achimha wrote:
I read the phones use fluxgates
I read the iPhone 6 uses a 3-axis electronic compass IC with high sensitive Hall sensor technology and I2C interface (yum 
)
Best adapted to pedestrian city navigation use for cell phone and other portable appliance.
(AKM 8963)
achimha wrote:
All electronic systems use fluxgates, just like the mobile phones.
What makes you think they use fluxgates?
Normally, these sensors use a magnetoresistive wheatstone bridge, like the classical Philips KMZ51
Typical phone compass chips still seem to use a magnetoresistive bridge, such as this ST one (see block diagram on page 8)
I read the phones use fluxgates. I have no idea how they got them so small and efficient. They also have Hall sensors but for things like sensing their cover. Hall sensors require a rather strong magnetic field. Incidentally, I’m actually in the business of selling all kinds of Hall sensors
I think the iPhone 6 uses a Chinese Fluxgate chip. It also has barometric altitude, by the way
Does the phone use a fluxgate? A fluxgate is a saturable magnetic core, which uses the principle of the relative permeability of the material collapsing when the flux density is too high for it, and that needs a fair bit of power (at 400Hz in the aircraft version) to drive it. I would think they use Hall effect sensors.
Jan_Olieslagers wrote:
Agree to that. But the difference is either in WCA*, which can be calculated if once there is a reliable source of wind data (and that will be needed anyway), or magvar, which can be determined even more easily from a table of magvar for given coordinates.
It’s the other way around actually, the wind is calculated based on the difference between heading and track and pitot speed versus ground speed. The mag var plays no role, everything we do is based on magnetic north (unless navigating near the poles where a different system is used for IFR).
A correct heading indication is a requirement for all IFR approved airplanes. All electronic systems use fluxgates, just like the mobile phones.
WCA = wind correction angle
ah! And I always tried to figure out what WCA means!! ;-))
GPS derived direction is track but we’re interested in heading.
Agree to that. But the difference is either in WCA*, which can be calculated if once there is a reliable source of wind data (and that will be needed anyway), or magvar, which can be determined even more easily from a table of magvar for given coordinates.
Come to think of it: are we really interested in heading? My own very primitive gps/moving map shows track as planned vs. track as flown – if they diverge too much I steer the other way – what need to make things more complicated?
*WCA = wind correction angle
They are actually pretty precise. I have used it once in the plane, for fun, and it worked just as good as the airplane’s whiskey compass
The phones have the same fluxgate magnetometers as the glass cockpits have. The biggest challenge is ambient magnetic noise.
GPS derived direction is track but we’re interested in heading.
