OK, let's talk about instrumentation and I agree that Lamotte’s product has been questioned. I ran an R&D lab for 20+ years for a company that made aquarium filters and commercial aquariums until the owner sold out and eventually all manuf. went to heck (China) and I “retired” (I was tired of the drive anyway). Although I was more into the mechanical and electrical part of the business, we had our own water chem lab with PhD on board, DNA sequencers, blah, blah and I'd fix, watch and study their instrumentation because they were clueless as to how the equipment worked. In my lab, I bought, made and built measurement systems across many physical parameters. The take away is this: accuracy and repeatability. I maintained several physical reference standards for comparison of my instrumentation. More important to me was the repeatability of the instrument. If it was repeatable, it could always be referenced to an absolute standard before submitting test results to UL , CSA, VDE or other standards based test labs. Believe me, manuf plunged ahead on every project with molds being cut, sales being lined up, etc. With hundreds of thousands of dollars already spent it was my job if my test results didn’t match theirs and approvals would be denied. Although there were plenty of skirmishes, my track record was 100% approval.
I have been helping my brother-in-law set up an exercise pool he was given. Like a “free” boat-you’ll spend thousands anyway. (Tip: Endless Pool helpline is not hydraulically savvy-good thing I am). Earlier, he had also acquired a $6,000 spa for $1,500 that he has been enjoying. But, he’s clueless about basic water chemistry, doesn’t care and I’m concerned that he or his family or the neighbor’s kids (or me and my wife for that matter) might get sick.
So, back to water chem 101 but how to measure? I'm old (71+) and although my hearing is excellent (having survived an earlier career in the rock and roll business) my eyesight is suspect. I tried some basic color comparison kits but couldn’t really tell the difference between slightly different shades even with glasses. Now, I never tried color comparison when I was young so I don’t know if it’s a matter of age or I never could do it anyway. So, even though it’s a very basic instrument, I decided on the Lamotte to get a readout. I read about possible non-repeatability on certain measurements but decided to get it anyway. I have had some strange Calcium hardness readings and I believe I read about this and supposedly it was resolved. Since I’ve used it only a few times I’m not ready to blame the instrument yet. Is it repeatable? My knowledge of sensors in general leads me to agree with someone in another post who opined that these inexpensive optical sensors are probably repeatable to a reasonable degree. I’m going to drill Lamotte on this issue and get a spec and it better be to my liking. For instance, my cat is diabetic, I’m using a meter to test him but the FDA allows a +/- 20% tolerance. 20% ?????? I called the manuf and asked how can I make a blood glucose curve with +/- 20% instrumentation??
If the Lamotte meter seems bogus I’ll get something else. BUT: when I do the DPD test for chlorine or Bromine, I can observe the reddish color. When Chlorine or Bromine levels are high, the color is a good reddish hue but when low, there is not much color. This is before the instrument produces a reading so, unless you are questioning the Lamotte reagents, the spa is not happy.