ADS Environmental Services Model 4000 530017 A0 - Manual (Page 19)

System Overview 2-7
Sensors
The 4000 flow monitor uses the sensors to gather raw flow data.
The ultrasonic and pressure depth sensors use independent
measurement techniques to collect information concerning the
depth of the flow. The Doppler velocity sensor gathers peak flow
velocity data.
A sewer system's hydraulics are much more stable and uniform in
the incoming pipe than in the manhole invert or outgoing pipe.
Therefore, the sensors mount to a stainless steel expandable ring or
stainless steel bands installed in the pipe upstream from the
manhole. Installing them upstream minimizes hydraulic effects and
erroneous data readings caused by foamy waters, flow waves,
sewer noise, non-laminar flow, and obstructions in the manhole.
The process of installing the sensors in the incoming pipe is
patented by ADS.
Ultrasonic Depth Sensor
The ultrasonic depth sensor, which mounts at the crown of the pipe,
transmits sound waves from the sensor face to the surface of the
flow. It then measures the time elapsed between transmission and
reception of the sound signal. The distance between the sensor face
and flow surface is the range. Based on the elapsed time and the
speed of sound, the monitor calculates the depth of the flow by
subtracting the range from the pipe diameter. The monitor
compensates for the speed of sound in the air using the temperature
recorded by one of two temperature sensors housed within the
ultrasonic depth sensor.