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Dumb Question: Do Magnetometers Need to be Recalibrated from Time to Time?

snopercod

Well Known Member
We know that magnetic North is drifting, so do our magnetometers (remote compasses) need to be recalibrated from time to time? Is this something to worry about?
 
No such thing as a dumb question. Only a dumb answer.

Yes you will need to recalibrate from time to time. But not because the north pole is drifting.

Your magnetometer is affected by aging of its internal sensors somewhat but mostly by magnetic deviation caused by soft and hard metal components in your aircraft changing magnetic properties over time.

Just parking your aircraft in a different orientation for a while will change this sufficiently for errors to creep in. The Earth magnetic field itself will magnetize some components of your aircraft over time and your magnetometer may be affected by this.

Best way to minimize this is to find a location in your aircraft that is as far away from any ferrous metals as possible. Beware of those little left over mandrels in pop rivets and mild steel screws.

Rainier
CEO MGL Avionics
 
Thanks, Ranier. It's been five years since my original calibration, so I guess I need to find an airport with a compass rose and check it again.
 
Thanks, Ranier. It's been five years since my original calibration, so I guess I need to find an airport with a compass rose and check it again.

Or, just put your trusty Boy Scout compass out on the wing away from the fuselage and outside the bell crank area, then walk the airplane around the four compass rose points.

Carl
 
Steel connector on a magnetometer

Well, I discovered a few days ago that my yet-to-be-installed Garmin GMU-11 has a STEEL connector shell! It looked like steel, but I was confident that it HAD to be stainless or plated brass just like the flux gates I have dealt with from time to time over the decades. Nope. Steel.

Now I may have a problem. The connector may have retained a little bit of magnetism from the bit holder on the screwdriver that I touched it with. Time will tell.

Calibration may take care of any anomalies cause by the connector, but I think it might be a better idea to not have a piece of iron so close to the sensors.

Ron
 
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Tried the boy scout compass but went with the GPS track

on the ramp, since everything had to be running when I did the calibrations. Seemed to work pretty well.

Ron

Edit: Vic makes a point -- be sure you are set up for magnetic North rather than true North.
 
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on the ramp, since everything had to be running when I did the calibrations. Seemed to work pretty well.

Ron

No problem doing it this way. Just check to see how your GPS track is set up. Some have the option for magnetic north or True North.

Vic
 
I re-checked my magnetometer calibration today and I'm glad I did. "North" was off by 15 degrees and the other cardinal points were off by 5 degrees. I used my Boy Scout compass to align the airframe as best I could, and recalibrated. All compass points are within 3 degrees now.

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