What are the physics being used

Questions, answers, discussions related to the FIND Technologies Inc. challenge

What are the physics being used

Postby johnray » Fri May 20, 2011 5:17 am

I would like more details about how it is possible to detect the type of matter with your sensor. From the project description the sensor is an "inexpensive instrument that detects passive electromagnetic emission from all matter" which sounds like it detects the infrared heat radiating from the samples. From the data it seems like the sensor is measuring the intensity of IR light it is receiving. This is outside my field of expertise but my understanding is that measuring the infrared will allow you to detect the temperature of an object. Different materials will radiate different amounts of energy at the same temperature so you must calibrate your instrument based on that. You could also reverse the process knowing that 3 different materials are all the same temperature you could determine which is which based on the average heat they are radiating. However from the data it appears that the 3 materials have very similar IR profiles plus we don't know if they are the same temperature.

My understanding is that the only way to reliably detect the type of material is to use absorption spectroscopy where the sensor can detect both the frequency and intensity of electromagnetic emissions. Alternatively you can use a sensor that only detects the intensity but then illuminate the sample with a tunable laser which is capable of changing it's color.

I've tried looking for a paper to better explain the detection process which would help in figuring out how to analyze the data but haven't been successful. At the moment the data just seems like thermal noise to me.
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Re: What are the physics being used

Postby franklabella » Tue May 24, 2011 2:50 pm

There is a commonly used technique of "passive microwave imaging or sensing". We believe the passive emission we are sensing may be microwave, although all matter also emits radiowaves 10-100 MHz ( my understanding from the literature). I note that the MHz signals are a common interference in MRI instrumentation.

Frank LaBella
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Re: What are the physics being used

Postby robertf » Tue May 24, 2011 7:00 pm

I am not an expert in digital signal processing, but something does not sound right: can you properly detect MHz range waves with your 16.667 kHz sampling rate?
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Re: What are the physics being used

Postby franklabella » Fri May 27, 2011 12:39 pm

No, The frequency range is from 0 to 16667/2 Hz.
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