K thermocupler question.

B

buckaroo

Well-Known Member
What part of the TC does the measuring. Is it the tip? How much needs to be exposed to get a true reading in the HT oven? I am on my third one in 3 months. Any suggestions?
 
Depending on the specific TC, it could be SLIGHTLY different, but in general they ALL "sense" within the first 1" of the end. TCs contain two dissimilar wires in the end, that produce "voltage" based on the expansion/contraction of the wire....that wire is always in the first 1" of the TC's end.
 
EdCaffreyMS said:
Depending on the specific TC, it could be SLIGHTLY different, but in general they ALL "sense" within the first 1" of the end. TCs contain two dissimilar wires in the end, that produce "voltage" based on the expansion/contraction of the wire....that wire is always in the first 1" of the TC's end.
Click to expand...

This is right in line with what I was told by the tech I talked to on the phone at Omega. He said only the very tip measures the temp. This can be easily verified with simple heating and cooling tests at home, if the Omega tech and Ed Caffrey's advice aren't enough. ;) :D
 
Thanks all for the information. The first one burned out after much use. I replaced it with a longer one on the advice of my supplier because it was tougher than the original. I moved it lower in the oven than the first one. I believe I damaged it while loading the oven.



Sent from my XT907 using Tapatalk
 
When using a TC in a heat treat oven application, make sure you place the TC as close to the height that the blades will sit as possilbe....it might seem trival, but there can be 75-100F difference between the very bottom and very top of an oven's chamber....not very significant for austinizing, but can make a huge difference for tempering.
 
Well, a type K TC all has the same wire (chromel for one conductor and alumel for the other wire. This wire should extend all the way from the tip of TC where the measuring takes place, all the way back to the meter (analog or digital) doing the indication. The actual temperature measuring takes place right at the tip where the two conductors are "welded" together to form the tip.

The low temperature rate type K TC are due to the insulation covering the wire, not the actual metal wire itself. FYI type of info: (from Wikipedia)

chromel: is an alloy made of approximately 90 percent nickel and 10 percent chromium that is used to make the positive conductors of ANSI Type E (chromel-constantan) and K (chromel-alumel) thermocouples.

alumel: s an alloy consisting of approximately 95% nickel, 2% manganese, 2% aluminium and 1% silicon. This magnetic alloy is used for thermocouples and thermocouple extension wire.

These alloys can be used up to 1100 °C in oxidizing atmospheres.

Ken H>
 
You must log in or register to reply here.
Back
Top