Frank's Random Wanderings

Welec Oscilloscope – Watch Out

Last year I was in the market for a cheap digital oscilloscope. After much looking around I finally settled on a Wittig Welec W2022A oscilloscope. 2 channels, colour VGA display, 1 GS/sec sampling rate, it looked awesome.

I purchased mine off ebay from tek4you_eu and it arrived in a week or so.

The big problem I had with it was noise on the inputs. Lots of noise. So much noise that I could regularly have one or both channels of the scope triggering, without even a probe connected to it!

This made it pretty useless for capturing single-shot events, like a lot of digital signals. Say you have a serial signal, like an RS232 line, which you want to catch. So you set up the scope for single-shot, but before the RS232 message is even sent, the scope false triggers on its internal noise. So you end up with a scope capture of nothing – you missed your RS232 message.

Similarly, it’s pretty useless for measuring low-level analog signals, because the front-end noise tends to swamp your actual signal – you cannot tell if the noise & glitches you see on the scope are real, or not.

In the end I was forced to sell the scope, because of its problems and uselessness for what I needed it for. I ended up selling it cheap to someone for whom those problems wouldn’t be an issue (he wanted to look at 120V mains waveforms) so I didn’t feel guilty for passing it on.

My experiences were not unusual – others have this & other problems too. Read this review:

I tried all the firmware versions to no avail. There are also folks trying to build their own firmware for this scope; perhaps one day they’ll get it done, and perhaps it’ll help. Who knows.

But in the meantime, if you’re looking for a cheap scope, I’d suggest staying clear of this brand. In the end, I purchased a “known brand” scope second-hand off ebay instead. When it comes to cheap oscilloscopes, it’s a jungle out there.

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