User's Manual

8 | P a g e
4.2 Tire Sensor Unit
Knob cover
Single Internal Battery
Knob cover – waterproof cover. Please ensure the red silicon ring
is intact to prevent water from getting into
electronics compartment.
Single internal battery - CR2032 coin cell battery. When replacing battery,
please ensure the “+” sign of the battery is facing up,
away from PCB.
Internal PCB - internal electronics circuit (The pressure sensor chip
is mounted within this PCBA, and it senses the tire
pressure against a built-in vacuum, resulting in an
Absolute Pressure reading. The internal firmware
will then subtract the sea-level pressure of 101.3
Kpa (14.7 psi) from this reading. This final reading
which will be shown in the App can be termed as i)
Tire Absolute Pressure minus sea level pressure,
or ii) Gage Pressure reference to sea-level altitude.
With this formulation, Fobo Ultra sensor will read
the same pressure value for any given time,
irrespective of altitude (assuming a constant
temperature). This will ensure the correct tire
footprint per vehicle manufacturer‟s pressure
recommendation, for all altitude above sea-level,
given a constant temperature.
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