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Selection Guide -- Products at a Glance

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.) and a water sampler to collect water samples for later analysis in the lab.

Sea-Bird manufactures CTDs as well as a number of other products. Our products are categorized into six groups, each with unique applications:

Profiling CTDs: A profiling CTD measures water parameters as it travels through the water, whether lowered over the side of a ship with a winch to take measurements of a vertical column of water or integrated with an autonomous vehicle or glider. Common to all Sea-Bird Profiling CTDs are purposeful designs built to perform under the unique dynamic conditions found on varying measurement platforms, pumped and ducted constant flow for matched temperature and conductivity response, measurements made on the same sample of water with a predictable delay and predictable flow effects, and aligning and coordinating measurements done with software or (for some models) automatically.
Water Samplers: A water sampler is often used in conjunction with a CTD. The water sampler collects 1 or more actual samples of water for analysis in the lab after recovery of the package. The water samples can be used to verify the accuracy of data measured by the instruments on the package, and/or to provide additional information that cannot be measured with an instrument in the field. Sea-Bird water samplers can be controlled (i.e., bottles closed) from deck via a Sea-Bird deck unit and software, or can be pre-programmed to close bottles at desired depths.
Moored Instruments: A moored instrument measures water parameters in one location, over an extended period of time, providing a time series of data. 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 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).
Inductive Modem Instruments: Sea-Bird's inductive modem uses a mooring cable as the communication link, permitting the underwater instrument(s) to be easily positioned at any depth without the use of cable connectors.
Shipboard Salinographs: Thermosalinographs are used to collect information about the sea surface, typically in flow-through systems operating continuously throughout a cruise. Thermosalinograph data can be used to calculate salinity, density, sound velocity, and other parameters of interest. Thermosalinographs are usually installed inside and near to the hull of a ship in order to make measurements on uncontaminated seawater. Optionally, you can plumb other types of sensors into the system for a wider range of measurements.
Oxygen Sensors: Oxygen sensors measure dissolved oxygen in the water. Sea-Bird oxygen sensors are designed to be integrated with a pumped CTD.
Other Products: Sea-Bird manufactures a number of other products, including autonomous profiling floats, data loggers and counters, CTD surface power and telemetry systems, and modular sensors and components.

Shown below are comparisons of features within each product group, to assist you in selecting the appropriate instrument for your application.

Profiling CTDs (Conductivity, Temperature, and Pressure)

SBE	Sampling Rate	Channels for Auxiliary Sensors	Memory	Power		Real-Time Data	Comments
SBE	Sampling Rate	Channels for Auxiliary Sensors	Memory	Internal	External	Real-Time Data	Comments
911plus (9plus CTD & 11plus Deck Unit)	24 Hz	8 A/D	16 Mb with optional SBE 17plus V2	√ (with optional SBE 17plus V2)	√	√	World's most accurate, high resolution CTD, premium sensors, multi-parameter support, water sampler control
25plus	16 Hz	8 A/D; 2 RS-232	2 Gb	√	√	√ (may require SBE 36 Deck Unit & PDIM)	High resolution logging CTD with multi-parameter support, water sampler control with SBE 33 Deck Unit
25	8 Hz	7 A/D	8 Mb	√	√	√ (may require SBE 36 Deck Unit & PDIM)	Replaced by SBE 25plus in 2012
19plus V2	4 Hz	6 A/D; 1 RS-232	64 Mb	√	√	√ (may require SBE 36 Deck Unit & PDIM)	Personal CTD, small, self-contained, adequate resolution, water sampler control with SBE 33 Deck Unit
19plus	4 Hz	4 A/D; optional PAR	8 Mb	√	√	√ (may require SBE 36 Deck Unit & PDIM)	Replaced by SBE 19plus V2 in 2008
19	2 Hz	4 A/D	1 - 8 Mb	√	√	√ (may require SBE 36 Deck Unit & PDIM)	Replaced by SBE 19plus in 2001
49	16 Hz				√	√ (may require SBE 36 Deck Unit & PDIM)	Intended for towed vehicle, ROV, AUV, or other autonomous profiling applications. Water sampler control with SBE 33 Deck Unit.
52-MP	1 Hz	1 frequency channel for dissolved oxygen sensor	28,000 samples		√	√	Intended for moored profiling applications on device that is winched up and down from a buoy or bottom-mounted platform
41 / 41CP	OEM CTD for sub-surface oceanographic float that surfaces at regular intervals, transmits new drift position and in situ measurements to ARGOS satellite system. CTD obtains latest temperature and salinity profile for transmission on each ascent. Also available is a Navis profiling float, Navis profiling float with Biogeochemical sensors, and Navis profiling float with Integrated Biogeochemical sensors.
GPCTD & Slocum CTD	OEM CTD for autonomous gliders. Generic Glider Payload CTD (GPCTD) is modular, low-power profiling instrument that measures C, T, P, and (optional) Dissolved Oxygen. Slocum Glider Payload CTD provides retrofit/replacement for CTDs on Slocum gliders. Designs share many features, but there are differences in packaging, sampling abilities, power consumption, and installation (see individual data sheets).
Notes: 1. See Application Note 82: Guide to Specifying a CTD. 2. CTDs in gray are no longer in production. See our Model List page for links to manuals for those CTDs.

Water Samplers and CTD Configurations

Water Sampler	Number of Bottles	Bottle Size (liters)	CTD	Control		Deployment Depth
				Real-Time Configuration	Self-Contained Configuration (auto bottle firing)
SBE 32 (full size)	12	1.7 - 30	SBE 9plus	SBE 11plus V2 Deck Unit	SBE 17plus V2	6800 m (aluminum), 7000 m (titanium)
	24	1.7 - 12
	36	Consult factory
	12	1.7 - 30	SBE 19, 19plus, 19plus V2, 25, or 25plus	SBE 33 Deck Unit (can also be used with SBE 49 CTD)	Auto Fire Module (can also be used with SBE 50 Pressure Sensor)
	24	1.7 - 12
	36	Consult factory
SBE 32C (compact)	12	1.7 - 8	SBE 9plus	SBE 11plus V2 Deck Unit	SBE 17plus V2	6800 m (aluminum), 7000 m (titanium)
			SBE 19, 19plus, 19plus V2, 25, or 25plus	SBE 33 Deck Unit (can also be used with SBE 49 CTD)	Auto Fire Module (can also be used with SBE 50 Pressure Sensor)
SBE 32SC (sub-compact)	12	1.7 or 2.5	SBE 19, 19plus, 19plus V2, 25, or 25plus	SBE 33 Deck Unit (can also be used with SBE 49 CTD)	Auto Fire Module (can also be used with SBE 50 Pressure Sensor)	6800 m (aluminum), 7000 m (titanium)
SBE 55	3 or 6	4	SBE 19, 19plus, 19plus V2, 25, or 25plus	SBE 33 Deck Unit (can also be used with SBE 49 CTD)	Built-in auto bottle firing, no additional equipment required	600 m
Notes: 1. Operation of all SBE 32 Carousel Water Sampler models with the SBE 33 Deck Unit requires an optional sea cable / serial data interface in the Carousel. 2. See Application Note 45: Guide to SBE 32 Carousel Water Sampler Configuration Options for information on selecting the appropriate Carousel options for your application.

Moored / Time Series Recording Instruments

SBE	Measures (C, T, P)	Auxiliary Sensors	Memory	Power		Communication	Real-Time Data	Comments
SBE	Measures (C, T, P)	Auxiliary Sensors	Memory	Internal	External	Communication	Real-Time Data	Comments
16plus V2	C, T, P*	6 A/D; 1 RS-232	64 Mb	√	√	RS-232	√	Optional pump
16plus	C, T, P*	4 A/D; optional RS-232 or PAR	8 Mb	√	√	RS-232 or -485	√	Replaced by 16plus V2 in 2008
16	C, T, P*	4 A/D	1 Mb	√	√	RS-232	√	Replaced by 16plus in 2001
16plus-IM V2	C, T, P*	6 A/D; 1 RS-232	64 Mb	√		Inductive Modem	√	Optional pump
16plus-IM	C, T, P*	4 A/D; optional RS-232 or PAR	8 Mb	√		Inductive Modem	√	Replaced by 16plus-IM V2 in 2008
19plus V2	C, T, P	6 A/D; 1 RS-232	64 Mb	√	√	RS-232	√	Programmable mode -- profiling or moored
19plus	C, T, P	4 A/D; optional PAR	8 Mb	√	√	RS-232	√	Replaced by 16plus V2 in 2008
19	C, T, P	4 A/D	1 - 8 Mb	√	√	RS-232	√	Replaced by 16plus in 2001
37-SM	C, T, P*		8 Mb	√	√	RS-232 or -485	√
37-SMP	C, T, P*		8 Mb	√	√	RS-232, RS-485, or SDI-12	√	Integral pump
37-SMP-IDO	C, T, P*	Integrated DO	8 Mb	√	√	RS-232 or -485	√	Integral pump
37-SMP-ODO	C, T, P*	Integrated Optical DO	8 Mb	√	√	RS-232, RS-485, or SDI-12	√	Integral pump
37-IM	C, T, P*		8 Mb	√		Inductive modem	√
37-IMP	C, T, P*		8 Mb	√		Inductive modem	√	Integral pump
37-IMP-IDO	C, T, P*	Integrated DO	8 Mb	√		Inductive modem	√	Integral pump
37-IMP-ODO	C, T, P*	Integrated Optical DO	8 Mb	√		Inductive modem	√	Integral pump
37-SI	C, T, P*		8 Mb		√	RS-232 or -485	√
37-SIP	C, T, P*		8 Mb		√	RS-232 or -485	√	Integral pump
37-SIP-IDO	C, T, P*	Integrated DO	8 Mb		√	RS-232 or -485	√	Integral pump
37-SIP-ODO	C, T, P*	Integrated Optical DO	8 Mb		√	RS-232 or -485	√	Integral pump
WQM	C, T, P	Integrated DO, chlorophyll fluorescence, turbidity (WQMx adds CDOM fluorescence, replaces turbidity with backscattering)	√		√	RS-232	√	Jointly developed by Sea-Bird and WET Labs; manufactured by WET Labs
39plus	T, P*		64 Mb	√	Optional	USB & RS-232	Optional	Replaces SBE 39 (Feb 2014)
39	T, P*		32 Mb	√	Optional	RS-232	Optional
39-IM	T, P*		32 Mb	√		Inductive modem	√
56	T		64 Mb	√		USB
26plus	T, P	C optional	32 Mb	√	√	RS-232	√ (tides, waves, & wave statistics)	Wave & tide recorder
26	T, P	C optional	8 Mb	√	√	RS-232		Replaced by SBE 26plus in 2004
53	T, P	C optional	32 Mb	√	√	RS-232	√	Bottom pressure recorder
54	T, P		128 Mb	Optional	√	RS-232	√	Tsunami pressure sensor
C = conductivity, T = temperature, P = pressure, DO = dissolved oxygen * = optional Note: Instruments in gray are no longer in production. See our Model List page for links to manuals for those instruments.

Inductive Modem Instruments

SBE	Measures (C, T, P)	Auxiliary Sensors	Memory	Power		Comments
SBE	Measures (C, T, P)	Auxiliary Sensors	Memory	Internal	External	Comments
16plus-IM V2	C, T, P*	6 A/D; 1 RS-232	64 Mb	√		Optional pump
16plus-IM	C, T, P*	4 A/D; optional RS-232 or PAR	8 Mb	√		Replaced by 16plus-IM V2 in 2008
37-IM	C, T, P*		8 Mb	√
37-IMP	C, T, P*		8 Mb	√		Integral pump
37-IMP-IDO	C, T, P*	Integrated DO	8 Mb	√		Integral pump
37-IMP-ODO	C, T, P*	Integrated Optical DO	8 Mb	√		Integral pump
39-IM	T, P*		32 Mb	√
44		1 RS-232	30 Kb buffer	√	√	Integrates sensor with standard serial interface (current meter, Doppler profiler, etc.) to inductive modem telemetry system
UIMM		1 RS-232	16 Kb Sample Data Memory		√	Integrates sensor with standard serial interface (current meter, Doppler profiler, etc.) to inductive modem telemetry system; more flexible and economical than SBE 44
C = conductivity, T = temperature, P = pressure, DO = dissolved oxygen * = optional Notes: 1. See Inductive Modem Module or Surface Inductive Modem (SIM), and Inductive Cable Coupler (ICC) to complete your inductive modem system. 2. See Typical IM Mooring Components for an overview of an inductive modem system, and Application Note 92: Real-Time Oceanography with Inductive Moorings and the Inductive Modem Module (IMM) for background information. 3. Instruments in gray are no longer in production. See our Model List page for links to manuals for those instruments.

Shipboard Thermosalinographs (Conductivity & Temperature)

SBE	Measures	Auxiliary A/D Sensors	Remote Temperature Sensor Input	NMEA Data Input	Memory	Power		Communication	Real-Time Data
						Internal	External
21	T, C	4	√	√	64 Mb		√	RS-232	√
45	T, C		√ *	√ *			√	RS-232	√
C = conductivity, T = temperature * With optional PN 90402 SBE 45 Power, Navigation, and Remote Temperature Interface Box

Oxygen Sensors

SBE	Sensor Type	Output	Depth (m)	User- Programmable?	Can be Integrated with	Use
43	membrane	0 - 5 volts	600, 7000		SBE 16plus, 16plus-IM, 16plus V2, or 16plus-IM V2 SeaCAT CTD SBE 19plus or 19plus V2 SeaCAT CTD SBE 25 or 25plus Sealogger CTD SBE 9plus CTD	Moored CTDs (with 1.0-mil membrane), or profiling CTDs (with 0.5-mil membrane)
43F	membrane	frequency	600, 7000		SBE 37 IDO MicroCAT (SMP-IDO, SIP-IDO, IMP-IDO) SBE 52-MP Moored Profiler CTD Glider Payload CTD	Moored CTDs (with 1.0-mil membrane), or profiling CTDs (with 0.5-mil membrane)
63	optical	RS-232	600, 2000, 7000	√	SBE 16plus V2 or 16plus-IM V2 SeaCAT CTD 19plus V2 SeaCAT CTD SBE 37 ODO MicroCAT (SMP-ODO, SIP-ODO, IMP-ODO) SBE 41 or 41CP Argo Float CTD	Moored CTDs or slow profiling CTDs

Other Products

Sea-Bird manufactures many other products, including:

Autonomous profiling floats
Data loggers and counters (SBE 17plus and SBE 31)
CTD surface power and telemetry systems (SBE 11plus, SBE 33, SBE 36 / PDIM, SBE 14, SBE 46, and Interface Boxes)
Modular sensor and components (conductivity, temperature, pressure, pH, and ORP sensors; and pumps -- SBE 3, 4, 5, 7, 8, 14, 18, 27, 29, 35, 35RT, 37-SI, 37-SIP, 37-SIP-IDO, 37-SIP-ODO, 38, 41/41CP, 46, 50, 52-MP, and Interface Boxes)