Have you ever played with magnets before? You know how they stick together or push each other away? Well, a MEMS magnetic field sensor is like a tiny, really smart magnet that can sense how strong and which direction a magnetic field is coming from.
This tiny sensor is made up of really small components, like a tiny magnet or coils of wire, that can detect even the tiniest changes in a magnetic field. It's so small that it can fit on the tip of your finger, and it's super sensitive to all kinds of magnetic fields, from the Earth's magnetic field to the magnetic field in your fridge door.
This sensor can be used in all kinds of devices, like your phone or your car. When you use the compass on your phone to figure out which direction you're facing, you're actually using a MEMS magnetic field sensor. And in your car, the sensor can detect the magnetic fields created by your engine and tell your car's computer what's happening.
So even though a MEMS magnetic field sensor is really small and might seem like a toy, it's actually very important in helping all kinds of devices work properly.