Thermistor

A thermistor with a positive (PTC) or negative (NTC) temperature coefficient.

blockType: AcausalElectricPowerSystems.Sensors.Thermistor

Thermistor

Path in the library:

/Physical Modeling/Electrical/Sensors & Transducers/Thermistor

PTC Thermistor

Path in the library:

/Physical Modeling/Electrical/Sensors & Transducers/PTC Thermistor

Description

Block Thermistor It is a thermistor with a positive (PTC) or negative (NTC) temperature coefficient.

Thermistor with negative temperature coefficient (NTC)

A thermistor with a negative temperature coefficient (NTC) uses the B-parameter equation.

For an NTC thermistor, resistance at temperature It is defined as follows:

where

— resistance at nominal temperature ;
— temperature coefficient.

Typical thermistor usage in models:

Connect the thermistor to the B port of the unit Convective Heat Transfer.
Connect the A port of the unit Convective Heat Transfer to the block Temperature Source, the temperature of which is set to the ambient temperature.
Set the parameter Area the block Convective Heat Transfer to the approximate area .
Set the parameter Heat transfer coefficient the block Convective Heat Transfer on the value .

Thermistor with a positive temperature coefficient (PTC)

The resistance of this type of thermistor decreases with increasing temperature 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 en

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

— the Curie temperature;
— resistance at nominal temperature ;
— resistance at the reference temperature ;
— the nominal temperature at which the resistance is indicated, usually room temperature. less Curie temperature ;
— reference temperature equal to or higher than the Curie temperature , which means that the PTC mode is in effect at this temperature;
— temperature coefficient at nominal temperature ;
— temperature coefficient at the reference temperature .

The following equation describes the thermal behavior of the block:

where

— heat flow in port A;
— dispersion coefficient, the value of the parameter Dissipation factor;
— time constant, parameter value Thermal time constant;
— the rate of temperature change.

Variables

Use the parameter group Initial Targets to set the priority and initial target values for the block parameter variables before modeling. For more information, see Configuring physical blocks using target values.

Ports

Conserving

# + — the positive terminal of the resistor
electricity

Details

The electrical port is the positive terminal of a resistor.

Program usage name

p

# – — the negative terminal of the resistor
electricity

Details

The electrical port represents the negative terminal of the resistor.

Program usage name

n

# A — thermal port
warm

Details

The thermal port that determines the temperature of the resistor.

Program usage name

thermal_port

Parameters

Electrical

# Block type — choosing the type of thermistor
Thermistor | PTC Thermistor

Details

Choosing the type of thermistor

Thermistor — thermistor with negative temperature coefficient (NTC);
PTC Thermistor — thermistor with a positive temperature coefficient (PTC).

Values	`Thermistor` \| `PTC Thermistor`
Default value	`—`
Program usage name	`type`
Evaluatable	No

# Nominal resistance R0 at reference temperature T0 — resistance at nominal temperature
Ohm | mOhm | kOhm | MOhm | GOhm

Details

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

Dependencies

To use this parameter, set for the parameter Block type meaning Thermistor.

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`1000 Ohm`
Program usage name	`R0_ntc`
Evaluatable	Yes

# Nominal resistance R0 at T0 — resistance at nominal temperature
Ohm | mOhm | kOhm | MOhm | GOhm

Details

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

Dependencies

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

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`1000 Ohm`
Program usage name	`R0_ptc`
Evaluatable	Yes

Details

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

Dependencies

To use this parameter, set for the parameter Block type meaning Thermistor.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`3500 K`
Program usage name	`B`
Evaluatable	Yes

Details

Ratio in an equation describing resistance as a function of temperature at a nominal temperature. The value must be less than zero.

Dependencies

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

Units	`1/K` \| `1/degR` \| `1/deltaK` \| `1/deltadegC` \| `1/deltadegF` \| `1/deltadegR`
Default value	`-0.01 1/K`
Program usage name	`alpha0`
Evaluatable	Yes

Details

The temperature at which the nominal resistance was measured.

Dependencies

To use this parameter, set for the parameter Block type meaning Thermistor.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`298.15 K`
Program usage name	`T0_ntc`
Evaluatable	Yes

Details

The temperature at which the nominal resistance was measured.

Dependencies

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

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`298.15 K`
Program usage name	`T0_ptc`
Evaluatable	Yes

# Reference resistance R1 at T1 — reference resistance at reference temperature
Ohm | mOhm | kOhm | MOhm | GOhm

Details

The reference resistance of the thermistor at the reference temperature.

Dependencies

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

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`10000 Ohm`
Program usage name	`R1`
Evaluatable	Yes

Details

Ratio in an equation describing resistance as a function of temperature at a reference temperature. The value must be greater than zero.

Dependencies

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

Units	`1/K` \| `1/degR` \| `1/deltaK` \| `1/deltadegC` \| `1/deltadegF` \| `1/deltadegR`
Default value	`1 1/K`
Program usage name	`alpha1`
Evaluatable	Yes

Details

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

Dependencies

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

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`398.15 K`
Program usage name	`T1`
Evaluatable	Yes

Thermal

# Thermal time constant — the time constant for the thermal equation
s | ns | us | ms | min | hr | d

Details

The time it takes for the temperature of the resistor to reach 63% of the final temperature change with an abrupt change in ambient temperature.

Units	`s` \| `ns` \| `us` \| `ms` \| `min` \| `hr` \| `d`
Default value	`5.0 s`
Program usage name	`time_constant`
Evaluatable	Yes

# Dissipation factor — the coefficient of dissipation for the thermal equation
W/K | kW/K

Details

The thermal power required to increase the temperature of the thermistor by 1 To.

Units	`W/K` \| `kW/K`
Default value	`0.00075 W/K`
Program usage name	`dissipation_factor`
Evaluatable	Yes