CH₄ – METHANE SENSOR FOR UNDERWATER APPLICATIONS

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 longterm 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.

ACCESSORIES

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.

HydroC® CH₄ data sheet

FEATURES

  • 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

OPTIONS

  • 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)

  REFERENCES

METHANE RELEASE RATES FROM ICE SHEETS DETECTED USING THE CONTROS HYDROC CH4
The Greenland Ice Sheet emits tons of methane according to a new study, showing that subglacial biological activity impacts the atmosphere far more than previously thought.

NATURE, DOI 10.1038/S41586-018-0800-0

SEDIMENT TRAPPING BY DAMS CREATES METHANE EMISSION HOT SPOTS
Applying continuous measurements of the CONTROS HydroC CH₄ reveals that dammed fresh water reservoir emission rates far exceed previous estimates for temperate reservoirs or rivers.

ENVIRONMENTAL SCIENCE & TECHNOLOGY,
DOI 10.1021/ES4003907

METHANE EMISSIONS DRIVEN BY HYDRODYNAMICS AND TEMPERATURE
“This work illustrates that small rivers can emit significant methane and highlights the need for further studies on the link between hydrodynamics and connected wetlands.”

ENVIRONMENTAL SCIENCE & TECHNOLOGY,
DOI 10.1021/ACS.EST.6B03268