Overview:
In regions where recreational boating and fishing activities are not a concern, using a rugged offshore cable to relay power and data from a shore station to the instrument is a good choice. The AWAC is a common choice for bottom mounted directional wave and current profiling equipment.
Advantages:
- Deployment length and sampling interval not limited by power requirements
- High bandwidth communications for full wave and velocity data set
- Direct communication access with instrument for diagnostic test and configuration changes
- Low maintenance
Limitations:
- Concern for cable damage by recreational boating and fishing activities
Technical considerations:
Careful power supply and data transmission considerations must be addressed when working with long cabled systems. The typical RS-232 communication protocol is changed to RS-422 for long (> 50 m) cable systems. Because of resistance in power cables over long distances, the original 12 VDC power voltage will often drop below the minimum required voltage. To alleviate this, 48 VDC is sent down the power cable to the instrument. Within the instrument, a small module is installed which lowers the 48 VDC power to a nominal 12 VDC. On the shore-side of the cable, an interface box is provided which will handle the power conversion and RS-232/RS-422 communications conversion.
Nortek typically supplies offshore cable in lengths up to 500 m. For longer range deployments, a series of 500 m sections can be linked together. This allows for modular deployment options and only requires a short length of cable to be replaced in the event of damage. Nortek has installed cabled systems up to 5000 m long.
An ActiveX toolbox with current and wave processing commands is supplied for real-time data conversion. These processed data are then ready for display on the users web site in real-time.
Examples:
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