DWR4 Wave measurements: same sensor, new data processing
The wave sensor of the Directional Waverider equipped with Acoustic Current Meters (DWR4 ACM) is identical to the sensor in the well known MkI, II and III. Processing of the measured data is now performed at the doubled sample frequency of 2.56 Hz. The high frequency limit of the heave and direction signals is shifted from 0.58 to 1.0 Hz. With this choice, the high frequency limit of the wave buoy is determined by the hydrodynamic response of the hull, not by the onboard instrumentation.
In addition, the DWR4 transmission protocol allows for a superior heave and horizontal displacement resolution. Easy comparison of the new DWR4 output to the familiar DWR-MkIII results is facilitated in the accompanying waves4 software suite.
Extra features of the DWR4 compared to the DWR-MkIII to facilitate operation are:
• For identification, the buoy is tagged with an electronic ID-number (or actually two ID’s for hull and hatch cover separately) which is transmitted along the measured data.
• As a kind of health parameters, the temperature of the Hippy-40 sensor as well as that of the hatch cover electronics are measured.
• For improved energy management, the energy used from the batteries and the energy supplied by the optional solar panel are measured.
• A power switch is included as standard on the hatch cover
An operational difference between the DWR-MkIII and the DWR4 is the criterion for activation of the flashlight. This has changed from light detection to a sunset/sunrise algorithm based on the GPS position and time.