Haptic Feedback Measurements with SoundCheck (100 Things #59)

SoundCheck makes haptic feedback measurements as well as audio measurements on devices like smartwatches, phones, and tablets. Setup with SoundCheck is simple as an accelerometer can be used in place of a microphone in a traditional loudspeaker test setup. We even have a pre-written sequence, available at the link above, to save you time with your next haptic measurement setup.

Making Haptic Feedback Measurements with SoundCheck

Learn more about Haptic Feedback Measurements

Our Linear Motor Measurement sequence measures the performance characteristics of a linear motor for haptic feedback using SoundCheck. This sequence can test any device with haptics from smart watches, smartphones, and more.

 

Video Script:

Everyone knows you can use SoundCheck for measuring audio, but did you know you can also use it for measuring haptic feedback, for example in a smartwatch, phone or tablet? You just need to use an accelerometer instead of a microphone.

Haptic feedback is usually generated using linear motors, sometimes called linear resonant actuators. They typically use a fixed coil in conjunction with a moving magnetic mass that is connected to the motor’s housing with a spring. These systems are designed to have a high-Q, in other words, a strong resonant frequency across a narrow frequency bandwidth. This ensures that you get the maximum output, or vibration, with 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.

Performance characteristics of a linear motor are easily measured using SoundCheck. It’s actually very similar to a basic loudspeaker test setup, except that you substitute an accelerometer for the microphone. You would typically use a custom test jig, mounted on foam isolation. Let’s take a look.

Here, we are going to excite the motor with a sine sweep. We’ve limited this to a frequency range of 150-300Hz, since typically, a linear motor operates at around 200Hz. We analyze the fundamental output of the accelerometer, and use post-processing steps to calculate the resonance frequency, f0 and the f1 and f2 (-3dB) values. Soundcheck also calculates the electrical impedance of the motor, as well as the electrical resonance, Zmax, Q and current at f0. We can also excite the motor with a single tone at f0 and use a Time Envelope of the recorded time waveform to calculate the motor’s Rise Time and Fall Time values.

So there you have it! With the addition of an accelerometer, you can use your audio measurement system to also measure the haptic feedback of your device. If you want to try it out, we have a free test sequence on our website that does exactly what I just demonstrated – check out the link in the video description!