External Sensors

by Torstein Pedersen — last modified Dec 10, 2007 11:15 AM

Here you will find external sensors which have been integrated by Nortek with Doppler instruments that have an analog input (basically all but the Vectrino). Surely there are many other external sensors that can also be integrated via the analog input, however for the moment these represent two which Nortek delivers with its Doppler instruments.

Perhaps one of the most under utilized features of Nortek instrumentation is the analog input.  The analog input greatly extends the versatility of the instrument and effectively transforms the current meter/profiler into the multi-sensor device.

How it works Nortek instruments have either one or two analog inputs.  These have an operating range of 0-5 Volts.  Sensors that have an analog output in this range will produce a voltage that corresponds to the physical quantity it measures.  The measured voltage is then recorded along with the current measurements.

The sampling on the analog channel is configurable to occur when the instrument measures current and/or waves.  The configuration of this is done in the deployment planning of the instruments software.

Typical Applications 

  • Turbidity - Optical backscatter sensors.
  • Oxygen sensors.
  • CTD (conductivity, temperature, depth).
  • Monitoring voltage for other devices in the system.
  • Acoustic altitude sensor (distance from bottom) / Frame burial avoidance.
  • The sync line, which is not part of the analog lines, can be used to initialize external devices.  This include starting such devices as a GPRS modem, which generally requires 20-30 seconds to log onto a network.

Considerations

  • A special cable between the Nortek instrument and the analog sensor needs to be ordered.
  • Power can be supplied to the external sensor.  This is selectable in the deployment planning, however estimates of "assumed duration" applies only to the Nortek instrument.  Powering external sensors will reduce the duration by an unknown amount.
  • The Vector has high sampling rates of up to 64 Hz and can sample the analog line at the same rate.

 

Examples Below you will find some examples of sensors commonly used with the analog channel

Seabird MicroCAT 37 xm (160x160)Seabird MicroCAT This is the standard CTD sensor offered by Seabird.  There are many different variants of this sensor so be sure to chose the one that suits your needs: http://www.seabird.com/

 

 

 

 

 

Valeport MiniCT (160x160)Valeport MiniCT  The miniCT probe is Valeport's direct reading Conductivity and Temperature sensor, featuring digital sampling techniques for improved performance, and high strength construction methods. 500m acetal and 6000m titanium versions available, both with RS232 or addressable RS485 data outputs as standard.

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