DIY pH Meter
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Displaced MassHole
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Although that looks simple to me (I'm an avionics tech and work with schematics/electronics daily) I think your every day joe schmoe might have a seizure while reading that article. Let alone trying to put one together.
Sorry if I sound harsh.
I might just give that a go, with all the "extra" parts that the govt. has lying around my shop.
Sorry if I sound harsh.
I might just give that a go, with all the "extra" parts that the govt. has lying around my shop.
Budzu
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I like the idea, however there are alot of cheap digi ph meters out there, plus this design doesn't seem to address temperature compensation so I'd worry about that.
shortyjacobs
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Woah, way cool.
As for Budzu's comment, I think any temp compensation, (if it exists), would be in the probe, would it not? Unless the probe also has a thermistor/thermocouple that also outputs to your standard digi pH meter, a standard pH meter would have no way of knowing the temperature...all it gets is a voltage reading from the probe, same as this circuit...
Be sweet to hook this up to a brewing computer...
As for Budzu's comment, I think any temp compensation, (if it exists), would be in the probe, would it not? Unless the probe also has a thermistor/thermocouple that also outputs to your standard digi pH meter, a standard pH meter would have no way of knowing the temperature...all it gets is a voltage reading from the probe, same as this circuit...
Be sweet to hook this up to a brewing computer...
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I worry more about if you really know what ATC is about. And how it is applied to your meter.
Maybe you do.
Most don't.
jkarp
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Care to rephrase GilaMinumBeer? Otherwise you're just sounding like a ******.
BrewBeemer
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That was wet and below the belt LOL!
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Done. Take it how you want. Balsamic or distilled white.
remilard
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Thats neat but, most of the cost of a pH meter is the probe so this doesn't save a ton of money.
Looks like it is time to get my soldering iron back out. Prep some copper sheets and some acid.
That looks a really simple circuit. It will be fun to see how well it works. Maybe I will incorporate it into the design of my new system.
That looks a really simple circuit. It will be fun to see how well it works. Maybe I will incorporate it into the design of my new system.
Displaced MassHole
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BrewBeemer
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You must post your results of this project.
EarthBound
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+1 on that. It's nice to see feedback containing value like what budza was trying to convey.
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Okay. That is all fine and well so long as you understand how the instrument you are using applies ATC. Not all ATC is created equal. Be it pH meters or refractometers.
Yes. Many reputable pH meters with ATC adjust for sample temp, provided they have an integral therm sensor in the probe. Many do not and they must be adjusted for ATC manually. Some of the cheap probes only adjust for moderate instrument temp fluctuations. Much like a refractometer does.
If you don;t know how your probe corrects then you might as well just use it like you do a hydrometer and note the sample temp and reference a correction table. Theres no extra charge for that. Or, just let the sample cool to a proper temp for the most accurate reading regardless of ATC or not.
Personally, I find such alarmist commentary irritating in that it compels some to look for a feature they either do not need, do not understand, and worse do not use peoperly. Had the post been more elaborated on regarding ATC functionality I would not have been so blunt.
To generically say that not having ATC is worrysome is as irresponsible as saying pH is un-important.
Capice'?
EarthBound
Well-Known Member
I think that was a REALLY good explanation.
What do you think is the best method of taking a pH sample?
Budzu
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Welly welly well its all good gents
I do not understand how temp compensation works on Ph meters, but what I DO know is that it is a feature that ph manufacturers always address. If I was to build this, I would make sure to understand and address the affect of temperature on the meter build. That's all I's sayin.
Lets chill and have a homebrew
I do not understand how temp compensation works on Ph meters, but what I DO know is that it is a feature that ph manufacturers always address. If I was to build this, I would make sure to understand and address the affect of temperature on the meter build. That's all I's sayin.
Lets chill and have a homebrew
jkarp
Well-Known Member
Well said GilaMinumBeer.
Interesting trivia: ATC in both refractometers and pH meters has nothing to do with the actual sample temp. In a refractometer, the sample is so small, it's instantly brought to the same temp as the instrument due to its thermal mass. ATC in a refractometer is compensating for the instrument temperature, not sample. In a pH meter, ATC compensates for the actual sensor's sensitivity errors due to temp. A solution's pH does indeed change with temp, but the meter doesn't care one bit about that. In other words, with a pH meter with ATC, you'd get different readings of the same wort at boiling and room temp. In fact, if you didn't, the meter's defective.
Interesting trivia: ATC in both refractometers and pH meters has nothing to do with the actual sample temp. In a refractometer, the sample is so small, it's instantly brought to the same temp as the instrument due to its thermal mass. ATC in a refractometer is compensating for the instrument temperature, not sample. In a pH meter, ATC compensates for the actual sensor's sensitivity errors due to temp. A solution's pH does indeed change with temp, but the meter doesn't care one bit about that. In other words, with a pH meter with ATC, you'd get different readings of the same wort at boiling and room temp. In fact, if you didn't, the meter's defective.
Budzu
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So if one were to build this, would the temperature of the sample and/or ambient temp have to be calculated into the reading? If so any idea how?
edit: err so I think I understand that this would be dependent on the probe only.
edit: err so I think I understand that this would be dependent on the probe only.
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Yes. It works much like a hydrometer sample.
You take the sample temp and the air temp and reference a chart.
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With a pH meter at it's calibrated design temp. that will be the most accurate reading and no correction is required.
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Fair enough but,
and
Budzu said:
is why so many meters address it. ATC meters cost more and are useful when the ATC function is understood and applied properly by the end user.
From my readings, ATC is really a design feature that was adopted for in-line pH sensors on pipeline or process systems where ambient temps would fluctuate moderately depending on the season or time of day.
The feature then was migrated into handheld and bench meters.
Most of the lab tech I have known just make sure their sample is at the proper testing temp. Much like we should do with our hydrometers. But, then again we aren't making rocket fuel here and ATC fluctuations are actually pretty small based on the wide pH range we are concerned about.
A good technical read on temperature effects on pH.
and a good industry reference on pH in general.
While the PH circuit looks simple to build it will need some calculations and a table to be able to get any meaning full PH information with that setup. There is no means of calibration and no 2 PH probes and transmitters I have calibrated and installed have ever had identical electrical response to buffer solutions or actual solutions out of the box. I would hate to see someone spend $100 on a probe only to find out that the circuit will not give any reasonable results. It would be better to spend the money on a temperature compensated hand held and test solutions so you could get reproducible results, and adjust calibration as the PH element ages.
I install and calibrate industrial instrumentation, PH and ORP devices included, so I feel that I am reasonably competent in this field.
I install and calibrate industrial instrumentation, PH and ORP devices included, so I feel that I am reasonably competent in this field.
As mentioned before I don't see this as being a cheaper alternative by any means but I do like the idea of being able to output. This would come in handy for those who are planning to make an automated rig (like myself). Make the program announce if the mash is getting out of range on the ph.
kladue, do you think the circuit could/should be modified to give better results or do you think it's simply a matter of calibrating correctly and keeping up with the calibration?
kladue, do you think the circuit could/should be modified to give better results or do you think it's simply a matter of calibrating correctly and keeping up with the calibration?
The circuit is a simple amplifier, you would need a way to apply a bias voltage to correct for sensor output in standard solution, and then that would only apply at that temperature. You would have to add another amplifier to bring signal level up to 0-5 volts for interface with an automation system input. If you added a temperature sensor for correction, then setup the formula in the software to correct PH sensor response you might be getting in the ball park for a reading. After all the circuit building, programming,and tuning, then the purchase of a PH sensor, it would likely cost as much as a handheld, or a used lab model with voltage output. The sensors degrade in use and will have to be recalibrated at intervals because the electrolyte diffuses through the bulb in use. So the initial setup will have to be revisited on a semi annual basis to keep getting meaningfull results.
What about using a probe that already has ATC or am I missing something? I found the one below for $68. Not sure if that could be used or not.
http://www.amazon.com/dp/B00132G102/?tag=skimlinks_replacement-20
http://www.amazon.com/dp/B00132G102/?tag=skimlinks_replacement-20
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Yeah brother you are missing it. That is a probe and a meter. This is talk about buying a probed (the bit that goes into the sample) and building the electrics by your onsies. the electrics have the ATC, not the probe itself. The probe is the white bit with the slots at the end. It's replaceable.
Here is an link to a more elaborate circuit for PH, but it still lacks the temperature compensation. http://www.emesystems.com/OL2ph.htm. This would be a better jumping off point for the Arduino crowd as there are interface circuits to deliver voltage signals to analog inputs.
Ok, I figured I was missing something. Thanks for the clarification.
