Pulsonic SB2001

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Sludge Blanket Measurement System


The Avocet monitors the sedimentation and scum accumulation in remote settlement tanks and clarifiers in water treatment works, waste water reclamation works and factories with treatment plant.

The Avocet is particularly suited for identifying auto-desludging and overspill alarm signals and for monitoring the general biological health of thick sludge blankets.

Designed to operate in most if not all aspects of sludge level monitoring the Avocet system comprises three components.



The outstation consists of an ultrasonic sensor and a local programmable instrumentation unit, which provides a histogram display of the sedimentation layer.

Telemetry Link (optional)

The telemetry link enables the local data to be transmitted to a base station

up to 2km away.

Base Station – pc based (optional)

The base station will centrally monitor and display the information from multiple outstations via the telemetry link.

Principle of Operation

An ultrasonic sensor is immersed just below the surface of the effluent pointing directly to the bottom of the tank. The Avocet 2000 uses time of flight echo processing to determine the distribution of solid particles scattered throughout the settling effluent. Scum formation is detected by the attenuation, backscatter and reflection time of the ultrasonic signal as it passes through the sedimentation.

This is then displayed in a histogram form on the local display. The Avocet 2000 has 2 integral programmable relays for alarm activation.

Installation and Operation

Typically the outstation is fixed to the handrail of the scrapper gantry on the settlement tank. The instrument panel displays the sediment relative density throughout the tank. During normal operation the signal strength will vary due to many factors but one these will be the build up of solids on the sensor. To overcome this an air purge facility is installed and at across the sensor which removes debris and reduces the need for continual maintenance.

The base station comprises of a pc based monitoring system. This enables each outstation to be consecutively polled to display real time information of the individual settlement tanks. Alarm states can be programmed for sensor failure/scum detection and high level sedimentation. A data storage facility will enable the operator to observe the sedimentation performance over any historical period.