My interest has been awakend by this thread and I thought that I would try to measure the change in capacitance caused by various fluids.
I made a probe which would lay in a shallow plastic tray.
The probe consists of two enamelled copper wires, 2mm daimeter and about 240mm long, bent into a Z shape.
The wires are supported by two paxolin blocks, the wires pass through holes in the blocks, the holes are spaced 3mm apart.
I connected the probe to my capacitance test jig, the capacitor in the photograph is there because the enamel on the wires is damaged and there is a DC leakage path between the wires. My test jig has a small polarising voltage between the terminals, and the electrolytic effects can be seen as a drift in the readings when the probe is in water.
The results I got are as follows:
Code:
Probe disconnected 4.7pF
Probe in air 16pf
Probe in tap water 416pF
Probe in sunflower oil 25pF
Probe in mineral oil 21pF
So we see there is a big change in capacitance between oil and water.
I dont have any soluble oil to test this out any further, but as a basic concept for a measuring system, I think that it is in with a good chance.
JimB