Table 1. Comparison of Physical Characteristics 



Characteristic 



Fisher 

 Pulse 8 



Garrett 

 XL500 



White's 

 PI- 1000 



Forster 

 Ferex 4.021 • 



Weight in Air 



8 1b 



7.5 lb 



4.25 lb 



11 Ib^ 



Weight in Seawater 



1 lb neg 



1 lb pos 



1 lb pos 



3.5 lb'' 



Visual Output 



Fair 



Poor 



Poor 



Good 



Audio Output 



Good 



Fair 



Fair 



Fair 



General Handling 



Poor 



Fair 



Good 



N/A 



Ruggedness 



Poor 



Fair 



Fair 



Good 



Maintenance 



Fair 



Good 



Good 



Good 



Repair 



Fair 



Fair 



Fair 



Fair 



^Includes only the sensing probe, electronics module, and power supply. 

 ''Includes only the probe with 2 pounds ballast weight. 



Detection Threshold. The objective of this test was to obtain baseline detection threshold 

 data on each unit in air. Figure 6 shows the test setup for the pulse- induced systems. As a 

 standard, twin 72 SCUBA tanks were used as the detection target by moving them toward the 

 detector from various angles. Upon initial detection of the tanks, the angle and distance of 

 detection were noted. Figure 7 shows the test setup for the Forster Ferex magnetometer. Since 

 proper operation requires that the probe be oriented with its major axis perpendicular to the 

 earth's surface, these tests were conducted by lowering the probe toward the tanks until a half- 

 scale reading was obtained. 



Appendix C contains detection thresholds of the pulse-induced systems plotted for coil 

 angles of degrees, 45 degrees, and 90 degrees at the various power settings of each unit. 

 Appendix D shows detection thresholds of the Forster Ferex plotted for sensitivities of 100 and 

 300 gammas. The results of these tests showed the following maximum ranges for each of the 

 units in air: 



1. Forster Ferex - 7.0 feet (sensitivity switch set at 100 gammas) 



2. Fisher Pulse 8 - 5.7 feet 



3. Garrett XL500 (with 13-inch coil) - 5.1 feet 



4. Garrett XL500 (with 7-inch coil) - 2.7 feet 



5. White's PI-1000 - 3.3 feet 



