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Underwater methane sensor


CONTROS HydroC CH4 subsea / underwater methane sensor

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The CONTROS HydroC® CH4 sensor is a unique subsea / underwater methane sensor for in-situ and online measurements of CH4 partial pressure (p CH4). The versatile CONTROS HydroC® CH4 provides the perfect solution for the monitoring of background CH4 concentrations and for long-term deployments.

Operating principle

Dissolved CH4 molecules diffuse through a custom made thin film membrane into the internal gas circuit leading to a detector chamber, where the CH4 concentration is determined by means of Tunable Diode Laser Absorption Spectroscopy (TDLAS). Concentration dependent laser light intensities are converted into the output signal from calibration coefficients stored in firmware and data from additional sensors within the gas circuit.

High accuracy and stability

Due to their narrow line-width, the Tunable Diode Laser Detectors have a high accuracy and an ideal selectivity for methane molecules. In addition, they feature a large dynamic range covering background partial pressures up to 40 matm. All detectors are subject to an individual calibration and an in depth quality check in our QA lab before they are integrated into our sensors. The quality of the calibration is then verified individually in calibration tanks. The sensor is stable over a long time as the detector tunes the laser to CH4 absorbing and non-absorbing wavelengths for each measurement thus compensating for potential drift influences.


  • High accuracy and low detection limit of background concentration
  • Large measuring range
  • Optimal long-term stability
  • Ideal methane selectivity
  • Non-consuming CH4 measurement
  • Very robust, can be used in water depths up to 3000 meters
  • User-friendly 'Plug & Play' principle; all required cables, connectors and software are included


  • Analogue output: 0 V - 5 V
  • Internal data logger
  • External battery packs
  • ROV and AUV installation packages
  • Profiling and mooring frames
  • External pump (SBE-5T or SBE-5M)
  • Easy deployment together with a CONTROS HydroFlash® O2


A wide range of available accessories ensures that each of the CONTROS HydroC® CH4 sensors can be adapted to meet customers' requirements. Underwater pumps and different flow head designs are the most popular options, which ensure fast response times. An antifouling head is used under conditions with significant biofouling pressure. The internal data logger can be used in conjunction with the CONTROS HydroC®'s flexible power management features and the CONTROS HydroB® battery packs to conduct unattended long-term deployments.

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