Author Topic: ph meter  (Read 1275 times)

Offline jimmykx250

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ph meter
« on: September 02, 2015, 08:21:55 PM »
Looking for some input on a ph meter. This one popped up on home brew finds. Right now I use the strips. Any one have this model or can recommend one that isn't a hundred bucks?
Thanks,
http://www.amazon.com/gp/product/B013QJ1JO2/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B013QJ1JO2&linkCode=as2&tag=hombrefin-20&linkId=ADAEZ4BYK3EHM5TG
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Offline wingnut

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Re: ph meter
« Reply #1 on: September 02, 2015, 10:51:43 PM »
I use a similar model.. it is 0.05 accurate instead of 0.1.  It works good with no complaints.

When you buy it, buy some calibration solution (4.01 is the one I use) to calibrate the meter before each brew session.

Also, keep in mind that with a precison of 0.1, when you read 5.3 on the meter, it might be 5.2 or 5.4 or anywhere in between.  To be honest, it is likely not a huge issue to be 0.1 off.  However, I bought the model that is 0.05 accurate so that I was within a point of the reading.  Compared to strips... it is a huge step forward in repeatability.   

I also bought one of these as a backup a while back.  THe price is sure right!
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Offline Wort-H.O.G.

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Re: ph meter
« Reply #2 on: September 02, 2015, 11:24:00 PM »
first mete ri purchased and first to get thrown away. erratic and couldnt get a calibration very well after just a short period.

much happier when switched to this:http://www.amazon.com/Hanna-Instruments-HI98128-Temperature-Tester/dp/B0085WV6GM/ref=sr_1_2?ie=UTF8&qid=1441236101&sr=8-2&keywords=ph+meter+hanna

also own this and it has been great:  http://www.thermoworks.com/products/ph/8100ph_meter.html
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Offline pfabsits

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Re: ph meter
« Reply #3 on: September 08, 2015, 07:05:25 PM »
Do not get caught up in accuracy of a pH meter. The accuracy statements are for the meter and not the probe and meter. It is very difficult to achieve better than 0.1 pH accuracy. It would require knowing how to use and an understanding of offest/slope.

The following are features in pH meters:
1) Replaceable electrode. The pH electrode will last 1-2 years based on use. Being able to replace allows you to invest in a meter with nicer features knowing that you will only replace the probe in the future

2) Waterproof - Waterproof meters tend to cost more but can be easily washed completely in fresh water.

3) Automatic Temp compensation - If you are measuring mash at 140-150 oF then ATC will be necessary to correct for the change in the pH membrane potential

4) Automatic calibration - Auto-calibration can be useful but be warned that with automatic calibration the meter will look for two criteria before accepting a calibration point. One is stability in that the readings are not stable then it will not lock on. The other is the voltage response of the electrode. If the voltage is outside a window +/-60-80 mV in pH 7  (Inside tip of pH probe is pH 7 solution, pH 7 on inside and outside = theoretically 0 mV) or slope is less than 85% then calibration will not be able to be performed. Not necessarily a bad thing since a bad offset and slope will lead to huge errors in readings. To be waterproof a meter will typically also have auto-calibration. Hard to have a meter that is waterproof with manual trimmers.

5) Automatic shut-off: With auto shut off the meter will turn itself off automatically after a set time. Other meters have a switch. Leave the switch on and the batteries will drain.

6) Battery % level indicator: Shows battery percentage remaining. Ensures not using batteries with low power that could impact the readings.

7) Temperature readout: Useful to know temp of a solution. Most meters will use a thermistor based sensor that offers pretty high accuracy.

8) Stability indicator: Shows when a  reading is stable. Good for those that have a 0.01 resolution meter and have a hard time deciding between 0.01 and 0.03 pH. It is nice to have but not that important.

Because I work for a mfg I am not going to reference models. The features above are common among mfg's in the market.

One thing to note is that the readings are only as good as the calibration solution and maintenance.

1) Depending on usage. sachets of buffers for 1 time use. Good for the person that might use 1x/month. Bottles are for the frequent user.  A small jar can be used for daily calibration and refreshed periodically (weekly).

2) Rinse probe in DI (purified) water before placing storage solution (ideally storage. If no storage is available then use pH 4). Either place a small sponge in the cap and soak with solution or place solution in a glass that the meter is then placed in. It is important that the bulb/junction remains damp.

3) Temperature kills pH probes! At 25 oC a probe will last 1-2 years. For every 25 oC increase cut that in half. So at 50 oC expect 6 month to 1 year. Be aware of pH probe limitations. Make sure that it is being used within operating specs (i.e. < 60 oC). There are pH electrodes that have a different glass and design for high temperatures. If you come to depend on pH then a portable might be the investment in the future.


One of the avid home brewers that work for Hanna Instruments

Offline mabrungard

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Re: ph meter
« Reply #4 on: September 08, 2015, 08:44:06 PM »
All very good recommendations above. I'll add some comments that are more applicable to the casual user.

1) I suggest that a meter with a cabled pH probe with a BNC connector may be one of your best bets since BNC replacement probes are widely available.

2) Waterproof is good in the brewery, but it will probably come at a cost. With an appropriate level of care, waterproof can be considered a nice option, but not a requirement. Evaluate your personal klutz quotient.

3) ATC is helpful and it does help refine your measurement capability. But since it is important to also account for the pH/temperature variation due to the chemistry of the wort, all wort pH measurements MUST be made at room-temperature (20C to 25C). For that reason, ATC becomes less important.

4) Auto calibration is a luxury and definitely not a requirement. However, if your klutz quotient is high, you might need this.

5) Auto shut-off. Good idea. May not be available in low-cost meters.

6) Battery indicator. Good idea. May not be available in low-cost meters.

7) Temperature readout. Great idea since you need to verify that the wort sample is at room temperature. May not be available in low-cost meters.

8 ) Stability Indicator. Good idea, but definitely not available in low-cost meters.

As mentioned, proper use and storage is critical to longevity. Do not stick a probe in hot wort or it will fail more quickly. I disagree with storing in pH4 calibration solution since it does not have the ionic strength necessary to help prevent the leaching of the valuable content out of the probe. Use only pH storage solution or create a solution by adding potassium chloride to pH4 calibration solution to create a KCl normality of around 1 to 2.

I've found that for the casual brewery user following those longevity recommendations, you can typically exceed the 2 year life span of a probe. I'm working on year 4 with my current probe and it still calibrates very well and is stable.
Martin B
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Offline AmandaK

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Re: ph meter
« Reply #5 on: September 08, 2015, 09:18:28 PM »
first mete ri purchased and first to get thrown away. erratic and couldnt get a calibration very well after just a short period.

much happier when switched to this:http://www.amazon.com/Hanna-Instruments-HI98128-Temperature-Tester/dp/B0085WV6GM/ref=sr_1_2?ie=UTF8&qid=1441236101&sr=8-2&keywords=ph+meter+hanna

also own this and it has been great:  http://www.thermoworks.com/products/ph/8100ph_meter.html

I currently have the Hanna you mentioned and finally replaced it a Thermoworks 8689 meter  8) - should be here tomorrow. My Hanna will attempt to dry up all of the storage solution if I look at it wrong. The "seal" between the black cap and the meter itself doesn't seem to be working very well, so I've been taping it up with electrical tape between uses - seems to slow the evaporation rate. At any rate, the Thermoworks seems to have a tighter seal than the Hanna and has the stability indication that Martin mentions. From what I can see, the 8689 is a steal at $69 and $29 electrodes but I could be wrong.
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Offline Wort-H.O.G.

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ph meter
« Reply #6 on: September 08, 2015, 11:04:24 PM »
first mete ri purchased and first to get thrown away. erratic and couldnt get a calibration very well after just a short period.

much happier when switched to this:http://www.amazon.com/Hanna-Instruments-HI98128-Temperature-Tester/dp/B0085WV6GM/ref=sr_1_2?ie=UTF8&qid=1441236101&sr=8-2&keywords=ph+meter+hanna

also own this and it has been great:  http://www.thermoworks.com/products/ph/8100ph_meter.html

I currently have the Hanna you mentioned and finally replaced it a Thermoworks 8689 meter  8) - should be here tomorrow. My Hanna will attempt to dry up all of the storage solution if I look at it wrong. The "seal" between the black cap and the meter itself doesn't seem to be working very well, so I've been taping it up with electrical tape between uses - seems to slow the evaporation rate. At any rate, the Thermoworks seems to have a tighter seal than the Hanna and has the stability indication that Martin mentions. From what I can see, the 8689 is a steal at $69 and $29 electrodes but I could be wrong.

Like my thermoworks the best. Replaceable cable probe, calibrates easily, stable, and fast reading. First probe only lasted about year because I was inexperienced in care. Second probe going on 3 years- always stored in storage solution and periodically cleaned with the low ph cleaning solution.


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« Last Edit: September 09, 2015, 01:13:15 AM by Wort-H.O.G. »
Ken- Chagrin Falls, OH
CPT, U.S.Army
https://www.facebook.com/pages/Harveys-Brewhaus/405092862905115

http://braukaiser.com/wiki/index.php?title=The_Science_of_Mashing

Serving:        In Process:
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Dort
Mead                 
Cider                         
Ger'merican Blonde
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Next:
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O'Fest

Offline jimmykx250

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Re: ph meter
« Reply #7 on: September 09, 2015, 12:28:43 AM »
Thank for the reply's. Think i will save a few penny's and get the thermoworks.
Jimmykx250

Offline Steve L

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Re: ph meter
« Reply #8 on: September 13, 2015, 04:30:46 PM »
I still love my MW101... although I do like the looks of the Thermoworks 8689 ;)
Corripe Cervisiam

Offline leejoreilly

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Re: ph meter
« Reply #9 on: September 14, 2015, 12:29:51 PM »
I still love my MW101... although I do like the looks of the Thermoworks 8689 ;)

+1 to the MW101

Offline pfabsits

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Re: ph meter
« Reply #10 on: September 14, 2015, 08:08:01 PM »
I disagree with storing in pH4 calibration solution since it does not have the ionic strength necessary to help prevent the leaching of the valuable content out of the probe. Use only pH storage solution or create a solution by adding potassium chloride to pH4 calibration solution to create a KCl normality of around 1 to 2.

All very good recommendations above. I'll add some comments that are more applicable to the casual user.

The use of storage solution is always first choice. Since most people as stated "are casual users" the I would expect that most will not buy storage solution.  Working for the manufacturer we have many that will only buy a single pH buffer value (i.e. 7.01). So for the user that does not invest in storage solution the use your pH buffer. The solution is only to maintain the hydration layer on the glass and to maintain a consistent junction potential. With testers, it is recommended to place a small sponge in the cap and keep that wet. We only need a drop or 2 to maintain a high enough humidity to prevent any drying of the glass and junction. This type of storage will not cause any diffusion or osmotic effect with regards to the reference electrolyte. So using pH 4 is less of a concern. Again storage solution is the first recommendation. 

I would not think the non-lab user will know how to make a 3.5M KCl solution. For double junction pH electrodes the fill solution is 3.5M KCl and not 1-2M. For a storage solution to isotonic in strength, it should match the fill solution. It would require having reagent grade KCl and an analytical balance to weigh (259 g/liter). The storage solution that we manufacture is not just a KCl solution adjusted to pH 4. There are other chemicals included as part of the formulation to minimize growth.

As far as the life of the pH probe, the only way to know is by understanding the offset and slope characteristics. To get a decent accuracy for the measurement the offset should be +/-30 mV and the slope greater  than 90%. If the probe is not within those specifications then just because the pH meter reads pH 7 buffer does not mean that the reading will be accurate in the sample. I have had customers being 1 pH unit off between meters after calibration.  In one case the customer was calibrating to pH 7 and 10 and they were also storing with ground water. The offset was >60 mV indicating a buildup on the glass and the slope was less than 85% due to the pH 10 buffer actually being pH 9.5. The customer know uses cleaning solutions periodically, sachets for calibration, and storage solution for storage. All is well and the portable field meters agree with the lab benchtops.

I know that the information above is a bit too much for the casual user. For that reason if you are using a tester or portable meter without a mV mode then I would recommend changing the electrode yearly, if not every other year. It is the razor blade of a pH meter. They do not last forever and the drift that occurs over time is well documented. If the offset and slope are within the tolerances stated then it can be used as long as the readings are fast, stable.

The biggest influencing factor in choosing a pH meter is to see what type of technical support is offered. Can you contact the company directly and get help. Once person commented that the first meter they purchased they had to throw away after a short period. If the short period is less than 6 months then the meter and probe are under warranty.I question whether they contacted the manufacturer.

One last thing to beware of are the companies that sell products on-line that are not necessarily selling fresh stock. The larger the company the more of an item that they purchase. It is very easy to have a warehouse person not rotate stock. When an on-line retailer has many warehousing locations to stock with an expansive number of sku's this becomes more probable than a small retailer that purchases direct from a mfg.
One of the avid home brewers that work for Hanna Instruments