Variations
All cable projects are not the same and Nortek has designed two different versions of our online cable system. The basic system is intended for applications where the initial investment is a important while the "strain relief" system is designed for systems that are intended to be deployed for a long period of time. In addition to these versions, it is possible to add a backup solution to an online system so that data can be collected and stored even if the instrument looses connection to shore.
Conceptually, online cable systems are quite simple. In real life, the story is a little less simple and long cables are both a technical and practical challenge. To address these challenges, we have taken many years of experience and designed what we believe to be a very good technical solution.
Version "Basic"
The basic version provides all that you need for online communication. First, the instrument is connected to a 2-m extension cable that is molded onto our tough online cable. To make sure the instrument connector does not easily come loose, a braided jacket ("Chinese fingers", see element 0 in the drawing below) with a strength of several 100 kg is attached to the online cable and should be attached to the deployment frame before or during deployment.
On shore, the online cable connects to the "interface box" (see element 3 in drawing below), which supplies 48 VDC power and RS-422 communication. To reduce the voltage, a DC-DC converter is mounted inside the instrument. The DC-DC converter comes in two physical versions, one that fits inside the AWAC housings and one that fits in all other housings.
Version "Exposed"
The "exposed" version of the online cable system is designed to take into the account the possibility of wear and tear (where parts of the cable would need to be replaced) or even the possibility that the cable is pulled by an anchor or by fishing activity.
For wear and tear problems, we recommend a segmented cable where the segments are linked with an underwater matable connector that can be detached or attached by a diver (optional diver tool is available). For example, it is possible to use four 250-m segments instead of one 1000-m segment. For problems with cables that are being pulled, the strain relief mechanism is designed to take a load of 200kg and then cause the underwater matable connectors to come apart before the power is automatically cut from the interface box. In most cases, this means that it is possible to get the system back and up and running simply be reconnecitng the underwater matable connector or in the worst case by replacing the damaged segment.
Element 1 is a machined from a plastic material with a known breaking strength and should be attached to the deployment frame. It can take a load of 200 kg before it breaks in a controlled way. The strain will then be transferred to the connectors (element 2) which are held together with a special plastic holder that will break with a 200kg load. The connectors will detach, the interface box (3) will sense the short and quickly power down.
Any Nortek ocean instrument can be used with the online cabled system and not just the AWAC, which is the instrument depicted in the illustratons.
Backup Option
In addition to the "Basic" or "Exposed" version of the cabled online system it is possible to add backup batteries and memory to the system. The battery will ensure that the instrument continues to collect data even if the cable is disconnected and the extra memory ensures that the data are stored.
This backup option is ordered as part of the standard instrument and it is similar to what it is normally used for stand-alone instruments. The Interface Box with 48V output combined with the DC-DC converter inside the instrument are important elements in the backup option to avoid depletion of the backup battery during regular operation.
Please contact Nortek if you have special online requirements that may require subsets or a special version of the online cabled system.
