Linear motors (also known as linear vibrators or linear resonant actuators) have become increasingly popular in handheld devices such as phones and tablets for providing haptic feedback to the device’s user. The performance characteristics of these devices can now be tested using your SoundCheck system – the same software you are familiar with from your audio tests! The main difference between linear motor testing and audio testing is that an accelerometer (rather than a microphone) is used to measure the performance of the device under test.
A linear motor is designed to have a strong resonant frequency across a narrow frequency bandwidth; the motor is then operated at its resonant frequency to produce maximum output (vibration) while having minimal power demands on the portable device. The strength of the vibration is controlled by adjusting the magnitude of the AC signal input to the motor. In this sequence, first a sine sweep is applied to the device to calculate the resonant frequency, impedance and related values, and then a single tone at resonance is applied to measure characteristics such as rise and fall time.