Sometimes, soil pH meters will not register any measurements when you stick them into your soil. It can vary but some will provide more accurate readings when the soil is moist. But, the soil may not “need” to be moist to achieve an accurate reading. With some pH meters, some different variables will affect the accuracy. Not only the moisture but also the current humidity outdoors could lead to an incorrect reading of the actual pH level. Say the humidity outdoors is 100 percent; it may not be wise to test your plant’s soil at that time as the reading could be ineffective.