It got me wondering, I googled for magnetometer (electronic compass) and the best i found is someone working with one to detect lightning strikes..

The Iphone 3GS, the Nokia N97/N97Mini/E72/6210/6710... the list goes on these days, as more and more mobile phones contain compass for pedestrian navigation (and more these days for augmented reality apps) more and more people have access to powerful hardware, GPS, Wifi, Magnetometer, Accelerometer , I've seen people with powerful functions like these and don't even know they had it let alone use it...

So getting back to my point, how sensitive are Magnetometers? is there a basic standard to one?.. for example what other uses is there for one other than giving a compass? or is that pretty much it? I'm curious as to how lightning storms can mess with a calibrated magnetometer, say an application to detect strikes?... or would that require a million dollar piece of equipment? i'm not sure how advanced or how good the hardware is unless all magnetometer have a base line where they can do interesting stuff with.

 

You are looking for a special case of magnetometer called a fluxgate compass - http://en.wikipedia.org/wiki/Magnetometer

 

A common brand of magnetometer used in industry used to be F. W. Bell. You can also make a Hall effect device to measure magnetic fields.

They can be used to measure magnetic fields on the order of T and above and resolve down to the order of nT. Do a web search on "magnetic field measurement" and you'll find lots of info. There are many uses for them; a common one is to measure the magnetic field of a permanent magnet. Another use is measuring magnetic fields due to DC and AC currents. A standard used to check the instrument's calibration is a calibrated permanent magnet in a magnetically-shielded holder.

If you're interested in how lightning can affect these instruments, look up the formula for calculating the magnetic field of a current in a wire, then estimate the field at a reasonable distance from the lightning bolt. Use currents in the range of 10 to 100 kA. Here's an interesting related tidbit.

 

If you do a little searching on Semiconductor Manufacturers' websites for those who make magnetic sensor ICs, you'll find several that sell a reference circuit for electronic compasses with no moving parts-some have a USB output, others are self contained. But there are several different types of semiconductor magnetic sensors, most are sensitive enough for use as an electronic compass. There are more types than just hall-effect types. And these are not going to cost a million dollars, more like US $ 100, perhaps even less. If you're competent enough to make your own prototype from the mfg's application notes, you can go cheap and just by the IC, and put the rest of the circuit together yourself. Then the cost of the IC would be more like $10.00 or so, and the rest of the parts are not expensive, perhaps another $10 to $15 or so. You can probably even get a few samples of some of these IC's for free or just for paying the shipping. It all depends on the manufacturer's policies. And as for lightning, just as any current moving thru a conductor produces a magnetic field, lightning has extraordinarily-high currents that flow thru metal and into the ground, producing transient magnetic fields of high intensity, which can be measured and recorded by this same type of magnetometer, or even by a regular old needle-type compass.
Regards,
Kamran Kazem