14
Searching Areas along a Chain Link Fence
Searching in the vicinity of a
chain link fence requires a
reduced sensitivity setting and
some control over the
orientation of the locator. As
illustrated in Figure 22, position
the locator horizontally with its
long axis perpendicular to the
fence. This insures that the
upper sensor is kept away from
the fence.
Figure 22: Searching in the Vicinity of a Chain Link Fence
Perform the search by slowly
moving the locator forward
along the fence while also
moving it to the right and to the
left. As you move forward, this
technique allows you to search
an area several feet wide.
Listen for an abrupt drop in the
signal (as shown by the null in
Figure 23) that will occur when
the lower sensor, located 1-1/2
inches from the end of the
locator, is directly over the
stake. Any variation in the
position of the locator will
produce an abrupt rise in the
frequency of the signal.
Figure 23: Abrupt Drop of Signal while Searching
Along a Chain Link Fence
Locating Valve Boxes
Both the valve and its casing, when iron, provide strong magnetic
fields that make them easy to locate. Plastic enclosures containing
magnets (which are typically used with non-ferrous valve boxes) are
easily located at depths of up to 9 feet.
Figure 24: Locating Valve Boxes and Casings