I finally got a TF100 kit and started using it a couple of days ago. I'm also still using the Basic K-1001 and Bio Guard Multi Test 1200V kits that I had previously purchased. Figured I might as well use the K-1001 / BG kits up and have the ability to triple check my results while I'm learning. All tests are done using water drawn 10-12" under the surface, in front of the skimmer.
Here are the results:
TF100 FC 5.5 (down from 11.5 yesterday !?) Tested twice...
K-1001 FC 2
BioGuard FC 2
The PH on all three is slighly different. All are within the ideal 7.4-7.6 range, but they are different.