AVR-Chat

Enki wrote:
> 	I need to measure the liquid level inside a transparent plastic 
> bottle. I need to know when the liquid is below half bottle height and 
> when the bottle is almost empty. Just two steps.
> 	The plastic bottle measures 12cm high x 8cm x 3cm.
> 	I'm not allowed to insert any probe in the bottle.
> 	There are four bottles side by side.

Is the liquid itself always the same?
Is the liquid clear or opaque?

I have detected used oil in a steel container where there was a sight 
glass. When oil is present it will reflect light. Other dark liquids 
may work the same.

If it is possible, the weight option already mentioned is probably the 
easiest and would allow the "trip point" to be easily adjusted.

Tim