Revised buying guide for pH meter (based on the book Water)

[Epos7]

UPDATE 8/9/16: It turns out I received a bad batch of pH buffers from Atlas Scientific, leading the the calibration errors. The Hach meter was not to blame after all.

I'm planning on brewing tomorrow, so tonight I decided to try out my Hach Procket Pro+ for the first time to test the pH of my water after my additions. FWIW, I work in a lab and use a laboratory pH meter on a weekly basis.

First observation: as mentioned in an earlier post, the Pocket Pro+ box arrived covered in some sticky/slimy substance which I later determined to be soap. I purchased the meter through Hach's Amazon storefront, but as it was fulfilled by Amazon I can't say if this is Hach or Amazon's fault. Strange and a little unsettling, but everything inside the box was unaffected.

The included instructions don't contain any information about probe storage, but they direct you to the online manual, which is in the form of a PDF. This manual does not have any storage information either, so it's not really clear if the probe is intended to be stored wet, as with most meters, or if it matters at all.

I set out to perform a three point calibration using brand new calibration solutions, at room temperature (72F). The sensor and sample cup were rinsed with distilled water and wiped dry with Kimwipes before calibration and in between each step. The first calibration attempt did not succeed. After calibration completed, "SENSOR?" was flashing on the screen. According to the manual, this has something to do with either a dirty sensor or a calibration slope plus/minus 10-15%. I had cleaned the sensor before starting, but decided to try again.

I attempted to perform two more calibrations after the first. The second calibration resulted in "ECAL" and the calibration icon flashing with a question mark next to it. This indicates a calibration slope greater than plus/minus 15%, according to the manual. The third calibration attempt produced the same results as the first, with "SENSOR?" flashing on screen.

Other observations: the paint for the fill line on the sample cup more resembles a dry-erase marker than anything permanent. Having used the meter one time it has smeared and started to come off. I suspect it doesn't stand up to the calibration solutions. The fill level isn't critical as long as the sensor is submerged, so this isn't a huge deal.

So, it looks like I received a dud.

 

[brick_haus]

Hach advertised a 6 week lead time on my replacement probe (I broke the original, my fault). The probe arrived in less than two weeks. After using pocket pH meters daily for 30 years at work, the pocket pro+ is by far the best one. I also have a MW102, but use the Hach for its quick readings and stability.

 

[Epos7]

Amazon had the Hach Pocket Pro+ Multi2 in stock, so I decided to purchase that, and it arrived today. The TDS feature will be useful to monitor the life of my RO filter.

I ran into the same problem calibrating this unit as I did with the last unit. I'm beginning to suspect bad calibration solution, in which case my original Hach meter was likely fine. Have the Hach owners on this board been performing a three-point calibration? If I can identify the calibration solution as the culprit, I'll edit my previous post to reflect that the Hach meter was not to blame.

 

[brick_haus]

I've been doing a 2 point calibration. 7 and 4

 

[CadiBrewer]

Two point calibration here. Works great for two plus years.

 

[ajdelange]

A 3 point calibration is really two two-point calibrations one for the 4 to 7 pH range and one for the 7 to 10 range. There is no benefit in a 3 point calibration if you are not measuring pH above 7.

Two identical failures is very strange and the probability is very low. I suspect a headset error of some sort. Try a two point cal (4 and 7) and check the Calibration Sticky at Brewing Science for tips. I believe you are the first to try one of the Hach meters with the conductivity option so perhaps there are QA problems with that model none of us know about. There were problems with the Pro + but those seem to have. been dealt with.

 

[ajdelange]

First observation: as mentioned in an earlier post, the Pocket Pro+ box arrived covered in some sticky/slimy substance which I later determined to be soap.

Still looking for possible explanations I reread the OP. This is indeed strange. Are we sure this is a reliable supplier? I believe Amazon does a good job of vetting but if there is a way to beat their system someone will find it.

Other observations: the paint for the fill line on the sample cup more resembles a dry-erase marker than anything permanent. Having used the meter one time it has smeared and started to come off. I suspect it doesn't stand up to the calibration solutions.

This is also strange. I don't have my unit with me but I certainly never noticed any reaction between any part of the meter and the buffers. Where did the buffers come from?

The fill level isn't critical as long as the sensor is submerged, so this isn't a huge deal.

The bulb must be immersed but so must the junction (little flat button thing on the sensor bulkhead). If it wasn't that would certainly explain the erratic readings.

 

[Epos7]

Still looking for possible explanations I reread the OP. This is indeed strange. Are we sure this is a reliable supplier? I believe Amazon does a good job of vetting but if there is a way to beat their system someone will find it.

Hach has an Amazon storefront and they are the supplier. Amazon fulfills the orders, so it's impossible to say how the box ended up in such condition. The second meter I received (the Multi2) did not have this problem.

This is also strange. I don't have my unit with me but I certainly never noticed any reaction between any part of the meter and the buffers. Where did the buffers come from?

Buffers also came from Amazon, brand was Atlas Scientific.

The bulb must be immersed but so must the junction (little flat button thing on the sensor bulkhead). If it wasn't that would certainly explain the erratic readings.

Everything was fully immersed in the buffers. I'm fairly certain at this point that both meters I've received have been functioning normally, I think the buffer solution is to blame. I'm going to try calibrating the meter with the buffer solutions we use at the lab where I work to confirm.

 

[Epos7]

I was able to calibrate the Hach Pocket Pro+ Multi2 today using Oakton pH buffers from the lab where I work. The meter calibrated withoutt any of the issues I encountered previously, so I am confident in saying the pH buffers I purchased from Atlas Scientific were no good. I've updated my previous post with this new information.

 

[ajdelange]

Which buffer was the bad one? The 5 and 7 buffers use, respectively, the pthallc acid and phosphoric acid systems and are quite stable but the 10 buffer used the bicarbonate system and is quite unstable against the CO2 content of the air.

In any case, glad to hear things worked out for you.

 

[Epos7]

Ah, interesting. The 10 buffer was the one that was off.

 

[JackiePaper]

As a cheaper alternative to some of the more recommended pH meters in this thread, I recently purchased this 'Just UTile' brand pH meter from Amazon for just over $20: https://goo.gl/EVWa1n

I (also) work in a research lab, so I'll be testing how it compares to our 'real' pH meter at work and I'll post my findings here to let you know how it turned out!

 

[JackiePaper]

Alright, so I got a chance to test this 'Just UTile' brand pH meter in my lab. The verdict: it works pretty OK.

I calibrated as instructed. It comes with three small packages of dry calibration buffer that you are to mix with 250mL of distilled (I used DI) water to make the calibration solution. I measured my 250mL of water with a graduated cylinder and mixed each solution on a stir-plate for about 1 minute. No solids were still visible after the minute.

First, I measured the pH of each of my calibration solutions with our Denver Instruments UB-10 pH meter. The 6.86 buffer came out at 6.87, the 4.00 buffer read at 3.99, and the 9.18 buffer was the only one substantially off at 9.38. Next, I calibrated the Just Utile meter using these solutions, making sure to rinse it off with DI water and dry it with a kimwipe in between each buffer.

To see how well the Just Utile performs, I used it to take readings from pH4.01, 7.00, and 10.01 buffers I had in the lab. I also took readings with my Denver Instruments meter.

Just Utile:
3.89
6.99
9.94

Denver Instruments:
4.01
7.04
10.03


So, basically, the Just UTile meter works, but is not very impressive. Personally, I probably wouldn't trust it if you need very accurate readings, but it seems like it should be able to give you 'ball park' readings without any trouble. We'll see how it holds up over time!

 

[juggabrew]

Alright, so I got a chance to test this 'Just UTile' brand pH meter in my lab. The verdict: it works pretty OK.

I calibrated as instructed. It comes with three small packages of dry calibration buffer that you are to mix with 250mL of distilled (I used DI) water to make the calibration solution. I measured my 250mL of water with a graduated cylinder and mixed each solution on a stir-plate for about 1 minute. No solids were still visible after the minute.

First, I measured the pH of each of my calibration solutions with our Denver Instruments UB-10 pH meter. The 6.86 buffer came out at 6.87, the 4.00 buffer read at 3.99, and the 9.18 buffer was the only one substantially off at 9.38. Next, I calibrated the Just Utile meter using these solutions, making sure to rinse it off with DI water and dry it with a kimwipe in between each buffer.

To see how well the Just Utile performs, I used it to take readings from pH4.01, 7.00, and 10.01 buffers I had in the lab. I also took readings with my Denver Instruments meter.

Just Utile:
3.89
6.99
9.94

Denver Instruments:
4.01
7.04
10.03


So, basically, the Just UTile meter works, but is not very impressive. Personally, I probably wouldn't trust it if you need very accurate readings, but it seems like it should be able to give you 'ball park' readings without any trouble. We'll see how it holds up over time!

Any further findings on the just Utile meter? Also is the cap able to hold storage solution to keep the probe moist?

 

[JackiePaper]

Any further findings on the just Utile meter? Also is the cap able to hold storage solution to keep the probe moist?

No, I haven't got the chance to brew with it yet, just been busy with work, and no the cap does not contain any kind of reservoir for storage solution.

 

[rhys333]

Just wondering which pH meter is currently recommended. Pages back, the Hach Pocket Pro + is viewed favorably. Is this still a good choice, and if so, have I found the right one here online? http://ca.hach.com/pocket-pro-ph-tester/product?id=17990686222

This one is sold online through Ontario Beer Kegs. Is it a good option as well? http://www.ontariobeerkegs.com/Hanna_Instruments_Checker_pH_Meter_p/ph-meter-checker.htm

 

[ercousin]

Just wondering which pH meter is currently recommended. Pages back, the Hach Pocket Pro + is viewed favorably. Is this still a good choice, and if so, have I found the right one here online? http://ca.hach.com/pocket-pro-ph-tester/product?id=17990686222

This one is sold online through Ontario Beer Kegs. Is it a good option as well? http://www.ontariobeerkegs.com/Hanna_Instruments_Checker_pH_Meter_p/ph-meter-checker.htm

If you are in Canada just stick with: http://www.omega.ca/pptst_eng/PHH-7000.html

Replacement probes for MW102 and Hach Pocket Pro+ aren't really available up here...

 

[mabrungard]

Probes for the MW102 are available anywhere in the world. That is the beauty of using a meter that accepts BNC-cabled pH probes. There are literally thousands of probes that fit when you have a BNC connector. And all pH probes have identical operational standards, so it will work on all meters.

Buying a meter that can only be used with a single manufacturer's proprietary probe is going to be more costly and less available.

Choose wisely.

 

[rhys333]

Thanks for the reply guys. So it sounds like the MW102 is the best unit as long as I can find replacement probes. @mabrungard - So I should be able to find a generic probe easily through online lab equipment suppliers? Sorry if I sound completely clueless on this... I have zero experience with lab equipment.

 

[Maylar]

Anybody know what the storage solution in the MW102 is? I'm surely gonna spill it some day and would like some handy.

 

[rhys333]

Anybody know what the storage solution in the MW102 is? I'm surely gonna spill it some day and would like some handy.

What's the deal with storage solution btw?

 

[mabrungard]

Storage solution typically has a high ionic content that helps reduce leaching of the electrolyte from the probe and keeps the bulb saturated. The solution is often a solution of potassium chloride along with some sort of preservative like sodium benzoate. Some probes include a water tight cap that helps the bulb stay saturated.

 

[ajdelange]

The art in the pH meter lies not, as you might at first think, in the pH sensing glass bulb but rather in the thing that connects to the other side of the circuit: the reference junction. This is usually a porous ceramic frit of some sort or even just a strip of rag but the important aspect of it is that ions must be able to flow through it. The interior part usually contains a solution saturated WRT potassium chloride (3M) and silver chloride. Potassium chloride solution is one of two substances (the other being Helium II) which is capable of creep i.e. it can easily make it's way through the frit unless the chemical potential of potassium chloride on the other side of the frit is the same as it is interior to the electrode. The same is true of water: it will migrate from one side of the frit to the other unless the chemical potential of water is the same on both sides. How do we equalize chemical potential of KCl and H2O across the frit? Bathe both sides of the frit is equimolar aqueous solutions of KCl. Thus most pH meter's storage solutions are saturated solutions of KCl.

Were it not for this situation with the reference junction electrodes could be stored dry (and indeed some are) but this can be inconvenient as the actual pH sensing requires a hydrated layer on both sides of the glass. If an electrode is stored dry it must be hydrated before use and this can take 20 minutes or more. Thus a second benefit of storing in 3M KCl is that the electrode is hydrated and ready to roll as soon as it is removed from the storage solution.

If your storage solution is indeed KCl the creep will signal this fact. The liquid will creep out around the edges of the cap and deposit crystals on the outside and up the probe body. These are harmless and easily rinsed away with a blast of DI water from a squirt bottle but the storage solution that has crept out must be replaced.

 

[Ferny78]

Hello, first of all I would like to thank all the people who posted useful information for purchasing a pH-meter. Taking into account the different options where I live (Spain), I decided to get the Omega PHH-7011. Today I performed a stability test after the first calibration and I wanted to share the results. I know it is too soon, but based on these results, I'm quite happy with the purchase.

 

[ajdelange]

Looks good to me.

 

[lurchalicious]

Anyone have feedback on meters since the last posting in 2016?

I have been reading over multiple threads however some of the information seems above my knowledge. I just want to make sure my mash water is in good range for efficiency.

Amazon is flooded with 14-16 dollar meters that seem like they fit the bill, but these can't possibly be worth dealing with are they?

 

[ajdelange]

There are some here that swear by these cheap meters but most who buy them wind up swearing at them.

 

[user 246304]

Am I being an idiot by keeping the MW102 probe in storage solution in a beaker, covered over with plastic film to slow evaporation (not very well - crystallization is crazy)? Can I safely saturate the - don't know what it's called, some sort of cap with a sponge at the bottom, a tube that slips over the electrode - can I saturate this, slip the probe in this, for storage? Seems like I'm burning a lot of storage solution and concerned about the amount of crystallization that gathers on the probe, beaker, everything.

 

[day_trippr]

"KCL creep happens", I get that on my Hanna big time, much less so on the Hach because it has an O-ringed cap unlike the Hanna.
I'm surprised the MW102 doesn't have a probe cap you could simply fill with storage solution, as I do with the Hanna and Hach models.

Is the cross-section above the bulb end round? If so I bet you could come up with some kind of cap for it...

Cheers!

 

[ajdelange]

Am I being an idiot by keeping the MW102 probe in storage solution in a beaker, covered over with plastic film to slow evaporation (not very well - crystallization is crazy)?

No problem with doing things this way except...

Seems like I'm burning a lot of storage solution and concerned about the amount of crystallization that gathers on the probe, beaker, everything.

Storage solutions are almost always saturated solutions of KCl. Thus water evaporation is not a problem from the POV of the strength of the solution. It stays saturated. Deposition of KCl crystals on the electrode is not a problem either. Just rinse them off with a stream of DI water from a lab squirt bottle.

Can I safely saturate the - don't know what it's called, some sort of cap with a sponge at the bottom, a tube that slips over the electrode - can I saturate this, slip the probe in this, for storage?

Yes. That is how the manufacturer intends it to be stored. The sponge is there to retain some liquid it being important to keep the bulb moist rather than wet. The only problem with the storage cap approach is that KCl creep will eventually remove the liquid even if the electrode with cap is stored vertically so be sure to check it and top it off from time to time if you are using it infrequently.

"KCL creep happens", I get that on my Hanna big time, much less so on the Hach because it has an O-ringed cap unlike the Hanna.

You shouldn't be seeing this in the Hach because you shouldn't be filling the cap with storage solution. A few drops of DI water in the bottom of the cap with the meter stored vertically keep the humidity inside the cap high enough to keep bulb and junction hydrated.

I'm surprised the MW102 doesn't have a probe cap

It does.

Can I safely saturate the - don't know what it's called, some sort of cap with a sponge at the bottom, a tube that slips over the electrode