A Micro-Processor Based System For Oceanographic Data Gathering, Analysis And Recording
Authors: Alexander Ernest , Hamilton Robert C. 
Published: October 2008

Oceanographic and meteorological data gathering, analysis, and recording on offshore structures and drilling rigs has been accomplished in several ways in the past. Pure analog recording of parameters with no real time analysis being performed has been used extensively. Digital recording, with varying amounts of analysis, has recently come into widespread use. These systems have generally used a minicomputer to perform the data analysis and to control the data gathering and recording functions. This paper describes such a system that uses a small computer called a microprocessor to perform the data gathering, analysis, and recording functions.

INTRODUCTION

Oceanographic and meteorological data collection and analysis on offshore structures and drilling rigs is a difficult task. Equipment must perform complex tasks, yet withstand the rigors of the offshore environment and be simple to operate and maintain. Recent advances in small computers called micro-processors make them especially attractive for application in this area. The system described in the following paragraphs utilizes such a computer.

The system accepts analog signals from wave, wind speed, wind direction, barometric pressure, air temperature, and three current speed and direction sensors and digitizes, analyzes, displays and records the data from these sensors. These parameters are sampled and digitized every 0.5 second. The system calculates significant wave height, average wave period, and average current speed and direction for all three current meters every 1024 seconds (17.07 minutes). The values are displayed on digital panel meters, recorded on the "Observed Data" cassette recorder, and once each hour printed on a small hard copy printer. The average wind speed and direction are calculated every minute and displayed on digital panel meters. Additionally, the average wind speed and direction are calculated for each 17 minute period and recorded along with the wave and current data. Instantaneous values of barometric pressure and air temperature from the end of each 1024 second sample period are displayed, recorded and printed in the same manner as the wave and current data.

In addition to printing the values automatically after the first calculation period of each hour, the system will print the values for the last calculation period whenever the "Manual Print" button is pressed.

The above processing and recording is referred to as "Normal Mode Operation." An additional mode of operation called "Storm Mode" is included in the system. This mode is automatically entered whenever the calculated significant wave height exceeds the value specified by the two decade digital switch labeled "Storm Threshold" in the rear of the console. In this mode of operation, the 0.5 second values of the sea surface profile, wind speed, and the "X" and "Y" current speeds from all three current meters are recorded continuously on the digital cassettes labeled "Storm Recorders No.1 and No.2." These 0.5 second samples will be recorded until the significant wave height falls below the storm threshold for three calculation periods. The two cassettes will hold up to 30 hours of continuous data and will switch from one recorder to the other automatically.