Recommendations for new pH meter?

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rsportsman

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I bought what I believe is the same unit (~$15 on Amazon) just for curiosity, to see how/if it works. The instructions are quite rudimentary, and I could not get calibration to work, 2-point or 3-point. When reading their buffers on our Vinmetrica SC-300, the pH 4.00 was fine, but in my hands their pH 6.86 buffer measured 6.97, and the pH 9.18 came out 9.02. So I returned it.

So... I bought one of these cheap pH pens just to check it out. I'm not sure if it's the exact model used by pproctorga; there are seemingly a dozen brands on amazon.com that all look alike, I'm sure they all come from the same factory in China. My first day impressions:

- The package came with a pH pen, 3 buffer powders and instruction sheet. There was also an envelope saying 'Please check the warranty card inside'; this had no warranty information but indicated that I could receive a $30 Amazon gift card by contacting them. A little digging around suggests that this is their way of trying to get me to leave a 5-star review on Amazon. Not a great first impression.
- I made up the buffers in 250mL each distilled water as directed. I left the probe in an aliquot of the pH 4.00 buffer for 45 minutes in case the glass bulb needed rehydrating. Nominal pH reading at this stage was ~3.1-3.2, though I wasn't too concerned as I would always calibrate before use in any case.
- I used a wash bottle of distilled water to clean the probe between measurements. The instructions say to wipe the probe clean, though I don't think this is a good idea: you shouldn't touch the glass bulb on a pH probe.
- Calibration involved placing the probe in the standard buffers for a few seconds while stirring gently, then holding the CAL button for 5 seconds. The instrument is supposed to autodetect which buffer you're using. The instructions say that just one buffer (6.86) is sufficient for accuracy of +/- 0.1 pH unit, but to calibrate in all 3 buffers for maximum (+/-0.01) accuracy.
- Calibration in the 6.86 and 4.00 buffers seemed fine, but I could not get it to register the pH 9.18 buffer. Following the 2-point calibration, the value of the third buffer seemed to be around pH 9 - but on pressing the CAL button it would always read 6.86.
- I figured that the 2 lower pH points should be sufficient for testing wine samples, though I don't know how their algorithm works; there are no instructions suggesting that you can use just 2 points. Nevertheless I repeated the calibration with the 6.86 and 4.00 buffers, and tested a sauvignon blanc sample that I had lying around. This measured as 3.60, which seemed reasonable; I knew that this particular wine was on the high pH/low acidity end of the scale.
- Repeat measurements of the buffer solutions gave values of 4.03 and 6.87, which I thought were surprisingly consistent.
- Repeating the wine and 2 buffers again gave values of 3.57, 4.07 and 6.92. Again, not too bad for a $10 instrument but maybe a bit drifty.

I think I've learned enough to conclude that while this isn't a total bust, it's definitely a bit squirrely. I would use this to get quick and dirty pH estimates where I didn't care about the 3rd significant figure, but I will look around for a more robust solution for my winemaking endeavors. All of the other options mentioned in this thread (Milwaukee, Extech, Apera, Hanna) seem like they might fit the bill.
 

BarrelMonkey

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I took my buffers and $10 pH pen to work today and compared it to the Thermo Orion Star A111 that we use for measuring pH in juice and wine samples. The results were remarkable and have led me to reconsider my evaluation of the pH pen.

First, I switched both instruments on and let the probes sit in pH 4.0 buffer for 10 minutes. The Thermo read 4.04 and the pen read 4.02 - both quite acceptable in my opinion since it’s been a while since the Thermo was calibrated.

I calibrated the Thermo meter at pH 7.0 and 4.0 and used it to test my pH pen buffers (from the samples included with the pen). Results:

Nominal pH 4.00, measured pH 4.00
Nominal pH 6.86, measured pH 6.84
Nominal pH 9.18, measured pH 9.15

This confirms that my buffers were good; in fact I was amazed at how close to the theoretical values they were.

Now to test some wines. I measured 2 separate wines using the Thermo meter as pH 3.03 and 3.45; both values were as I would expect for these wines. Next, I calibrated the pH pen using the pH 6.86 and pH 4.00 buffers and measured the same 2 wine samples. The pH pen gave values of 3.02 and 3.43 (!)

Bottom line: I was astonished at how closely the measurements with the $10 meter tracked with those of the (much) more expensive instrument. Even replacing just the probe on the Thermo costs ~15x as much as the cheap pH pen. I will re-test in a few months (harvest time!) and see how it holds up.
 

BarrelMonkey

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Update after ~1 month: I'm revising my opinion, looks like this is a piece of junk after all.

I equilibrated in pH 4.0 buffer as before and tried to repeat the calibration procedure. Although the pH 6.86 calibration worked, I couldn't get it to calibrate at pH 4.00. Tried several times, also tried to reset it by removing and replacing the battery - no luck. After calibration at the single pH 6.86 point, the pH 4.00 buffer read 4.06-4.08 - so perhaps still usable if you just want a ballpark estimate, but it isn't something I would want to use for an important measurement.
 

Michael T

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I have an Apera PH60 meter and have had no problems with it. I also purchased the buffer and storage solutions, so the price came to about USD 100. I don't use it often but it seems to be a quality piece of gear.
 

JBP

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Ditto - I just did a forced side-by-side comparison with a $13 pH meter (well-rated on Amazon) and the Apera pH60 (AI311). The quality difference was profound and the results significantly different (using the word significant as a scientific academic).

Thought I might save the cheap one for rough ROM back-up. Nope.
 

Ignoble Grape

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Ah, sorry, just saw the original post of under $100.

Anyways, I finally broke down and got a commercial grade meter. Reached out to a friend who works in the lab for a producer in Sebastabpool.

They use a Beckman portable pH meter, but it is old, and replace the probe every couple of years but with home winemaking use that shouldn't be necessary.

Her outside lab guy recommended ebay. It might sound a little sketch by he says he has purchased both new and used equipment with only success. She trusts his experience as he runs a highly accredited lab.

I wound up getting: Thermo Orion Star A221 pH Meter off of ebay. Very happy with it. It was $280, but I hope to never buy another pH meter again.
 
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