Haven done some work with gas analysis, I know that certain gases have a
frequency of absorbtion.  Example: CO2 will let most frequencies of light pass
right thu it with no attenuation at all.  However, there are certain specific
frequencies of light where the light will be blocked if CO2 is present.  You
might need to check if "milk froth" has an absortion frequency and use that.

Maybe it has the opposite.  Instead of looking at a frequency that blocks the
light.  Maybe there is a frequency that reflects the light.  Shine a VERY
NARROW BEAM emittor at an angle, wait for the froth to get to a certain level
and look for the reflection and the other side of the angle.

"Kresho @ Advanced Technika" wrote:

> Hello All.
>
> This might sound like a weird one but maybe someone can help.
>
> I'm trying to detect when some milk froth comes to the top of a cup for an
> automatic cappuccino maker. The cup will always be the same size and will
> have a coffee base already in it. What i want to do is place this cup under
> a nozzle and press a button so that milk froth is poured into the cup till
> it reaches a set height so that the cappuccino making is more of an
> automated process.
>
> Measuring weight is a no-goer since the froth is very light can vary in
> density. Using some probes may be troublesome because the froth will stick
> to them over time. Timing alone is also unsuitable. A distance measurement
> device which can operate over the required range (5-10cm) might be an idea
> but then again i don't know how well milk froth can be sensed since it is
> not very solid.
>
> Hope someone can help.
>
> Regards, Kresho
> Sydney, Aust.
>
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