Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Mon, 10 Jun 2002 09:10:08 -0400
Message-ID: <redirect-1288135@logan.com>
Subject: Dielectric Constant of Avgas ?
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From: "Allan Saul" <asaul@rfdesign.co.za>

Does anyone know the Electrical Dielectric Constant of Avgas ?

I need this to calculate the range of Capacitance change on the=20
L-IV-P capacitive probes. The capacitance changes from a fixed
value when the tanks are empty and the probes have air in them
(DK=3D1) to a higher value when the tanks are full.

This change in capacitance drivers a simple NE555 IC capacitance
to frequency converter circuit mounted on the end of the probes,
and this frequency is then typically sent to Electronics International
Fuel Gauge which interprets the frequency as a fuel level.

I am not using the EI gauge, and have rather opted for different=20
resistive float type gauges. I will be designing a circuit to drive any
resistive gauge using a PIC microprocessor which can be calibrated
accurately. However for me to get started on the design I need to
know the frequency range from full to empty in the tanks so I can
get started. I will share the design with anyone that's interested.

Anyone that actually has measured the range of frequencies coming
out of the probes would be even better.

Allan Saul / Lancair IV=3DP=20