PoolDoc is exactly on the money concerning the ColorQ and the LaMotte Waterlink Express professional water testing stations have similar limitations (I used to use the system). When you convert a titration test to a colormetric test you limit its range and sensitivity, even with a meter to read the sample. I had converstions with LaMotte tech support when the system first came out and was told that for a $100 meter it's not bad but is is a $100 meter!