pH Meter - MW102 or Hach Pocket Pro+

[user 141939]

I got one of those coming on the slow boat from Hong Kong right now. The youtube video of it says 0.1 resolution and the picture shows two calibration fluids which leads me to believe it is two points. Anyways I have pH meters at work so I can check it there to see if it's accurate.

If not, oh well, it won't be the biggest waste of money for me!

 

[ajdelange]

I got one of those coming on the slow boat from Hong Kong right now. The youtube video of it says 0.1 resolution and the picture shows two calibration fluids which leads me to believe it is two points.

It is 0.1 resolution but the accuracy spec from the link you posted indicates that accuracy is ±0.2. It is single point calibration. There is only 1 trimpot (on the back) and the calibration instructions say to stick it in the 6.86 buffer and adjust that pot til the display says 6.9.

Anyways I have pH meters at work so I can check it there to see if it's accurate.

Be sure that the ones at work are good meters properly calibrated with fresh buffers before drawing conclusions. The Sticky at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/ may be helpful to you.

 

[CyclingCraig]

Before I purchased the MW102 I was using that meter... actually the Milwaukee pH600 .

It looks EXACTLY the same as the one in the link provided.

To give you some information as to what AJ is saying: I was curious as to what it was reading my mash pH on the brew day I had.

My new MW102 and the pH600 were both calibrated at the same time with the same buffer at the same temperature.

The MW102 read the mash pH at 5.40.. SAME sample less than a minute later read 5.8 on the pH600

If I was trusting the pH600 I would have added acid to drop the pH of the mash, which would have actually put my mash in the 5.0 RANGE !!

 

[user 141939]

It is 0.1 resolution but the accuracy spec from the link you posted indicates that accuracy is ±0.2. It is single point calibration. There is only 1 trimpot (on the back) and the calibration instructions say to stick it in the 6.86 buffer and adjust that pot til the display says 6.9.



Be sure that the ones are work are good meters properly calibrated with fresh buffers before drawing conclusions. The Sticky at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/ may be helpful to you.

IDK, I'm looking at the same link and if you zoom in on the pick of the documentation it says accuracy +/- 0.1 pH. The instructions in the picture are covered and you can read the first two but not the third, unless you found a link to the whole manual which I can't seem to find.

At any rate in the picture it seems to me like the third step is telling you to place it in the other buffer, and plus I'm not sure why there would be two calibration buffers if you only used one.

Maybe you're right, no sense in trying to figure it out from the link anyways since it will be coming in the mail sometime in the next month or two and who knows if it's the same one in the picture anyways.

Not a worry about my work meters. I am well versed in the use of pH meters, this is why I am not afraid to buy this as I will be able to tell pretty quick if it will work or not.

I suspect a good portion of negative (and probably positive) reviews from this meter and others are from people who don't know how to use them properly.

For example I read a lot of people complaining about the meters loosing calibration, or lauding the fact that they keep it for a long time. When the fact is meters should be calibrated before each use anyways.

 

[user 141939]

Before I purchased the MW102 I was using that meter... actually the Milwaukee pH600 .

It looks EXACTLY the same as the one in the link provided.

To give you some information as to what AJ is saying: I was curious as to what it was reading my mash pH on the brew day I had.

My new MW102 and the pH600 were both calibrated at the same time with the same buffer at the same temperature.

The MW102 read the mash pH at 5.40.. SAME sample less than a minute later read 5.8 on the pH600

If I was trusting the pH600 I would have added acid to drop the pH of the mash, which would have actually put my mash in the 5.0 RANGE !!

Did you check both pH meters in the buffers after you calibrated? What I mean is, after calibration you could go back through the buffers to check to see if the calibration worked. Sometimes meters need to be calibrated more than once in a row if they are very far off.

If you calibrated them both, and confirmed they were both right by re-checking with the buffers, then getting that different a result would be very strange indeed.

 

[ajdelange]

IDK, I'm looking at the same link and if you zoom in on the pick of the documentation it says accuracy +/- 0.1 pH.

Yet the website plainly says ±0.2. Why would the seller advertise accuracy twice what the unit can deliver? Perhaps a hint is found in the price. These guys are going to ship this to you from China for $7.80 and make a profit (presuming they aren't doing this for fun). That suggests that they are paying at most $1-2 for each and that suggests that perhaps they are buying the factory's rejects i.e. meters that couldn't pass the 'quality control' (have to put that in quotes for an $8 meter) check to which the manufacturer subjects his units. Why not? Accuracy of 0.2 is apparently good enough for hydroponics applications.

The instructions in the picture are covered and you can read the first two but not the third, unless you found a link to the whole manual which I can't seem to find.

I did find the complete manual though I don't remember where. The same site had a picture. No reference to a second pot; no second pot hole in the picture. Even with what you can see at the website you referenced the instructions do not indicate that you should adjust the offset pot when in the close to 7 buffer. Just the pot. From this it is apparent that there is no slope adjustment.

Not a worry about my work meters. I am well versed in the use of pH meters, this is why I am not afraid to buy this as I will be able to tell pretty quick if it will work or not.

I have to ask because
1) It's pretty naive to think you are going to get decent performance out of something worth a dollar or two
2) You'd be amazed at what some guys who think they know all about pH meters and their use don't know. If I sat down with someone from Thermo's pH electrode group I would doubtless get up amazed at what I didn't know.

I suspect a good portion of negative (and probably positive) reviews from this meter and others are from people who don't know how to use them properly.

Amen to that.

For example I read a lot of people complaining about the meters loosing calibration, or lauding the fact that they keep it for a long time. When the fact is meters should be calibrated before each use anyways.

A pH meter needs to be calibrated as often as it needs to be calibrated. Modern electrodes can be amazingly stable holding cal for weeks. In critical applications (drug manufacture...) protocols require calibration before each measurement. In brewing once a day is usually enough if you know your electrode is stable but a calibration check before and after measurement is always a comfort.

 

[user 141939]

The "Seller" that you speak of is just that, the seller. They are not the manufacturer. The whole description is inaccurate, because the seller also states pH 4 equals neutral, below that is acidic, and above that is alkaline. Therefore I would trust what I can read in the manual over what the seller wrote.

I do appreciate your concern over making sure I understand what I am doing as we don't want people screwing up their mash. I realize it will probably be a waste of money but sometimes I am surprised by these things. I order these little LED lights from hong kong, they cost a dollar each shipped, they come with batteries, and they work awesome! I strap them to my dog when we are out at night.

I will get it and check it out and report back, although I suspect you've already made up your mind regardless of what I see. If it's not good for brewing, at the very least maybe I can use it to check my garden soil.

 

[ajdelange]

No, I have not made my mind up. I understand how these things work. I understand that it is possible that you could get one of these with rms accuracy as good as 0.029 pH (the lower limit for an 'instrument' with 0.1 resolution) but that it is very unlikely that you will. If you accept that ±0.2 accuracy is sufficient for some purpose you have in mind that is fine. My main concern here is that some innocent will read this thread and conclude that a meter useable for brewing can be had for less than $10.

And please do not speak to me of dogs for at least 24 hrs. I just got back from the vets where I spent 2 hrs on the floor pulling porcupine quills. Two techs and the vet himself took shifts. Even with my efforts the bill was near $700. The dogs are in the dog house.

 

[youngdh]

I received my new meter on Friday 8/29 along with bottles of 7.01 and 4.01 ref solutions just in time for my brew day yesterday 8/31. I spent Sat running a stability test as outlined in ajdelange's sticky (see attached jpg file for my time series). Following calibration I did 2 min readings up to t+20 min then went to 20 min readings for total time of t+2 hours. Between 2 min readings I left probe in 4.01 solution. Between 20 min readings I rinsed in DI water and stored in storage solution. Prior to each reading I rinsed probe in DI water and blotted dry with paper towel. The 2 min interval readings appear consistent with all but one reading within the 0.01 accuracy rating of the meter. The 20 min interval readings slipped 0.03 points below calibration point. Gotta wonder if I would have stayed closer to 4.01 cal point if I'd left probe in 4.01 solution instead of returning to storage solution. Returning to storage solution between readings would reflect reality of probe usage day to day.

On brew day, yesterday, prior to testing my first mash sample I checked calibration in the 7.01 solution to see how well it held from previous day's calibration. It was reading 7.06, so, did another 7.01/4.01 calibration.

 

[ajdelange]

Looks good to me.

Holding pH to within 0.06 overnight is pretty good but you really should calibrate these meters daily.

 

[TrickyDick]

"The bitterness of poor quality remains long after the sweetness of low price is forgotten."

I am going to be using this quote frequently, I just love it!



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[TrickyDick]

I use the mw102 for the past year. I have not performed the tests as outlined in the sticky, but will soon. I use the recommended method for calibration in the manual with the 7.01 and 4.01 solutions. I use the Bru'n water spreadsheet for planning my brewing water, built up from RO as my tap water is poorly suited to brewing. For the last two brew days, I suspected my meter wasn't keeping cal. I had to recalibrate between each measurement. I'm wondering if its a bad battery, or probe needs replacing, or the calibration solutions are no longer good/fresh. They are about a year old, all stored at room temps. Probe is stored in the probe storage solution when not being used. I calibrate the probe on every brew day usually just before taking my first measurement.
I see that there is a replacement probe on amazon for 30 something dollars. The picture gives a different model number than what is on the probe I have now. I will point out that the bru'n water sheet is very very close to the probe readings in the dozen or so brews I've done since buying the probe. I have heard that the probes do need replacing over time. I have been mostly careful to cool the liquid to room temp before taking a reading, however there may have been a couple times I forgot to do this early on in my use of the the meter.

TD


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[ajdelange]

The electrodes don't last forever but with a modern meter we hope for more than a year.

The calibration solutions should be freshly prepared or, if from stock, freshly removed from unexpired stock and should never, after use, be returned to stock. If the buffers are off that will, of course, add error to pH readings but will not have an effect on stability. Stability simply means the meter reads the pH of the buffer as being the same each time the buffer is read.

 

[CyclingCraig]

I received my new meter on Friday 8/29 along with bottles of 7.01 and 4.01 ref solutions just in time for my brew day yesterday 8/31. I spent Sat running a stability test as outlined in ajdelange's sticky (see attached jpg file for my time series). Following calibration I did 2 min readings up to t+20 min then went to 20 min readings for total time of t+2 hours. Between 2 min readings I left probe in 4.01 solution. Between 20 min readings I rinsed in DI water and stored in storage solution. Prior to each reading I rinsed probe in DI water and blotted dry with paper towel. The 2 min interval readings appear consistent with all but one reading within the 0.01 accuracy rating of the meter. The 20 min interval readings slipped 0.03 points below calibration point. Gotta wonder if I would have stayed closer to 4.01 cal point if I'd left probe in 4.01 solution instead of returning to storage solution. Returning to storage solution between readings would reflect reality of probe usage day to day.

On brew day, yesterday, prior to testing my first mash sample I checked calibration in the 7.01 solution to see how well it held from previous day's calibration. It was reading 7.06, so, did another 7.01/4.01 calibration.

These are similar to my results: MW102 Stability thread.

One thing to note, is the temperature of the sample. For example @65F your calibration buffer should (Maybe depending on brand) would be 4.00 NOT 4.01.

So make sure you check the package for the temp/pH values when evaluating your results. You might be a WHOLE .01 pH closer than you thought :cross:

 

[ajdelange]

I've put the temperature dependencies for these technical buffers at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/. The meter's ATC program has these formulas, or their equivalents programmed in. As these buffers have standard formulations they should all exhibit the same temperature dependence regardless of the manufacturer subject to the proviso that the manufacturer uses the standard formulation.

Note that I got the formulas posted by fitting the given polynomial to the data on Hach buffer packaging. There may be more 'official' formulae posted elsewhere.

It is particularly important to note that these buffers are specified as being at their given pH values ± 0.02 pH (in most cases but ±0.01 products are available too).