Your smartphone
is a remarkable feat of engineering. It’s half a dozen or more gadgets packed
into a single slab. Much of it’s coolest feats are accomplished with a wide
range of sensors — but what are they and what do they all actually do?
How does your
phone count your steps and replace your fitness tracker? Does GPS use up your
data? Which sensors should you make sure are in your next handset?
Here’s all you
need to know.
Accelerometer
Accelerometers
handle axis-based motion sensing and can be found in fitness trackers as well
as phones—they’re the reason why your smartphone can track your steps even if
you haven’t bought a separate wearable.
They also tell
the phone’s software which way the handset is pointing, something that’s
becoming increasingly important with the arrival of augmented reality apps.
As the name kind
of gives away, accelerometers measure acceleration, so the map inside Snapchat
can put a cute toy car around your bitmoji when you’re driving, plus a host of
other actually useful applications.
The sensor is
itself made up of other sensors, including microscopic crystal structures that
become stressed due to accelerative forces. The accelerometer then interprets
the voltage coming from the crystals to figure out how fast your phone is
moving and which direction it’s pointing in.
From switching
apps from portrait to landscape, to showing your current speed in a driving
app, the accelerometer is one of your phone’s most important sensors.
Gyroscope
The gyroscope
helps the accelerometer out with understanding which way your phone is
orientated— it adds another level of precision so those 360-degree photo
spheres really look as impressive as possible.
Whenever you
play a racing game on your phone and tilt the screen to steer, the gyroscope
rather than the accelerometer is sensing what you’re doing, because you’re only
applying small turns to the phone and not actually moving through space.
Gyroscopes
aren’t exclusive to phones. They’re used in altimeters inside aircraft to
determine altitude and position, for example, and to keep cameras steady on the
move.
The gyroscopes
inside phones don’t use wheels and gimbals like the traditional mechanical ones
you might find in an old plane—instead they’re MEMS (Micro-Electro-Mechanical
Systems) gyroscopes, a smaller version of the concept embedded on an
electronics board so it can fit inside a phone.
The first time
MEMS gyroscopes really hit it big was with the iPhone 4 in 2010. Back then, it
was incredibly novel to have a phone that could detect orientation with such
accuracy—nowadays, we take it for granted.
Magnetometer
Completing the
triumvirate of sensors responsible for working out where a phone is in physical
space is the magnetometer. Again the name gives it away—it measures magnetic
fields and can thus tell you which way is north by varying its voltage output
to the phone.
When you go in
and out of compass mode in Apple Maps or Google Maps, that’s the magnetometer
kicking in to work out which way up the map should be. It also powers
standalone compass apps.
Magnetometers
are found in metal detectors as well, as they can detect magnetic metals, which
is why you can get metal detector apps for your smartphone.
However, the
sensor doesn’t work alone for its primary purpose, which is inside mapping
apps—it operates in tandem with the data coming from the phone’s accelerometer
and GPS unit to figure out whereabouts you are in the world, and which way
you’re pointing (very handy for those detailed navigation routes).
GPS
Ah, GPS—Global
Positioning System technology—where would we be without you? Probably in a
remote, muddy field, cursing the day we ditched our paper maps for the
electronic equivalents.
GPS units inside
phones gets a ping from a satellite up in space to figure out which part of the
planet you’re standing on (or driving through). They don’t actually use any of
your phone’s data, which is why you can still see your location when your phone
has lost signal, even if the map tiles themselves are a blurry, low-res mess.
In fact, it
connects with multiple satellites then calculates where you are based on the
angles of intersection. If no satellites can be found—you’re indoors or the
cloud cover is heavy—then you won’t be able to get a lock.
And while GPS
doesn’t use up data, all this communicating and calculating can be a drain on
your battery, which is why most battery-saving guides recommend switching GPS
off. Smaller gadgets like most smartwatches don’t include it for the same
reason.
GPS isn’t the
only way your phone can work out where it is—distance to cell towers can also
be used as a rough approximation, as Serial taught us—but if you’ve got some
serious navigating to do then it’s essential. Modern-day GPS units inside
smartphones actually combine GPS signals with other data, like cell signal
strength, to get more accurate location readings.
The best of the rest
You’ve got
plenty more sensors in your handset, though they’re perhaps not all as
important as the four we’ve just mentioned. Many phones, including the iPhone,
have a barometer that measures air pressure: it’s useful for everything from
detecting weather changes to calculating the altitude you’re at.
The proximity
sensor usually sits up near the top speaker and combines an infrared LED and
light detector to work out when you have the phone up to your ear, so that
screen can be switched off. The sensor emits a beam of light that gets bounced
back, though it’s invisible to the human eye.
Meanwhile the
ambient light sensor does exactly what you would expect, taking a measuring of
the light in the room and adjusting your screen’s brightness accordingly (if indeed
it’s set to auto-adjust).
Like the rest of
the tech packed inside your handset, these sensors are getting smaller,
smarter, and less power-hungry all the time, so just because phones five years
apart both have GPS doesn’t mean they’re both going to be as accurate. Add in
software tweaks and optimizations too and it’s more reason to upgrade your
handset on a regular basis, even if you’ll almost never see these sensors
listed on a specs sheet.
