Fisher GEMINI-3 warranty Tracing, Inductive Trace

TRACING

Inductive Trace

   The Inductive Trace mode is usually used to trace a long object (pipe, ore vein, etc.) that shows no exposed portions, but two starting points are known.

Set Up

Locate two points along the conductive object at least 30 feet apart as described in the Wide Scan or Narrow Scan Inductive Search sections. The transmitter and receiver should be in line with each other, both facing the same direction. The transmitter should be on the ground and the receiver should be held by the operator.

Figure 8.

Inductive Trace

SEARCHING

5. For even more accurate pinpointing of short objects, (i.e., a pipe, cable, etc.) approach the test object at right angles from your previous direction. Mark the ground as you did before. Your test object should be about centered between four marks.

6. To establish the path of a pipe, cable, or other long conductor, pinpoint two more locations 15-20 feet apart. From these three locations you should be able to draw a straight line (unless the pipe isn’t straight). Careful additional locations may be necessary if no prints (maps of underground lines) of the area are available.

7. It may be necessary to reduce sensitivity with the SENSITIVITY knob when the pipe or cable is large and/ or shallow. If the meter needle has peaked and sound is at a high level, you will want to bring the sensitivity down to see the peak of the needle at a point less than 100 as you move in half or quarter steps back and forth to get your peak reading.

Tuning

1.Set the transmitter: Power: ON

2.Set the receiver: Power: ON Sensitivity: ZERO

3.Increase the receiver SENSITIVITY control until you have an audio response and at least a mid-scale meter

deflection.

4.Determine that you are not direct air coupling by moving the receiver back and forth. The audio meter indications should peak over the object. No peak will be observed if the receiver is too close to the transmitter and direct air coupling is occurring.

Figure 6. Handle strap: Using the handle strap increases depth; however, it may be difficult to tune the GEMINI-3 this close to highly mineralized ground.

8.If at all possible, practice over some buried targets of known size and depth.

9.  There are several things to consider when locating buried objects:

a. Precise location depends on operator skill. b. Position of the ground marks does not indicate size of the object or its path.

c. More than one metal object may cause a wider or stronger response than expected.

d. Deeper targets may not produce a signal until the operator has passed directly over them.

e. Reducing the receiver SENSITIVITY control will narrow the area between the ground marks for more precise pinpointing.

f. Small or deeply buried objects such as a cache of coins, require a tight, closely traversed search pattern. Large or shallow objects can be located successfully with a larger, more widely traversed search pattern.

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