Measured soil pH can vary quite markedly with the method used. What I mentioned above is the preferred method used by soil chemists (allowing for the use of paper rather than pH meter). Most labs will use a 2:1, 5:1 water to soil or even 5:1 Calcium chloride to water ratio. Why? They are a lot quicker (and hence cheaper) and more convenient than doing it by a soil paste method, but also the water or calcium chloride can have a significant impact on measured pH, changing the reading by upto 1 pH unit. Can make it difficult to compare results across labs that used different methods reliably. If you are using the one lab to test samples consistantly, then no big issue

If posting samples off they need to be dry.

I have used the Sonkir brand 3 in one meters for measuring moisture only, in my grow bags for 5 years now and have found the moisture measurement to be pretty consistent. As far as the 2 other measurements go I can say the PH measurement is useless. And I never checked the light measurement at all. If you use it to check moisture only, it works pretty well. I have a much more expensive meter for checking the PH of my nutrient mix.

Dan