The Seabird GPCTD+DO sensor measures water Conductivity, Temperature, Depth (pressure), and dissolved oxygen, and is located on the base of the float. The sensor supports 4 different sampling profiles:
Continuous Sampling - The pump runs continuously, and the CTD samples once every 1, 2, 3, or 4 cycles. This produces a time series suitable for application of high-quality finish corrections for dynamic errors observed in the data.
Fast Interval Sampling - When the interval between samples is 5 to 14 seconds, the pump runs continuously and measurements are made at the chosen interval, allowing users to conserve power by reducing the sample rate.
Slow Interval Sampling - When the interval is 15 to 3600 seconds, the pump runs for 11.3 seconds before each CTD measurement, plus 2.1 seconds during the measurement. Then the CTD turns off the pump and goes into a low-power state until the next measurement. Dissolved oxygen is not measured in this mode. Dissolved oxygen measuring is not supported in this mode.
Spot Sampling - Single measurements and transmission can be commanded for testing, diagnostic, vehicle-control, or situational awareness purposes.