I have a TF-100 and am very happy with most of the tests.
However I find using the OTO PH test to be somewhat of a guess. The block seems to go from orange thru red to purple. However my test samples always seem redder than the block. Most the time I think I am somewhere in the range from 7.5 - 8.0 - but exactly where I am in this range is really a guess.
Any hints on making a more accurate reading?
My fill water is well water with high PH - so I really would like a way of getting a better measurement.
I have read some of the posts on digital meters here and the consensus seems to be the requirement to regularly calibrate makes them a bit of a pain.
My other levels currently are FC 5, CC 0, TA 100, CH 240, CYA ~45 (I find this one a bit of a guess as well)