1. Applications Team Sensing Products
TMP006 Customer Training
Applications Team
Sensing Products

2. What is a Thermocouple / Thermopile+
Thot
Tcold + -
Heat
Absorber
Heat Sink
Vout
Thot
Vout
Thot
Tcold
Thot -
Thot
Heat Absorber
Cold Junction
Vout = n x G x (Thot – Tcold)
G: Seebeck Constant
Vout = G x (Thot – Tcold)
G: Seebeck Constant

3. Heat Transfer (1): Conduction
Conduction: Heat is transferred through direct touch.
Example: Touching a hot cup of coffee

4. Heat Transfer (2): Convection
Convection: Heat is transferred by a moving liquid or gas.
Example: Fan cooling

5. Heat Transfer (3): Radiation
Radiation: Heat is transferred by waves (photons)
Example: The warmth you feel from the sun
The amount of energy radiated is dependent on the absolute (Kelvin) temperature of the object.

6. Device Principle of Operation
Object
Infrared Radiation
TMP006
PCB
TMP006 at its core is a heat sensor. It converts the heat being transferred to a voltage.

7. PCB Recommended Layout
The sensor at it’s core is a heat sensor and is sensitive to conduction and convection in addition to radiation.
Recommended PCB layout isolates the sensor from the rest of the PCB
Via Connecting to Circuit
Copper Dot
Thermal Break
GND

8. TMP006 Conduction & Convection Offsets
The sensor, is a heat sensor at its core. It will detect heat from all three sources: conduction, convection, and radiation.
The signal created by heat conduction and convection is relatively small in a setup with the recommended PCB layout but it is not zero.
Calibration is needed to cancel out remaining offsets

9. Field of View Consideration (1)
For best performance it is recommended that the diameter of object is 4 times the distance to the TMP006 sensor.
d = h – 250µm
object size ≥ 4×d
Case
object size ≥ 4d
distance = d h
TMP006
PCB

10. Field of View Consideration (2)
For best performance it is recommended that the diameter of object / opening is 4 times the distance to the TMP006 sensor.
d = h – 250µm
Opening size ≥ 4×d
Case/Lens
PCB
TMP006
distance = d
opening size ≥ 4d h
heat sink

11. Emissivity Considerations
Not all objects emit the same amount of energy at the same temperature.
Emissivity is the ratio of energy radiated by an emitter to the theoretical ideal emitter. Emissivity is always less than one.
Since the emissivity may change for different systems, then the system gain will need to be calibrated.

12. TMP006 Equation
Needs calibration. Depends on field of view and emissivity of object
System independent: No need to calibrate
Models voltage offset due to conduction & convection. System dependent & needs calibration
System independent: No need to calibrate

13. Transient Correction Basics
The hot junction is isolated from the rest of the sensor by the sensor’s thermal resistivity
When the sensor’s cold junction temperature is changed through heat conduction from the outside, the hot junction follows, but is delayed by a time constant
This effect can be modeled with a first order RC filter that delays the hot junction relative to the sensor substrate temperature
Thermopile
Rth
Cth
Thot
Tcold
Thot
Tcold + -
Heat
Absorber
Heat Sink
Vout
Rth Thermal resistance of thermopile
Cth Thermal capacitance of thermopile

14. Transient Error Example
Thot
Tcold
time
Temperature

15. Transient Correction Basics (2)
A temperature gradient is created on the thermopile during transients that is proportional the slope of the transient itself.
This gradient generates a voltage error through the Seebeck effect.
Alpha is a constant which corresponds to the multiplication of Seebeck constant and the thermal time constant

16. Effect of Transient Correction
Without transient correction
With transient correction

17. Coefficient Calibration
Coefficients that get calibrated are: S0, b0, b1 & b2
Before calibrating the coefficients, transient correction should be applied to the sensor’s output voltage to cancel out the transient effects.
At this point in time it is recommended that the customer send us the data of their system and we will provided a custom set of “b” coefficients for optimum accuracy.
An automatic calibration software is being developed at this point and should be available for customer use in the near future

18. Setting Up The System For Calibration
Object
Reference Temperature Sensor (Example: TMP112)
Glued to object using thermal epoxy
TMP006
PCB
For calibration: the data from the reference: Tobj as well as the TMP006 data: Tdie & Vout need to be collected simultaneously.

19. Calibrating S0
To be able to accurately calibrate S0 you need at least two points with the same Tdie values but different Tobj values.
More than one measurement is recommended to reduce the effect of noise

20. Calibrating “b” Coefficients
The residual offset based on the calibrated S0 value is calculated according to the equation above.
The calculated offset is drawn versus (Tdie – Tref) and a second order curve fit for the data is done to calculate the b0, b1 and b2 coefficients.
2nd order curve fit
(use excel)
Coefficients of curve fit are b0, b1 and b2
Vos = Vobj – S(Tobj4 – Tdie4)
Tdie – Tref

21. Importance of the Number and Range of Points
Error at the extreme points
Calibrated curve based on only middle three points
y-axis
Actual device behavior
Points collected don’t exactly match the actual curve due to noise
x-axis
The larger the number of points the lower the effect of noise.
The further apart the points are the better the correction.

22. Default Versus Calibrated Coefficients
Default coefficients
Calibrated coefficients