CastAway - Onyx River


CastAway-CTD, Alaska

CastAway-CTD, Haiti

CastAway-CTD, New York

CastAway-CTD, Florida

CastAway-CTD, South Africa

Designed for coastal profiling, the CastAway-CTD® incorporates a 6-electrode conductivity cell, coupled with a fast response thermistor to provide highly accurate, high resolution CTD measurements to depths of 100 m. Now Integrated with HYPACK!

NOW AVAILABLE: The CastAway-CTD educational curriculum with emphasis on ocean chemistry for use by high school and university level instructors who wish to provide students:

  • The theory behind SALINITY: why is the ocean salty and how is salinity measured?
  • What is the Law of Constant Proportions and how does it apply to salinity?
  • Hands-on CastAway field activity emphasizing proper scientific data collection procedures;
  • Post-field work analysis of CastAway data and comparisons to global ocean temperatures and salinity data-sets available online;
  • Conservative and non-conservative elements;
  • Residence Time worksheet for tracers;
  • and more!

>> DOWNLOAD LESSON PLAN  (CastAway-CTD serial number required)

  • Features
  • Specifications
  • Software

Field Ready and Rugged

The CastAway-CTD is a small, rugged and technically advanced CTD designed for profiling to depths of up to 100m. The system incorporates modern technical features which allow it to achieve a 5 Hz response time, fine spatial resolution and high accuracy. It uses a six electrode flow-through conductivity cell with zero external field coupled with a rapid response thermistor to attain high measurement accuracies. The instrument is simple to deploy, does not require a pump and is hydrodynamically designed to free fall rate of 1 m/s.

The integrated real-time data display screen, internal GPS sensor and automated wireless data transfer are unique features that simplify data collection.

  • Salinity Accuracy: 0.1 PSU
  • Temperature Accuracy: 0.05°C
  • Small size
  • Integrated GPS position
  • Real-time display screen
  • Wireless data transfer
  • 5 Hz sampling rate

Each CastAway-CTD cast is referenced with both time and location using its built-in GPS receiver. Latitude and longitude are acquired both before and after each profile. Plots of conductivity, temperature, salinity and sound speed versus depth can be viewed immediately on the CastAway's integrated color LCD screen in the field.  Raw data can be easily downloaded via Bluetooth to a Windows computer for detailed analysis and /or export at any time.

*US Patent #8272262

Parameter Specification Range Resolution Accuracy Method
Conductivity 0 to 100,000 µS/cm 1 µS/cm 0.25% ±5 µS/cm Measured
Density 990 to 1035 kg/m3 0.04 kg.m3 ± 0.02 kg/m3 EOS80••
Depth 0 to 100 m 0.01 m ±0.25% FS EOS80••
GPS - - 10m -
Pressure 0 to 100 dBar 0.01 dBar 0.25% of FS Measured
Salinity Up to 42 0.01 ±0.1 PSS-78
Sound Speed 1400 –1730 m/s 0.01 m/s ±0.15 m/s Chen-Millero
Specific Conductivity§ 0 to 250,000 µS/cm 1 µS/cm 0.25% ±5 µS/cm EOS80••
Temperature -5 to +45°C 0.01°C ±0.05°C Measured

Based on temperature resolution and accuracy.
••International Equation of State for sea water (EOS-80).
1978 Practical Salinity Scale
Chen-Millero, 1977. Speed-of-sound in sea water at high pressures.
§ Based on 100,000 µS/cm at -5°C.

Communications Internal BlueTooth Radio (Class 2)
Up to 10m range
Dimensions — Diameter 7.11 cm | 2.8 in
Dimensions — Height 20.32 cm | 8.0 in
Dimensions — Weight 0.45 kg | 1.0 lbs
Power 2 Standard AA batteries for 40+ hours of operation
Recorder 15 MB recorder
Good for 750+ casts during typical use
Sample Rate 5Hz

CastAway-CTD Screenshot

CastAway-CTD Software — v 1.5 — 30Jan2012

The CastAway-CTD basic software was designed specifically for the CastAway-CTD system and is used to communicate with the instrument, download data, configure the instrument, upgrade the CastAway-CTD's firmware, in addition to offering a suite of data visualization, management and exporting capabilities.

CastAway-CTD Firmware — v 1.63 — 07Jan2022

The CastAway-CTD is a profiling instrument that measures conductivity, temperature, and pressure.  Its embedded firmware controls all of the instrument's functions and assures the data is of the utmost quality.  This firmware is free to any CastAway-CTD owners/users and does not require any activation code. Please follow the instructions in the CastAway-CTD manual for details on how to check the version of your instrument's current firmware version and how to upgrade it if necessary.

Get the Software

Options & Accessories


Castaway CTD Kit

Each Castaway kit includes a hard plastic storage/shipping case, Polyurethane jacket, 15m deployment line, Bluetooth dongle, (2) locking carabineers, (3) magnetic stylus pens, and cleaning brush. Download Brochure.


Catlin Arctic Survey

CTD Monitoring Technology Helps Reveal Arctic Secrets

A group of Arctic researchers has employed the latest monitoring technology to investigate the effects of climate change, by measuring temperature and salinity in the water column beneath surface ice. The results of the investigation, which utilised SonTek's new CastAway-CTD™ instrument, could cast new light on our understanding of the ways in which shifting ocean currents impact the climate in northern Europe.