am I late to the party again?
Having used 'computerized' testing systems in pool stores I can say without a doubt that either a TF100 or a Taylor K-2006 is going to provide much more accurate and precise results. Strip readers (such as the ALEX system and it's cousins) are useless because of the inherent problems with strips.
Colorimeters (such as LaMotte Waterlink and the Hach units) are a bit better BUT still suffer from limitations from the range of the meter and are not necessarily more precise. For example, the TA test on the Waterlink system will read low when the FC is above about 3 ppm according to LaMotte tech support. Conveniently this helps to sell a LOT of expensive baking soda labeled as alkalinity increaser and then helps to sell a lot of acid to then lower the resultant too high TA and the resultant too high pH the next time the customer comes in.
The CH test with the same unit will read low when the calcium hardness approaches the upper range of the meter, whihc is around 400 ppm. This means that someone could come in with over 600 ppm CH and the system will say their calicum is only around 300 ppm. I have seen this happen too many times for me to even trust the CH test in this $1000+ SYSTEM.
FWIW, the CYA test on this system has a precision of +10/-25 ppm which means it's more likely to read low than high (very convenient for selling trichlor) but, more importantly, has a precisionrange of 35 ppm! This is worse than the somewhat subjective dispappering dot test we all know and hate!
For those pool stores that are using Taylor labs or other drop based systems you are often at the mercy of employees who are really clueless as to what they are doing. I have seen titration tests ended before endpoint and one time I was having my water tested at a competing store just for fun and the young girl did a DPD test and wrote down 2 ppm. I knew it was higher and asked to see the comparator. I told her that it looked like 4 ppm to me (which it was) and asked for another opinion. The owner came over and verified 4 ppm.
Bottom line, learn to test properly and do your own testing.
Keep in mind that the fancy equipment in pool stores serves a few purposes that are not really in the best interest of the pool owner:
1. it looks impressive and gives a printout so it must be better, right? (NOT)
2. It is designed to allow a whole battery of tests in a minimum of time. The LaMotte system will test 8-10 water parameters in 3-5 minutes. Strip readers are even faster. Minimize the time spent testing and maximize the profits, that's the ticket. Accurate results? We don't need no steeenkin' accurate results!
3. it looks impressive and makes the employee look like he actually knows what he is doing (NOT)
4. it helps to sell a lot of chemicals because the printout says you need them and the computer is always right (NOT)
5. did I mention it looks impressive and it gives you a computer printout?