Hanna Calcium Checker Qusestion

NY_Caveman · Jul 27, 2018

Which steps in the Hanna Calcium test would most likely lead to a lower limit error resulting in a reading of 200 ppm?

Last night I used my Hanna Calcium Checker for the first time. I attempted the test three times. For each test the result was the lower limit of 200 ppm which is obviously not correct. This is a more involved test that other Hanna Checkers, but I believe I did everything correctly each time. I believe this unit (which I bought used) may just be defective. Before making that conclusion, I would like to narrow the possible variables for error. I am curious which steps in the test process would lead to an unmeasurably low Calcium level. I will note, I used 0 TDS RO/DI water for the tests and not distilled water. I will redo the test with distilled water as well before giving up on the unit.

I have used several other Checkers from @Hanna Instruments with great success. I believe I may just have a bad, used colorimeter. If anyone has any insight I would be most appreciative. Thank you!

rkpetersen · Jul 27, 2018

The most common source of problems with this checker is getting exactly 0.1 ml of test water into the cuvette. Then getting absolutely all of the chemical granules in. Then making sure that everything is well-dissolved before inserting it in the checker for a reading. I use 0 TDS RODI as well and get accurate measurements; distilled is not necessary, as long as your RODI water is truly squeaky clean.

Also, there's this, to tell you if your meter is working more or less correctly.

Randy Holmes-Farley · Jul 27, 2018

Traces of calcium in the blank also lead to low levels.

NY_Caveman · Jul 27, 2018

rkpetersen said:
The most common source of problems with this checker is getting exactly 0.1 ml of test water into the cuvette. Then getting absolutely all of the chemical granules in. Then making sure that everything is well-dissolved before inserting it in the checker for a reading. I use 0 TDS RODI as well and get accurate measurements; distilled is not necessary, as long as your RODI water is truly squeaky clean.

Also, there's this, to tell you if your meter is working more or less correctly.

Randy Holmes-Farley said:
Traces of calcium in the blank also lead to low levels.

Thank you!

NY_Caveman · Oct 23, 2018

Just a quick update for future searchers. I figured out my problem with the Hanna Checker. It was user error. @rkpetersen was correct that is was the 0.1 ml of test water portion I was doing incorrectly.

I had never used a device like the 0.1 ml pipette in the test. I had bought a used test kit and I believe the pipette was worn. It was not clear to me where the second stop was. I had opportunity to use a brand new one recently and it was clear that the first stop was about 75-80% depressed on the plunger. Far further than I was pressing. Next time I used the older pipette, I was able to find the stop no problem and it worked perfectly.

Hope this helps someone in the future.

Sal Amadeo · Nov 14, 2018

i just bought the Hanna checkers and my calcium is reading 309 not sure if I can trust it. using the red sea checker my calcium is 430. din't want to does if i don't have to, any suggestion?

rkpetersen · Nov 15, 2018

Couple things. First, you have to use good RODI water. Second, be super careful measuring out the 0.10 ml amount of tank test water. If there's a drop hanging at the end, make sure that gets included. Third, make sure all of the crystals get into the cuvette; the more that don't make it, the lower your reading. I use a small funnel to get them all in there very quickly. Fourth, give the cuvette a good number of mixing shakes before putting it in the checker. The liquid gets dark so you may not see it, but there can still be undissolved material after just 4 or 5 shakes. It's a slightly tricky test but I find it gives me pretty good accuracy.