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AP Sensor is a mobile app developed by the Department of Applied Physics of Hong Kong Polytechnic University. The project envisions mobile and easily accessible physical measurement with the use of built-in sensors in mobile devices, such as smart phones and tablets. It aims to encourage students to make observations to daily environment. It also encourages teachers to co-create experiments with students.

 This project is supported by QEF (2014/0761) and the PolyU TDG 2012-15 (42B2).

7 Functions in 1 App

All built-in sensors in your mobile devices



It is one of the most basic sensors incorporated in modern smart devices. With any inertial motion in 3 axes, the tiny polysilicon semiconductors slightly bend to give different capacitance, from which the acceleration of the device is determined.



Similar to a traditional search coil used in physics laboratory, the magnetometer encompasses tiny "search coils" in 3 axes within which current would be induced when perpendicular magnetic field passes through it. The device converts the readings into magnetic field strength.



The working principle of gyroscope is similar to that of accelerometer except that gyroscope detects rotational motion rather than translational motion.


Light Sensor

The light sensor relies on the famous photoelectric effect from Albert Einstein where photocurrent is generated across photocell upon receiving light. The photocurrent is then converted into corresponding light intensity.


Sound Level Meter

Every smart device, especially smartphone, is equipped with a microphone that is usually made of sensitive conductor vibrating in different amplitude upon sound pressure exerted on it. The louder the sound, the more vigorous is the vibration, and thus the sound level can be determined.


Sound Analyzer

Even a single source of sound in daily life actually comprises multiple frequencies (pitches). Using the same essential component of a mobile device, the microphone, the processor is able to resolve the "ingredients" or "fingerprint" of that sound by a famous mathematical operation called Fourier Transformation.


Sound Generator

The speaker built in modern mobile device is an extremely powerful tool that broadcasts high quality and complexity of sound from media such as music and videos. It is such an easy task to generate a desired pitch, simply by a mode of vibration consisting one uniform frequency.

AP Sensor App for Android (.apk)

Download Application

Download User Guides

More instruction to the use of AP Sensor app

Download Lab Manuals

Suggested study guidelines with the use of AP Sensor


Study of Standing Waves to Find Speed of Sound in Air (PDF)


Apparent Weight in Elevator (PDF)


Gravitational Acceccleration along Inclined Plane (PDF)


Impact upon Collision (PDF)


Magnetic Field Strength of Straight Wire and Solenoid (PDF)


Introduction to Decibel (PDF)


Young's Fringes of Sound Waves (PDF)

Video Demonstrations

Demonstration of suggested experiments


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