Hello, I’m a physics Bachelor student from Los Andes University. I’m currently working on my thesis but due to the economical/political situation we do not have resources in experimental physics areas. Which is what brought me here because I want to consult idea about measuring temperature in a domestic microwave oven, my sample is in vacuum inside a crystal tube. We tried using a thermocouple but giving that is a violent rise in temperature, the resistance is overpass quickly so one cable company gave us 2 meters of optical fiber cable and in order to set the efficiency of this possible method we took one of the “hairs” of the O.F. and tried to measure the temperature of a common laboratory oven but (of course) got burned. So my question or cry for help is if anyone of you have an idea of how to make a decent measure of temperature with basics? In advanced, I’m sorry if my English is not good. Thank you.
It may be possible to use a laser thermometer or a thermal camera positioned outside the oven. This would be accomplished by using a waveguide below the cutoff frequency.
http://www.hep.princeton.edu/~mcdonald/examples/cutoff.pdf
Basically, if the diameter is small enough, and the waveguide is long enough, the waveguide attenuation prevents energy transfer to the equipment. Infrared and visible light have a much shorter wavelength, which means the waveguide can be sized to pass the light frequencies of interest .
Double-checking your math and the operating frequency is important here, because a mistake means you cook your equipment!
My thought is an external infra-red thermometer in line with Andrew's comments above.
Good suggestion. Gordon. That made me think of the thermochromic liquid crystal strips if the temperature rise isn't too great.
In ceramic sintering experiments above 400 oC the emitted light is analyzed, but it works only at high temperatures
It might be possible to arrange a rod of material e.g. brass which protrudes through one wall of the oven. Knowing the expansion coefficient of brass and measuring the expansion of the brass via say a dial calliper would give an easy way of determining an average temperature across the oven. This system utilises parts that can be found in any physics laboratory and can easily be modified, by shortening the brass bar to give finer resolution.
I appreciate all of your answers and I'm taking them into consideration for the experimentation. Luckily we found a thermocouple with a metallic cover which was isolated in order to not cause electrical arcs and only left uncover the part that is in contact with the crystal tube. Soon enough we'll be getting results. Thank you all very much.
where did you find that thermocoule? I have a similar problem
Edna Magdalena Hernández we were unable to take measurements but it was a regular termocouple isolated with glass fiber.
Jeff Darland
I will pass the information to the people still working in that project, thank you
is it dangerous if we measure temperature using thermocouples in domestic microwave oven?
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