How do tyre pressure sensors in aircraft work?
On a Boeing 777, a tire pressure sensor/fill valve is installed on each of the 12 main gear wheels and two nose gear wheels. There is an in-axle transformer in each of the axles.

The tire pressure sensor/fill valve is made of an air fill valve and three independent pressure sensing channels which provide accurate tire pressure.

The tire pressure sensor/fill valve is installed in the wheel.

A relay transformer hubcap assembly connects to the tire pressure sensor/fill valve. The left 28V DC MAIN bus supplies the electrical power to operate the tire pressure indication system.





(Image source: 777 AMM)

You can see the sensor in these images:



(Source: airliners.net)



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