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Thermocouple

Posted by IanJohnson 
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IanJohnson
Thermocouple
July 31, 2012 03:46PM
I'm looking at getting a thermocouple for measuring the hot end. Is this the correct type?

[www.amazon.com]

Do you tape the end of the wire to the bottom of the nozzle to measure the temp?
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NewPerfection
Re: Thermocouple
July 31, 2012 03:53PM
That should work, but remember that you will need a thermocouple amplification board too. Most people use thermistors as they are cheap and accurate enough for our purposes, and can be hooked up directly to our electronics.

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brnrd
Re: Thermocouple
July 31, 2012 04:19PM
If you want to use the thermocouple for the purpose of calibrating your thermistor, then the best way is to insert it into the hot end where the feed would usually go so that the sensitive end of the thermocouple is at the nozzle.
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IanJohnson
Re: Thermocouple
July 31, 2012 04:43PM
I'm looking to calibrate the thermistor, or at least get a real world point of reference for its readings. Are the wire types like this usually thin enough to go into hot ends sized for 1.75 filament?

This is the one I had meant to link to - [www.amazon.com]

Descriptions generally don't say what the size of the wire is with the insulation. Would the insulation be OK at inside a 200C barrel?
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Andrew Smith
Re: Thermocouple
July 31, 2012 04:59PM
Its teflon insulated, so its good for about 260C. I'd keep a safe margin from that temperature though, teflon fumes can be nasty for humans, and lethal for birds so be careful if anyone in the building has a budgie they want to keep.
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Andrew Diehl
Re: Thermocouple
July 31, 2012 05:17PM
I would buy a cheaper one with fiberglass insulation more like this [www.amazon.com]

www.Fablicator.com
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nophead
Re: Thermocouple
July 31, 2012 06:10PM
I find the black heat-shrink insulation on those melts inside an extruder and makes a mess. I put it inside PTFE sleeving about 150mm long to protect it and make it stiff enough to feed into an extruder. It would be too thick for a 2mm barrel though.

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Andrew Diehl
Re: Thermocouple
July 31, 2012 11:30PM
I just remove the heat shrink entirely. Would fit fit in 2mm no problem that way.

www.Fablicator.com
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Traumflug
Re: Thermocouple
August 01, 2012 05:37AM
Quote

I'm looking to calibrate the thermistor

Getting an ordinary thermometer? Also, a water-ice mixture has pretty exactly 0 °C and cooking water 95 to 100 °C, depending on the height of the water above main sea level. Two points which can be reproduced well.

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rhmorrison
Re: Thermocouple
August 01, 2012 06:24AM
True but 0°C and 100°C are only two points and not in the area of interest.
Who cares if we see 10°C or 30°C when the room temperature is 21°C?
What we want is accurate readings between 180°C and 260°C!

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
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brnrd
Re: Thermocouple
August 01, 2012 07:06AM
Quote
Traumflug
Getting an ordinary thermometer? Also, a water-ice mixture has pretty exactly 0 °C and cooking water 95 to 100 °C, depending on the height of the water above main sea level. Two points which can be reproduced well.

The idea is to measure the actual temperature in the nozzle to also compensate for temperature gradient from the sensor to the nozzle.
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Bertho
Re: Thermocouple
August 25, 2012 01:34PM
Here is a link to Thermocouple trouble shooting and heater measurements. I got tired of keep commenting so I wrote it up in one place.
TC Info and troubleshooting
Bertho
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brnrd
Re: Thermocouple
August 26, 2012 07:59AM
The question is on using a thermocouple to calibrate the hot end, not to control it.
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