In this example a Stedham Electronics a Flatpack capacitive sensor
is mounted outside of a container. The tank can be up to 1" thick or so. The tank doesn't have to be clear.
It can be plastic, fiber glass, glass or just about any non-metal and non-conductive material.
Unshielded sensors are best for detecting conductive liquids (aqueous based) through non-metallic materials, but sometimes a shielded sensor is needed when the target fluid is non-conductive. Call us if you aren't sure. We'll be glad to help.