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My Hanna Alk meter drives me nuts. "It ramps up slow".

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sjbro

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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?
 
I went through a phase where I was using a syringe and pushing the plunger fast introducing a bunch of bubbles. The C1 would take awhile to pull up a number, as would C2. My values were all off, usually way high. Once I realized I was doing that, I inject really slow and invert multiple times to get all the bubbles out, and clean the outside of the vial before placing it in the device. Now I get the insert C2 notification within 2-3 s reliably, and haven't had any issues with weird numbers. Hope this helps!


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Don't use different vials to calibrate and measure.

Make sure the vial is very clean.

Orient the vial the same way when calibrating and testing.

If those are your alk numbers, it's way low!


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Vhuang168 said:
Don't use different vials to calibrate and measure.

Make sure the vial is very clean.

Orient the vial the same way when calibrating and testing.

If those are your alk numbers, it's way low!


Sent from my iPhone using Tapatalk
Click to expand...
It sounds defective to me but you can try what others have said. I have the dkh version of it (same thing just reads out dkh instead of ppm) and it's always worked great. 30 seconds and I've got an accurate reading. There have been times I've thought it was off and retested with the same results.

The only other thing you could try is a reference solution. Fauna Marin sells one.
 
Thanks, guys. I ordered a reference solution and a new reagent bottle - they're on the way. I'll retest the meter with the reference and then try the new reagent.

I used to measure with just one cuvette, but since this meter gives me the first test numbers wrong, I had to switch to both. I made sure to wipe them clean and remove any bubbles from the glass.

Vincent, 143 ppm is 8dkh. This number is correct, I verified it with a Salifert test kit. Are you saying that my Alk is too low? My goal is to keep the Alk above 7 dkh.
 
sjbro said:
Thanks, guys. I ordered a reference solution and a new reagent bottle - they're on the way. I'll retest the meter with the reference and then try the new reagent.

I used to measure with just one cuvette, but since this meter gives me the first test numbers wrong, I had to switch to both. I made sure to wipe them clean and remove any bubbles from the glass.

Vincent, 143 ppm is 8dkh. This number is correct, I verified it with a Salifert test kit. Are you saying that my Alk is too low? My goal is to keep the Alk above 7 dkh.
Click to expand...

Ah, didn't see the 143. Just the 1st 2. 8 is fine.


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Unless this checker has been updated I believe the instructions call for gently
shaking the vile for 2min.
Agree with above that the vile must be keep clean in and out.

Dick flanagan
 
Yes, the instructions say to gently invert the cuvette 5 times. That's what I did. I was also careful not to have bubbles and dirt on the cuvette.

I have now the reference kit. I changed the battery in the meter to a new one, then tested with the reference. The first 2 tests were low again, 70 and 82. Then it stabilized at 94-95 which is correct (The valid result for reference is anything between 90 and 100 ppm).

Next I left the reference containers and the meter alone for 6+ hours. Then I tested again without shaking the containers. First 2 tests were low again, then the next 3 tests showed 95.

This pinpoints to the meter unit being defective. I'll get a replacement.
 
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