SonTek CastAway® CTD

SonTek Castaway CTD meter

NEW! Now integrated with HYPACK®! [Learn more]  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 100m.

  • Features
  • Specifications
  • Software
  • Webinars
  • Video


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


207.22 MB
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.


881.4 MB
The CastAway-CTD optional large offline map software displays the locations for all the casts in the software's database. It is best used when the host computer is connected to high-speed internet connection. For applications where an internet connection is not available, the software comes standard with a with a small (~1 MB) World Map. Warning - the installation file itself is very large (1GB) and is also best dowloaded with a high-speed internet connection.


245 KB
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.

Download Software

2016,May - Below the surface in ports: topography, navigation and pollution

Increasing ship size and higher demands for more efficient ports have increased the responsibilities for port and navigational authorities. This application oriented webinar will show how solutions from Aanderaa, HYPACK and SonTek help one harbour deal with increasing demands:

  • HydroSurveyor M9 compact high performance systems to measure bathymetry and currents in ports and harbors
  • CastAway CTD offers seamless integration of sound speed information
  • HYPACK software powerful tool to plan missions and analyze data
  • HydroSurveyor M9, CastAway and HYPACK - a complete survey package from Xylem
  • Aanderaa have offered turn key hydro-meteorological soltuions for ports and harbors globally
  • Side looking insturments suitable for pier mounting
  • New buoys combine single point and profiling Doppler current sensors to cover the entire water column
  • Mulitparameter insturuments like SeaGuard RCM and SeaGuard II DCP are suitable for lead detection and pollution spreading studies from wrecks

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