ADS Environmental Services FlowAlert QR 775011 A2 - Manual (Page 22)

2-10 ADS FlowAlert Manual
If accurate depth measurements are not necessary or applicable,
mount the sensor to the wall of the manhole or wet well.
The pressure depth sensor can measure depths greater than a full
pipe that might extend up into the manhole (i.e., surcharges). The
FlowAlert supports pressure sensors with ranges from 0-5 (11.5), 0-
15 (34.5), and 0-30 PSI (69.0 ft).
The pressure depth sensor contains a differential pressure
transducer that transmits an output voltage corresponding to the
difference between the water pressure and the air pressure in the
sewer. It measures water pressure through a port on the underside
of the sensor and air pressure using an integral vent tube running to
the top of the manhole. The monitor calculates the depth of the
flow by reading the difference in pressures.
Float Switch
The float switch typically is anchored just below the manhole rim
and hangs suspended in the center of the manhole from its
supporting cable at an elevation designated in the project
requirements. It includes an integrated switch and weight system
that enables the float to change position (which activates a switch)
when the flow elevates to and recedes from a specific elevation in
the manhole. This elevation represents the point at which the state
of the switch changes. The FlowAlert receives notification from the
float whenever the change in state occurs.