2.1.1 Submersible Pressure Transducers
Submersible pressure transducers are used extensively in groundwater level measurements, but their use has been expanded to surface water applications [2]. The
submersible pressure transducer is deployed at a fixed depth—it measures pressure
change in response to change in the water level and translates pressure change to
water level through calibration. Submersible pressure transducers can be categorized as absolute sensors and vented sensors. Absolute sensors are not vented to the
atmosphere, and therefore water level measurements can be biased by changes in
atmospheric pressure.
Water level data collected with an absolute submersible pressure transducer
should either be corrected in real time with measurements using an atmospheric
barometric pressure sensor or post-corrected based upon logged atmospheric barometric pressure. In contrast to absolute sensors, vented submersible pressure transducers have a vent tube that vents the sensor to the atmosphere. This venting
eliminates any potential bias on water level from changes in atmospheric pressure
and therefore results in a higher accuracy sensor (Fig. 1).
Table 2 Continuous water level measurement sensor-type capabilities and limitations
Site properties
Pressure sensor
(transducers)
Bubbler
system
Shaft
encoder
RADAR
level
Brackish water
o
o
o
o
Flash floods
o
o
*
*
Large debris in water o
o
o
*
Snow/ice cover and
flows
*
*
o
–
Migrating channels
o
o
o
*
Unstable banks
–
–
–
*
Stilling well
*
o
*
–
Bridge
*
*
*
*
Weir/flume
*
*
*
o
Symbols: (*) perfect match, (o) sensor will work, (–) limited
Advances in Water Sensor Technologies and Real-Time Water Monitoring
175
Submersible pressure transducers are used extensively in groundwater level measurements, but their use has been expanded to surface water applications [2]. The
submersible pressure transducer is deployed at a fixed depth—it measures pressure
change in response to change in the water level and translates pressure change to
water level through calibration. Submersible pressure transducers can be categorized as absolute sensors and vented sensors. Absolute sensors are not vented to the
atmosphere, and therefore water level measurements can be biased by changes in
atmospheric pressure.
Water level data collected with an absolute submersible pressure transducer
should either be corrected in real time with measurements using an atmospheric
barometric pressure sensor or post-corrected based upon logged atmospheric barometric pressure. In contrast to absolute sensors, vented submersible pressure transducers have a vent tube that vents the sensor to the atmosphere. This venting
eliminates any potential bias on water level from changes in atmospheric pressure
and therefore results in a higher accuracy sensor (Fig. 1).
Table 2 Continuous water level measurement sensor-type capabilities and limitations
Site properties
Pressure sensor
(transducers)
Bubbler
system
Shaft
encoder
RADAR
level
Brackish water
o
o
o
o
Flash floods
o
o
*
*
Large debris in water o
o
o
*
Snow/ice cover and
flows
*
*
o
–
Migrating channels
o
o
o
*
Unstable banks
–
–
–
*
Stilling well
*
o
*
–
Bridge
*
*
*
*
Weir/flume
*
*
*
o
Symbols: (*) perfect match, (o) sensor will work, (–) limited
Advances in Water Sensor Technologies and Real-Time Water Monitoring
175