SRH2, Diagnostic Sling Psychrometer

I'm not a tech, but am reading books on how to charge residential A/C units. In a nutshell and simplistically explained... To "properly" charge a non-TXV system you need a psychrometer. You need to obtain the outside, inside, and inside wet bulb temps. With the proper A/C chart you manually calculate your target superheat (amount of system charge). The Fieldpiece psychrometer is more than a regular psychrometer. It also displays what your target superheat should be. For a few bucks more it will make the calculations for you without needing a chart, it will do it quicker, and more accurately to get the refrigerent charge dead-on. I've never seen a tech use a psychrometer when I have hired one, but to do it right, accurately, quickly, and easily I use this for my rental houses and family. The price is right and I would not do without it. Fieldpiece makes excellent products and has knowledgable tech support. Go Fieldpiece!