Products > Test Equipment
OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
Gyro:
Welcome to the forum hexalamy.
I'm glad you've spent time reading through the thread, and in particular, that you have pulled out a relevant mains measurement safety discussion. As far as the "just once" goes, that's quite sufficient to take one life. By "controlling mains power" I'm thinking that you may be intending to do someting with SCPI data on the PC, but I'm not sure. I can think of many better ways of doing most things related to mains sensing (voltage sensing? maybe waveform distortion?) that don't involve a scope and danger of the PC hanging etc. I don't know what you intend for the 'control' part either - this is a safety risk area too.
For other readers. just a reminder that the VDS1022I is galvanically isolated at the USB interface, so the BNC skirts (ground clips) and metal case are not grounded, this is intended for ground loop isolation and PC USB port protection rather than elevated voltage working.
Even with the galvanic isolation, I still wouldn't risk connecting the probe ground clip(s) to mains Neutral, there is still too much risk of accidents causing live case events. The way I would approach it is to connect the ground clips to a solid mains earth/ground and then probe the Neutral wire. If there is no significant voltage or waveform, I would then probe live relative to mains earth/ground. There shouldn't be any significant voltage between solid ground and Neutral (if there is, the first thing to investigate is why?), but you may find that there is a nuisance noise waveform. If this is the case, probing both Live and Neutral (still both referenced to your solid earth/ground) and using the scope Maths function (select Invert CH2 and CH1+CH2 for the Maths waveform) will then give you the differential waveform between Live and Neutral.
A note about probes. The switchable X1/X10 probes are always a danger. The VDS1022I will only tolerate high voltage with the probes in the x10 position - accidentally selecting X1 will blow the scope input, an easy error to make. In X10, the scope is specified for +/-400V peak - bear in mind that mains peak will hit around 340V on 230-240V AC mains, and that doesn't include spikes and surges, there is very little headroom and dangerous spikes can go to several kV. A scope doesn't have the safety protection of an expensive CAT III DMM, it is only CAT 1 at mains voltage - a heavy surge will make something (probably the probe) explode! For higher voltages, X100 fixed probes are safer, but still not normally CAT rated.
As somebody starting out, I am hoping that you will treat the above as educational rather than practical advice. I would really warn you against doing this, but I can't control whether you do. Hopefully the above will give you more knowledge to be safer.
hexalamy:
Thank you for the explanation, Gyro.
Ah, after reading your comment, I realized I had misunderstood some points. It's good to me that I shouldn't attempt this without thorough deep knowledge and proper equipment!
Thank you for your kind and detailed response.
TizianoHV:
Just after getting it (VDS1022insulated version) I connected it to mains to try out the FFT function. Since the 50V/div range isn't enough to measure 230V I added in series a 10Mohm resistor. This makes everything much safer, because even if you set the probe to 1X everything should be fine. Still, mains voltage it not it's not his job. I always use a dedicated DIY wattmeter (attiny microcontroller + high voltage divider + isolation) build with all the protections.
Here a story: a few years ago, before buying the VDS1022I, I was repairing a switching power supply, and I was using a non-isolated USB scope. To get the required "isolation" I was using a laptop. It wasn't the first time using that setup, but in those days I was stressed for some university exams and I forgot to disconnect all the USB ports of the laptop. Since the ground probe was connected to the negative of a full bridge rectifier (for half period stays at Live potential!) after applying power around 30A went through the GND probe->oscilloscope->usb cable->laptop->other grounded USB port (connected to a multimeter).
At the end I fried both the oscilloscope and the laptop. Luckily, the laptop was old but still I had to buy a new one!
A sketchy setup will be ok for a quick test, but it won't be ok for everyday work.
--- Quote from: Gyro on November 15, 2024, 07:18:17 pm ---If this is the case, probing both Live and Neutral (still both referenced to your solid earth/ground) and using the scope Maths function (select Invert CH2 and CH1+CH2 for the Maths waveform) will then give you the differential waveform between Live and Neutral.
--- End quote ---
Doing that will get rid of the ground probe, the only issue is that, due to the high capacitance to ground of the VDS1022I all the voltage will drop on the probe measuring Live (so if you need to measure 230V it won't help)
SIBtronics:
--- Quote from: Gyro on November 15, 2024, 07:18:17 pm ---In X10, the scope is specified for +/-400V peak - bear in mind that mains peak will hit around 340V on 230-240V AC mains, and that doesn't include spikes and surges, there is very little headroom and dangerous spikes can go to several kV. A scope doesn't have the safety protection of an expensive CAT III DMM, it is only CAT 1 at mains voltage - a heavy surge will make something (probably the probe) explode! For higher voltages, X100 fixed probes are safer, but still not normally CAT rated.
As somebody starting out, I am hoping that you will treat the above as educational rather than practical advice. I would really warn you against doing this, but I can't control whether you do. Hopefully the above will give you more knowledge to be safer.
--- End quote ---
are you sure its +/-400V? on amazon it says 400v pk-pk which to me indicates +200V to -200V, however i have to agree to the rest of the statement, and to add to this id not trust these probes you get with the scope to survive the mains tbh. while they arent crap or too bad feeling, especially in the switch and the plastics you can feel the cheapness. https://www.amazon.de/OWON-Oszilloskop-Dual-Channel-USB-Isolation-Oscilloscope/dp/B07CJH57XR?crid=RM4IUBUJZY45&dib=eyJ2IjoiMSJ9.u-zaJgbZ7zNa74s2ETl0RA.PjIlSIuJHZbPYdx_y4sR1PNRB59gABRc5pKPh98fMwI&dib_tag=se&keywords=owon+vds1022i&nsdOptOutParam=true&qid=1731840236&sprefix=owon+vds%2Caps%2C147&sr=8-3 user manual also says the same thing, unless my understanding of pk-pk is wrong
TizianoHV:
With the 10x probe it goes up to 50V/div (or +-250V)
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