They may contain vapours, foams, aggressive materials or fats that disable many of the common technologies including ultrasonic, conductivity, float, and magnetostrictive sensors. Guided wave radar and Capacitance can work, but are expensive.
ECEFast has developed a hydrostatic sensor with isolating diaphragm, and wetted parts are all non metal. This rigid [hence "stick"] sensor is based on PVC pressure rated pipe and fittings with a special tip assembly.
All component parts, fully sub assembled, can be shipped to site in an air bag and assembled with the 32mm PVC pressure pipe, in situ. The pipe is available at all building supply companies in lengths up to 6 metres. All other parts including adhesives are included in the kit.
The sensor is mounted, and the diaphragm filled before shipment. It has an IP67 M12 connector, for further protection, mounted inside the tube. The top is sealed with an end cap and cable gland and the cable is vented for reference to the sensor. Standards sensor output is 4-20mA for 0-10.2MWG with supply voltage 1-30VDC.
An in line, internally mounted lightning protection device is optionally fitted internally on the two wire sensor connection.
Assembly required on site is simply two solvent adhesive joints - top and bottom - on the 32mm PVC pipe, exactly as done for PVC pressure and non pressure pipes and electrical conduit.
Wetted materials are PVC, BunaN and Nitrile [or Viton]. Readings will not be affected by high levels of suspended solids, fats and other floating material, or chemicals compatible with the wetted materials. This sensor is designed with sewerage pumping pits and waste water systems in mind, but can be mounted in tanks with flanges, for water, chemicals, diesel fuel and mineral and vegetable oils