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Conductivity-Temperature-Depth (CTD) Sensors

Instrument Point People

Water Properties

Conductivity-Temperature-Depth (CTD) instruments provide data on primary water properties, such as salinity and temperature. Over large areas, the variability in these water properties may help characterize variability in the North-East Pacific Ocean and coastal waters off British Columbia. Data recorded by CTD in the NEPTUNE Regional Network have shown changes in temperature and salinity that appear to be related to the presence of El Nino and La Nina. These measurements have also shown less variability in temperature and salinity in the deep ocean, which is affected by processes on longer time-scales. The increased variability of water properties in shallow oceanic environments may be due to seasonal processes like solar heating, run-off, mixing and wind-forcing.

In future, core instruments at each node location (including CTD) will be installed so that fundamental parameters like temperature and salinity are measured consistently over the entire network.

Seabird CTD Types

SeaCAT 16plus

Sea-Bird's 16plus SeaCAT Profiler measures conductivity, temperature, pressure, salinity, sound velocity, density and SigmaT to depths of 10,500m. This device can operate in three different sampling modes. In autonomous mode, it can take intermittent measurements at intervals between 10 seconds and 4 hours. In polled sampling mode, it can provides sample data by request from a surface controller. In serial line sync mode, it responds to a command pulse from the surface by waking up, sampling, storing data, transmitting it and powering off again.

SeaCAT 19plus

Sea-Bird's SBE 19plus SeaCAT Profiler measures conductivity, temperature, pressure, salinity, sound velocity, density and SigmaT to depths of 7000m. When used in profiling mode, it runs continuously, sampling at 4Hz, and can average up to 32,767 samples. When used in moored mode, it can take intermittent measurements at intervals between 10 seconds and 4 hours.

SeaCAT 37-SIP

Sea-Bird's SBE 37-SIP MicroCAT is a high-accuracy, externally powered, CTD, which includes an RS-485 serial interface and integral pump. MicroCATs have non-corroding titanium housings rated for operation to 7000 meters. This instrument measures conductivity, temperature, salinity, pressure, sound velocity, density and SigmaT.


(Click the pictures to enlarge them.)

ADM CTD Types

ADM miniCTD Probe

An ADM CTD is installed on Barkley Benthic Crawler Wally II. The ADM miniCTD is a direct reading probe for fast profiling or monitoring. It is equipped with highly accurate fast response sensors for conductivity, temperature and pressure for depth measurements. Optionally, sensors for oxygen, pH, redox and H2S can be adapted. External sensors for turbidity or chlorophyll can be connected with an analogue input at the top of the probe. The miniCTD is lightweight and allows easy handling for in-situ profiling and for horizontal profiling with towed vehicles as well as from small boats for depths of up to 2000m.

2 Comments

  1. Unknown User (dwowens)

    Discuss NEPTUNE Canada's CTDs (click Add Comment below.)

  2. Please note that the pressure measured by the CTDs is gauge pressure by convention, not absolute or total pressure. So like a tire pressure gauge, when at sea level, the pressure will be read as zero, even though atmospheric pressure is generally around 10 decibars total pressure. This convention is useful in this context because a decibar of pressure is approximately 1 meter of water depth. For further information, please see: http://www.seabird.com/application_notes/an27druck.htm