Thermocouple question

[doughboyshredder]

I put it between the aluminum of the casette and the aluminum of the blanket.

so: aluminum, heat blanket, aluminum, tc, aluminum, laminate, aluminum, tc, aluminum, heat blanket, aluminum.

[falls]

Hi Nick
I think with the help of these guys I have worked it out.
The following picture is a bit confusing

The 5SRTC type highlights the large yellow adaptor, which originally I thought was the thermocouple. However, this is actually just a means of connecting and disconnecting the TC for ease of use (just think of it like the plug on any electrical item). The coil of wires of that 5SRTC are actually joined at the end like happy monkey's picture below:

that joined area is the actual part where the temperature measurement is made.
On the 5LSC in the first picture the wires are wrapped around the body and you can see the joined end (top right).

What happymonkey has then done is mounted a female adaptor for the yellow plug on the thermocouple to the side of his enclosure (think of it like a powerpoint).

this is where the yellow plug from the TC plugs in for ease of use

in the last picture it is the other side of the female adaptors mounted to his enclosure where he has joined wires that then go to the back of the PID.


Those yellow plugs are just so you can easily disconnect and reconnect your thermocouples rather than having them permanently wired to your PID enclosure.


Am I right?

Monkey has more pictures and explanation here, which is very helpful.
http://www.happymonkeysnowboards.com/HM ... mocouples/

[Head Monkey]

Correct Falls.

[nick]

wow falls... that makes so much more sense now. thanks. So, if i dont have those connectors (and dont care if i can connect them and disconnect them) what options do i have? because then i would have to buy female adapters and everything which I dont really have much $ for anymore after my whole press is built. Is the one i have ok? its just really bulky, it appears that there is some way to screw an adapter onto my thermocouple i already have. Do you know anywhere to find something like that? Or just something that I can permanently connect to my PID's. At least for right now. I just want to make a board quickly with out a lot of extras. And, I had NO idea I needed that much freakin aluminum. I thought there were only 2 spots i needed it for.

[falls]

Those thermocouples come in a bag of 5. I think 35 dollars for all 5. The female connectors are 3 or 4 dollars I think. If you have that k type one with a bulky end you could use it just need to find a way to mount it in a meaningful place to read temp (maybe harder in a snowboard, in skis I think montucky has a recess in his bottom mold between the skis where his tc goes). My impression is the best thing about that one with the yellow connector is more it's narrow end and 36 guage wire so you can mount it right under the board in the layup (the yellow connectors just make things easier). You could try and find another tc with the same 36 gauge wires and small exposed tc end that just has bare wires on the other end you can screw to the pid. You might just be able to cut the yellow plug off and strip the wires and screw them on to the pid but don't quote me on that I'm a very very amateur electrician. And actually that would be stupid because if you had the tc with yellow plug you would just spring the few bucks fir the female adaptor!

[nick]

haha true stuff. Thanks, I am just trying to weigh my options. I see that there is a difference in the sheath of the thermocouple...the cheapest 5SRTC has a glass braid insulation, the second is PFA, and the third is kapton. Does any of that matter? I dont want a glass insulation to crush since we are putting a lot of pressure and heat on the insulation part itself.

[falls]

http://www.omega.com/ppt/pptsc.asp?ref= ... 5SRTC&Nav=
Nick the info on that link says the PFA insulation is good to 260 degrees C (well above 170F which a lot of people press at for epoxy cure). It seems the 36 gauge wire is crucial as it is thin enough to not cause indentation in the layup.

In regards to the aluminium sheets. You don't need to use that many sheets. You can just lay your blanket on the wood of the bottom mold then have Al either side of the layup then the top blanket on the top of that Al layer followed by a masonite layer to stop indentation on your blanket from the cat track + some insulation.
BUT head monkey and doughboy are using the extra layers of aluminium to protect their investment in the heat blankets and also if you are running larger numbers of skis/boards through the press having the blankets permanently or semi-permanently in place using the extra aluminium layers would be much easier and safer for the blankets.

here's another link from head monkey's "process" journal page.
He and ben have the discussion at the bottom of the page about what all the layers of Al are for.

http://www.skibuilders.com/phpBB2/viewt ... 6&start=15

Protecting your blankets is a pretty good idea. The link below shows some pictures of the ON3P site after one blanket malfunctioned. Not sure what actually happened and from the look of their pictures their blankets were sheathed in 2 layers of aluminium. But they had a fire that ruined the blanket and I think the hose too.
http://on3pskis.com/?p=907

[falls]

Hi all
Going to dredge the thermocouple info page again.
I have just ordered a few of these thermocouples
http://www.tcdirect.net.au/deptprod.asp?deptid=180/21
I got the 2m long ones with miniature connectors attached. The wire is 32 gauge (0.2mm) not 36 like recommended for indent free bases.
Please let me know what you think (I have a backup plan for indent free TC placement if you think the wire is too thick to place it directly between the blanket and cassette.

The above thermocouple has an end like the omega ones others use like this


Last question
I asked about wiring from the back of the panel mount quick conectors to the PID controller and they recommended using TC wire (ie. the same pair of metals as the K type thermocouple being used).
like this

I have ordered some of this so will do it anyway, but was wondering if everyone else has done this too?
Thanks as always

[SHIF]

Here in the USA, those yellow TC plugs are typically for type K thermocouples. And the wire colors are counter-intuitive, RED is (-) and YELLOW is (+).

Here is a handy chart:
http://www.omega.com/techref/colorcodes.html


-S

[falls]

Thanks shif. So you're saying in that picture it is k type thermocouple wire that has been used?
In Australia everything is green and White for these applications.

[SHIF]

Yes, the photo looks like an Omega type K thermocouple with yellow/red wires and a yellow connector shell.

International standard TC wire colors are green and white.

TC connectors are made using special alloys, hence the different colors of connector shells that are available.

http://www.omega.com/Temperature/pdf/NMP.pdf

Also don't use regular wire lugs and hook-up wire in a thermocouple circuit. I suggest using TC wire to hook-up the panel mount connector socket to your PID controller too.

-S

[Jekul]

Keep in mind that TC wires are made of special alloys, and connecting them to different-material wire terminals will change the voltage potential between the wires (affecting the calculated temperature). Like SHIF said, as long as you use the connectors specifically designed for that type of TC you should be fine.

[falls]

thanks.
I have some type K thermocouple wire (green and white) so will definitely use this to connect the panel socket to the PID controller. The PID and the panel sockets have screw terminals so won't use lugs on the end of the wires, just screw them straight on (I did notice you can buy special pairs of TC lugs/spade terminals, but I don't think they are necessary).