DIGITUS DN-170010 best sample of worst ups ever made (electric evaluation)

[Kiriakos GR]

One friend of my gave me this DIGITUS DN-170010 ups at a time that my own ups (large APC ups)  this was damaged and out of operation.
I was waiting for a spare part to arrive and therefore this was better than nothing.
Now that my own SUA1000XL this is back in action and fully refurbished (looking as new), I thought to have a look at power quality that comes out of this DIGITUS ups.

What attracted my attention so to do this inspection was noises as clicking sounds coming from this cheap ups when was operating in back-up mode.
The noises was like clicking relay but actually this sound was coming from output Mosfet, some type of pulse this sound as hammering.
This sound can simile as someone saying the words: klong - klong - klong (repeatably).

Bellow are pictures of what I managed to capture by my oscilloscope speaking of output power quality.
Yes it is a terrible ups with noisiest square wave output.
But worst than all this is voltage output at just 50% of load (150W light bulb) and this is around 200 ACV. 

From now and on I am not going to use it again as ups, but it an interesting working specimen as dirty square wave generator.
Therefore I am going to use it about testing True RMS multimeter at ITTSB Blog