Metal Ceramic Compound Resistors

Power Dissipation and Resistance

The tolerance for resistance values amounts generally to ± 20%.

The resistance is measured at room temperature (RT = 20 °C).

With high power dissipation or increased ambient temperature, the Temperature Coefficient of Resistance (TCR) must be taken into account:

  αt = - (6 ... 20) . 10-4 . K-1

 

The resistance at increased ambient temperature follows the equation below:

  R1 = R0 . [1 - (5 . log10R0 + 2.5) . 10-4 . Δv] (Ω)
with R1 Resistance at process temperature (Ω)
  R0 Resistance at room temperature (Ω)
  Δv Difference of temperatures (K)
  Range of validity: 0 to 360 °C  

 

The power dissipation P resp. the surface temperature v of Metal Ceramic Tube Resistors in horizontal mounting and with free air convection could be calculated with the following equation:

  P = 0.0372 . I . Δv1.75 (Wm-1 . K-1)
  Δv = + 6.58 . (P . I-1)0.571 (K)
  I Length of the metal ceramic resistor (m)
  R0 Resistance at room temperature (m)
  Δv Difference of temperatures (K)
  Range of validity: 0 to 360 °C  

Surface Temperature - Metal Ceramic Tubes 25/13

Medium surface temperature of metal ceramic tube resistors with different standard length and continuous load.

Horizontal mounting and cooling by convection.

 

TCR Effect - Metal Ceramic Tubes 25/13

Effect of the Temperature Coefficient of metal ceramic tube resistors on the resistance.