b

specification.voltageLimit[0] = { 40 , 100 , 200 , 202 , 198 , 198 , 396 , 990 };

OpenHantek6022/openhantek/src/hantekdso/models/modelDDS120.cpp

Line 35 in c365d9b

specification.voltageLimit[1] = { 40 , 100 , 200 , 202 , 198 , 198 , 396 , 990 };

to:

specification.voltageLimit[0] = { 32 , 80 , 160 , 155 , 170 , 165 , 330 , 820  };
specification.voltageLimit[1] = { 32 , 80 , 160 , 155 , 170 , 165 , 330 , 820  };

Also adapt

OpenHantek6022/openhantek/src/hantekdso/models/modelDDS120.cpp

Line 51 in c365d9b

double calibration = settings.value( ranges[ iii ], ch == 0 ? 1.18 : 1.21 ).toDouble();

double calibration = settings.value( ranges[ iii ], "0.0" ).toDouble();

[Ho-Ro]

@msiegert Please check how the scope behaves without *.conf file in place.
Target should be to get a reasonable display on 1st usage without need of special user action.

[msiegert]

Sorry, but I can't test this right now. My DDS120 is in Japan (had to leave it there to monitor CAN bus communication on a prodction tool I am working on). I bought a LOTO OSC482 as a replacement since the DDS120 seems to be end of life/out of stock. But despite the fact that the USB PID/VID are the same as the DDS120, the configuration is somewhat different from the DDS120 and I had to patch the firmware and OpenHantek6022 a bit to get it to work. I am not sure how to merge my changes to OpenHantek6022 since those will break support for the DDS120...

[Ho-Ro]

Ok, no problem, I've just removed your 1.18 : 1.21 correction if there is no conf file and therefore adjusted the specification values accordingly, so it should give a +- 5% accuracy for 1st time users - only offset has to be adopted individually.
Pity that the LOTO has same PID/VID and behaving differently, any chance to check other USB id values?

[msiegert]

I'll see if I can find a differentiation parameter between the OSC482 and the DDS120 as soon as I get the DDS120 back, but this will be a while. There is some hope, the OSC482 is detected as:

OSC482:
Product ID: 0x8102
Vendor ID: 0x8102
Version: 0.00
Speed: Up to 480 Mb/sec
Manufacturer: OS19040
Location ID: 0x14200000 / 25
Current Available (mA): 500
Current Required (mA): 500
Extra Operating Current (mA): 0

by my Macbook. So we should be able to use the name and/or the manufacturer to distinguish between the DDS120 and the OSC482