Pressure sensors for sub-sea level measurement

17 May 2011

Sub-sea level measurement can be accomplished with the use of a pressure sensor.

Typically an Remotely Operated Vehicle (ROV) is lowered into the ocean with a pressure port either installed inside an enclosure or completely exposed to the sea water. As the ROV is submerged, water pressure is exerted on the diaphragm of a pressure sensor. The deeper the system is submerged, the higher the pressure. By calculating salt water density at 1.025 (or 2.5% more dense than fresh water at 4°C) a correlation between pressure and output signal can be made to measure equipment depth.

For example, when a pressure sensor is packaged with a pressure range of 350 Bar and a 4-20mA output signal, the pressure sensor will read 4mA at the surface. When the sensor is submerged with the equipment, the pressure will increase along with the linear output signal up to 20mA at a depth of approximately 3657.6m.

Pressure sensors submerged in sea water need certain mechanical considerations to survive the corrosive environment. To meet this need, American Sensor Technologies has produced its 4000 series of pressure sensors with all 316L stainless-steel wetted parts, including the pressure sensing element, housing and electrical connection to survive sub-sea environments.

Electrical termination is also a key factor for sub-sea applications. AST 4000 series pressure sensors use a wet, plug gable style connector which completely seals the electronics of the sensor. The threaded connector is made with gold contacts and glass reinforced epoxy to maintain media compatibility and long-term use.

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