Inexpensive Expendable Conductivity Temperature and Depth (CTD) Sensor

The Conductivity, Temperature, and Depth (CTD) sensor is one of the most used instruments in the Oceanographic field. These devices are the number one, most important sensor for any research of the ocean depths. CTD measurements are found in every marine related institute and navy throughout the world because they are used to produce the salinity profile for the area of the ocean under investigation. In order to deploy large numbers of CTD sensors, an inexpensive version is needed, especially if used as a one-time (throw-away) system. Oceanographic institutes and navies require instruments such as these that are reliable, accurate, precise and inexpensive. The CTD developed in this paper is low cost and disposable that can be easily and rapidly deployed to obtain measurements throughout the earth's oceans. Five (5) specific specifications for the device (ECS Unit Sensor) were paramount: 1) Its weight had to be under 5-lb (2.27-kg) maximum, but ideally as close to 1 to 2lb (0.45-kg to 0.9-kg) as possible; 2) Its dimensions must be no bigger than 10-in (25-cm) in height and 3-in (7.6-cm) in diameter; 3) It must be reasonably priced to be expendable; 4) It must have wireless communication; and 5) It only has to record the top 10m of the water column. This paper describes the design, development, construction and testing of the Expendable Conductivity Sensor Unit (ECS Unit), which when deployed, takes multiple snapshots of the water profile and sends its data out via a satellite communications chip. The ECS Unit was tested against other CTDs for accuracy. When compared to the other expendable CTDs the ECS Unit, along with being much more economical, is able to provide more snapshots than any other expendable CTD instrument currently available on the market. The CTD instrument (ECS Unit Sensor) developed in this project costs around $982.00 per unit to make.