Peter, I notice the empahasis on the 'insulate' part; should they be or
should they not?

I had fabricated a sensor using a pair of aluminium strips the height of the
tank, separated by plastic spacers ever few inches. The strips themselves
were NOT insulated from water. Worked as expected, but the problem came from
elsewhere; the sensor was too sensitive to noise, even when connected using
a shielded, or co-ax. cable; the readings would go haywire if one touched
even the plastic insulation on the connecting wires.

Despite the issues involved, I eventually settled for a conducting type of a
sensor; a ladder of 10 100K resistors in series; as the water level rises,
it progressively 'shorts' out the resistors underneath. This sensor was then
used as the lower half of a potential divider and fed to the ADC on the PIC.
Cant complain with the results, its been working for over a year now!

Regards,

Anand Dhuru

----- Original Message -----
From: "Peter L. Peres" <plp@ACTCOM.CO.IL>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, February 01, 2003 05:47 PM
Subject: Re: [PIC]: waterlevel (on/off) on a PIC pin


> On Sat, 1 Feb 2003, cdb wrote:
>
> *>On Sat, 1 Feb 2003 11:22:38 +0200, Peter L. Peres wrote:
> *>
> *>
> *>That is precisely what I did, and with the dip in the water yes the
> *>capacitance changed from about 10pF to 20nF, however the 74LS132 refused
> *>to oscillate and the 4093BE didn't do much better.
>
> Were the electrodes *insulated* from the water ?
>
> If you're happy with your solution, then I am happy too.
>
> Peter
>
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