ADS Environmental Services FlowAlert QR 775011 A2 - Manual (Page 21)

System Overview 2-9
Flow Depth Devices
The FlowAlert monitor uses measurement devices to gather flow
depth data or status. The pressure depth sensor obtains static gauge
pressure data for use in determining the depth of the flow. The float
switch provides status (or state) information regarding its position
to indicate whether the depth of the flow has exceeded beyond or
fallen below a certain threshold.
Pressure Depth Sensor
The pressure depth sensor (ADS p/n 3704-0010/15/16 –
representing 5/15/30 psi pressure sensor ranges, respectively)
mounts to a stainless steel expandable ring or stainless steel band
installed in the pipe upstream from the manhole or to a small
stainless steel band secured to the manhole/wet well wall.
Pressure depth sensor
A sewer system's hydraulics are much more stable and uniform in
the incoming pipe than in the manhole invert or outgoing pipe.
Installing it upstream minimizes hydraulic effects and erroneous
data readings caused by flow waves and obstructions in the
manhole. Therefore, install the sensor in the incoming pipe (at or
near the bottom of the pipe) for accurate depth measurements.