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pH Sensors

SeaFET Ocean pH Sensor
pH (potential Hydrogen) is a measurement of the level of acids and bases in water. Our pH sensors have been used extensively to research ocean acidification, coral reefs, coastal marine biology, and to conduct environmental monitoring.

Ocean acidification is the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of atmospheric carbon dioxide (CO2) as water and air mix at the water’s surface. Oceans, rivers, and lakes absorb roughly one third of human-created CO2 emissions (22 million tons) each day. Stress on marine life due to acidification (lowering the pH) leads to dying or severely affected ecosystems.

High-resolution in-situ measurements of pH in the ocean are now possible with innovative adaptations of ion-sensitive field-effect transistors (ISFET). Oceanographic instruments based on ISFET technology have been in development for more than a decade, but earlier instruments had depth limitations or significant drift and environmental constraints that limited their adoption. Sea-Bird Scientific’s line of ocean pH sensors use Honeywell’s innovative ion-sensitive field effect transistor (ISFET) technology to provide a level of precision and stability not before possible.

The SeaFET™ V2 Ocean pH sensor uses the ISFET technology for stable, long-term pH measurements in salt water. The pH sensor has been used extensively around the globe for ocean acidification research, coral reef research, coastal marine biology and environmental monitoring. The SeaFET™ V2 Ocean pH sensor is fully autonomous with internal power, sample scheduling and data logging capabilities. The advantages of the ISFET include robustness, stability and precision that make it suitable for ocean pH measurement at low pressure.

The Sea-Bird Scientific SeapHOx™ V2 system is comprised of the SeaFET™ V2 Ocean pH sensor and the SBE 37-SMP-ODO MicroCAT CTD+DO sensor. This system allows for collection and combination of pH data and critical oceanographic/biological measurements of temperature, salinity, and oxygen. The integrated package also enables the SeaFET™ V2 to take advantage of the MicroCAT’s pumped flow path and anti-fouling technology, extending deployment durations.

Depth Variations

  • The SeapHOx™ V2 is intended for moored applications of up to 50 m in depth
  • The Deep SeapHOx™ V2 (bottom right) is intended for moored applications of up to 2000 m deep

Sea-Bird Scientific’s Deep SeaFET™, an ISFET-based pH sensor, demonstrates that the technology has reached the stability and robustness necessary for a transformation in the quality of in-situ pH measurements. The Deep SeaFET™ extends accurate pH measurements to two applications where depth, drift, and environmental constraints previously limited the availability of quality data:

  • Autonomous profiling floats, which can perform hundreds of profiles in the ocean from depths of 1 to 2 km
  • Deep, long-term moorings

The HydroCAT-EP uses a field-serviceable and replaceable glasselectrode sensor to measure pH to an initial accuracy of ± 0.1 pH. Specifically designed for long-term deployments in remote, biologically rich environments, it comes equipped with multiple anti-fouling systems. Factory calibration and streamlined reference checks enable users to generate scientifically defensible data with minimal time and cost required for field maintenance. Most sensors, including pH, are protected within the unique internal flow path by EPA approved anti-foulant devices. An integral pump minimizes the sensors' exposure to environmental waters, significantly reducing the impact of bio-fouling on sensor performance and drift. A copper faceplate and wiper protect the combination chlorophyll and turbidity sensor. The HydroCAT-EP measures:

  • pH
  • Conductivity
  • Temperature
  • Pressure
  • Dissolved Oxygen
  • Chlorophyll
Navis BGCi + pH Float

Autonomous profiling float with Sea-Bird CTD, Dissolved Oxygen sensor, MCOMS fluorometer/backscattering sensor and Float pH sensor, which adapts the field-tested MBARI/SIO/Honeywell Deep-Sea DuraFET technology to measure pH.

SeaFET™ V2 Ocean pH Sensor

ISFET-based pH sensor for high accuracy, resolution, and long-term stability.

SeapHOx™ V2 Ocean CT(D)-pH-DO Sensor

ISFET-based pH sensor for high accuracy, resolution, and long-term stability. Integrated CTD provides temperature, salinity, pressure, and dissolved oxygen data, with pumped flow and anti-fouling technology.