Long story short: I had a Hanna Alk ppm meter similar to this one http://www.bulkreefsupply.com/alkalinity-colorimeter-hi755-hanna-checker-hc-marine-water.html. After less than 6 months use it broke, its internal LED would not turn on. Before that it worked really good. I contacted Hanna support, and they were super nice, shipped the broken unit to them, couple days letter they confirmed that it is broken and sent me a replacement. Well, this replacement has an interesting behavior. It ramps up slow, first 1-2 measurements on the same samples are wrong. For example, here are the tests I did today (and that's my process pretty much since I got this replacement unit): First I filled both cuvettes with tank water and I prepared 1 ml of reagent in the included syringe. I also wiped the cuvettes clean with a microfiber cloth. Test 1: - turn the unit on. - insert cuvette 1 into the unit. Press C1 - wait for display to change to C2, take the cuvette out, pour in the reagent, invert the cuvette 10+ times. - wipe the cuvette again, put it inside the meter, press button - after a few seconds it says 29 !!!!!!!!!! Test 2: - turn off the meter, then back on. - place in cuvette 2 (clear water), press button, wait for C2 - place in cuvette 1 (water +reagent) press button ,wait for result - it says 97 !!!!!!!!! Test 3: - repeat test #2. - now it says 143 ! Test 4, 5, 6: repeat test #3. Same result, 143. I thought that maybe the reagent is slow to color the water. But the reagent is new, it is actually the one they sent with the replacement. And even if I wait in Test 1 for a minute or so, it still says a low number for the first 2-3 tests. And then the result is very stable, at most varies by +/- 2. Has anyone experienced something similar? Am I doing something wrong?