There are some very useful USB oscilloscope add-ons for computers, about $65. Plenty accurate enough for taking a look at your incoming ac power. They can record on your computer screen Hz and voltage excursions.
After that, it depends on how clean and robust you want your power to be. The PS Audio Generators rectify and filter the incoming ac. Then it has precision inverters to rebuild the 50/60 Hz to very precise % with virtually no noise. It produces a very exact sine wave at 110/120 vac that doesn’t budge at all with your load. Clean, noise-free, unwavering ac voltage, sine wave, current, and frequency. Even if your power line goes down to 20 vac, 45 Hz, with lots of noise, you’re going to get 120 vac/ 60 Hz clean to your load.
After that, it depends on how clean and robust you want your power to be. The PS Audio Generators rectify and filter the incoming ac. Then it has precision inverters to rebuild the 50/60 Hz to very precise % with virtually no noise. It produces a very exact sine wave at 110/120 vac that doesn’t budge at all with your load. Clean, noise-free, unwavering ac voltage, sine wave, current, and frequency. Even if your power line goes down to 20 vac, 45 Hz, with lots of noise, you’re going to get 120 vac/ 60 Hz clean to your load.