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Old 12-14-2013, 08:04 AM   #1
aamcle
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Default thermocouple and thermowell advice please

Hi.

My current build is a Stainless Vessel with a Stainless Thermowell fitted through the base with stainless screw fittings.

When I got the thermocouple the tip (junction) was slightly exposed protruding just beyond its cover I slid the the cover over the the tip prior to use. However I want the fastest response I can get so I would prefer not to cover the tip with rubbery insulation which would slow down heat transfer.

My question is this; does the tip of my k type thermocouple that I intend to use need to be electrically insulated from the thermowell?


Atb. Aamcle

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Old 12-15-2013, 05:34 PM   #2
crane
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No you do not need to electrically isolate the tip of the thermocouple and as you mention you will get a faster response time by leaving it exposed. I would also suggest getting some thermal paste and put enough on the tip of the thermocouple to guarantee that the thermocouple tip has good contact with the end of the thermal well. You don't need to fill the whole thermal well with it, just enough to get contact. Thermal paste will reduce you response time and improve accurate measurements. I consider thermal paste a must for a thermal well/probe.

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Old 12-15-2013, 06:35 PM   #3
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Thanks, that's what I needed to know.


Aamcle

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Old 12-16-2013, 02:26 PM   #4
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Just one more question.

Should I change the thermocouple for a pt100? I know the pt100 is more accurate but it responds more slowly and that could be an issue with this build. I have a 3Kw element and the thermocouple under the bottom filter in the malt pipe of a Ghetto Spiedal knock off.

Thanks for you input.

ATB. Aamcle

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Old 12-16-2013, 06:49 PM   #5
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I'm not sure why you say an RTD has a slower response time. At any rate the water you are heating will not be changing temp faster than the response time of any temp sensor out there.

RTDs can have more accuracy but the probe itself is not the only contributing factor to accuracy. You have to take into account the ADC and the circuitry around it to have an overall accuracy. Point being a crappy PID with an RTD could have less accuracy than a good PID with a thermocouple. For brewing beer either will be fine.

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Old 12-16-2013, 08:29 PM   #6
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I looked up the specs for both thermocouples are listed as faster.

http://digital.ni.com/public.nsf/all...2572D00083350E

Thanks for your help you have put my mind to rest.


ATB. Aamcle

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