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Home Brew Forums > Home Brewing Beer > Electric Brewing > Why use an analog thermometer?
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Old 01-12-2012, 08:57 PM   #1
DFP51
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Default Why use an analog thermometer?

OK, so as I am punching holes in my shiny kettle, and begin wndering why I need to keep the analog thermometer in place if I will have a RTD mounted in the same kettle? I am constructing a two vessel, recirculating, Brutus 20 style system. My question is will the RTD/PID be adequate to monitor the temperature of the wort as I am cooling the wort, as well as when I am heating it?

Thanks guys

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Old 01-12-2012, 09:04 PM   #2
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Sure. But by what will you quick reference that you may have a RTD issue?

An analogue is just a cheap assurance.

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Old 01-12-2012, 09:49 PM   #3
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the resistance of an RTD probe should be extremely solid and linear. if you calibrate it once, it should remain the same almost indefinately. there is no real need to check against another thermometer.

and then you get into the problem of- if you have an RTD and an analog temp probe that do not match, how do you tell which is correct? the only almost-guaranteed-accurate analog thermometer are the glass alcohol-type ones. the analog dial gauge thermometers rely on the either gas pressure or metal memory, neither of which are extremely accurate, and can be influenced by outside sources.

I trust my RTDs over just about any other thermometer in the house.

thermocouples are a different story. some cheaper ones do have considerable drift, and since thermocouples rely on a measured voltage instead of a measured resistance, that voltage can easily be partly lost in transit to the controller.

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Old 01-12-2012, 11:49 PM   #4
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I had the same "dilemma". I ditched the analog thermometers and went the "digital" only route. If I have a question I have a small handheld I use to verify.

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Old 01-13-2012, 02:10 PM   #5
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Thanks guys. I think I am going to dump the analog and just monitor with the RTD. Now the question is whether I want to put an RTD in the tun as well as the boil kettle. Really not sure that I need it since my tun is a cooler, but it does have the "Ohh shiny!" factor.

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Old 01-13-2012, 02:33 PM   #6
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I agree DFP51. Don't over complicate things. the analog dial is just as likely to be off. Streamline and Simplify!

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