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 http://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:


http://www.hamamatsu.com/jp/en/L13201-0430C.html


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


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



Do you think it will work?

Best regards,
Krystian

 

Question ... If a simple IR emitter diode were to transmit a beam so that it's reflection was received be a standard IR receiver photo-diode, would there be a resulting signal reception difference with the phase change from ice to liquid water?

 

I came up with an idea, that the easiest solution is to measure the intensity of the reflected wave...

Why do you think the reflected wave is going to be affected? When dealing with absorbance, you normally measure transmittance -- that is, the light that passes through it, not the light reflected by it.

Reflectance is a function of the index of refraction of the material and angle of incidence at the surface.

Absorbance/transmittance is a function of the material composition and geometry.

 

Thank you for your answers!

Do you suggest that we can see no differences between two different states of H20 if we measure only the reflectance?

We want to meseure the state of water being on a concrete. We cannot meseure a transmittance because we cannot put the detector behind our sample.

Do you have any other idea how to measure the state of H20?

 

Do you have any other idea how to measure the state of H20?

There is a slight difference in the index of refraction of water vs. ice (1.30 vs. 1.33). Perhaps use Brewster's angle? A light source in the visible band, perhaps a laser, a polarizer, and an array detector may be able to do this.

 

Honestly I don't know the incidence angle. The subsoil is not regular. What about case when the ratio ice:water is 50:50? Probably I don't receive any signal.

I guess I still need something "optoelectronic" what shows the diffrence between water and ice. Maybe something with scattering? Do I receive any measuring signal if I don't know the incidence angle?

Krystian

 

Up

Could you please post some detail of the concrete problem you are trying to solve.
When you mention "phase of water", do you mean...
(liquid vs vapor (humidity))
(liquid vs ice)
(Liquid vs hydrated concrete)
(Wet concrete vs cured concrete).

Or any combination thereof?

 

Well, I'm gonna build a detector which can recognize the icy and wet beton.

I don't need to catch every drop of water or ice. Just I need more or less know what kind of substance is on the surface of beton. I would like to measure it with frequency min 100-200Hz and it will still be fine if I receive the result as a average of 10-20 measurments.

Cheers,
Krystian

 

Well, I'm gonna build a detector which can recognize the icy and wet beton.

I don't need to catch every drop of water or ice. Just I need more or less know what kind of substance is on the surface of beton. I would like to measure it with frequency min 100-200Hz and it will still be fine if I receive the result as a average of 10-20 measurments.

Cheers,
Krystian

Beton? And no accent, béton, so you're not French. Where are you from? Romania?

So, as mentioned above, you have some competing effects going on with this idea.

First, if you want absorption of light (IR), it has to pass through the ice (or water). Unfortunately, a significant change in refractive index of at an interface causes reflection rather than transmission through the media (ice or water). The grater the angle of incident, the greater fraction of the light will reflect rather than pass through the next material.

So, your IR incident light will be traveling through air, hit the (ice or water) and reflect (because water has an refractive index of 1.38 vs air (about 1). Then the small bit of light travels through the ice/water and eventually hits the concrete or asphalt. The black asphalt will absorb all IR (no return light to detect), concrete will reflect some but even more will reflect back into the ice when the light gets back to the air/H2O interface.

Now, one very thin pass is not much of a signal so scientific instruments use a double beam (or split beam) to increase signal v noise by using one beam as a reference and the other as signal. And absolute intensity change just won't work, it is too attenuated and noisy.

You'll have to think of another physical property to exploit.

 

I think measuring the surface temperature by IR would likely be more feasible. It would not help when you're at the freezing point, since you could be anywhere from 0 to 100% ice and still be at 32. But any other temperature would tell you ice or not.

Not all ice looks the same, and even a human can be fooled. It's hard to imagine a machine using visual methods could discern water from ice

 

Thank you for your answers.

The thing is that the layer of ice or water on the concrete is very thin - maximum 3 milimeters.

Do you have any other ideas how to measure it?

 

Thank you for your answers.

The thing is that the layer of ice or water on the concrete is very thin - maximum 3 milimeters.

Do you have any other ideas how to measure it?

The traction-control on the car should be detecting any wheel slippage (both by unnatural acceleration/deceleration of wheel speed AND by unnatural wheel speed vs the speed of the other three wheels).

I would make an assumption if road surface temp is near or below 0°C AND traction-control light turns on, you have ice on the road.

 

GopherT,

Acording to your last post I was looking for something using for detecting the ice and water on asphalt. I have found something like that:

http://blog.lufft.com/en/reflection-and-absorption-this-is-how-marwis-works/

and

Do you know how it works? I think that the mechanism of action is pretty simmilar to that which I described, isn't it?