I agree with piper; ph readings are not as important as finding out your ammonia, nitrites and nitrates of the tank when cycling it- ph is more important to know when you are choosing fish or already have them in the tank (its still important to test the ph every now and then especially if you have fish in the tank, as if something causes the ph to fluctuate a lot it can be very stressful for the fish).
How are you going about cycling the tank?