So you've purchased a quality compass, zeroed it in and have identified where you want to place it. Before you mount it, check for magnetic influences. All such influences affect your compass, causing it to deviate from its correct heading. For obvious reasons, then, you want to eliminate those influences or keep them to an absolute minimum.
Check out your intended compass location with care. You want you compass positioned a minimum of 2 feet away from most metal and/or electrical equipment. This "equipment" can be anything from engine instruments and VHF radios, to stereo speakers, electric gauges, a cast-iron skillet or a screwdriver. Even stainless steel, which is normally not magnetized, can be a problem, so you'll want to check it out rather than assume anything.
If you find your compass is too close to these magnetic influences, you'll need to remove either the compass or the magnetic material. Before you panic, the distance of additional separation needed isn't necessarily great. In fact, if you double the distance from the offending item, the magnetic influence on your compass from that particular object is effectively reduced by 75 percent. One thing to note as you take your influence inventory is that all magnetic materials may not be immediately apparent. (Remember that cast-iron skillet? It probably wasn't lying beside the helm.)
You can use your compass to test for these magnetic influences. Move around the proposed location, taking care to maintain the compass's orientation with the centerline of your boat and keeping your eyes focused on the card. If the card moves, you've found a magnetic influence.
Now you need to make some decision, which are relatively simple if you can remove the object or replace it with one made of non-magnetized components. If not, test to see if the object is actually magnetized or is merely a magnetic metal. You do this by bringing first the North, then the South pole of your compass into close proximity with the suspect object. If one pole is attracted and the other is repelled, the object itself is magnetized.
Sometimes it's possible to demagnetize an object. (Your local electronics repair shop can tell you how.) If demagnetization fails, reposition it or reposition your compass.
As you conduct your influence inventory, make sure you use your compass to test any metal objects that move or are likely to move during normal during operations, and test them in varying positions, too. In other words, if you have a ship's wheel, turn it in both directions; manipulate the throttle, windshield wipers and gearshift levers; open and close windshields and even the cabin door. Whatever is close to your compass's proposed location needs to be carefully scrutinized.
Once you've done your homework and your compass is in place, there's one thing more to remember. Should you decide to install additional electronics pay attention to the manufacturer's directions, which give suggested minimum distances between their product and your compass.
- Linda Hoff
