Fluxgate...how close is too close.....

[Jeff Bacon]

....to metal objects or wiring ? The manual is silent on this point, and only indicates not to get it too close. Mounting near the centerline creates issues with "too close" on my boat. But, I don't know how close too close is.Has anyone done any experimenting ?Thanks...... Jeff

 

[Gord May]

distance squared

Sorry, I don’t have a direct answer to your question - but FWIW - The intensity (flux) of a magnetic field varies inversely with the square of the distance - so doubling the separation (distance) would reduce the interference by a factor of 4.

 

[Fred Ficarra]

And,

you don't have to mount it on the centerline. Think about what the flux-gate sees when installed on the boat. Does the hull at the point of maximum beam point in a different direction when the boat is heeled? Just stick it someplace that avoids interference and impact damage. On my web site, photo #39 shows the locker that my flux-gate is mounted in. It's against the outer hull. Oh, it's been there for 18 years.

 

[Ed Schenck]

Too close to what?

What is on the centerline and how close is it Jeff? My Nexus compass is mounted on a bulkhead directly behind the chain locker. One hundred feet of chain sits about twelve inches in front and a little below. Compared to the binnacle and the GPS it is right on the money. And without any adjustments on my part.With your fluxgate, I assume for the autohelm, I believe that you can compensate. That would not work if the "too close" object changes position or size.

 

[jeff10600]

use a compass

i have installed a couple of these and found if you run the engine and turn on all eletrical componets in the boat (radio, microwave,lights ect.) then use a hand held compass and move it around the place where you intend to mount it. you will see movement on the needle if there is some eletrical curent or metal that could affect the true reading. also make sure that you auto piolet(if that is what you are installing) has its own power supply, a quick drop in voltage when sharing a circuit can cause the unit to change course for no reason.  good luck.

 

[Don12364]

The Silent Manual

Jeff,The manual is silent because it is the responsibility of the makers of all the other equipment which could interfere with a compass to state their "Compass Safe Distance". This is the distance at which each 'other' item will cause a 1° deviation. Try looking in their manuals or asking the equipment makers for this.Some years ago I asked Raymarine for the CSD of their Autopilot drive motor and they told me that it was a function of which compass I was using - worrying information to receive from the world's largest autopilot manufacturer!

 

[RichH]

Use twisted paired wire

If you twist all the paired (+ & -) wiring on your boat, especially near fluxgate and magnetic compasses, the electric field from energized wiring will be minimized. I use 1 full twist per inch. Someone on these boards may know better how many twists per foot is optimal.