IL55BV2 Sensors

In-Line Sensor for Monitoring Suspended Solids and Sludge Density

The IL55BV2 Sensor provides reliable and repeatable, continuous in-line measurement of sludge density, suspended solids and turbidity. The sensor is installed through a mounting boss onto any pipeline that is larger than 65 mm diameter. The sensing element is positioned flush with the inside wall of the pipe, this ensures that the optical surface is kept clean by the flow passing the sensor and that the sensor does not cause an obstruction to the flow. The optical element has a sapphire window, this offers excellent resistance to fouling and to damage caused by the abrasion from particles in the flow.

The sensor is suitable for a variety of applications including the auto de-sludging of primary and final settlement tanks, where reliable sludge density measurement ensures that downstream treatment processes can operate at their optimum level. When detecting turbidity the sensor can give immediate warning of a filter failure or of contamination of a process by suspended particles. The sensor is also well suited to the monitoring of sludge at tanker intake points, giving an excellent indicator of the strength of the incoming liquor allowing both process adjustments and the charges to be applied to the tanker operator.

The sensor uses infrared back-scatter at 960nm, the light is transmitted and received through a lens that is optically split. The infrared measurement principle allows the sensor to work in applications where entrained air prevents the use of ultrasonic sensors.


  • Sludge Inlet Monitoring
  • Returned Activated Sludge
  • De-Sludging Control


  • Air Bubble Tolerant
  • Low Cost of Ownership
  • Removable Under Pressure

Technical Specification


Dimensions (hxwxd)392 mm long
Weight4.2 kg
Protection ClassIP68
Material of ConstructionBlack Acetal Co-Polymer, 316 Stainless Steel, Sapphire
Seal MaterialNitrile
Cable EntriesIntegral Cable Gland
Cable Type4 core, 5mm O/D Polyurethane Coated
Cable Length10 metres standard, 100 metres maximum
Service RequirementSensor cleaning is required at a frequency determined by site charactersitics

Environmental Data

Operating Temperature 0 - 50ºC
Storage Temperature -20 to 60ºC
Location Indoor or Outdoor
Pressure Rating2 Bar

Interface to Monitor

Sensor Output0-5mA
Power12 VDC from Monitor

Measurement Principal

Principal of OperationLight Back Scatter
Wavelength960 nm Infrared

Measurement Characteristics

AccuracyBetter than +/- 5% FSD on real sample
ResolutionDependent on rangesetting, typcially +/- 2%
RepeatabilityBetter than +/- 1% FSD on real sample
Response Time0.5 seconds - damping provided by monitor
FlowrateNot affected by flowrate, avoid deadspots and extreme turbulence
Maximum Range0 - 50,000 mg/l or 0 - 5%SS
Minimum Range0 - 1,000 mg/l or 0 - 0.1%SS
Measuring range will depend on the nature of the sample being monitored

Process Connection

Normal MountingIn-Line via Mounting Boss
Process Connection1 1/4" BSP Male
Minimm Line Size65 mm
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