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Hi Eoin,
this is a simple circuit (I'm a newbie in electronic) so I don't know his
limits. I haven't necessity of an accurate measure and it is very essential
(but also cheap). Frequency output It is sensible to V+ variations, so a
regulator will be nice.
The C1 cap. value in the schematic may be very different due to water
hardness. You can start with a 0,1uF and then test other values. I think
this note is important:  to obtain a linear freq. variation versus water
conductivity, is mandatory that the electrodes of the probe will not "free"
but into a confined vane (with open sectors for water).
bye
Marco


----- Original Message -----
From: "Eoin Ross" <eross@CHEMSTATION.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: 22 febbraio, 2002 15.29
Subject: Re: [EE]: A cheap A/D interface


Would you be able to send me a copy of the conductivity side of the circuit?
Been looking on the net for something like that and not had much success.

>>> marco.genovesi@LIBERO.IT 02/22/02 05:43AM >>>
<snip>

because I use it also for other types of frequency sensor (example: a
4093-based circuit for water conductivity measurement).

Many thanks to All for suggestions

Marco

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