9
through photolithographic procedures. In contrast to the original monolithic double
junction transistors, incorporating three fused mineral phases (NPN and PNP), a single mineral phase can serve as source and drain. A constriction at the virtual gate is
overlain by the field effect element where signal charge accumulates or depletes
varying resistance across the gate thus modulating the higher power source current.
Paired complementary MOSFET units of opposite electronic configuration
constitute the so-called cMOS, fast logic switches that draw current only during the
switching operation minimizing energy consumption. Integrated circuits are now used
to condition power for sensor energization, and instrument detection circuitry, to generate and modulate active electromagnetic or acoustic probe signals and to generate and
modulate radio frequency or microwave communication signals. Proton-ion selective
MOSFET triodes are now integrated into instruments capable of precise, continuous
remote pH measurement. Junction photodiodes, semiconductor PN junctions sensitive
to light, have allowed the design and construction of a wide variety of light-sensing
optoelectronic devices for optical applications. Silicon photodiodes perform best in the
visible region (400–700 nm), while SiC formulations are used for near UV detection
(200–400 nm) and InGaAs alloys are used for the near IR band (>700 nm).
The following sections of this chapter are devoted to detailed description of the
principles of operation of a wide variety of environmental transducers applicable to
ocean observing and to the specific capabilities of various commercially available
instruments (referred to occasionally as sensors) operating on these principles.
Examples of basic transducers as well as circuitry, power requirements and endurance of typical instruments are discussed. Sensors are categorized according to discipline. Instruments measuring physical phenomena including temperate, pressure,
winds, waves, tides, and ocean currents are discussed first followed by instruments
targeting chemical and biogeochemical variables.
The advanced user is directed to the online publications of the nonprofit US-based
Alliance for Coastal Technologies (ACT) http://www.act-us.info/ accessed
11/16/2017) for further reference to the subject matter discussed below. The mission of ACT is the evaluation of commercially available sensors for coastal ocean
observing. In fulfilling this mission ACT has developed stringent protocols for
sensor testing under a wide variety of environmental conditions. Invaluable technical reference is provided by ACT Workshop Reports, Sensor Evaluations, and
Technologies Database.
2.2 Electronic Sensors and Instruments for Ocean Observing
2.2.1 Seawater Temperature
Temperature (T) is perhaps the most widely measured environmental property since,
together with pressure, it governs such fundamental properties as the physical state
of water and the electrical conductivity of ions in seawater. An intensive property, T
depends not only on the heat content of the recipient matter but also its heat capacity
which can vary widely. The atmospheric thermosphere at altitudes of 100–1000 km
with temperatures ranging beyond 2000 °C is in this sense a rather paradoxical
2.2 Electronic Sensors and Instruments for Ocean Observing
through photolithographic procedures. In contrast to the original monolithic double
junction transistors, incorporating three fused mineral phases (NPN and PNP), a single mineral phase can serve as source and drain. A constriction at the virtual gate is
overlain by the field effect element where signal charge accumulates or depletes
varying resistance across the gate thus modulating the higher power source current.
Paired complementary MOSFET units of opposite electronic configuration
constitute the so-called cMOS, fast logic switches that draw current only during the
switching operation minimizing energy consumption. Integrated circuits are now used
to condition power for sensor energization, and instrument detection circuitry, to generate and modulate active electromagnetic or acoustic probe signals and to generate and
modulate radio frequency or microwave communication signals. Proton-ion selective
MOSFET triodes are now integrated into instruments capable of precise, continuous
remote pH measurement. Junction photodiodes, semiconductor PN junctions sensitive
to light, have allowed the design and construction of a wide variety of light-sensing
optoelectronic devices for optical applications. Silicon photodiodes perform best in the
visible region (400–700 nm), while SiC formulations are used for near UV detection
(200–400 nm) and InGaAs alloys are used for the near IR band (>700 nm).
The following sections of this chapter are devoted to detailed description of the
principles of operation of a wide variety of environmental transducers applicable to
ocean observing and to the specific capabilities of various commercially available
instruments (referred to occasionally as sensors) operating on these principles.
Examples of basic transducers as well as circuitry, power requirements and endurance of typical instruments are discussed. Sensors are categorized according to discipline. Instruments measuring physical phenomena including temperate, pressure,
winds, waves, tides, and ocean currents are discussed first followed by instruments
targeting chemical and biogeochemical variables.
The advanced user is directed to the online publications of the nonprofit US-based
Alliance for Coastal Technologies (ACT) http://www.act-us.info/ accessed
11/16/2017) for further reference to the subject matter discussed below. The mission of ACT is the evaluation of commercially available sensors for coastal ocean
observing. In fulfilling this mission ACT has developed stringent protocols for
sensor testing under a wide variety of environmental conditions. Invaluable technical reference is provided by ACT Workshop Reports, Sensor Evaluations, and
Technologies Database.
2.2 Electronic Sensors and Instruments for Ocean Observing
2.2.1 Seawater Temperature
Temperature (T) is perhaps the most widely measured environmental property since,
together with pressure, it governs such fundamental properties as the physical state
of water and the electrical conductivity of ions in seawater. An intensive property, T
depends not only on the heat content of the recipient matter but also its heat capacity
which can vary widely. The atmospheric thermosphere at altitudes of 100–1000 km
with temperatures ranging beyond 2000 °C is in this sense a rather paradoxical
2.2 Electronic Sensors and Instruments for Ocean Observing