Maintain accurate test results with your Hanna Checker
One thing to keep in mind is that all of the Hanna Checkers work by measuring light transmitted through little glass cuvettes. So, keeping them clean is essential to getting long-term, accurate results. The easiest way to do this is cleaning the outside of the glass of lint, oils and fingerprints.
Keeping the inside of your cuvette clean is extremely important also, so make sure to always empty and rinse it as soon as you complete your test. The reagents used in the checkers contain a dye, and most of them will stain the glass if left sitting too long. Unfortunately, once the glass is stained it pretty much has to be replaced for accurate results going forward.
If you accidentally forget to empty your cuvette after testing, Hanna does sell replacements at 4 for $20, which is kind of expensive. Honestly, if this happens you are likely better off purchasing the standard for that particular checker and using the zero/blank cuvette from it for future tests.
Speaking of standards, for those of you that take your testing very seriously, you can pick up one of these kits to measure your checker against. Most of them come with a blank/empty cuvette as well as a solution with a known amount of what you are testing for, along with a certificate of analysis.
Something to keep in mind; like every test or colorimeter, there's always some margin of error. Don't be shocked if your 1ppm total chlorine test doesn't read exactly 1ppm.
Some of the standards are reusable while others are single use, so be aware of this when you are buying them.