Author Topic: Digital Thermometer Options for Beer Brewing  (Read 268 times)

Offline BeerSmith

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Digital Thermometer Options for Beer Brewing
« on: November 29, 2017, 03:39:00 PM »
Digital Thermometer Options for Beer Brewing
  http://beersmith.com/blog/2017/11/29/digital-thermometer-options-for-beer-brewing/

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Offline Oddball

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Re: Digital Thermometer Options for Beer Brewing
« Reply #1 on: December 06, 2017, 05:31:15 AM »
Hi Brad,

I work with infrared camera's and Infrared ray-techs similar to what you reviewed here. To get accurate readings on different surfaces you need to know their emissivity (The % amount of temperature the material emits), The other factors are Reflection and Refraction. There are very few materials that get above 99% emissivity and are generally only used for calibrating cameras. Liquids are generally pretty poor to take accurate temperature readings on because you will get a lot of Reflection from surrounding objects as all objects emit heat, and also refraction through the liquid. So, although you may have got a decently accurate reading from the water you would need to change emissivity once there are bubbles, and different solids to measure off of. You may be able to get a bit more accuracy if you set the emissivity higher (0.90 or so) and only open the lid a bit, just enough to get the gun in and take a reading so that any reflection would be coming off of surfaces that are also reflecting the water/wort. Or just use a common style thermometer as they will be more reliable in this application.

Offline KellerBrauer

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Re: Digital Thermometer Options for Beer Brewing
« Reply #2 on: December 06, 2017, 06:04:46 AM »
Hi Brad,

I work with infrared camera's and Infrared ray-techs similar to what you reviewed here. To get accurate readings on different surfaces you need to know their emissivity (The % amount of temperature the material emits), The other factors are Reflection and Refraction. There are very few materials that get above 99% emissivity and are generally only used for calibrating cameras. Liquids are generally pretty poor to take accurate temperature readings on because you will get a lot of Reflection from surrounding objects as all objects emit heat, and also refraction through the liquid. So, although you may have got a decently accurate reading from the water you would need to change emissivity once there are bubbles, and different solids to measure off of. You may be able to get a bit more accuracy if you set the emissivity higher (0.90 or so) and only open the lid a bit, just enough to get the gun in and take a reading so that any reflection would be coming off of surfaces that are also reflecting the water/wort. Or just use a common style thermometer as they will be more reliable in this application.

I use an infrared thermometer to measure the temperature of my fermenter and have found it works very well.  I keep a dial thermometer next to my fermenter to read ambient temperature so I can compare ambient temperature to the temperature of the fermenter.  I occasionally check the accuracy of these two measuring devices with a thermometer that was calibrated and certified according to ANSI standards. The dial thermometer is within +/- 1.0 degrees and the infrared is within +/- .5 degree - both numbers I?m quite satisfied with.

https://www.amazon.com/Non-Contact-Thermometer-Temperature-58℉-1022℉-50℃~550℃/dp/B06Y2V6VNQ/ref=sr_1_16?ie=UTF8&qid=1512565078&sr=8-16&keywords=infrared+thermometer&refinements=p_72%3A2661618011 (Amazon Link)
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Offline GigaFemto

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Re: Digital Thermometer Options for Beer Brewing
« Reply #3 on: December 06, 2017, 09:00:41 AM »
I use an infrared thermometer at various stages in beer making, and find it very handy. I use it to measure the temperature of my cooling wort when making a yeast starter, where a few degrees don't matter, and when measuring temperatures of samples being cooled down for gravity and pH measurements. In those cases a quick measurement on a small sample is needed, and then a more accurate and slower measurement can be made once the infrared says the temperature is close.

One problem when measuring hot liquids is that the thermometer reads the steam and not the underlying liquid.

I don't see that reflection or refraction are important here because the measurement is not as Brad described. The laser is a visible laser and has nothing to do with the measurement and is only used to tell you where the instrument is pointing. The actual measurement uses the infrared (blackbody) emission that is captured by the sensor. Emissivity is important, so measuring the outside of a shiny kettle versus a dark wort would give different results.

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Offline Oddball

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Re: Digital Thermometer Options for Beer Brewing
« Reply #4 on: December 06, 2017, 11:02:33 AM »
I use an infrared thermometer at various stages in beer making, and find it very handy. I use it to measure the temperature of my cooling wort when making a yeast starter, where a few degrees don't matter, and when measuring temperatures of samples being cooled down for gravity and pH measurements. In those cases a quick measurement on a small sample is needed, and then a more accurate and slower measurement can be made once the infrared says the temperature is close.

One problem when measuring hot liquids is that the thermometer reads the steam and not the underlying liquid.

I don't see that reflection or refraction are important here because the measurement is not as Brad described. The laser is a visible laser and has nothing to do with the measurement and is only used to tell you where the instrument is pointing. The actual measurement uses the infrared (blackbody) emission that is captured by the sensor. Emissivity is important, so measuring the outside of a shiny kettle versus a dark wort would give different results.

--GF

The reflection and refraction would have more to do with your surroundings is what I was intending to imply. Since all objects that are not at absolute zero (−273.15C) give off heat, whether less than or more than the object being measured it can affect the overall temperature. For example if you try to take a temperature of your stainless steel kettle and have the IR Gun angled so that it is catching part of the reflected heat from your body it will average that into it's calculation and will read a lower temperature. I understand those IR guns do not use the laser to measure, as I mentioned I am a thermographer and use IR Thermography Cameras every day, but they do take an average of an area that gets larger as you move further away and if your emissivity is not set correctly it can be taking all these ambient reflections into consideration. I attached some images I just went out and took quickly to give some examples of the effects of reflection. The first one is a bucket of water, the warmest part that have the temperature marker (20.6C) on it is actually a reflection of my face and hand (yeah it's a little pixelated). The actual water temp is more around 18.0C. The second I added as a more easy to see example of reflection. It is an image of a piece of glass, you cannot see anything on the other side of the glass, everything you see is a reflection (Me standing with my camera and some objects behind me). It would be very difficult to get a truly accurate temperature on this because of all the reflection.

My comment was simply a possible technical explanation and solution to the issue that brad may have faced when he could not get accurate readings in the mash tun in the article. The solution being reduce outside reflections as much as possible and check for proper emissivity.

 

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