Model sensor that converts thermal potential difference into electrical potential difference
The Thermocouple block represents a thermocouple using the standard polynomial parameterization defined in the NIST ITS-90 Thermocouple Database .
For thermocouples Type B, E, J, K (t<=0 degC), N, R, S or T, the voltage E across the device in mV is
ci is the ith element of the Coefficients [c0 c1 ... cn] parameter value.
t is the temperature difference in degrees Celsius between the temperature at the thermal port A and the Reference temperature parameter value.
The equation for voltage across the device as a function of temperature difference is defined in mV. The units of the voltage across the actual device is V.
For thermocouples Type K (t>=0 degC), the equation contains an additional exponential term:
where a0, a1, and a2 are additional coefficients, required only by the Type K thermocouple, defined by the Coefficients [a0 a1 a2] parameter value.
The following equation describes the thermal behavior of the block:
T is the temperature at port A.
Q is the net heat flow into port A.
Kd is the Dissipation factor parameter value.
tc is the Thermal time constant parameter value.
dT/dt is the rate of change of the temperature.
To model the thermocouple in free space:
Connect the thermocouple 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 Anom.
Set the Heat transfer coefficient parameter of the Convective Heat Transfer block to Kd/Anom.
The model is based on the following assumptions:
The high-order polynomials this block uses are very sensitive to the number of significant figures used for computation. Use all available significant figures when specifying the Coefficients [c0 c1 ... cn] parameter.
Coefficients [c0 c1 ... cn] are defined for use over a specified temperature range.
The maximum supported value for
n in the
Coefficients [c0 c1 ... cn] parameter is 14, that is,
the vector cannot have more than 15 elements.
Select one of the modeling options:
Type B, E, J, K (t<=0 degC), N, R, S or
T — This option is equivalent to
the block functionality in previous releases.
Type K (t>=0 degC) —
This option adds an exponential term to the block equations
when the temperature difference is greater than 0 degrees
The vector of coefficients c in the equation that describes voltage as a
function of temperature. The maximum length of the vector is 15
elements. The default value is
[ 0 0 0 0 0 0 0 0 0 ].
You can download parameters for standard thermocouple types from the NIST database . For information on how to do this, see the Simulink® Approximating Nonlinear Relationships: Type S Thermocouple example.
The vector of additional coefficients
a2, required only by the
Type K thermocouple. This parameter is only visible when you select
Type K (t>=0 degC) for the
Thermocouple model parameter. The default
[ 0 0 0 ].
The temperature the block subtracts from the temperature at
the thermal port in calculating the voltage across the device. The
default value is
The time it takes the thermocouple temperature to reach 63%
of the final temperature change when a step change in ambient temperature
occurs. The default value is
The thermal power required to raise the thermocouple temperature
by one K. The default value is
The temperature of the thermocouple at the start of the simulation.
The default value is
The block has the following ports:
Thermocouple thermal port
Positive electrical port
Negative electrical port
 NIST ITS-90 Thermocouple Database http://srdata.nist.gov/its90/main