In this study, an Arduino controller is used to build a low-cost data acquisition (DAQ) sensing device with a sampling frequency of up to 50 kHz. The utility power signal captured through the Arduino controller is converted into digital data, which are then transmitted through a WiFi module to an Android mobile device so that mobile devices can display the signal waveform and power quality information. Using a discrete Fourier series (DFS) filtering algorithm, noise and high harmonics are filtered out, and then a zero-crossing algorithm is applied to accurately calculate the fundamental frequency of the power signal. Since the power signal is an AC signal with high voltage, we designed a voltage step-down circuit for signal preprocessing to adjust the signal level to the standard level accepted by the Arduino controller. Research confirms that we can design a portable power signal acquisition device to view signal waveforms using an Android app and calculate the frequency variation of power signals. Additionally, the power signal data can also be conveniently transmitted to a cloud server to record and analyze unusual power events.