KTY sensors

KTY temperature sensors

A KTY sensor is a PTC resistor made of silicon. Its resistance increases at higher temperatures. The material's temperature coefficient A is positive and approximately twice the magnitude of the coefficient in metals.

A typical temperature range is from -50ºC to +150ºC although for this course 20ºC to 100ºC is sufficient. The temperature dependence is described by the following equation:

R(J): Resitance at temperature J
R₀: Resistance at reference temp. J₀ = 25°C

Material constants A and B for the KTY sensor used are

The temperature can be calculated from the resistance value according to the (complex) formula :

For reference the results of this equation are summarised in a Table.

The following graphic shows a general characteristic for a KTY sensor.

KTY resistance graph

From the graphic it can be seen that the resistance of the KTY sensor is non-linear, but it will be seen later on that a resistor connected in parallel with the sensor can "linearise" the curve allowing relatively linear gradients to be achieved.

These resistors are suitable for measuring, open-loop and closed-loop control of temperature-dependent systems.