I'm trying to come up with a viable alternative to a float sensor as a water level sensor in an automated tank. I've designed everything to be under tank thus far and don't want a plastic switch in the tank.
I've been around and have found these as resources. I'm not good enough with electronics to start this project all on my own but if you've any input that'd be great. I'm thinking about capacitance based sensors as described here:
"Capacitance Level Sensors (also called RF)
Capacitance level sensors excel in sensing the presence of a wide variety of solids, aqueous and organic liquids, and slurries. The technique is frequently referred to as RF for the radio frequency signals applied to the capacitance circuit. The sensors can be designed to sense material with dielectric constants as low as 1.1 (coke and fly ash) and as high as 88 (water) or more. Sludges and slurries such as dehydrated cake and sewage slurry (dielectric constant 50) and liquid chemicals such as quicklime (dielectric constant 90) can also be sensed. Dual-probe capacitance level sensors can also be used to sense the interface between two immiscible liquids with substantially different dielectric constants, providing a solid state alternative to the aforementioned magnetic float switch for the “oil-water interface” application.
Since capacitance level sensors are electronic devices, phase modulation and the use of higher frequencies makes the sensor suitable for applications in which dielectric constants are similar. The sensor contains no moving parts, is rugged, simple to use, easy to clean, and can be designed for high temperature and pressure applications. A danger exists from build up and discharge of a high-voltage static charge that results from the rubbing and movement of low dielectric materials, but this danger can be eliminated with proper design and grounding.
Appropriate choice of probe materials reduces or eliminates problems caused by abrasion and corrosion. Point level sensing of adhesives and high-viscosity materials such as oil and grease can result in the build up of material on the probe; however, this can be minimized by using a self-tuning sensor. For liquids prone to foaming and applications prone to splashing or turbulence, capacitance level sensors can be designed with splashguards or stilling wells, among other devices.
A significant limitation for capacitance probes is in tall bins used for storing bulk solids. The requirement for a conductive probe that extends to the bottom of the measured range is problematic. Long conductive cable probes (20 to 50 meters long) suspended into the bin or silo, or subject to tremendous mechanical tension due to the weight of the bulk powder in the silo and the friction applied to the cable. Such installations will frequently result in a cable breakage."
and have been meaning to get a post onto this board: