On 06/01/2012 17:25, The Natural Philosopher wrote:
Neil wrote:
If you have a container and you put two vertical parallel wires in it,
why can't you determine the quantiy of a liquid poured into that
container based on the resistance measured between the two wires?

you can.


If the material is conductive.


You can also measure the capacitance if its an insulator


But modern oil gauges and height gauges prefer to use ultrasonic
rangefinding on the top of the liquid.


Not always a good idea to have electrical conductors in flammable liquids..

That's when you use intrinsically safe devices and either zener barriers
or galvanic isolators - restricting the voltage (typically 28V dc max)
and current (typically 20-odd milliamps) so that there is not enough
energy supplied or stored to ignite any vapours.

SteveW