Absorption detector.

Good Morning,


I am going to build a device to detect the physical state of water. I came up with an idea, that the easiest solution is to measure the intensity of the reflected wave, which length is 4150nm. According to https://www.nature.com/nature/journal/v439/n7073/fig_tab/nature04415_F1.html there is a significant difference in absorption of liquid and solid water. The device is created for ordinary applications, so it doesn’t need to be as sensitive as ones for laboratory use. I found that there is a possibility to buy a thermopile with 4.3 μm band-pass filter, but there is a lack of 3050nm detectors. The device should also have the second reference detector, but I don’t know which wavelength will be the most desirable. Another point is selection of IR emitter that will match the detectors, I am not sure which one should I buy.

Or maybe there is a completely different solution that is easier/better than presented above?

I thought about opto elements below:


**broken link removed**


https://www.hamamatsu.com/jp/en/product/category/3100/4007/4219/T11361-01/index.html


https://www.hamamatsu.com/jp/en/product/category/3100/4007/4219/T11361-05/index.html



Do you think it will work?

Best regards,
Krystian

IR bandpass filters with various center wavelengths are either available from stock or can be made according to customer specifications. Specialized detector manufacturers have a number of band pass filters for popular gas measurement applications on stock, some might be useful for your application, see e.g. a 3.09 µm filter from Infratec https://www.infratec-infrared.com/sensor-division/products/ir-filter.html

Thank you for your answer and the link to the store.

Anyway I'm not still sure if it be working. Do you have some experience in this area?

I've been designing IR gas analyzers.

Do you think IR gas analuzer can be used for that task?

Not particularly. But both measurements are implementing IR absorption photometers, using the same IR sources, detectors, filters, lenses, windows etc.