K Type Thermocouple vs RTD temperature sensor - Home Brew Forums

Register Now!
Home Brew Forums > Home Brewing Beer > DIY Projects > Brew Stands > K Type Thermocouple vs RTD temperature sensor

Reply
 
Thread Tools
Old 10-19-2009, 02:50 PM   #1
maxbing
Recipes 
 
Nov 2008
Posts: 84
Liked 2 Times on 2 Posts



I am about to pull the trigger on some PID temp controllers from Auber Instraments. I can't decide on the type of temp sensors to go with K Type Thermocouple vs RTD temperature sensor. RTD is a little more expensive but not enough to really matter.

Does anyone have any advice? Pros or cons of each?

Thanks

 
Reply With Quote
Old 10-19-2009, 03:03 PM   #2
Yuri_Rage
Gritty.
HBT_MODERATOR.png
 
Yuri_Rage's Avatar
Recipes 
 
Jul 2006
Southwest
Posts: 14,285
Liked 804 Times on 510 Posts


This link gives a nice comparison of the two: http://www.smartsensors.com/spec.htm

I've seen a lot of posts recommending RTDs for their higher accuracy and linear response. However, it's splitting hairs, IMHO. Both sensors are capable of less than +/-1% accuracy (effectively, less than +/-1.5 degrees at mash temps). For brewing applications, a decently calibrated thermocouple is just fine. I chose thermocouples for my rig, mostly due to the faster response time.
__________________
Homebrewed Blog..........YouTube Channel .......... Shirts, posters, etc

 
Reply With Quote
Old 10-19-2009, 03:05 PM   #3
conpewter
HBT_SUPPORTER.png
 
conpewter's Avatar
Recipes 
 
Nov 2007
East Dundee, Illinois
Posts: 5,108
Liked 53 Times on 48 Posts


In our application I don't think you'll see a lot of difference. Just make sure to match your controller to the type of temperature sensor you are going to get. Here's a chart that tells some of the differences
http://www.smartsensors.com/spec.htm

Edit:
darnit, beat by a couple minutes
__________________
"People should not be afraid of their governments. Governments should be afraid of their people." - V

Primary: Nothin
Secondary: Shady Lord RIS, Water to Barleywine, Pumpkin wine, burnt mead
Kegged: Crappy infected mild
Bottles: Apfelwein, 999 Barleywine, Oatmeal Stout, Robust Porter, Robust smoked porter, Simcoe Smash

 
Reply With Quote
Old 10-19-2009, 03:24 PM   #4
maxbing
Recipes 
 
Nov 2008
Posts: 84
Liked 2 Times on 2 Posts


Nice link,

Thanks guys.

one column made my decision for me...Ruggedness. other than that for the temps we are talking about both look like they would be fine.

 
Reply With Quote
Old 10-19-2009, 05:47 PM   #5
Sawdustguy
Recipes 
 
Mar 2009
Manorville, New York
Posts: 2,708
Liked 35 Times on 29 Posts


Thermocouples are just a junction between two dissimilar metals where a RTD is simply a resistor that changes value with temperature. As the previous posters pointed out, for our purposes, it's a non issue. I went with a thermocouple because I found one, for not too much money that had a 1/2" NPT thread on it so I could screw it right into my keggle.
__________________
Guy

 
Reply With Quote
Old 10-21-2009, 03:23 AM   #6
ILOVEBEER
Recipes 
 
Sep 2009
CA
Posts: 718
Liked 6 Times on 6 Posts


The tech at Auberins told me that the RTD coupler is a more accurate sensor. The price difference is not much. What I like about mine is that the actual 1/4" NPT probe is able to be removed from the probe via a quick disconnect. I did not plan on this, just discovered it after I ordered it (to be honest with you I had no idea what I was ordering) after talking to the Auberins tech....who I pissed off with all of my elementary questions.



 
Reply With Quote
Old 10-21-2009, 06:12 AM   #7
StMarcos
Recipes 
 
Apr 2008
Sebastopol, CA
Posts: 971
Liked 34 Times on 27 Posts


RTD is my vote. They offer more repeatable readings over time, and thus more robust in my opinion. I use 3wire RTDs that compensate for the resistance of the wires, which is important if you want to use long runs like I do. 4wire will compensate for different resistances between the wires.

Doorbell wire is a cheap source for wire... get some quick connectors from omega they are only a couple of bucks. Mine have 1/8mpt which I thread into 1/8fpt - 1/8straight thread. A silicone oring and a nut are used to make watertight connections. That's how I modded my stainless conicals to monitor temperature of the beer. I use a dial probe on the kettle... only used to gauge approach to boiling. Good luck!

 
Reply With Quote
Old 11-01-2009, 07:39 PM   #8
Bigscience
Recipes 
 
Sep 2009
Woodinville, WA
Posts: 626
Liked 29 Times on 26 Posts


Any thoughts on the type of thermocouple to choose? J vs K vs T ect?

Also, I'm thinking about ordering from omega since they seem to have better quality than the Auberins ones I've gotten. The question is the configuration. I can get a connector on the end of the probe, braided line with a connector on the end of the line as well. Does anyone have the connector at the end of the probe? If so, do you like it?

 
Reply With Quote
Old 11-01-2009, 10:03 PM   #9
Sawdustguy
Recipes 
 
Mar 2009
Manorville, New York
Posts: 2,708
Liked 35 Times on 29 Posts


Quote:
Originally Posted by StMarcos View Post
RTD is my vote. They offer more repeatable readings over time, and thus more robust in my opinion.
Not true. You can't change Physics. A junction between between two dissimilar metals will always induce an EMF and unless the two metals change their chemical composition over time the EMF will stay constant.
__________________
Guy

 
Reply With Quote
Old 11-02-2009, 12:14 AM   #10
StMarcos
Recipes 
 
Apr 2008
Sebastopol, CA
Posts: 971
Liked 34 Times on 27 Posts


It is true. There are more sources of drift in a thermocouple than in an RTD. They are also more accurate.

 
Reply With Quote


Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
What type of thermocouple probe to use? stoutaholic Equipment/Sanitation 2 10-11-2010 01:46 AM
DIY Sensor Probes for RANCO Controllers gregdech Brew Stands 7 09-01-2010 02:12 AM
freezer sensor doug1395 Bottling/Kegging 1 10-02-2009 02:40 AM
This thermocouple?? kickflip_mj Equipment/Sanitation 3 04-03-2008 08:46 PM
Thermocouple or thermocouple wire source? e lo Equipment/Sanitation 22 11-08-2007 09:09 PM


Forum Jump