Other Parts Discussed in Thread: TMP117
Tool/software:
Hi Team,
What is the minimum airgap to be maintained between metal hot surface and the sensor?
Thanks and Regards,
Vidhya
This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
You may need an air gap for voltage isolation, but the sensor IC does not have a specification for that. That is a system level requirement. The sensor can contact a hot surface within the absolute max ratings of the IC.
thanks,
ren
Copper Projection from the housing wall (with screw) as shown is image.
Temperature of that metal has to be measured. TMP117 is right below the metal projection. want to know if any airgap to be maintained for the sensor TMP117 to read properly.
As I've stated, your system may require an air gap for other reasons. The sensor itself does not have a requirement for air gap. It can make contact.
ren
All ICs are characterized for thermal performance. This information is in the Thermal Metrics portion of the datasheet. Theta J is an industry standard measurement of thermal resistance through the IC packaging.
The supporting application note, http://ti.com/lit/SPRA953, describes how theta JC is characterized.
While this is meant to model heat dissipated through a heatsink, I would say its also an accurate model of temperature sensed at the surface of the package. Yes, the TMP products sold by TI can measure temperature at their surface.
thanks,
ren
Thanks Ren.
This is understood that to record the surface temperature, TMP117 can contact package and heatsink via thermal grease or pad.
can we use same TMP117 for contactless <1mm airgap between package and heatsink?
Regards,
Vidhya
The sensor will still report a temperature. Whether it is accurate enough for your purposes would have to be tested or simulated.
ren
Thanks Ren,
Do you have any test report for contactless measurement of Surface temperature using TMP117?
How to Simulate this part? There is only IBIS model available in Website. Any other models (PSPICE) available?
Also, How to emulate the surface temperature by simulation?
Thanks and Regards,
Vidhya
I don't have such a report available.
Thermal modeling is accomplished by FEA and/or CFD. Ansys and Cadence make tools that can do this.
There is a 3D model of the package in UltraLibrarian. https://www.ti.com/product/TMP461#cad-cae-symbols You would import this 3D model into the thermal modeling tool. The black parts of the package are mold compound, and should be assigned a thermal coefficient of 1 W/mk and emissivity of 0.95 inside the modeling tool. You could then run the simulation to see heat transfer to the package.
thanks,
ren
Thermal modeling, when performed correctly, would encompass all three methods of thermal transfer: conduction, convection and radiation. Your question of sensor effectiveness would be determined by these transfer methods between the heat source and the sensor package.
ren