Model NTC thermistor using B-parameter equation

Sensors

The Thermistor block represents an NTC thermistor
using the B-parameter equation. The resistance at temperature *T* is

$$R={R}_{0}({e}^{B(1/T-1/{T}_{0})}-1)$$

where:

*R*is the nominal resistance at the reference temperature_{0}*T*._{0}*B*is the characteristic temperature constant.

The following equation describes the thermal behavior of the block:

$$Q={K}_{d}{t}_{c}\frac{dT}{dt}$$

where:

*Q*is the net heat flow into port A.*K*_{d}is the**Dissipation factor**parameter value.*t*_{c}is the**Thermal time constant**parameter value.*dT/dt*is the rate of change of the temperature.

To model the thermistor in free space:

Connect the thermistor to the B port of a Simscape™ Convective Heat Transfer block.

Connect the A port of the Convective Heat Transfer block to a Simscape Ideal Temperature Source block whose temperature is set to the ambient temperature.

Set the

**Area**parameter of the Convective Heat Transfer block to an approximate area*A*_{nom}.Set the

**Heat transfer coefficient**parameter of the Convective Heat Transfer block to*K*_{d}/*A*_{nom}.

**Nominal resistance R0 at reference temperature T0**The nominal resistance of the thermistor at the reference temperature. Many datasheets quote the nominal resistance at 25°C and list it as R25. The default value is

`1000`

Ω.**Characteristic temperature constant B**The coefficient

*B*in the equation that describes resistance as a function of temperature. The default value is`3500`

K.**Reference temperature T0**The temperature at which the nominal resistance was measured. The default value is

`298.15`

K.

**Thermal time constant**The time it takes the sensor temperature to reach 63% of the final temperature change when a step change in ambient temperature occurs. The default value is

`5`

s.**Dissipation factor**The thermal power required to raise the thermistor temperature by one K. The default value is

`0.75e-4`

W/K.**Initial temperature**The temperature of the thermistor at the start of the simulation. The default value is

`298.15`

K.

The block has the following ports:

`A`

Thermal port

`+`

Positive electrical port

`-`

Negative electrical port

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