Having an email exchange with a major Marine electronics vendor's support staff, as they sell a VHF handset that looks interesting, and claims inductive charging from a 12V DC starting power. That would infer that they have to create some type of varying magnetic field to couple across the airgap, and my question of them was what was the distance to my compass(es) needed to be safe from their device.
They responded somewhat off the cuff that the 'industry standard" was 1 meter, (though their VHF console only requires 1 1/2 feet). Not sure where that came from, nor on reflection that it's a simple answer. I would like to have the charging cradle on a navpod at the helm, so that I would have a convenient Radio while steering..
My default navigation compass is mounted in a binnacle ahead of the wheel, and has been deviated every time I add major gear. My new electronic compass will self correct if given a few slow circles, but that's only for the magnetic state at the time of the correction.
I do have a rotary drive mounted almost directly below the compass and about 6 feet lower, that is fed by 15Amp DC and would be changing as the Autopilot works. I envision a feedback loop that I had not previously anticipated. and will have to see if that changes the compass reading while the boat is stationary.
Given a terrestrial Field of about 250 milliGauss (25 uT for MKS) what level of field do I need to stay below, and does it matter if the field is in plane of the sensor as the prospective handset would be, or is orthogonal as my autopilot drive is?
A related yet separate issue is the placement of the fluxgate and GPS sensors, previously they had been aft to be quiet and out of the way, not vulnerable to being broken or having a can set adjacent. Now thinking that placing them closer to center of mass/moment and turn/buoyancy makes a lot more sense to get quality signals, and minimize the amount of jitter on the MARPA, and overlay. (though the radar will be mounted aft on mizzen.
Any thoughts?
Looking for a copy of IEC60945, any suggestions that don't involve spending $350?
It would seem to be a logical starting point.
Place the GPS as close to the bow as you can
Fluxgate? With all the electronics your obtaining, you don't have a solid state compass?
It seems to be industry standard to write 1 or more meters on the instructions of all electronic devices. Perhaps consider your binnacle compass as decorative and keep a handheld compass that is easy to use in the rain.
Solid state compasses generally are a form of flux gate. Hall effect is not sensitive enough. http://www.ti.com/lit/ds/symlink/drv421.pdf This one was developed by colleagues.
I don't think of these as being fluxgate
http://www.airmartechnology.com/uploads/brochures/H2183.pdf
https://www.panbo.com/archives/2009/02/airmar_h2183_compass_best_in_class.html
Raymarine EV-1
http://www.starmarinedepot.com/raymarine-autopilot-ev-1-sensor-core/pzz18955.html?gclid=Cj0KEQiA3t-2BRCKivi-suDY24gBEiQAX1wiXHp2DG6XA19JYYmO1qWwXq129wRtNlqhT3z3ScF0kIIaAgMW8P8HAQ
The EV-1 has autocompensation for on board magnetic fields.
Those probably contain multi axis flux gates, or possibly magneto-resistive bridges as well as accelerometers. The system of sensors and signal conditioning with connector and mount is what makes the "compass" bigger than ~1mm cube.
Still the question remains. A simple deviated binnacle is far more reliable than a boatload of interconnected stuff that's feeding back errors. Guess I'll have to bring the handset into the lab and fire up the gauss probe.