Author Topic: pH probes  (Read 1938 times)

Offline brewinhard

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pH probes
« on: February 06, 2017, 04:55:17 PM »
I have owned my MW-101 pH meter for just over 1.5 yrs now and fully have enjoyed using it.

In the past few months (4-5) I have been noticing that it has been taking a considerably longer time to calibrate on the first 7.0 buffer. Almost up to 10 minutes. Then when I go to calibrate the 4.0 solution it takes a normal amount of time (about 1 minute give or take).

I typically brew about 20-25 batches (sometimes more) per year and have taken great care with the probe always rinsing with distilled water, only using it at room temps, and storing it in proper storage solution.

Do these probes really only last about 1 solid year of brewing?  Has anyone else experienced these fluctuations?

I just yesterday ordered another probe and am hoping things will go better with it. Just kind of sucks that that is a yearly (or 1.5 yr) expense when using these.   


Offline narcout

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Re: pH probes
« Reply #1 on: February 06, 2017, 05:12:30 PM »
I have that same meter.  After awhile, it started becoming very difficult to calibrate so I replaced the probe (I can't remember exactly how long ago that was, maybe 18 months?).

That solved the issue, but now it is starting to happen again. 

I know a lot of people like these meters, but the manual calibration drives me nuts.  I'm about to replace it with an Extech 110.
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Offline Stevie

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Re: pH probes
« Reply #2 on: February 06, 2017, 05:16:14 PM »
My new Extech 110 was acting wonky the other day. It was giving me questionable readings and seemed to drift over the course of a couple of hours. As a test I checked some distilled vinegar and it was at 2.9 after calibration. I dumped and refilled the probe and it's dead on 2.4. Very happy with that feature.

Online The Beerery

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Re: pH probes
« Reply #3 on: February 06, 2017, 05:34:46 PM »
My new Extech 110 was acting wonky the other day. It was giving me questionable readings and seemed to drift over the course of a couple of hours. As a test I checked some distilled vinegar and it was at 2.9 after calibration. I dumped and refilled the probe and it's dead on 2.4. Very happy with that feature.

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Offline brewinhard

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Re: pH probes
« Reply #4 on: February 06, 2017, 06:00:16 PM »
I have that same meter.  After awhile, it started becoming very difficult to calibrate so I replaced the probe (I can't remember exactly how long ago that was, maybe 18 months?).

That solved the issue, but now it is starting to happen again. 

I know a lot of people like these meters, but the manual calibration drives me nuts.  I'm about to replace it with an Extech 110.

so it really seems like you (at best) get 1.5 yrs out of these probes depending on how often one uses them.
Kind of crappy as those replacement probes are about 40 bucks a shot.

Good to know that solved the issue. Looking forward to "nailing" my pH's again. Or at least verifying that I am.  ;)

Offline narcout

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Re: pH probes
« Reply #5 on: February 06, 2017, 06:09:42 PM »
so it really seems like you (at best) get 1.5 yrs out of these probes depending on how often one uses them.

I think Martin said he has been using the original probe for 5 years without issue. 

My experience has been different, but I don't really know why.  I store the probe in the storage solution, only test the pH at room temperature, etc.
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Offline jimmykx250

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Re: pH probes
« Reply #6 on: February 06, 2017, 06:12:21 PM »
So when do you guys take your ph readings? If its at the 15 min mark in the mash do you draw a sample and let it cool before reading with your meter? I noticed the thermoworks model im looking at says it has temperature compensation built in.
Jimmykx250

Offline Stevie

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Re: pH probes
« Reply #7 on: February 06, 2017, 06:13:29 PM »
I'm sure there is a wide range of qualities when it comes to these probes. They are a standard used by many units and manufactured by multiple companies.

Offline Stevie

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Re: pH probes
« Reply #8 on: February 06, 2017, 06:15:00 PM »
So when do you guys take your ph readings? If its at the 15 min mark in the mash do you draw a sample and let it cool before reading with your meter? I noticed the thermoworks model im looking at says it has temperature compensation built in.
The temp compensation is to accommodate the different ph at different temps and not to adjust the reading to what it would be at room temp.

I pull a small sample at 10 minutes and put it in the freezer for about 10 minutes to test.

Offline jimmykx250

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Re: pH probes
« Reply #9 on: February 06, 2017, 06:21:41 PM »
So when do you guys take your ph readings? If its at the 15 min mark in the mash do you draw a sample and let it cool before reading with your meter? I noticed the thermoworks model im looking at says it has temperature compensation built in.
The temp compensation is to accommodate the different ph at different temps and not to adjust the reading to what it would be at room temp.

I pull a small sample at 10 minutes and put it in the freezer for about 10 minutes to test.

Thanks Steve
Any opinions on the thermowoks stuff? Thermometers are stellar.
Jimmykx250

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Re: pH probes
« Reply #10 on: February 06, 2017, 06:27:22 PM »
In some of my correspondence with AJ DeLange at HBT, it was made clear that 25-30 in is the best time to take a reading.

This seems to jive with what Bryan is doing, essentially taking a read towards the end of his β rest.


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Offline Stevie

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Re: pH probes
« Reply #11 on: February 06, 2017, 06:29:40 PM »
I know a few people here have that meter and like it. I almost bought this meter, but switched to the Extech because it measures to the hundredths and also because I had an Amazon gift card that was "to be used on something fun that I normally wouldn't buy on my own"

Offline pfabsits

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Re: pH probes
« Reply #12 on: February 06, 2017, 06:44:13 PM »
On average we state that a pH electrode will last 1-2 years. It is very possible to have a probe work longer. As long a pH electrode has a good offset (mV value in pH 7.01) and slope (mV difference from pH 4- pH 7) then the probe can be used.

A good offset value is +/- 30 mV while slope should be greater than 160 mV (90%).

Since the meter is calibrated manually and it does not have a GLP feature it can be difficult to determine the pH electrode characteristic. I would recommend the following:

1)   Short the BNC connector on the meter with a paperclip. That is put one end in the center hole and touch the outside of the connector.  This is 0 mV.
2)   Dial pH 7.01 calibration trimmer until pH 7.01 is displayed
3)   Reconnect the pH electrode to the meter and place in pH 7.01 fresh buffer
4)   Record the pH value in the buffer.

It is now possible to determine the offset of the pH electrode. Ideally the meter would display pH 7.01 since the theoretical mV at pH 7.01 is 0 mV at 25 oC. An acceptable offset of +/-30 mV would be displayed as a pH from 6.5 to 7.5. Meters will typically allow a calibration of +/- 60 mV which would show as a pH reading around 6 (+60 mV)  and 8 (-60 mV).

If you see reading outside pH 6.5 to 7.5 then the electrode needs to be cleaned. Any coating on the glass will shift the voltage read by the probe.

Instability in readings that occurs with aging are due to various factors including:
1)   Dirty electrode – as there is a build up on the glass the measurement circuit is impeded.
2)   Clogged junction – on the side of the probe should be a white plug. That is the junction. When it gets clogged the measurement circuit gets impeded.
3)   Storage -  It is very important to store the pH electrode in storage solution. The storage solution maintains a hydrated layer on the glass bulb, hydration of the junction, and hydration of the gel used inside the probe.


Below is a link to some basic maintenance information:
http://hannainst.com/ph-electrode-maintenance-calibration-guide

Products for Beer Analysis.
http://hannainst.com/beer-ph

Recommended cleaning solutions
http://hannainst.com/industries/beer/ph/maintenance-solutions/cleaning.html

If you have any questions then feel free to message me.
One of the avid home brewers that work for Hanna Instruments

Offline pfabsits

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Re: pH probes
« Reply #13 on: February 06, 2017, 07:00:26 PM »
So when do you guys take your ph readings? If its at the 15 min mark in the mash do you draw a sample and let it cool before reading with your meter? I noticed the thermoworks model im looking at says it has temperature compensation built in.
The temp compensation is to accommodate the different ph at different temps and not to adjust the reading to what it would be at room temp.

I pull a small sample at 10 minutes and put it in the freezer for about 10 minutes to test.

Thanks Steve
Any opinions on the thermowoks stuff? Thermometers are stellar.

I cannot state for Thermoworks but as far as temperature goes:

Most pH electrodes are made of General Purpose (GP) glass. The rule of thumb for GP glass is
At 25 oC expect 1-2 years
At 50 oC expect 6 month to 1 year
At 75 oC expect 3-6 months
At 100 oC expect less than 1 month.

The guidelines are for probes in continuous use. I would expect a longer time for probes that are used intermittently.

It would be recommended to cool samples to less than 140 oF (60 oC). If it is planned to measure at a higher temperature then a pH electrode with high temperature (HT) glass would be recommended. The HT glass has a higher resistance at 25 oC than GP glass. As the temperature increases then resistance decreases. The HT glass resistance at high temperature approaches that of GP glass at an ambient temperature.

The temperature compensation is used for voltage response as according to the Nernst equation for membrane potentials.  For a meter with manual temperature compensation it is important to adjust the calibration trimmer to match the value on the bottle at a specific temperature. The value on the bottle is the actual pH of that solution at a given temperature. For example pH 7.01 and 4.01 at 25oC.
One of the avid home brewers that work for Hanna Instruments

Offline brewinhard

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Re: pH probes
« Reply #14 on: February 06, 2017, 07:36:58 PM »
Phewwww. That is a ton of good information there. Thanks for sharing.

In your first post with steps 1-4, can this be performed with any pH probe or just Hanna Instrument ones?