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Hello,

I have an Arduino Yun and I brew beer.

I would like to log the temperature of the beer at all time during the fermentation process (final stage). This means the thermometer would have to remain in the beer during this time (10 days). The temperature would be < 40 degrees Celsius (probably around the 20 degree mark).

Question: What temperature sensor would be best suited to this task?

It must be:

  • Food grade
  • Can be used in alcohol for extended periods
  • Can be hooked up to Arduino (i.e. add a library and ready to go)

Thanks, Dan.

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  • You can relax the immersion requirement if you tape the thermometer to the side of the fermenter and cover it with some insulation--I cover the stick-on thermometer on my carboy with a rag to make it match the contents more than the ambient temperature.
    – Dave X
    Apr 29 at 2:31

2 Answers 2

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I am not a brewmaster but from what I understand the temperature will change slowly. Your problem is not to contaminate the beer, you can use a stainless possibly even a plastic tube that is sealed on the immersion side and use a DS1820B sensor commonly used on Arduinos as well as other platforms. The response will be slower then if the sensor is inserted directly but since the change is slow it should work AOK. This keeps it simple and probably something you have done before.

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You are looking for a thermocouple.

They need some specific chip to be read, so you'll probably want to spend a bit more and get a chip with a digital interface, there are some witch has arduino library, like MAX6675 (output at 1Hz, 0.25° precision).

As this chip read "C type" thermocouple, you just have to find the right probe for your needing, with probably can be found in many specialized store.

You may even buy a normal k probe, and then wrap it up in some protective case. Obviously that case should be designed to let the heat flow easily, but without short circuiting the probe; a food plastic bag;

or just spend a little more money and buy a stainless steel probe

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  • Thanks - I will take a look at thermocouples (new term for me thanks). I don't mind spending a little bit of money. I would prefer not to use plastic bags due to the fact there will be an aquarium heater in the container also.
    – DanAbdn
    Mar 4, 2015 at 20:59
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    A Thermistor is what you are really looking for, I would downvote this answer but I don't have the rep here to do so. A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. On the other hand, a thermocouple is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more spots, where a temperature differential is experienced by the different conductors (or semiconductors). Two differnt technologies, for your usage you are really looking for the thermistor.
    – Tyson
    Mar 5, 2015 at 3:28
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    A thermocouple generates a few millivolts of current, and is most typically used in the flame of a pilot light and connected to a fail-safe gas valve. On the other hand a thermistor must be powered by it's circuit and is much more useful at 20-40C than a thermocouple.
    – Tyson
    Mar 5, 2015 at 3:36
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    @tyson write it as your own answer, not as comment. I don't think a thermistor is better as it is slower and with less precision.
    – Lesto
    Mar 5, 2015 at 7:32
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    First, speed doesn't matter in a long term monitoring application with a lot of its own thermal mass like this. Next, a thermocouple is not more accurate, but less. Thermocouples do not measure temperatures directly, but rather compare them. Therefore to use one you need to establish a reference temperature. That can be done literally, by means such as dunking the reference junction in an ice-water bath, or virtually by measuring the temperature of the other junction or isothermal terminal block where it is located - typically with a thermistor or other type of resistance-based sensor. Jun 4, 2015 at 14:49

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