anyone have experience with these external liquid level sensors? they don't seem to be optical, but i could be wrong. i'm looking for an externaly mounted liquid level sensor with an opaque container.
spectrapure.com

LiterMeter® Capacitive Liquid Level Sensor Assembly -LM-LLS-01
SpectraPure, Inc. is an Industry Standard in the Water Purification world. From Drinking Water to Aquarium Systems, you don't just want pure water, you want the PUREST Water! Get it with SpectraPure!
