I'm a cheap-... so I was hoping not to have to buy anything else
I understand not wanting to buy anything anymore, this becomes an expensive hobby (yes I said hobby) but a meter is a good investment. I have a fluke 77 and use it constantly and not just for vaping.
Craftsman Digital Multimeter: Meter at KMart
20 bucks on this and you can use it for other things. checking battery voltage, car battery voltage. resistance of atomizers, you get the point.