My dishwasher has a simple optical liquid level sensor... it's a rod of
clear plastic with the end cut at an angle (or maybe a V), the angled end is
toward the liquid, the other end is the viewing window. When the end is
clear of the liquid any incident light is reflected down then back up the
rod; when liquid touches the end the light path is extended into the
reservoir and the viewing window looks dark.

So put a reflective sensor at the "viewing" end... Not sure how well that'd
work with gasoline though.

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Andrew Hooper
> Sent: 24 September 2001 11:17
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: Conductive Liquid Sensor
>
>
> Why not just use optical sensor's?
> Seems to me that the depth of the fuel could be calculated by the amount
> of light able to penitrate.
>
> Top of tank with led or ir emitter
> |----\_/----|
> |~~~~~~~|
> |----/^\----|
> bottom of tank with ir receiver.
>
> Or another alternative is an ultrasonic sensor in the top.
> most industrial ultrasonic units are stainless and work well in fluid.
>
> Or cheap and nasty, pezio transducer stuck to one side of the tank
> on the other side a mechanical hammer, strike the tank and pickup
> sound vibration from the pezio. :) need better resolution then install
> a bigger hammer :)
>
> Andrew

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