A tale of two pH meters

MonteCarlo

Hi guys,

So, I wanted to buy a pH meter. My reasoning is that the two chemical test kits I had did not agree, and it seemed convenient in general. The API kit with indicator liquid/test tube/color card was showing 7.2-7.6. The Tetra 6 in 1 EasyStrips were showing about 6.8. Not a huge difference, but is my water acidic or basic? I'll also add that I'm a chemist by training and have plenty of experience with high end pH meters.
Unfortunately, pro grade meters start at about $500 and the electrodes need to remain submersed in DI water or KCl solution, which is a pain.

First up was a relatively inexpensive meter from Amazon:

Sunzeal Meter Link

~$14. What a piece of junk. Even the plastic felt cheap, and the injection molding was poorly done with flash hanging off the sides. It felt like a dollar store flashlight. This meter comes with 3 buffer solutions for checking and calibration. The electronics is smart enough to detect which solution you are trying to calibrate with and do the appropriate math. However, like I said, its a piece of junk. Prior to calibration, I put it in water straight out of the tap and it read pH ~4.5. Not good. I tried to calibrate it with the first buffer solution, pH 6.86 nominal. The meter was so inaccurate, it thought I was putting it in the pH 4.01 solution and further warped the calibration to the point that it was reading a pH of ~ 3 in pure tap water. Needless to say, it went back to Amazon.

For the second meter, I realized that $15 just wasn't going to cut it. I selected this model instead:

Apera Instruments Meter Link

~$50. This is a nice little meter. Put it in tap water, got pH 7.5. Tested out both calibration solutions it came with and got values that are spot on. My only possible regret is wondering if I should have spent the extra $30 to get the unit with 0.01 accuracy instead of 0.1. So, at least for the time being, this seems to be a good choice. Next time I have access to a good balance and some volumetric flasks, I may make up some test solutions, but for now, thinks are looking up.
 

AvalancheDave

I don't think the extra resolution would be useful for aquariums.

I've always wanted to warn people about the super cheap pH meters on Amazon but never got around to it.
 
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MonteCarlo

I don't think the extra resolution would be useful for aquariums.

I've always wanted to warn people about the super cheap pH meters on Amazon but never got around to it.
Agreed, but you also get 5x calibration solutions, etc etc. I'm happy with my purchase.
 
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Johnez

The meter with .01 accuracy should be considered, not for the accuracy but for the replaceable probe. You *will* have to replace it eventually, better to buy the probe instead of a new meter. The meter is cheap enough tho so might be a wash.
 
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MonteCarlo

The meter with .01 accuracy should be considered, not for the accuracy but for the replaceable probe. You *will* have to replace it eventually, better to buy the probe instead of a new meter. The meter is cheap enough tho so might be a wash.

100% my rationale. Plus, I've shown the API liquid kit is probably good enough to determine gross swings in pH.
 
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