Based on these results, the following recommendations were made for the Engineering 

 Development Model system: 



1 . The Forster Ferex magnetometer should be modified for use in both dipping mode 

 (from an inflatable) and self-contained diver-operated mode. This system should also be 

 designed for quick and easy conversion between these two operating modes. 



2. The dipping mode should incorporate a spring wound reel for paying-out and 

 handling the cable between the probe and the electronics module. 



3. The self-contained diver-operated mode should incorporate ready access to all 

 control adjustments and a standoff mechanism between the sensors and the diver. No electronic 

 modifications are anticipated. 



ENGINEERING DEVELOPMENT MODEL (EDM) SYSTEM 



From May through August 1987, laboratory and ocean tests of the engineering 

 development model BP&CL were conducted to verify reliability and performance thresholds (as 

 specified in the Test and Evaluation Master Plan, TEMP) and identify any safety or human 

 factors deficiencies. 



System Description 



The EDM system consisted of a commercially available Forster Ferex (Model 4.021) 

 system modified for use by the UCTs. Modifications to the magnetometer consisted of new 

 waterproof housings and accessories for use in two different operational modes: (1) as a dipping 

 mode from an inflatable boat, and (2) as a self-contained, hand-held diver tool. Figure 9 

 illustrates the two op)erational modes. 



The stock Forster Ferex 4.021 magnetometer is designed to sense anomalies in the earth's 

 magnetic field resulting from the presence of a ferrous object. To sense the anomaly, the 

 magnetometer uses two fluxgate sensors located a fixed distance from each other inside a 

 cylindrical probe. The output from the fluxgate sensors are processed and converted to provide 

 the operator with both audible and visual signals. As the magnetic field disturbance increases, 

 the intensity of the signal output increases. The visual output is a meter with an indicator needle 

 that shows increasing signal strength by moving off-center to the right or left depending on the 

 polarity of the section that the probe is approaching. As the probe is passed over the object, the 

 needle swings across the meter to indicate signal strength in the opposite polarity. The earphone 

 indicates increasing signal strength by increasing the frequency of the audio output. 



Standard control features of the Forster Ferex 4.021 magnetometer include the following: 



1 . Mode Selector Switch - Any one of four different search functions can be selected 

 with this switch. Mode 1 is for normal searching of all ferrous metals. Mode 2 is also for 

 normal searching but eliminates disturbances from small ferrous objects. Mode 3 is used when 

 searching next to a large ferrous object (such as a pipeline). Mode 4 allows the tool to be used 

 as a magnetic compass. 



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