I have removed a heavy transformer from a UPS box. The rechargeable battery had gone and the replacement battery costs almost as much as a new UPS. On the 12v side are three thick wires; blue, red in the centre and black. The other side of the transformer (the 220v side) has in order the following six wires; red, black, green, black, red and blue. I want to use this transformer if possible as a source of 12v with a centre tap to operate a 12v DC model railway. In the setup in the UPS the red wire in the centre of the 12v side is connected to the first red wire of the 220 side. How do I check out the voltages safely with a multimeter?

 

I do tht every time.
I always series connect the 220V side.
But I dunno what type you have.
Post a picture.
If you have a DVM, first check the continuity and mark them down on a piece of paper.
Next note down the resistance of the wires from each wire to all of them. Note them down and show us

 

I do tht every time.
I always series connect the 220V side.
But I dunno what type you have.
Post a picture.
If you have a DVM, first check the continuity and mark them down on a piece of paper.
Next note down the resistance of the wires from each wire to all of them. Note them down and show us

Thank you for your reply. I followed your advice and checked the resistance between the various wires with a digital voltmeter. My dvm is not a Fluke or anything similar so I had a reading of 1 on all the settings I tried. My mobile telephone is steam powered so it doesn't have a built in camera and I tried to view the transformer with my Skype camera but the image on the screen didn't remain. Is there any way I can utilise this webcam to send you a picture of the transformer?

 

I believe a web cam can tale good pictures with enough lighting.
All web cam software can take still pictures, I think.

The reading '1' you are getting is because your DVM is set to diode range or continuity.
Try the Ohm or "omega" logo range