/diy/ - Do It Yourself

So im building this power supply and im trying to make sense out of the volt and ampmeter i bought that didnt come with a wiring diagram except some paint drawn images on ebay. Im having trouble implementing this meter in my setup. I hooked the meter up according to "wiring diagram 1" but the meter shows essentially double the current of what is actually pulling (tested with my DMM) So i started playing about with the adjustment pot which only changed it by 5% ish (no where near enough). Gave up and hook it up accordingly to diagram 1 (basically just cut off the negative that goes directly from the 12v supply to the meter. And the fucking thing works accuratley even under 4volts which is stated to be the lowest possible for only 1 PSU. So im not even understand where my meter is getting the power from at this moment but all readings are verified and accurate. Can someone help me understand what the hell is going on. Im a beginner as you can probably tell and i just want to wrap this up in a box and use as my stationary supply but im affraid of doing it now thinking something is going to catch fire.