Thermocouple question

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nick
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Thermocouple question

Post by nick »

I am setting up my heating unit now and am wondering about my thermocouple. I have read that I need a j-type. I got a k-type like this http://www.auberins.com/images/TC-K3.jpg but i thought that i would need something like a flat piece to put in between the board and the blanket. I would just think that even a j-type thermocouple would leave an indentation in the board. Could someone please explain to me how this works? Do you just set the thermocouple to the side of the press and tape it to material? is it accurate that way?
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falls
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Post by falls »

J type thermocouple is a flat style sensor
Most people I think use an aluminium/steel layer in their layup below and above the ski/board. The thermocouple is mounted to this metal next to the ski so as to actually sense the temperature being conducted to the ski rather than the temperature of the blanket.
I haven't done this stage yet, but from reading it seems this is the most common method.
doughboyshredder
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Post by doughboyshredder »

j, k, t, and e refer to the different calibrations, not to any specific shape or style of thermocouple. Most PID's are programmable for whichever calibration you want.
Image

These are the ones I am using, thanks to Head Monkey's recommendation. http://www.omega.com/ppt/pptsc.asp?ref= ... SRTC&Nav=

5srtc's are the ones I am using. I forget which gage, I will check tomorrow. I think the 30 with the glass braid, but I don't remember. Might be the 40
doughboyshredder
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Post by doughboyshredder »

wtf, my whole post disappeared
doughboyshredder
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Post by doughboyshredder »

I guess I'll start over.

j,k, t, or e refers to calibration (temp range and tolerances). It has nothing to do with shape or size.

J type is the most appropriate for our application.

These connectors per Head Monkey's recommendation seem to be the best

http://www.omega.com/ppt/pptsc.asp?ref= ... 5SRTC&Nav=

5srtc's are the ones I am using. You need to order the connectors also.

I think scott at On3P has some of these they aren't using that he probably would sell, but I know he's super slammed right now, so it might not be worth bothering him.
iggyskier
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Post by iggyskier »

doughboyshredder wrote:
I think scott at On3P has some of these they aren't using that he probably would sell, but I know he's super slammed right now, so it might not be worth bothering him.
I have 4-5 that I won't be using for now. Let me know if you are interested.
feldybikes
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Post by feldybikes »

AFAIK, thermocouple type (J, K, etc) refers to the metals used in the TC and not the shape. Your TC reader may or may not be able to read more that one type. I don't know if the TC will leave an indentation or not, but I don't see a huge problem with putting it on the top side of the heat blanket and using that for controlling the temperature. What the TC reads isn't *really* the temp of your laminate anyway, and as it's just a reference, all you should need is that it's a precise enough reference to consistently control the heat, not that the temperature is dead-on accurate.
nick
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Post by nick »

Wow, I didn't know that. That makes a lot more sense. I thought it was the shape. My PID's will take anything. thanks...
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falls
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Post by falls »

I'll stop offering my ill informed information for now!
doughboyshredder
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Post by doughboyshredder »

I just looked and the ones I have are actually K type. all calibrations will work just fine for what we are doing.

http://www.omega.com/prodinfo/ThermocoupleSensor.html

is a good info page on thermocouples including pdf spec sheets, etc..
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falls
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Post by falls »

That's a good link doughboy. Understand it much better now.
Can I ask where you mount your thermocouple in the layup and physically how you do it. I saw some washer type bolt on probe ends and some self adhesive ends on that site, but permanently attaching it doesn't sound that practical. thanks

Could you mount one of these quick disconnect probes on each cassette then just plug your thermocouple wires in when necessary?

Image
doughboyshredder
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Post by doughboyshredder »

the 5srtc 36gage is fine enough that you just lay the probe between your cassette and heat blanket.
nick
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Post by nick »

so would soemthing like that just screw onto my type of thermocouple i have now? or do i just toss that all together?
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falls
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Post by falls »

pretty sure the TC would come with exposed wire ends at the end opposite the sensor. You would need to crimp on terminal ends that can then be screwed onto the back of your PID where all the electrical inputs and outputs are.
Image fork style terminal ends
doughboyshredder
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Post by doughboyshredder »

falls wrote:pretty sure the TC would come with exposed wire ends at the end opposite the sensor. You would need to crimp on terminal ends that can then be screwed onto the back of your PID where all the electrical inputs and outputs are.
Image fork style terminal ends
nope. Whatever you do do not crimp any connector on to any wires going in to your pid. All pid's have screw terminals that do not require connectors.

A lot of the tc's come with quick disconnects. The 5srtc's come with sub miniature connectors. You also have to purchase the female part of the connector which you then connect a short set of wires to that plug in to the back of the pid.
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