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RE: Re: Measuring bath water depth



I sure ultrasound would work, the problem may be to do with the beam divergence. The ultrasound will reflect off most surfaces in the sensors field of view, ie the shower rail, windowsill, the bath rim, water or bottom of bath. I’m not sure with the ultrasonic tape measures what the beam angle is like, I don’t have one. If it could be made very narrow there should be no problems.

 

Alternatively, given that the ranges of interest are known, you maybe able to filter the unwated refelections out by selectively sampling the reflected sound wave at the desired time. You should be able to get an accuracy of about .5cm over the range of bath empty to bath full.

 

A colleague of mine developed a cheap sonar sensor that gave rs232 out and measured the distance to the first 8 objects. This may work as it is likely that the water could be made to be the second object, given that the first would probably be the bath rim.

 

Just a few thoughts…

 

Iain

 

-----Original Message-----
From: PatrickLidstone [mailto:patrickl@xxxxxxx]
Sent: 12 August 2002 13:45
To: ukha_d@xxxxxxx Subject: [ukha_d] Re: Measuring bath water depth

 

--- In ukha_d@y..., Stuart Grimshaw <stuart@s...> wrote:
> On Monday 12 Aug 2002 1:20 pm, Stuart Poulton wrote:
> > Patrick,
> >
> > I like the idea of this,  be interesting to see if anyone is able
to try
> > this.
> >
> > There are of course ustrasound sensors used in robotics available.
>
> What about using a capacitence probe? Two strips of metal, the more
water in
> the tub, the greate/lesser the capacitence. Have a look at
epanorama.net for
> more info.

I was interested in ultrasound because it is non-intrusive. Probes in
the bath are unsightly, are difficult to secure mechanically, have a
poor SWMBO factor, and, perhaps most importantly, would, I think, be
unreliable - since most probes rely on the wet-dry factor, resulting
in false readings in any situation in which the probe starts off from
anything other than bone dry...

Patrick



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