Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

13.9.1 Resistive Temperature Detectors (RTDs)

 

· These devices use the effects of temperature change on conductivity.

 

· Uses resistive wires made of materials such as,

  1. - platinum
  2. - nickel
  3. - copper
  4. - nickel-iron

 

· Typical material properties are, [Bryan]

 

 

· Wires are wound about an insulator, for support, and covered for protection.

 

· These devices typically have positive temperature coefficients that cause resistance to increase linearly with temperature.

 

· Typical changes are doubling of initial resistance value over range of use.

 

· Advantages,

  1. - stable
  2. - accurate
  3. - more linear than thermocouples

 

· Disadvantages,

  1. - expensive
  2. - requires a power supply
  3. - small absolute resistance and resistance change
  4. - self heating