Mash Temperature Techniques

CornyKegs 728
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sengsational

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I've seen some pretty advanced brewers screw up on mash temperature for lack of good measurements. Even with expensive thermometers, the mash temperature varies hugely within inches. Brewers are able to "dial in" crappy equipment over many batches, but that can be an expensive proposition as they end up with over and under attenuated batches. So to prevent myself from going through that pain, I decided I'd measure the heck out of my mash to make sure I'm right where I want to be. One step in that process is covered in a video that I recorded today.



The video talks about how I used a very accurate laboratory thermometer to make a cheat-sheet that will take the output from a cheap digital thermometer (wire probe type) and convert it to an accurate value in degrees F.
 
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Always good to calibrate, but I still wouldn't trust a cheap digital...especially if the error is not a constant. It would be interesting to see if you get the same results repeating the experiment a few more times in different conditions. That's the real test :mug:
 
Temp sensors, working over the range of freezing to boiling water, are really pretty linear. Thermocouples, temp sense diodes, RTD's, Hg thermometers, all are linear to any measurement any of us are doing (Brewing anyway. In my labs it gets a bit trickier.) The linearity is in the measurement noise over the distance of an inch of a mash. A simple 2 point cal is plenty good enough for any of these sensors over that range.

The OP is absolutely correct that the temp differentials over a mass as large as a mash will vary greatly. Especially with localized heat sources and large surface areas. Hence stirring to smooth that variation.

However, in actuality, those variations probably work to our advantage. Rather than having every molecule of every enzyme at exactly 152F, we will have a range of enzyme working temps between 148F and 156F, or some such. So, we get an average of that enzymatic action which allows us to relax, etc, etc...

It's all good.

Cheers
 
CryoEng said:
Temp sensors, working over the range of freezing to boiling water, are really pretty linear. Thermocouples, temp sense diodes, RTD's, Hg thermometers, all are linear to any measurement any of us are doing (Brewing anyway. In my labs it gets a bit trickier.) The linearity is in the measurement noise over the distance of an inch of a mash. A simple 2 point cal is plenty good enough for any of these sensors over that range.
Click to expand...

Cheap thermsitors tend not to be particularly linear, though rtds do well enough. The problems tend to come from the rest of the circuit, though: proper voltage regulation, shielding, etc. I've seen no shortage of cheap temp sensors with errors that are both non-linear and inconsistent from test to test. Whether or not this matters, of course, depends on how tightly you are interested in measuring. Plenty of people aren't worried about less than 4ºF variation.

CryoEng said:
The OP is absolutely correct that the temp differentials over a mass as large as a mash will vary greatly. Especially with localized heat sources and large surface areas. Hence stirring to smooth that variation.

However, in actuality, those variations probably work to our advantage. Rather than having every molecule of every enzyme at exactly 152F, we will have a range of enzyme working temps between 148F and 156F, or some such. So, we get an average of that enzymatic action which allows us to relax, etc, etc...

It's all good.

Cheers
Click to expand...

Unless, of course, you want consistency from batch to batch. A range of temperatures isn't a bad thing, perhaps, but it becomes increasingly difficult to know if a given reading sits at the low end or the high end of the spread.
 
I agree with the OP that the real source of uncertainty in mash temperature measurement is that the actual temperature of the mash varies with location. I tried to get all technical and calibrated my digital probe thermometers with my mercury-in-glass Kodak Process Thermometer, but it was a waste. I BIAB, and I can easily get a 5 degree C difference depending if I jam my probe thermometer down in the center of the grain or put in outside the bag near the side like I prefer. I base my actual temp on when I am vigorosly stirring the mash around the probe thermometer. If the outside cools, I just let it, reasoning that the grain is in the center. If I had a short probe thermometer installed in the wall of my mash tun/kettle, I would be several degrees off without a doubt.

Pro breweries have mechanical stirrers and constantly stir the mash; I always wondered why homebrewers never bother with stirrers.
 
would constant recirculation like in the advanced systems help even it out or is the effect negligible?
 
If you have poor connections in your electronics or something similar, you might have considerable variations in the system responses. The physics of the sensors and the electronics is about as well understood and consistent as the cosmos allows (background limited). The semiconductor doping isn't going to change over the human existence timescale on the planet.

If anyone wants to measure the short and long term stability of any commercially available temperature measuring system, I'm happy to review the effort.

Any temp measurement with a standard deviation of 0.25K is suspect in any environment. Radiative, conductive and convective loads and variations are always significantly more important than the scaled measurement of an amplified voltage from a well understood physical response to the energy of a system. I.E. the temperature/output of a thermocouple.

We've been sticking temperature dependent variable voltage/resistance devices onto the front of Op amps for about 100 years now. Trust me, if your cell phone works, any set of thermometers used in cooking should be the least of the brewer's worries.

Cheers... really...
 
CryoEng said:
If you have poor connections in your electronics or something similar, you might have considerable variations in the system responses. The physics of the sensors and the electronics is about as well understood and consistent as the cosmos allows (background limited). The semiconductor doping isn't going to change over the human existence timescale on the planet.

If anyone wants to measure the short and long term stability of any commercially available temperature measuring system, I'm happy to review the effort.

Any temp measurement with a standard deviation of 0.25K is suspect in any environment. Radiative, conductive and convective loads and variations are always significantly more important than the scaled measurement of an amplified voltage from a well understood physical response to the energy of a system. I.E. the temperature/output of a thermocouple.

We've been sticking temperature dependent variable voltage/resistance devices onto the front of Op amps for about 100 years now. Trust me, if your cell phone works, any set of thermometers used in cooking should be the least of the brewer's worries.

Cheers... really...
Click to expand...

Well...okay.

I'm not trying to turn this into a who's-more-sciencey pissing contest, but the only fact that's relevant to me is that I've seen the same cheap digital thermometer read 3 degrees above a lab thermometer at 150ºF one day and four degrees below it a week later. And then, when I tested a couple other completely different models, I saw exactly the same thing. The thermometer ends were sitting a half-inch from each other in recirculating water.

I believe you that the physics are well understood, but that doesn't change the fact that there are some really crappy digital thermometers out there. Was it the sensor or was it the rest of the circuit? I didn't bother to troubleshoot because it didn't really matter.
 
MalFet said:
Well...okay.

I'm not trying to turn this into a who's-more-sciencey pissing contest, but the only fact that's relevant to me is that I've seen the same cheap digital thermometer read 3 degrees above a lab thermometer at 150ºF one day and four degrees below it a week later. And then, when I tested a couple other completely different models, I saw exactly the same thing.

I believe you that the physics are well understood, but that doesn't change the fact that there are some really crappy digital thermometers out there. Was it the sensor or was it the rest of the circuit? I didn't bother to troubleshoot because it didn't really matter.
Click to expand...

Sorry MalFet. I don't want to cause friction either. Seriously, my apologies for coming across in a high handed way.

Measuring temperature, especially around the temps we live, in is old hat. I have to live around temps 200 degrees below that and study differentials of micro-degrees. Most people don't realize, but even that isn't all that difficult. (Don't tell my boss.)

The energy of a system (measured by the temperature) is so incredibly dominated by the environment that measuring it is almost impossible.

If you take the crappiest "thermometer" on the planet and try to measure the temperature of a mash from at one inch from the edge of the container to 3 inches from the edge of the container, that variation is orders of magnitude greater than the integrated sensitivity and stability of that device.

I regularly have to place a sensor on a 5kg block of copper, drop it into a bucket of LN2, then take that and drop it into a vacuum chamber (to make it "freeze" and shield it from convective/conductive/radiative heat loads) and then integrate (average) the sensor measurement over a week of amazingly stable energy/temperature conditions to report any variation.

In that daily effort, I come across a fair number of "measuring devices."

Nobody is close to measuring "the" temperature while brewing. It's a rough estimate at best, and fortunately, that's good enough for people to brew beer.

This is an amazing forum.

Cheers
 
CryoEng said:
Sorry MalFet. I don't want to cause friction either. Seriously, my apologies for coming across in a high handed way.

Measuring temperature, especially around the temps we live, in is old hat. I have to live around temps 200 degrees below that and study differentials of micro-degrees. Most people don't realize, but even that isn't all that difficult. (Don't tell my boss.)

The energy of a system (measured by the temperature) is so incredibly dominated by the environment that measuring it is almost impossible.

If you take the crappiest "thermometer" on the planet and try to measure the temperature of a mash from at one inch from the edge of the container to 3 inches from the edge of the container, that variation is orders of magnitude greater than the integrated sensitivity and stability of that device.

I regularly have to place a sensor on a 5kg block of copper, drop it into a bucket of LN2, then take that and drop it into a vacuum chamber (to make it "freeze" and shield it from convective/conductive/radiative heat loads) and then integrate (average) the sensor measurement over a week of amazingly stable energy/temperature conditions to report any variation.

In that daily effort, I come across a fair number of "measuring devices."

Nobody is close to measuring "the" temperature while brewing. It's a rough estimate at best, and fortunately, that's good enough for people to brew beer.

This is an amazing forum.

Cheers
Click to expand...

No worries man, glad to learn something from you :mug:

I get what you're saying I think, but I disagree about the futility of reliable temperature measurements. I recirculate the entire volume of my mash tun every four minutes or so, and likewise I see very consistent temperatures throughout my mash. Except for right up against the outer wall, I don't get more than a half degree's difference between any two given points in my tun.

Likewise, I am interested in having a reliable thermometer, because I know that whatever I measure will be reasonably representative. I'm not interested in tenths of a degree, and of course that many significant digits wouldn't be reliable. But, I am quite confident that I can deliver mash results consistent to within a degree or two. Likewise, measurement errors of two or three times that are both very possible with cheap equipment and very undesirable.
 
I'm using a Fluke 52II unit with thermcouples that can be submerged (stainless steel). I find that if I let them go deep enough, I get a good read for the entire mash. I'm also about to replace the dial thermometer on the side of the keg mash tun with a fitting that will allow me to place another thermocouple there (~2.5" reach into the keg). Since I can display both readings on the Fluke, I can average them.

The thermocouples I'm using are NOT cheap (over $30 each) nor is the 52II. I also have some Fisher Scientific thermometers that I can use when I wish (also not cheap).

IMO, thermometers (and other temperature sensors) are one place you shouldn't go cheap on. You don't need to spend a ton, simply find the best rate for the same item. Of course, I could have gone with a cheaper main unit, instead of the Fluke, but the accuracy of that other unit wasn't even close to what I have now (the Fluke was over double the cost though).

For clarification, I'm using the instrumentation I am so that I can get an accurate read of inside the mash tun/in the mash. On my last brew day, once I had stabilized the temperature, it didn't shift enough to warrant adding heat to it. Being able to hit your mash temps within a reasonable tolerance is really what matters. Do whatever you must to make that happen.
 
MalFet said:
No worries man, glad to learn something from you :mug:

I get what you're saying I think, but I disagree about the futility of reliable temperature measurements. I recirculate the entire volume of my mash tun every four minutes or so, and likewise I see very consistent temperatures throughout my mash. Except for right up against the outer wall, I don't get more than a half degree's difference between any two given points in my tun.

Likewise, I am interested in having a reliable thermometer, because I know that whatever I measure will be reasonably representative. I'm not interested in tenths of a degree, and of course that many significant digits wouldn't be reliable. But, I am quite confident that I can deliver mash results consistent to within a degree or two. Likewise, measurement errors of two or three times that are both very possible with cheap equipment and very undesirable.
Click to expand...

Absolutely! Repeatability is the key. You got it!

Absolute values are meaningless. But, with whatever you use, use it in the same, consistent way, and it will be fine. Hey, if you can get the thing to read near 273K when sitting in melting ice and 373K when in boiling water (atmospheric pressure above the surface of the water not withstanding... (what a load of useless BS...)) I dare anybody to question your effort!!

It's all just too easy today to focus on the instrumentation. Lazy effort... Insulation of the system, measuring at different places in the system, multiple points of data acquisition, homogenization, integration of measurements, etc are so amazingly more important than ANY error in the crappiest thermometer available that I just laugh.

Sorry. "Just my job , ma'am..."

Good to talk with you.

Cheers
 
CryoEng said:
It's all just too easy today to focus on the instrumentation. Lazy effort... Insulation of the system, measuring at different places in the system, multiple points of data acquisition, homogenization, integration of measurements, etc are so amazingly more important than ANY error in the crappiest thermometer available that I just laugh.
Click to expand...

Except when the error itself is inconsistent...that's the trouble I've had with all of the cheap thermometers I have bought. When you're getting the same error consistently, that's still consistency. The trouble is when the margin of error shifts in response to things that aren't readily obvious. I suspect a lot of the low grade stuff has trouble with power regulation and shielding, though there are plenty of good options to be found in the ~$20 range.
 
MalFet said:
Except when the error itself is inconsistent...that's the trouble I've had with all of the cheap thermometers I have bought. When you're getting the same error consistently, that's still consistency. The trouble is when the margin of error shifts in response to things that aren't readily obvious. I suspect a lot of the low grade stuff has trouble with power regulation and shielding, though there are plenty of good options to be found in the ~$20 range.
Click to expand...

What are you basing that variation on?

Clamp the thing onto a high specific heat mass, shield it from external heat loads and integrate the measurement. Does IT vary or is the variation in the experimental environment ie, the UUT (Unit Under Test).

Don't answer this too quickly. It's amazing how much variation there is in any REAL PHYSICAL TEMPERATURE. The object, substance, location of measurement, re-location of measurement, heat flow, thermal diffusivity of a material, etc, affect a temperature measurement in overwhelming ways.

Not to press too harshly, but I swear, a $2.99 Walgreens "measure the temp in your pants pocket" device will most likely embarrass you when you study the long and short term stability of the measurement.

Think about it. Try to imagine any substance or system you can use as a "perfect" temperature reference. Come up with one and let me know about it. Perfectly stable, energy loss/gain over seconds/minutes/hours and averages to a consistent temperature.

Convert that to a mass of water/grain in some sort of bucket with the top closed, maybe open, could be a compressed mass of vegetable matter or slightly less compressed mass of vegetable matter with a breeze blowing over the top of the somewhat more open container that was the full thickness of PTFE but has lost the material in the bottom and is sitting on the concrete in the garage instead of it being in the the NASA environmental test chamber which recently had it's seals upgraded but aren't as thermally resistive as the butyl seals we used in the last calibration of the Walgreens thermometer testing....

In thermal monitoring, the system will drive the testing FAR beyond our ability to measure it.

But it's so much fun!

Thanks!

Cheers
 
Golddiggie said:
I'm using a Fluke 52II unit with thermcouples that can be submerged (stainless steel). I find that if I let them go deep enough, I get a good read for the entire mash. I'm also about to replace the dial thermometer on the side of the keg mash tun with a fitting that will allow me to place another thermocouple there (~2.5" reach into the keg). Since I can display both readings on the Fluke, I can average them.

The thermocouples I'm using are NOT cheap (over $30 each) nor is the 52II. I also have some Fisher Scientific thermometers that I can use when I wish (also not cheap).

IMO, thermometers (and other temperature sensors) are one place you shouldn't go cheap on. You don't need to spend a ton, simply find the best rate for the same item. Of course, I could have gone with a cheaper main unit, instead of the Fluke, but the accuracy of that other unit wasn't even close to what I have now (the Fluke was over double the cost though).

For clarification, I'm using the instrumentation I am so that I can get an accurate read of inside the mash tun/in the mash. On my last brew day, once I had stabilized the temperature, it didn't shift enough to warrant adding heat to it. Being able to hit your mash temps within a reasonable tolerance is really what matters. Do whatever you must to make that happen.
Click to expand...

I agree completely. The Fluke gear is an excellent reference for work well beyond brewing. Seriously good stuff for this effort. Cool.

You'd be hard pressed to do more than what you're doing to monitor your temps.

I once built a "paddle-stick" with six Lakeshore diodes (cause I could... don't repeat this.. (http://www.lakeshore.com/Pages/Home.aspx) to use to stir a mash. Frankly, my data showed exactly what one would predict. If you apply heat from the bottom.... the lower areas will warm up more than the areas exposed to the unheated air on top. Stir and it homogenizes. Wow.

Could have guessed, but didn't want to negate the possibility that Kirk and Spock would throw some extra physics into the mix.

I seriously respect the efforts of everyone making beer who contribute to this forum. However, sometimes we tend to make magic out of things people have understood and have integrated into their automobile seat warmers for a few decades now. Technical instrumentation trades for cooking is a subject for "Rachael Ray's, How to boil an egg" show. Not us.

Cheers... Really, I luv you man... Cheers....
 
I have my keg mash tun setup so that I can recirculate the wort while adding heat to it. I can do either that (via a pump) or simply stir...

I am rather stoked about getting my new mash paddle for this. Going to be interesting to see how it performs compared with my cheap one (3' wood stir paddle from restaurant supplier with a few 1" holes drilled into it)... The new mash paddle is shown here... ETA is Wednesday, so in time for my next brew day (the 16th)... :D
 
MalFet said:
No worries man, glad to learn something from you :mug:

I get what you're saying I think, but I disagree about the futility of reliable temperature measurements. I recirculate the entire volume of my mash tun every four minutes or so, and likewise I see very consistent temperatures throughout my mash. Except for right up against the outer wall, I don't get more than a half degree's difference between any two given points in my tun.

Likewise, I am interested in having a reliable thermometer, because I know that whatever I measure will be reasonably representative. I'm not interested in tenths of a degree, and of course that many significant digits wouldn't be reliable. But, I am quite confident that I can deliver mash results consistent to within a degree or two. Likewise, measurement errors of two or three times that are both very possible with cheap equipment and very undesirable.
Click to expand...

As far as I'd comment, you have an excellent handle on what actually matters. I'm guessing you have some fun poking at the thermal processes going on here. It's really a great challenge, yes???

You can get a reasonable calibration on most any decent monitoring gear and then get an "understanding" of that "specific" set of equipment. You can do some amazing measurements, and control your process to a high quality level.

The consistency you have is really the goal. if you control your process, you can fine tune it to better your quality. Absolute values are not as important as consistency. Absolute temperatures are (seriously) a topic for quantum physicists, but process consistency can be obtained by Rachel at the lettuce cutting board...

Six Sigma and Lean drives are based on control of process. A completely understood B+ process is far more desirable that an intermittently successful A+ process.

If the output varies, you know immediately what, in the process, caused the variation. Unfortunately, thermal control and monitoring is one of the hardest physical challenges that exists.

It's in the fabric of the cosmos/God/whatever. Carnot said it would be hard, and he was right.

Cheers, I'm drinking a Boulevard Pale and enjoying our banter.
 
Golddiggie said:
I have my keg mash tun setup so that I can recirculate the wort while adding heat to it. I can do either that (via a pump) or simply stir...

I am rather stoked about getting my new mash paddle for this. Going to be interesting to see how it performs compared with my cheap one (3' wood stir paddle from restaurant supplier with a few 1" holes drilled into it)... The new mash paddle is shown here... ETA is Wednesday, so in time for my next brew day (the 16th)... :D
Click to expand...

I think what you're doing will ultimately have more impact for us small scale brewers than all of the "super fine details" we focus on.

Something like a "multiple temp sense point mash paddle" could be the next the cool product for the home brewer's kit.

Why do I think I just blew a chance to retire early....???

Cheers.... I want first dibs on the stock options....
 
CryoEng said:
What are you basing that variation on?

Clamp the thing onto a high specific heat mass, shield it from external heat loads and integrate the measurement. Does IT vary or is the variation in the experimental environment ie, the UUT (Unit Under Test).

Don't answer this too quickly. It's amazing how much variation there is in any REAL PHYSICAL TEMPERATURE. The object, substance, location of measurement, re-location of measurement, heat flow, thermal diffusivity of a material, etc, affect a temperature measurement in overwhelming ways.

Not to press too harshly, but I swear, a $2.99 Walgreens "measure the temp in your pants pocket" device will most likely embarrass you when you study the long and short term stability of the measurement.

Think about it. Try to imagine any substance or system you can use as a "perfect" temperature reference. Come up with one and let me know about it. Perfectly stable, energy loss/gain over seconds/minutes/hours and averages to a consistent temperature.

Convert that to a mass of water/grain in some sort of bucket with the top closed, maybe open, could be a compressed mass of vegetable matter or slightly less compressed mass of vegetable matter with a breeze blowing over the top of the somewhat more open container that was the full thickness of PTFE but has lost the material in the bottom and is sitting on the concrete in the garage instead of it being in the the NASA environmental test chamber which recently had it's seals upgraded but aren't as thermally resistive as the butyl seals we used in the last calibration of the Walgreens thermometer testing....

In thermal monitoring, the system will drive the testing FAR beyond our ability to measure it.

But it's so much fun!

Thanks!

Cheers
Click to expand...

I understand what you're saying...believe me. I've probably destroyed $10k worth of temperature sensors over the years while trying to understand the stability of measurement with commercial coffee roasters.

I'm sure there are some great thermometers out there for $3.99. There are also some terrible ones, and this is all I'm suggesting. Everything I am saying is based on the following calibration procedure: five gallons of turbulent/recirculating water, temperature probe secured less than an inch away from a NIST traceable glass thermometer, readings from 0ºC to boiling. When a digital thermometer is 3º above the glass one one day and 2º below it a week later, there's no fixing it with calibration. It's just a bad piece of equipment.

This isn't about finding a "perfect" temperature reference. This is about thermometers that are simply inconsistent. Heck, I've got a thermometer here right now that is reading 6ºC different when I switch between a new and an old battery. This kind of thing is far more common than I think you might suspect.
 
sengsational said:
Even with expensive thermometers, the mash temperature varies hugely within inches.
Click to expand...

My little non-scientific eyes zero'd in on the "varies hugely within inches" part of this hypothesis.

And I have to say, after doing a mash just for this, um, no it doesn't.

My mash temp varied from 151.8 to 152.1, throughout the entire mash bed. I checked.

I stirred the mash thoroughly, as always. Then stirred some more. And then checked the temperature in +/- 25 places. The only discrenpency was measured at 152.1, which was .3 difference than 20 other places.
 
MalFet said:
I understand what you're saying...believe me. I've probably destroyed $10k worth of temperature sensors over the years while trying to understand the stability of measurement with commercial coffee roasters.

I'm sure there are some great thermometers out there for $3.99. There are also some terrible ones, and this is all I'm suggesting. Everything I am saying is based on the following calibration procedure: five gallons of turbulent/recirculating water, temperature probe secured less than an inch away from a NIST traceable glass thermometer, readings from 0ºC to boiling. When a digital thermometer is 3º above the glass one one day and 2º below it a week later, there's no fixing it with calibration. It's just a bad piece of equipment.

This isn't about finding a "perfect" temperature reference. This is about thermometers that are simply inconsistent. Heck, I've got a thermometer here right now that is reading 6ºC different when I switch between a new and an old battery. This kind of thing is far more common than I think you might suspect.
Click to expand...

Hey, been there man!

There's junk everywhere and temp measurement is not protected from the BS.

It's your observations that make the difference It's so easy to blame the gear when the measurements are not quite what we would like, but blame the UUT when we want to point to a larger process (system).

I've seen some seriously poor implementations of the technology, but the tech in general is about as basic as there is. It's not magical and it's not perfect either. There is a lot of background and research and a whole lot of application experience over the range people live in.

It gets even more weird at lower and higher temps. Still, every experience is a data point.

If we stay at it, we'll figure a way to make it all even easier.

Cheers
 
Yooper said:
My little non-scientific eyes zero'd in on the "varies hugely within inches" part of this hypothesis.

And I have to say, after doing a mash just for this, um, no it doesn't.

My mash temp varied from 151.8 to 152.1, throughout the entire mash bed. I checked.

I stirred the mash thoroughly, as always. Then stirred some more. And then checked the temperature in +/- 25 places. The only discrenpency was measured at 152.1, which was .3 difference than 20 other places.
Click to expand...

Be careful. The resolution of any measurement is based on bandwidth and integration time. The fact that your data points are very closely spaced does not necessarily point to consistent physical conditions of the system under test.

The fact that you are reporting such a small variation is not automatically supportive of your hypothesis. What is you standard deviation? (error)

Not being able to resolve a difference is not support for a small deviation.

You can simply have a measurement device which has a long measurement time constant or the resolution of the sensor may be lower than your reporting differentials.

Take a glass of water and put it on a stove element. I guarantee that there is a huge difference between the temperature of the bottom "layer" of water and that of the the boiling surface. When one speaks of the "boiling point" they are talking about the very surface of a boiling liquid under a certain surface pressure. In fact, there are 3 distinct phases of "boiling" which are going on in that particular glass. Some research suggests a few more.

You CAN measure the difference between the temp of the bottom of the liquid and the surface of the liquid under those conditions. It's just not that simple to do so.

I absolutely guarantee you that the physical temperature of any mass has a differential through it. If one square micrometer, that a surface sees, is one billionth of a degree different than the surface exposed, there is a temp differential in the mass. If not, you've just written some seriously new physics and we're eagerly anticipating the publication.

Cheers
 
CryoEng said:
Be careful. The resolution of any measurement is based on bandwidth and integration time. The fact that your data points are very closely spaced does not necessarily point to consistent physical conditions of the system under test.

The fact that you are reporting such a small variation is not automatically supportive of your hypothesis. What is you standard deviation? (error)

Not being able to resolve a difference is not support for a small deviation.

You can simply have a measurement device which has a long measurement time constant or the resolution of the sensor may be lower than your reporting differentials.

Take a glass of water and put it on a stove element. I guarantee that there is a huge difference between the temperature of the bottom "layer" of water and that of the the boiling surface. When one speaks of the "boiling point" they are talking about the very surface of a boiling liquid under a certain surface pressure. In fact, there are 3 distinct phases of "boiling" which are going on in that particular glass. Some research suggests a few more.

You CAN measure the difference between the temp of the bottom of the liquid and the surface of the liquid under those conditions. It's just not that simple to do so.

I absolutely guarantee you that the physical temperature of any mass has a differential through it. If one square micrometer, that a surface sees, is one billionth of a degree different than the surface exposed, there is a temp differential in the mass. If not, you've just written some seriously new physics and we're eagerly anticipating the publication.

Cheers
Click to expand...

It's clear that you know a lot about this kind of stuff, but...seriously...you need to give people a little more credit. When Yooper says that there isn't any temperature variation in her mash bed, I'm willing to bet that she's not making claims about billionths of a degree. The point, I believe, is that the mash bed is consistent within the range she is talking about.

We get it...all masses have temperature differentials. But there's a measurable and consequential difference between 6º differentials and .3º differentials. That's the point here.
 
MalFet said:
It's clear that you know a lot about this kind of stuff, but...seriously...you need to give people a little more credit. When Yooper says that there isn't any temperature variation in her mash bed, I'm willing to bet that she's not making claims about billionths of a degree. The point, I believe, is that the mash bed is consistent within the range she is talking about.

We get it...all masses have temperature differentials. But there's a measurable and consequential difference between 6º differentials and .3º differentials. That's the point here.
Click to expand...

Yes, that's all I was saying. I believe that mash temperature is very important in brewing, and that it's important to have a good thermometer and to take measurements. I think a range of +/- a degree in an entire 30 pound mash is not anything to get worked up about. There should be no noticeable effect on the beer, and that is the important thing.

My HLT has an electric stirrer, as I recognize that the water needs to be agitated to avoid "hot spots" and cold spots. I stir my mash when I dough in, and then I do recirculate the wort later on.
 
MalFet said:
Everything I am saying is based on the following calibration procedure: five gallons of turbulent/recirculating water, temperature probe secured less than an inch away from a NIST traceable glass thermometer, readings from 0ºC to boiling. When a digital thermometer is 3º above the glass one one day and 2º below it a week later, there's no fixing it with calibration. It's just a bad piece of equipment.
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Isn't it possible that the temp was rising in the first experiment and falling in the second and that the digital was quicker to resolve the temperature changes due to less mass of the sensor vs the glass thermometer? Or was your 3º above consistent from 0ºC to boiling?
 
mobly99 said:
Isn't it possible that the temp was rising in the first experiment and falling in the second and that the digital was quicker to resolve the temperature changes due to less mass of the sensor vs the glass thermometer? Or was your 3º above consistent from 0ºC to boiling?
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I'm summarizing quite a bit here, as I've spent many, many obsessive hours trying to find reliable, cheap digital thermometers (for business, not for brewing). I've tested with temps rising, with temps falling, and with temps holding constant. I've tested in high heat mass substances like water, and in low heat mass substances like air.

To be honest, I'm not sure why this is so controversial. A circuit is only as reliable as its crappiest part, and in many of these cheap-o thermometers the power regulation leaves a lot to be desired.
 
MalFet said:
I'm summarizing quite a bit here, as I've spent many, many obsessive hours trying to find reliable, cheap digital thermometers (for business, not for brewing). I've tested with temps rising, with temps falling, and with temps holding constant. I've tested in high heat mass substances like water, and in low heat mass substances like air.

To be honest, I'm not sure why this is so controversial. A circuit is only as reliable as its crappiest part, and in many of these cheap-o thermometers the power regulation leaves a lot to be desired.
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Any chance you could put up a list of the makes/models to avoid (the real crappy ones especially) and maybe even the ones you found to be really good from your testing? I think that would go a long way towards helping others pick a solid thermometer to use.

Personally, the thermometers I've purchased (made by Fisher) for the brewing process all have the NIST sheets with them. They're also not what I would call cheap. I find it difficult to trust a digital thermometer that costs less than $15-$20. This is one of the ones I have and use (from time to time). I have another that has a 10' cord connecting the display to the probe, that I've used as well.
 
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I'll see if I can dig up my notes, but this was a couple years ago so I'll have to look for them.

There were plenty of reliable units in the ~$10 range. A pretty good rule of thumb is that if the company also makes high end stuff their cheap units will be solid. The trouble was always with the no-name units you see in the grocery store.

I have a CDN probe that I got for $15 that I like nearly as much as my thermapen.
 
I've had pretty much all the BB&B purchased digital thermometers (instant read) fail on me after using them for brewing. They don't seem to have the electronics sealed, or sealed well enough, to survive. The Fisher models are solid, and call out either waterproof, or damned close to it.

I used a candy thermometer early on in my brewing life. It failed after about 2-3 batches (had it clipped to the side of the pot, so that I could see the temperature). It was digital and too much moisture got into it and killed it. I also don't use the oven probe thermometer for brewing. I did that one time, to see how it would work out and it wasn't even close on the reading. It was ok in the lower temperature range, but once it started getting past about 150F (maybe 160F+) it was drifting a lot. Not something I would trust for a mash tun. I'm sure there are good units out there, it's just not what I have. It's fine for a roast, and such (usually under 140F anyway) just not something I'll use for brewing.
 
This a great topic. There is a lot of discussion about temps, but not much about methods and measurement.

Personally I rely on strike temperature, stir well and put it in the oven.

The best method I have found to measure the mash temp is to attach the sensor to the mash paddle, though it’s awkward. I wish somebody would market a paddle/thermometer combo.

It’s a little off topic, but would somebody tell me how much variation there is in an active fermentation? I say the top center of the fermenting wort is 5-10°F hotter than the outside of the carboy. The conventional wisdom is that they’re about the same and I think that’s absurd.
 
Wynne-R said:
This a great topic. There is a lot of discussion about temps, but not much about methods and measurement.

Personally I rely on strike temperature, stir well and put it in the oven.

The best method I have found to measure the mash temp is to attach the sensor to the mash paddle, though it’s awkward. I wish somebody would market a paddle/thermometer combo.

It’s a little off topic, but would somebody tell me how much variation there is in an active fermentation? I say the top center of the fermenting wort is 5-10°F hotter than the outside of the carboy. The conventional wisdom is that they’re about the same and I think that’s absurd.
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In my experience, during an active fermentation the beer is churning pretty well, and the temperature of the beer varies very little throughout- about a degree at the most.
 
Yooper said:
In my experience, during an active fermentation the beer is churning pretty well, and the temperature of the beer varies very little throughout- about a degree at the most.
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+1 on that. I have a thermowell on my sanke fermenter cap that goes into the middle of the fermenting beer. I trust that temperature reading far more than on the outside. I want to know what the majority of the batch is fermenting at, not the last 1/2" from the outside.
 
Golddiggie said:
+1 on that. I have a thermowell on my sanke fermenter cap that goes into the middle of the fermenting beer. I trust that temperature reading far more than on the outside. I want to know what the majority of the batch is fermenting at, not the last 1/2" from the outside.
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I used to do that, until I actually ran a bunch of comparison tests to see the difference between the thermowell's temperature and the temperature of a probe taped and insulated to the side of the (ss) fermentor. Even during the most vigorous fermentation, I never saw more than 1/2 ºC difference. YMMV.
 
1°F, really? I saw 5° on a floating thermometer compared to the stick-on lcd thermometer. That was before the krausen engulfed the floating thermometer. Does it make a difference that the carboy is in a water bath?
 
Wynne-R said:
1°F, really? I saw 5° on a floating thermometer compared to the stick-on lcd thermometer. That was before the krausen engulfed the floating thermometer. Does it make a difference that the carboy is in a water bath?
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Insulating the probe tip is key, otherwise you'll just read some kind of average of the wort and the ambient air. I'm not a huge fan of the LCD stickers for this reason.
 
I also plug up the top of the thermowell, so ambient air doesn't impact the reading.

Plus, with the thermowell, there's less things to move to another fermenter.

Not saying either is better than the other, just I like what I do better than trying to take readings from the outside.
 
You all are way smarter than I am! But I doubt anyone has spent less on their equipment, hehe.

Consistency of the el-cheapos I got from Hong-Kong - So far very accurate. I've had them for about 3 months, tested them all at boiling and ice when I first got them, but didn't have the allafrance lab thermometer to calibrate. I tested them all again recently and they came in the same (within .1 degree C). Like I said three of them were spot on together, and two were in left field, but they too were consistenly off. If they ever get inconsistent, I'll order another half-dozen from Hong-Kong.

About mash temperature varying with position - Obviously depends on the equipment, but I brewed last weekend with the three probes. I placed the probes (roughly) bottom outside, center inside, and top outside (in a diagonal). This was a cylindrical insulated mash tun (rubbermaid, I think it is, $42.88 delivered). I stirred well, but obviously the outside is going to be loosing heat faster than the center, and that's what I saw. If I stirred again, the differences became less, but when folks are making a big deal about exact mash temperatures (150F vs 152F), it's a bit disconcerting to see temperatures larger than that that are, and I maintain it's true, just inches from each other. But I also agree with the comment that it's probably good to have a mix of temperatures.

The rest of it - Like I said, you're all a hell of a lot smarter than I am, hehe.

--Dale--
 
sengsational said:
Consistency of the el-cheapos I got from Hong-Kong - So far very accurate. I've had them for about 3 months, tested them all at boiling and ice when I first got them, but didn't have the allafrance lab thermometer to calibrate. I tested them all again recently and they came in the same (within .1 degree C). Like I said three of them were spot on together, and two were in left field, but they too were consistenly off. If they ever get inconsistent, I'll order another half-dozen from Hong-Kong.
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Great!

I certainly didn't mean to come down on every cheap thermometer. There are plenty of good ones out there, even for small money. I would, however, recommend testing again a few months down the road...once the batteries have faded a bit. This, I suspect, was the principle source of tbe problems that I saw.
 

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