# Estimating internal (junction) temperature

• Eli Hait
In summary, the conversation discusses using a motion sensor in a sealed metal enclosure and performing temperature offset calibration using an external temperature sensor. However, this method does not account for fast temperature gradients, resulting in a large difference between the case temperature and internal temperature. The person is seeking a simple method to estimate the internal temperature in this scenario. They also ask if there is good information about this topic available online.
Eli Hait
Hello.

I use a kind of motion sensor located in a sealed metal enclosure.
I perform temperature offset calibrating to this device, using an external temperature sensor (attached to the enclosure). This solves the most of temperature problems except when the temperature gradient is large - for instance for 1'st 5 minutes afrer powering the device.
After checking this issue my conclusion was that in fast temperature gradients the temperature delta between the case temperature (Tcase, the one i measure) and internal (Tj) temperature is too large so i don't compensate the real offset error.

My question is if there is a simple method to estimate the internal temperature (Tj), if at the beginning (before powering up the sensor) the external and internal temperatures are equal Tcase=Tj.

Is there good information about it on the web?

Thanx,
Eli.

Hello Eli,

Thank you for sharing your method for estimating internal temperature in your device. It sounds like you have a good understanding of the factors that can affect temperature readings, such as temperature gradients and offset errors. In regards to your question about estimating internal temperature when the external and internal temperatures are equal, there are a few methods you can try.

One method is to use a thermal simulation software to model the temperature distribution in your device. This can give you an estimate of the internal temperature based on the external temperature and other factors such as material properties and heat dissipation. Another method is to use a thermal imaging camera to visually see the temperature distribution in your device and estimate the internal temperature based on the external temperature.

Additionally, there are resources available on the web that discuss techniques for estimating internal temperature, such as articles and forums on thermal management and temperature sensing. It may also be helpful to consult with a thermal engineer or expert in the field for more specific guidance on your particular device and situation.

I hope this information helps you in your temperature estimation process. Good luck!

## 1. What is internal (junction) temperature and why is it important in scientific research?

Internal (junction) temperature refers to the temperature at the junction of two materials, such as a semiconductor and a metal. It is important in scientific research because it affects the performance and reliability of electronic devices.

## 2. How is internal temperature estimated in scientific experiments?

Internal temperature can be estimated using various methods, such as thermal imaging, thermocouples, and infrared cameras. These tools allow researchers to measure the temperature at specific locations within a material.

## 3. What factors can affect the accuracy of internal temperature estimates?

The accuracy of internal temperature estimates can be affected by factors such as the type of material being measured, the surface conditions, and the calibration of the measuring tool. It is important for researchers to consider these factors when interpreting their results.

## 4. Can internal temperature estimates be used to predict the lifespan of electronic devices?

Yes, internal temperature estimates can be used to predict the lifespan of electronic devices. Higher internal temperatures can lead to accelerated degradation of materials, which can affect the longevity of electronic devices.

## 5. How can internal temperature estimates be applied in real-world applications?

Internal temperature estimates can be applied in various real-world applications, such as the design and development of electronic devices, thermal management in buildings and vehicles, and monitoring the health of machines and equipment. They can also be used to optimize energy efficiency and improve the overall performance of systems.

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