Self Cleaning Suspended Solids Sensor Range: 0 - 20,000 mg/l The TurbiTechw² LA Sensor has been designed for use in aeration systems monitoring suspended solids also known as mixed liquor suspended solids or activated sludge where solids are typically in the range of 1,500 to 3,500 mg/l. The sensor can also measure Returned Activated Sludge (RAS), Surplus Activated Sludge (SAS) and suspended solids or turbidity. The fully automatic self cleaning system ensures that manual intervention on a routine basis is not required.