You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Reply
 
Thread Tools Display Modes
Old October 8th, 2010, 09:56 PM   #1
randy741985
Member
United States

randy741985 is offline
 
randy741985's Avatar
 
Join Date: Oct 2006
Location: US
Posts: 138
What is a Thermocouples true range.

Looking at thermocouple ranges on the internet, they very mixed.
you will find type J measures up to 2000F other say 1500F, 1400F.

Type K 2200F to 2500F.

using Omega site it list Type J scale to 32F to 1382F
type K -328 to 2282F.

Just thought this was interesting.

thnaks for any input.
  Reply With Quote
Old October 8th, 2010, 11:10 PM   #2
longshanks
Member
United States

longshanks is offline
 
Join Date: Aug 2009
Location: Carlton, Or
Posts: 69
I worked at a firm that built wood fired burners. At the throat of the furnace, we measured the output, typically at up to 2200F. However, those TC's were encased in a 3/4" diameter Ceramic tube and the TC wire itself consisted of #8AWG TC wire. Very heavy to withstand the heat. Smaller sizes don't last very long at those temperatures. Smaller responds to temperature changes faster, but aren't as robust. They were type K and were wired to 4/20maDC converter modules. They were about 3' long to get the "head" end well outside the heating zone. We went by the Omega listings and most of the TC's were from Omega. Just FYI..
  Reply With Quote
Old October 9th, 2010, 12:27 AM   #3
Tharon
Member
United States

Tharon is offline
 
Join Date: Jan 2007
Location: Michigan
Posts: 1,095
I would trust the Omega site. They are a big name with good data. All my thermocouple Temp vs. Voltage charts come from Omega as well.
  Reply With Quote
Old October 9th, 2010, 08:03 AM   #4
ndzied1
Lifetime Supporting Member
United States

ndzied1 is offline
 
ndzied1's Avatar
 
Join Date: Aug 2002
Location: Chicago, Illinois
Posts: 1,995
Maybe a little over simplistic but my thought is that from a control standpoint it doesn't matter. What matters is the signal conditioner or input card you put the T/C into. This is the range usable by yourcontrol process.

Now I have never worked near the end of a range of a T/C or On a bight heat load system so there are definately other considerations and indeed the materials and type of construction could be very different even for the same letter designation and limit it more than the simple physics of the metal joint. So I guess they all could be right for their particular design.
__________________
nOrM
======================
nOrM=Norman Dziedzic Jr.
Your program may do things you never intended/ When the inputs are in a state you never expected.
  Reply With Quote
Old October 11th, 2010, 10:04 AM   #5
TConnolly
Lifetime Supporting Member
United States

TConnolly is online now
 
TConnolly's Avatar
 
Join Date: Apr 2005
Location: Salt Lake City
Posts: 5,860
The temperature rating accounts for the sheath material as well. For example a Type K T/C in a stainless steel sheath is rated to 900C, but the same T/C in an inconel sheath can be rated to 1200C, while the Type K T/C range covers up to 1370C. Atmospheric conditions should be considered as well. A type K TC can be used at higher temperatures in a vacuum or a reducing atmosphere, but should be derated when used in an oxidizing atmosphere.
__________________
True craftsmanship is only one more power tool away.

That's the beauty of processors, they don't have emotions they just run code - The PLC Kid.

Last edited by TConnolly; October 11th, 2010 at 10:09 AM.
  Reply With Quote
Old October 12th, 2010, 08:21 AM   #6
shooter
Member
Netherlands

shooter is offline
 
shooter's Avatar
 
Join Date: Sep 2002
Location: duketown
Posts: 1,647
The max temp is the temp nothing will happen with the sensor, like oxidation, melting etc. or the insulation will melt are become glass or something other.
it is absolute temp not the difference between the sensor and the CJ.
__________________
shooter@home.nl
skype paul.deelen
Computer Shooter
Paul Deelen
J. Wassenaerstraat 29
NL 5224 GG 's-Hertogenbosch
+31653300739
  Reply With Quote
Old October 12th, 2010, 08:49 AM   #7
Tom Jenkins
Lifetime Supporting Member
United States

Tom Jenkins is offline
 
Tom Jenkins's Avatar
 
Join Date: Apr 2002
Location: Milwaukee, WI
Posts: 5,260
It is my opinion that, as Shooter implied, the limitation on the T/C are physical destruction and not output. A T/C creates a voltage as a function of its temperature. This is non-linear, and the voltage temperature relationship varies dpending on the two metals at the hot juncion. I think that the useable range is more a function of the degree of non-linearity at various temperatures, and depending on the supplier (and the transmitter if used) the defined range will vary.
  Reply With Quote
Old October 12th, 2010, 01:27 PM   #8
randy741985
Member
United States

randy741985 is offline
 
randy741985's Avatar
 
Join Date: Oct 2006
Location: US
Posts: 138
Thanks For the Input,

I asked because if I were scaling this in a PID what should be my max scale.

Other words if brought a T/C in as scaled for pid 0-16383 what would be
MIN. and MAX.?


Thanks In advance.
  Reply With Quote
Old October 12th, 2010, 01:53 PM   #9
TConnolly
Lifetime Supporting Member
United States

TConnolly is online now
 
TConnolly's Avatar
 
Join Date: Apr 2005
Location: Salt Lake City
Posts: 5,860
It would be whatever value 16383 represents in your hardware, not the value from your sensor. Eg, if your PLC TC input card specified that 16383 was 1370C then that is what you would use.

Be careful and check your specs, most T/C cards perform the linearization for you and return a value in engineering units.
__________________
True craftsmanship is only one more power tool away.

That's the beauty of processors, they don't have emotions they just run code - The PLC Kid.
  Reply With Quote
Old October 12th, 2010, 07:06 PM   #10
randy741985
Member
United States

randy741985 is offline
 
randy741985's Avatar
 
Join Date: Oct 2006
Location: US
Posts: 138
Quote:
Originally Posted by Alaric View Post
It would be whatever value 16383 represents in your hardware, not the value from your sensor. Eg, if your PLC TC input card specified that 16383 was 1370C then that is what you would use.

Be careful and check your specs, most T/C cards perform the linearization for you and return a value in engineering units.

Thanks
  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
Trying to enhance my Siemens SCL abilities ELake20 LIVE PLC Questions And Answers 22 July 29th, 2010 05:36 AM
bitswaps in a byte SCL Combo LIVE PLC Questions And Answers 2 November 5th, 2008 08:58 AM
Functionality of the XOR Instruction? randy741985 LIVE PLC Questions And Answers 33 April 19th, 2007 12:50 PM
Momentary Push button plcnovel LIVE PLC Questions And Answers 7 March 17th, 2006 05:47 AM
one button two functions bulletin blues LIVE PLC Questions And Answers 22 March 16th, 2003 08:30 AM


All times are GMT -5. The time now is 02:47 PM.


.