Doing the math: 2.24V/1.5V = 1.493 or 49% high 18.14/1.493 = 12.15V. So just use this simple conversion factor for future use. It's definitely trustworthy to + or - 1mV. Definitely trustworthy. Completely. Undisputedly. You've read it in a forum post on the internet for god's sake; it's got to be right.
Got multiple flukes I like my fluke 179 has thermo couple and there really cheap on eBay. Very popular meter there. There’s hundreds of them on eBay. I like using my fluke 123 oscope too as a dvm. That’s really handy to use on cars. But for a all around meter for casual use can’t go wrong with a fluke clamp meter it measures current has a standard vom with leads but the ac current clamp really handy if you dabble in home ac work. There cheap on eBay or amazon like $90 you’ll own it for a life time. The $40 ones aren't bad either I keep that one in my car trunk. They also make an AC line splitter for a clamp meter that splits the ac cord on any ac plug so you can clamp the hot side only of any ac cord and measure it’s current draw. Also has recessed test points where you can measure the voltage too. Works good. I use it all the time. You can measure the current draw on anything in your house. Very handy with a clamp meter.