Valeport Ltd

- Model SVX2 CTD/SVP - Combined Sound Velocity Sensors



The MIDAS SVX2 is the latest version of Valeport's unique instrument. Recognising the conflict faced by users requiring the superior Sound Velocity data from an SVP, but still needing the Salinity and Density data from a CTD, the MIDAS SVX2 combines both technologies to give the best of both worlds.

Now fitted with a 0.01% pressure sensor as standard, the SVX2 also uses synchronised sampling to ensure perfect profiles, and since the digital time of flight SV sensor is the most accurate in the world, it's also possible to compare the true sound velocity data with that generated by commonly used equations.

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The MIDAS SVX2 is fitted with Valeport’s digital time of flight sound velocity sensor, high stability conductivity sensor, a high accuracy temperature compensated piezo-resistive pressure transducer, and a fast response PRT temperature sensor.

Sound Velocity

  • Range: 1375 – 1900m/s
  • Resolution: 0.001m/s
  • Accuracy: ±0.02m/s


  • Range: 0 to 80 mS/cm
  • Resolution: 0.003mS/cm
  • Accuracy: ±0.01mS/cm


  • Range: -5°C to +35°C
  • Resolution: 0.005°C
  • Accuracy: ±0.01°C


  • Range: 10, 50, 100, 300 or 600bar
  • Resolution: 0.001% range
  • Accuracy: ±0.01% range

Data Acquisition
The MIDAS SVX2 uses the concept of distributed processing, where each sensor has its own microprocessor controlling sampling and calibration of readings. Each of these is then controlled by a central processor, which issues global commands and handles all the data. This means that all data is sampled at precisely the same instant, giving superior quality profile data.

Sampling Modes

  • Continuous: Regular output from all sensors at 1, 2, 4 or 8Hz.
  • Burst: Regular sampling pattern, where instrument takes a number of readings, then sleeps for a defined time.
  • Trip/Profile: Data is output as a chosen parameter changes by a set value, usually Pressure for profiling.
  • Conditional: Instrument sleeps until a selected parameter reaches a set value.
  • Delay: Instrument sleeps until predefined start time


  • Internal: 8 x C cells, 1.5v alkaline or 3.6v lithium
  • External: 9 - 30vDC
  • Power: 0.7W (sampling), <1mW (sleeping)
  • Battery Life: <100 hours operation (alkaline), <250 hours operation (lithium)
  • Connector: Subconn Titanium MCBH10F

System is supplied with DataLog Express Windows based PC software, for instrument setup, data extraction and display. DataLog Express is licence free.

The instrument will operate autonomously, with setup and data extraction performed by direct communications with PC before and after deployment. It also operates in real time, with a choice of communication protocols for a variety of cable lengths, all fitted as standard and selected by pin choice on the output connector:


  • RS232 Up to 200m cable, direct to serial port via USB adaptor
  • RS485 Up to 1000m cable, addressable half duplex communication


  • FSK 2 wire power & communications up to 6000m cable (cable dependant)
  • Baud Rate: 2400 - 115200 (FSK fixed at 19200, USB 460800)
  • Protocol: 8 data bits, 1 stop bit, No parity, No flow control

The MIDAS SVX2 is fitted with 16Mb solid state non-volatile FLASH memory. Total capacity depends on sampling mode; continuous & burst modes have a single time stamp at the start of the file, trip mode (profiling) stores a time stamp with each reading. A single line of SVP data uses 10 bytes, and a time stamp uses 7 bytes.

  • Continuous: >1,600,000 data points
  • Profile: >980,000 data points (>80 profiles to 6000m).


  • Materials: Titanium housing, polycarbonate & composite sensor components, stainless steel (316) cage
  • Depth Rating: 6000m (may be limited by pressure sensor)
  • Instrument Size: 88mmØ x 665mm long
  • Cage Size: 750 x 140 x 120mm
  • Weight (in cage): 11.5kg (in air), 8.5kg (in water)
  • Shipping: 100 x 18 x 49cm, 24kg

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