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FIELD USE
READOUT INTERPRETATION: The key to successful magging is interpretation of the READOUT. If you
follow the recommendations below, you will become an expert at it very quickly.
1. Practice on land - have a friend walk (slowly) by the Head carrying different size metal objects and
at different distances from the Head. Observe the READOUT while watching him. Keep in mind
that the READOUT can only change at the end of READ time (readout will go blank during 1/4
second READ time. Try approaching the Head from different angles. Recommended metal
objects: five gallon can, wheelbarrow, car (drive it past Fish).
OBSERVATIONS: (as you are walking past head with metal).
Small object up close - Large change in READOUT but only lasts for one or two cycles.
Small object at distance - Small change in READOUT that lasts for one or two cycles.
Large object up close - Large change in READOUT that lasts for many cycles.
Large object at distance - Small change in READOUT that lasts for many cycles.
2. READOUT will normally change (up or down) while towing - When you are towing the FISH, the
READOUT will gradually change as you are making a run (the earths magnetic field is different
every 20' or so). This is especially true when magging just off-shore. What you look for is a
deviation of the pattern.
DEVIATION EXAMPLE
We were magging for a large object (1/2 of a tanker) and making 1/2 mile runs approximately 200'
apart. At the east end of the run, the READOUT was 57,768; at the west end, 57,624. Each run
was about the same with the READOUT gradually changing (one pulse difference at a time) during
the run. On our eighth run, the count was stepping down as normal when suddenly it dropped -
20, then -60 more, followed by -200 more. As we continued our run, the READOUT jumped back
up +150, +125, and by the end of the run was back to normal. Many passes were made, looking
for the maximum change (from 57,768) before we dove on the wreck.
3. Verify reading - Never dive as a result of a single reading. Periodically, you may receive a false
reading due to a noise or a malfunction of the mag. Always make several passes to verify.
