Realtime sampling rate 2.5 MS/s and bandwidth of 200 kHz provide reliable waveform capture for common measurements. Works effectively with both periodic analog signals and aperiodic digital signals, offering versatile analysis in multiple scenarios. 138 PRO is a practical and costeffective MINI handheld oscilloscope designed for maintenance and education applications, delivering essential measurement capabilities in a compact form. Full trigger function including single, normal, and automatic modes enables controlled data capture and repeatable results. Use scenarios Field service and equipment maintenance: diagnose sensors, monitor power supplies, and troubleshoot compact automation components on site. Education and training: demonstrate waveform concepts and measure student projects in classroom labs. DIY electronics and embedded development: debug microcontroller PWM signals, observe digital transitions, and capture sporadic events.