pH Meter Calibration

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z-bob said:
I would want manual calibration mainly for high pH -- for doing water treatment, both for brewing and for aquariums. High pH buffer solutions don't have a very long shelf life (or so I've heard) because they absorb atmospheric CO2.
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'Tis true. The 10 technical buffer is, I believe, a carbonate buffer (pK2 = 10.38) obviously subject to drift upon exposure to CO2.
 
z-bob said:
I would want manual calibration mainly for high pH -- for doing water treatment, both for brewing and for aquariums. High pH buffer solutions don't have a very long shelf life (or so I've heard) because they absorb atmospheric CO2. 7.01 and 4.01 are more stable.

I'll see if I can download a MW102 technical manual. The one I found online earlier looked more like a "quick start" guide and didn't really say much.
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The manual that comes with the meter isn't all that informative. The only variation on the method I know of is that you don't have to hit the confirm button when it tells you too. It seems you can let the probe sit longer. If it were that automatic it wouldn't have the confirm button.
 
The better meters all have that feature. It lets you, the analyst, decide when a buffer reading is stable enough to accept rather than having the meter make that decision for you. It is a big plus. The Hanna pHep pen would be a pretty good meter if it had that feature IOW it is quite stable but accepts buffer readings too early.

In any case apparently the meter under consideration doesn't let you calibrate to buffers other than the standard ones though I'm still not sure why you would want buffers other than the standard ones. Any basic buffer will absorb CO2 from the atmosphere.
 
So when you're opinion what's the best meter on the market if you want to buy one under 200-300$


Sent from my iPhone using Home Brew
 
Two seem to have emerged: the Hach Pocket Pro + and the Milwaukee MW 102. This does not mean that there may not be others equally as good. Omega has a relatively new pen style meter that one or two people have tried and seemed pleased with. The Hach and the Milwaukee get the best marks from the HBT Consumers Union because several users have done the stability checks described at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/ and had favorable results.

The Hach meter is a pen type and it does, IIRC, allow calibration with buffers of arbitrary pH whereas the MW102 has a separate electrode.
 
z-bob said:
I was about to buy a MW102, but I've about talked myself into the MW101 *because* it has manual calibration. I think that means I can use whatever pH buffers I want to calibrate the slope
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Hey,

I have the MW-102 and looked at the 101. I am pretty sure you are NOT correct about how the manual calibration works.

The manual calibration has to deal with the temperature of the calibration solution. NOT the pH of the calibration solution.

The MW102 has a separate temperature probe you use when taking measurements that reads the temperature of the sample.

The MW101 DOES NOT have a temp probe at all. The dial on front is for setting the temperature of the sample you are taking the pH of. So with the MW101 you have to measure the temp of your sample and set the dial on the front of the meter to the temperature you took manually.

With my MW102 the only calibration points you have are 4, 7 and 10

-Craig
 
Actually he is right. The calibration process has to account for both the temperature and pH of the buffers. To calibrate a manual meter one sets the gain for the temperature of the buffers and then goes into 7 buffer adjusting the offset control until the meter reads 7. He then goes to another buffer which can have any pH and adjusts the slope control until the meter reads the pH of that buffer whatever it may be.

In an automatic meter temperature and mV readings are taken in a pair of buffers at any pH and temperature and a pair of equations solved for slope and offset.
 
I'm getting ready to pull the trigger on a meter in the next couple of weeks and I have a question about the supplies I need for the Hach Pocket Pro+. After reading everything I am going to get the following:

4.00 ph solution
7.00 ph solution
HCl for cleaning the electrode ( I don't anticipate need the cleaning solution since I won't be checking fat,grease, or oil)
Deionized water

Am I missing anything?
 
You will definitely want the 4 and 7 pH buffers and the deionized water. You will not need HCl. A squirt bottle for dispensing the DI water is good to have as are some of Hach's sample containers (with the thumb flip lids) for storage (and or make up if you get the 'powder pillows' form) of the buffer solutions and for samples.
 
You may also consider the storage solution?

People have been on the fence with that for the Hach meter. I have the MW-102 so I "Have" to use it.
 
ajdelange said:
You will definitely want the 4 and 7 pH buffers and the deionized water. You will not need HCl. A squirt bottle for dispensing the DI water is good to have as are some of Hach's sample containers (with the thumb flip lids) for storage (and or make up if you get the 'powder pillows' form) of the buffer solutions and for samples.
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Thanks AJ. Last thing is it DI water that you put in the cap for keeping some moisture in the cap for the electrode?
 
Don't you need KCl solution to store the electrode? (this one doesn't have to be precise; you should be able to mix the storage solution yourself from supermarket KCl.)
 
ggriffi said:
Thanks AJ. Last thing is it DI water that you put in the cap for keeping some moisture in the cap for the electrode?
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Yes, that is what I use though I believe the instructions said that tap water was OK. That is to say, the instructions that came with it over a year ago when I bought it. Always do what the current set of instructions directs.
 
Nope. Just the two buffers and deionized water to rinse it off. At least that is all I have done, no special cleaning solution.
 
 
Aj,

My Hach pocket pro+ won't calibrate anymore. Auto calibration is on, I have tried resetting to factory, and go step by step with the directions.

I can get it to go to calibration mode, put it in the 7.00 calibration solution, but when it stabilizes and it's time to hit the calibration button again it won't flash three times. It will either leave calibration mode or if I hold longer will go into settings. It used to calibrate just fine when it I bought it. I have hardly used it so I figure the problem is user error instead of faulty equipment.

It seems to stabilize the 7.00 solution around the mid 5.90's.

Any thoughts?
 
Bensiff said:
My Hach pocket pro+ won't calibrate anymore....
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Your unit can, of course, fail, as can any other piece of equipment. I guess I would suggest removing the batteries, leaving them out for a minute and replacing them. Then be sure you follow the directions exactly and try again. If this fails, remove the batteries again and try removing and replacing the electrode. The idea here is that there may be corrosion, dirt or film on the contacts. If that fails call Hach. How long have you had it?
 
ajdelange said:
Your unit can, of course, fail, as can any other piece of equipment. I guess I would suggest removing the batteries, leaving them out for a minute and replacing them. Then be sure you follow the directions exactly and try again. If this fails, remove the batteries again and try removing and replacing the electrode. The idea here is that there may be corrosion, dirt or film on the contacts. If that fails call Hach. How long have you had it?
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I posted my calibration numbers on 9/1/14 so probably a few weeks before that. I have maybe used it 3-4 times as after that it started having issues where it seemed hit and miss if it would accept a calibration point. It was always stored rinsed with deionized water and then with a few drops in the cap per directions.
 
Got my hach pocket pro+ in november and it's failing to calibrate now as well.
It just won't ever stabilize on a reading.

I've got an email in to hach, we'll see what they say.
Used it every 1-2 weeks since november, rinsed and stored with distilled water.
Calibrated every usage with the buffer packets from hach, 7 and 4. Only ever took readings at 65-72f.
 
@stat Distilled water is contra-indicated as a storage media. That could be the problem. You want a storage solution as per the manufactures guidelines.
 
With meters in which the storage solution contacts the reference junction distilled water is not a good choice for a storage solution as KCl from the interior of the electrode will migrate into the water and water will migrate into the gel, both along gradients of chemical potential. In the Hach design the 'storage solution' isn't really that but only a few drops of water (distilled or otherwise) in the cap to keep the humidity up. The junction is not in contact with the liquid. This sounds more like a bad electrode or, possibly, dirty connections. You might want to try removing the electrode and replacing it a few times to see if that cleans off contacts. Don't get too hopeful though.
 
Thanks for the correction @AJDelange I have been using storage solution. Will this do harm? I did wonder why it did not ship with storage solution in the sample vessel. Just some drops of water exactly as you describe.

I will desist in proffering any advice in the brew science forum. Clearly above my abilities. My apologies to the previous poster. It was not my intent to give you misleading and potentially harmful advice.
 
Gavin C said:
Thanks for the correction @AJDelange I have been using storage solution. Will this do harm?
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Possibly, by the mechanisms I described.

Gavin C said:
I did wonder why it did not ship with storage solution in the sample vessel. Just some drops of water exactly as you describe.
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Ordinarily my response to this would be RTFM but is this case there is, apparently, even at Hach some puzzlement exactly as how to store this electrode.

Gavin C said:
I will desist in proffering any advice in the brew science forum.
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Don't do that! For any electrode except this one your advice would have been sound. Your post has brought an important though obscure bit of the art into the limelight for discussion.
 
ajdelange said:
With meters in which the storage solution contacts the reference junction distilled water is not a good choice for a storage solution as KCl from the interior of the electrode will migrate into the water and water will migrate into the gel, both along gradients of chemical potential. In the Hach design the 'storage solution' isn't really that but only a few drops of water (distilled or otherwise) in the cap to keep the humidity up. The junction is not in contact with the liquid. This sounds more like a bad electrode or, possibly, dirty connections. You might want to try removing the electrode and replacing it a few times to see if that cleans off contacts. Don't get too hopeful though.
Click to expand...

I took it apart and everything is spotless inside.
I was able to complete a custom calibration but when I went from 7 to 4 and saved that, then went back to the 7 it was reading in the 5's.

When not in anything, just on and hanging out in the air it started around 4 and dropped quickly under 0 and all that was on screen was ------ after that.

When I try to calibrate it like usual with the setting set on USA it just wont save no matter how many times I hit the button. Unless I hold it and then it just quits.


I guess some sort of probe cleaning solution would be a waste of time? The bulb looks clean but I've never wiped it off or anything, just sprayed it with distilled water from a spray bottle.
 
ajdelange said:
Yes, I think it would be. Sounds as if this one is TU. Still under warranty?
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Supposedly there is a 1 year warranty on the pocket pro +

They wrote me back and said this :

"Thank you for contacting Hach Technical Support regarding the Pocket Pro+. You may be able to improve the function of the probe by using fresh, unopened pH buffers to do the calibration. However, since the probe has been working for several months, it is likely that the sensor needs to be replaced. Here is a link to the Replacement sensor 9532001 on our website.

I hope this information is helpful. If you have any other questions please let us know. Thanks again for contacting Technical Support and have a great day."

I'm trying to start the warranty return process but they don't make it very easy. Sent them some more emails, we'll see what comes of it.


Am I crazy for thinking this meter should have at least lasted a year with my usage? Room temp testing, only once a week to once every other week. It didn't even make it to month 5.

Or are ph meters just that sensitive? I guess there's always a chance I just got a bad probe.
 
stat said:
Supposedly there is a 1 year warranty on the pocket pro +

Am I crazy for thinking this meter should have at least lasted a year with my usage? Room temp testing, only once a week to once every other week. It didn't even make it to month 5.
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No, you aren't at all crazy. With modern technology you should expect more than a year.

stat said:
Or are ph meters just that sensitive? I guess there's always a chance I just got a bad probe.
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This particular meter has been on the market for about a year and a half now. Initially it was plagued with bad sensors and that is to be expected of a new product because yes, pH electrode design is as much art as science. It was clear from Hach's response to problems (replace bad meter/electrodes without question 2 or 3 times) that this was the case and that they clearly expected to resolve the manufacturing problems. The fact that this hasn't come to pass after 18 mos. is troubling and if they are backing off on the willing easy replacement too that is disturbing as well. Keep us posted.
 
stat said:
Got my hach pocket pro+ in november and it's failing to calibrate now as well.
It just won't ever stabilize on a reading.

I've got an email in to hach, we'll see what they say.
Used it every 1-2 weeks since november, rinsed and stored with distilled water.
Calibrated every usage with the buffer packets from hach, 7 and 4. Only ever took readings at 65-72f.
Click to expand...

I did as AJ suggested I do before calling up Hach and removed the batteries...I'm assuming this causes a hard boot situation. Anyway, that is all that it needed, it went from refusing to to stabilize and not blinking three times to show a calibration point was accepted by the user, to working exactly as it should.
 
Bensiff said:
I did as AJ suggested I do before calling up Hach and removed the batteries...I'm assuming this causes a hard boot situation. Anyway, that is all that it needed, it went from refusing to to stabilize and not blinking three times to show a calibration point was accepted by the user, to working exactly as it should.
Click to expand...

Guess I'll try that again. I will report back with results, mixing solution now.
 
Looks like it's working again.

I tried the battery thing yesterday and it didn't do anything.
This time I had it on and popped the batteries out while it was running. Left them out the whole time it took me to mix some buffer solutions, less than 5 mins.
Now it is calibrating correctly and stabilizing pretty quick.
I wonder if I should just store it without the batteries in it between brew sessions.
 
stat said:
Looks like it's working again.

I tried the battery thing yesterday and it didn't do anything.
This time I had it on and popped the batteries out while it was running. Left them out the whole time it took me to mix some buffer solutions, less than 5 mins.
Now it is calibrating correctly and stabilizing pretty quick.
I wonder if I should just store it without the batteries in it between brew sessions.
Click to expand...


How long did you have the batteries out yesterday? It can take a few minutes for the memory to clear so it will hard boot. I also wondered about leaving batteries out but decided since I now know the trick I'm not going through the extra hassle of taking them in and out all the time.
 
Bensiff said:
How long did you have the batteries out yesterday? It can take a few minutes for the memory to clear so it will hard boot. I also wondered about leaving batteries out but decided since I now know the trick I'm not going through the extra hassle of taking them in and out all the time.
Click to expand...

1-2 mins maybe, I was right at the point that I needed it and I had a newer brewer over trying to get him started with water chemistry. So I was a bit flustered.
Of course everything that could of gone wrong, did go wrong.
 
stat said:
1-2 mins maybe, I was right at the point that I needed it and I had a newer brewer over trying to get him started with water chemistry. So I was a bit flustered.

Of course everything that could of gone wrong, did go wrong.
Click to expand...


I was in the same boat on a few occasions, couldn't calibrate when needed. I decided a while back that the first stage of brewing up to the mash rest is like making a stir fry, things move very fast so the best way is to have everything prepared ahead of time. The night before a brew I fill the HLT, connect all of the hoses, weigh out the grains, and figure out my salt additions. While the strike water is heating up I calibrate my pH meter and mill the grains. That way when it's time to dough in I can toss everything in, stabilize, and take pH without feeling a massive time crunch.
 

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