Moored / Time Series Instruments
A Moored instrument measures water parameters in one location, over an extended period of time, providing a time series of data.
A CTD measures Conductivity, Temperature, and Depth. Despite the name, all CTDs actually measure pressure, which is not quite the same thing as depth. The relationship between pressure and depth is a complex one involving water density and compressibility as well as the strength of the local gravity field. The CTD data can be used to calculate salinity, density, sound velocity, and other parameters of interest. The term CTD is often used today to describe a package that includes the actual CTD as well as auxiliary sensors to measure other parameters (such as dissolved oxygen, pH, turbidity, fluorometer, altimeter, etc.). The term Sonde is sometimes used as an alternative to CTD. To reduce costs, a moored CTD may not include a pressure sensor, because the deployment depth is known (approximately); the pressure sensor is optional in most Sea-Bird moored CTDs.
Sea-Bird also manufactures moored temperature sensors as well as instruments for high-accuracy pressure measurements (wave and tide recorder, bottom pressure recorder, and tsunami sensor).
See the following for more details on CTDs:
- CTDs Explained provides an introductory overview of CTDs.
- Click here for a 25-minute webinar introduction to Sea-Bird, with a focus on Long-Term Deployments with Moored CTDs.