On Fri, 4 Jun 2004, John Rodgers wrote:

> Not to mysterious. There are fuel guages used in airplanes that measure
> the resistances in fuel as the volume changes, and translates this
> measurement into units on the guage in the cockpit. Why not measure the
> density of the antifreeze in relation to the water to operate a warning
> light?? Less water, more antifreeze, more resistance, the light comes on
> and blinks.

Technically, it's measuring the resistance, not the density.  They aren't
the same.

The fresh water tank level sensor in early Westies is also a resistive
sensor.  If you go somewhere with very soft water and fill the tank, the
level gauge won't work very well because there aren't enough ions in the
water to conduct electricity.  If you filled the tank with pure distilled
water it wouldn't work at all.

David Brodbeck, N8SRE
'86 Volvo 240DL wagon
'82 VW Vanagon Westfalia Diesel