Current Sensors

Single point or profile

A single-point current meter measures speed and direction at the one depth where it sits. That is enough when the question is about a specific depth — at a riser clamp, or at an intake — and the instruments are compact and straightforward to deploy.

A current profiler (ADCP) measures a whole column at once, dividing it into cells and reporting speed and direction in each. Currents often vary sharply with depth and sometimes reverse, so the profile is usually what is wanted. That difference tells most during an offloading operation: a tanker coming alongside an FPSO is handled on the current where the tanker is, which is not necessarily the current at the FPSO’s own hull.

Frequency sets the trade-off. A high-frequency instrument gives fine resolution over a short range; a low-frequency one reaches hundreds of metres with coarser cells. Which to use is a question of water depth and of what the data is for — and several sensors can be run together, with the profiles merged by the system software.

Horizontal profiling

Where the interest runs across rather than down — approach channels, berths, intake protection — a horizontal profiler looks sideways from a fixed structure and reports the current out to a hundred metres or more.

What matters offshore

• Getting it in and out. A profiler over the side needs a way down and, more importantly, a way back. Winch and davit systems make recovery routine rather than an operation — see deployment systems. Seabed frames are the alternative where the instrument is placed rather than suspended.
• Fouling. Anything left in the water grows. Marine growth on the transducer heads degrades the signal long before it stops it, which is why easy recovery and a cleaning interval matter as much as the instrument specification.
• Power and data. A cabled instrument reports continuously and runs off the installation; a self-contained one logs internally on battery and gives up its data on recovery. The choice follows whether anyone needs the current in real time.
• Servicing and calibration. A recovered instrument needs cleaning and a check over, and its calibration interval kept to. We turn instruments round with a fast-track supply line for spare parts, and manage calibration returns to the manufacturer on your behalf.

Examples from our range

A few of the current sensors we specify, install, integrate and maintain. We supply more types and variants than are listed here.