Engee documentation

PTC Thermistor

Thermistor with positive (PTC) or negative (NTC) temperature coefficient.

thermistor v1

ptc thermistor v1

Description

The Thermistor block represents a thermistor with a positive (PTC) or negative (NTC) temperature coefficient.

Thermistor with negative temperature coefficient (NTC)

Negative temperature coefficient (NTC) thermistor, uses the B-parameter equation.

For an NTC thermistor, the resistance at temperature is determined as follows:

,

where:

  • - resistance at nominal temperature .

  • - temperature coefficient.

Typical use of thermistor in models:

  1. Connect the thermistor to port B of the Convective Heat Transfer unit.

  2. Connect port A of the Convective Heat Transfer unit to the Ideal Temperature Source unit with the temperature set to ambient temperature.

  3. Set the Area of the Convective Heat Transfer unit to the approximate area .

  4. Set the Heat transfer coefficient parameter of the Convective Heat Transfer block to .

Positive temperature coefficient thermistor (PTC)

The resistance of this type of thermistor decreases with increasing temperature up to the Curie temperature. Above the Curie temperature, the resistance increases very rapidly with increasing temperature, as shown in the following graph. The area to the right of the Curie temperature is called the PTC mode.

thermistor 1 s

For a PTC thermistor, the resistance at temperature is defined as follows:

αприαпри

αααα

  • - Curie temperature.

  • - resistance at nominal temperature .

  • - resistance at reference temperature .

  • - The nominal temperature at which resistance is indicated, usually room temperature. less than the Curie temperature .

  • - reference temperature equal to or greater than the Curie temperature , meaning that the PTC mode is valid at that temperature.

  • α - temperature coefficient at the reference temperature .

  • α - temperature coefficient at reference temperature .

The following equation describes the thermal behaviour of the block:

,

where:

  • - A port heat flux.

  • - dissipation factor, the value of Dissipation factor.

  • - time constant, the value of Thermal time constant.

  • - is the rate of temperature change.

Ports

A - heat port
heat

A thermal port that determines the temperature of the resistor.

+ is positive
electricity

Electrical port, represents the positive terminal of a resistor.

- is the negative
electricity

Electrical port, represents the negative terminal of a resistor.

Parameters

Electrical

Block type - selection of thermistor type
Thermistor (by default) | PTC Thermistor

Thermistor type selection

  • The Thermistor is a negative temperature coefficient (NTC) thermistor.

  • The `PTC Thermistor' is a positive temperature coefficient thermistor (PTC).

Nominal resistance R0 at reference temperature T0 - resistance at nominal temperature
`1000 ohms (by default).

Resistance of the thermistor at nominal temperature. Many specifications specify resistance at 25°C (298.15 K); denoted R25.

Dependencies

To use this parameter, set the Block type parameter to `Thermistor'.

Characteristic temperature constant B - temperature constant coefficient
3500 K (by default) | `positive scalar'.

Coefficient in the equation describing resistance as a function of temperature.

Dependencies

To use this parameter, set the Block type parameter to Thermistor.

Reference temperature T0 - nominal temperature
298.15 K (by default) | `positive scalar'.

The temperature at which the nominal resistance was measured.

Dependencies

To use this parameter, set the Block type parameter to Thermistor.

Nominal resistance R0 at T0 - resistance at nominal temperature
`1000 ohms (by default).

Resistance of the thermistor at nominal temperature. Many specifications specify resistance at 25°C (298.15 K); denoted R25.

Dependencies

To use this parameter, set the Block type parameter to `PTC Thermistor'.

Temperature coefficient alpha0 at T0 - temperature coefficient at nominal temperature
-0.01 1/K (by default) | `negative scalar'.

Coefficient α in the equation describing resistance as a function of temperature at nominal temperature. The value must be less than zero.

Dependencies

To use this parameter, set the Block type parameter to PTC Thermistor.

Nominal temperature T0 - nominal temperature
298.15 K (by default) | positive scalar

The temperature at which the nominal resistance was measured.

Dependencies

To use this parameter, set the Block type parameter to PTC Thermistor.

Reference resistance R1 at T1 - Reference resistance at reference temperature
10000 ohms (by default).

Reference resistance of the thermistor at reference temperature.

Dependencies

To use this parameter, set the Block type parameter to PTC Thermistor.

Temperature coefficient alpha1 at T1 - temperature coefficient at reference temperature
1 1/K (by default) | positive scalar

Coefficient α in the equation describing resistance as a function of temperature at reference temperature. The value must be greater than zero.

Dependencies

To use this parameter, set the Block type parameter to PTC Thermistor.

Reference temperature T1 is the reference temperature
398.15 K (by default) | positive scalar

The temperature at which the reference resistance is measured. This temperature must be in PTC mode.

Dependencies

To use this parameter, set the Block type parameter to PTC Thermistor.

Thermal

Thermal time constant is the time constant for the thermal equation
5 s (by default) | positive scalar

The time it takes for the resistor temperature to reach 63% of the final temperature change when the ambient temperature is jumped.

Dissipation factor - dissipation factor for thermal equation
0.75e-3 W/K (by default) | `positive scalar'.

The thermal power required to raise the thermistor temperature by 1 K.