user220: I've seen many temperature sensors, but the highest temperature they go up to is 125 degrees C (257 degrees F). I want to reach higher temperatures than that. I'm thinking about rigging up a closed loop sensor for my soldering iron (for a convenient LCD display), but I can't find out how to sense the temperature of the tip due to the higher operating temperature than most sensors.

user65: One of the options to measure high temperatures would be to use thermocouples. This table provides a basic description of the types and the corresponding temperatures that they can sense.
A simple search led me to these components.

Thermocouple Type-K Glass Braid Insulated - A mid range thermocouple
Thermocouple Amplifier MAX31855 breakout board - Board to interface the thermocouple with the Arduino. This is needed as the voltage changes in the thermocouple are extremely small, and the rise is non-linear. 


This is how the board is connected to the thermocouple.
  

There is also a tutorial on Adafruit that deals with using and interfacing thermocouples. 

This is an image of the thermocouple interfaced with the Arduino.
  


user11: You probably want to use a thermocouple. It'll give you the ability to measure much higher temps than regular temperature sensor. You'll also need a IC like the MAX6675 to interface with it.

The MAX6675 performs cold-junction compensation and digitizes the
  signal from a type-K thermocouple. The data is output in a 12-bit
  resolution, SPI™-compatible, read-only format.
This converter resolves temperatures to 0.25°C, allows readings as
  high as +1024°C, and exhibits thermocouple accuracy of 8 LSBs for
  temperatures ranging from 0°C to +700°C.


Page 6 of the datasheet has the serial interface protocol information and. You can really just set the Chip Select line and it'll give you 16 bits of information, 12 of which will be the temperature.

220: <p>I've seen many temperature sensors, but the highest temperature they go up to is 125 degrees C (257 degrees F). I want to reach <em>higher</em> temperatures than that. I'm thinking about rigging up a closed loop sensor for my soldering iron (for a convenient LCD display), but I can't find out how to sense the temperature of the tip due to the higher operating temperature than most sensors.</p>
 65: <p>One of the options to measure high temperatures would be to use <a href="http://en.wikipedia.org/wiki/Thermocouple" rel="noreferrer">thermocouples</a>. This table provides a basic description of <a href="http://en.wikipedia.org/wiki/Thermocouple#Thermocouple_comparison" rel="noreferrer">the types</a> and the corresponding temperatures that they can sense.</p>

<p>A simple search led me to these components.</p>

<ul>
<li><a href="https://www.adafruit.com/products/270" rel="noreferrer">Thermocouple Type-K Glass Braid Insulated</a> - A mid range thermocouple</li>
<li><a href="https://www.adafruit.com/products/269" rel="noreferrer">Thermocouple Amplifier MAX31855 breakout board</a> - Board to interface the thermocouple with the Arduino. This is needed as the voltage changes in the thermocouple are extremely small, and the rise is non-linear. </li>
</ul>

<blockquote>
  <p>This is how the board is connected to the thermocouple.
  <img src="https://i.stack.imgur.com/oV37Y.jpg" alt="enter image description here"></p>
</blockquote>

<p>There is also a <a href="http://learn.adafruit.com/thermocouple/" rel="noreferrer">tutorial on Adafruit</a> that deals with using and interfacing thermocouples. </p>

<blockquote>
  <p>This is an image of the thermocouple interfaced with the Arduino.
  <img src="https://i.stack.imgur.com/tvzG0.jpg" alt="enter image description here"></p>
</blockquote>
 11: <p>You probably want to use a <a href="http://en.wikipedia.org/wiki/Thermocouple" rel="noreferrer">thermocouple</a>. It'll give you the ability to measure much higher temps than regular temperature sensor. You'll also need a IC like the <a href="http://www.maximintegrated.com/datasheet/index.mvp/id/3149" rel="noreferrer">MAX6675</a> to interface with it.</p>

<blockquote>
  <p>The MAX6675 performs cold-junction compensation and digitizes the
  signal from a type-K thermocouple. The data is output in a 12-bit
  resolution, SPI™-compatible, read-only format.</p>
  
  <p>This converter resolves temperatures to 0.25°C, allows readings as
  high as +1024°C, and exhibits thermocouple accuracy of 8 LSBs for
  temperatures ranging from 0°C to +700°C.</p>
</blockquote>

<p><img src="https://i.stack.imgur.com/pyNbk.gif" alt="enter image description here"></p>

<p><a href="http://datasheets.maximintegrated.com/en/ds/MAX6675.pdf" rel="noreferrer">Page 6 of the datasheet</a> has the serial interface protocol information and. You can really just set the Chip Select line and it'll give you 16 bits of information, 12 of which will be the temperature.</p>
