Remote monitoring of sedimentation processes


Sludge level monitoring solution with wireless communication for scraper bridges

  • Optical sludge blanket measurement with remote data transfer via Bluetooth or wireless Radioline gateway for simple I/O communication
  • Providing the control room with continuous readings of sludge concentration and sludge/water interface
  • Increased operational safety through prevention of sludge washout


OPTISYS SLM 2100 and Radioline on the scraper bridge


Sludge level measuring systems are often installed on rotating scraper bridges. Communication between the field devices on the scraper bridge and the process control system cannot be wired due to the rotation movement. The use of sliding contacts for data transmission has proven to be susceptible to maintenance and faults. Corrosion and low signal power, but also the limited bandwidth for data transmission do not guarantee a sustainable solution. The wireless transmission of sludge level measurements offers significant advantages here.

KROHNE offers a tailored measurement solution with remote transmission of sludge level, clear water zone or sludge concentration. Depending on distance and customer requirements, data transfer can be either carried out using a Bluetooth gateway with two fixed pair modules (without IP and configuration effort) or a licence-free wireless system (Radioline).

Measurement solution with Bluetooth:

  • The measurement solution with Bluetooth can be used for data transfer of analogue output signals over a distance of up to 200 m / 281 yd.

Measurement solution with free radio modem:

  • The solution with license-free Radioline communication allows the 4…20 mA output signals of the sludge level measuring system to be transferred over 20 km / 12.4 mi. Due to the possibility of meshed and modularly expandable systems, this technology is ideally suited for networking secondary clarifiers, sludge storage tanks and other structures as well as measurement technology on the plant. The intelligent Radioline technology also compensates for partial failures in the overall network since the system itself looks for an alternative route to transmission via other intervening stations. Latest encryption standards provide data security.

OPTISYS SLM 2100 and Radioline on the scraper bridgeRadioline receiving unit

Antenna of the receiving unit installed on building

Related products


Radioline gateway


Radioline gateway for continuous data transfer

  • Modbus, 4 digital and 4 analogue inputs and outputs
  • Licence-free radio: range of up to 20 km / 12.4 mi (per station point-to-point)
  • Mains powered and pre-wired system in rugged boxes (IP66); with modular extension option
  • For infrastructure applications with large networks (up to 250 stations)



Sludge level measuring system OPTISYS SLM 2100 – Standard version


Optical sludge level measuring system for sedimentation profile measurement and continuous tracking of sludge blanket

  • Integrated electronics with 2 x 4…20 mA, 3 relays (e.g. for limit switches)
  • 3 measurement modes: profile, sludge blanket/ fluff levels, zone tracking; automatic change of modes possible
  • 0.1…30 g/l; max. 10 m / 32.8 ft
  • Optional automatic flush cleaning unit for low maintenance

Bluetooth gateway


Bluetooth gateway for continuous data transfer

  • 16 digital and 2 analogue inputs and outputs
  • Based on Bluetooth 4.0: range of max. 200 m / 218.7 yd
  • Mains powered and pre-wired system with fixed pair modules in rugged boxes (IP66)
  • For fast and small networks