# Thermistor

Negative temperature coefficient thermistor using B-parameter equation

**Libraries:**

Simscape /
Electrical /
Sensors & Transducers

## Description

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

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

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}.

### Variables

To set the priority and initial target values for the block variables before simulation,
use the **Initial Targets** section in the block dialog box or Property
Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Use nominal values to specify the expected magnitude of a variable in a model. Using
system scaling based on nominal values increases the simulation robustness. Nominal values
can come from different sources. One of these sources is the **Nominal
Values** section in the block dialog box or Property Inspector. For more
information, see System Scaling by Nominal Values.

## Examples

## Ports

### Conserving

## Parameters

## Extended Capabilities

## Version History

**Introduced in R2008a**