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Old 07-18-2014, 08:43 PM   #1
hellbent77
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Default Stability report on a new Hach Pro+ pH meter

As an avid lurker, I've learned a lot from you all. I thought I'd post my stability test results to contribute a trifle at least. Maybe it'd help somebody decide what they want to buy or not buy.

I got the Hach Pro+ and used it for the first time yesterday. It came with only a few micro-specs of liquid in the sample cup. I missed the part of the instructions that said it should be "conditioned" in tap water for a couple of hours before use. Without doing this, I calibrated it twice and did a stability test yesterday. Stability test results were good for one hour (4.01 to 4.03) but got wobbly after that (rising to 4.11 after 3 hours).

Overnight I let it soak in Hach storage solution with the buffer containers nearby so they all came to the same temperature by morning.

This morning I calibrated again giving it 7 minutes to soak in 7.00 and 8 minutes to soak in 4.01 before saving the settings.

Then I did a stability test with the results below. The extra care taken helped a lot. It is so stable, I kept thinking the display lock was on. As I read in the lurked posts, it does take some practice to learn how to use it, to get confidence in your technique, and to get confidence in the meter.

Time is hr:min

Time pH Deg F
0:00 4.00 71.1
0:05 4.00 71.1
0:10 4.00 71.6
0:15 4.00 72.1
0:20 4.00 72.5
0:25 4.01 72.7
0:30 4.01 72.9
0:35 4.01 73.0
0:40 4.01 73.2
0:45 4.01 73.4
0:50 4.01 73.4
0:55 4.01 73.6
1:00 4.01 73.8
1:05 4.01 73.8
1:10 4.01 73.9
1:15 4.01 74.1
1:20 4.01 74.3
1:25 4.01 74.5
1:30 4.02 74.7
1:35 I tested some 7.63 pH pool water
1:40 4.05 75.4 <-- meter not stabilized after one minute soak in 4.01??
1:45 4.04 75.6
1:50 missed test time
1:55 4.02 75.7
2:00 4.02 75.7
2:15 4.02 75.9
2:30 4.02 75.9
2:45 4.02 75.9
3:00 4.02 75.9
3:30 4.02 75.7
4:00 4.02 75.6
5:00 4.01 74.7
5:40 4.01 74.5

I can't hover over it any more today. Maybe I'll let it sit all night and see what it looks like tomorrow morning.

Is there a way to read calibration info like slope % with autocalibration on the Pro+? I couldn't find a way on this unit.

Anyway hope the info helps or interests someone.
Cheers!

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Old 07-18-2014, 09:43 PM   #2
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No, I don't believe there is a way. The meter itself doesn't display offset and slope and there is no way to get a mV display (from which you could calculate slope and offset) either AFAIK.

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Old 09-05-2014, 01:13 AM   #3
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My Hach didn't work on the second brew day I wanted to use it. The pH display only read "----", so I brewed without it.

I emailed Hach about it and confessed to dropping it a couple of feet onto a towel-covered counter once. The storage cap was on at the time and didn't come off. I didn't think that broke it, but felt obliged to tell them about it.

They replied quickly asking for answers to a few questions and asking for photos of it. I sent them and offered to pay for repairs if they felt I broke it. If the repairs were a big percentage of the original cost, I wouldn't have opted out of paying.

The next day they said to call them to arrange for a warranty replacement, which I did. I don't even have to return the faulty one! Impressive support!

I may take the old one apart and look for an electrical problem. It shows a pH reading for a couple seconds before going out when first turned on. There could still be some life left in it. Temperature displays just fine.

So ends my report.

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