5.2. Measured UPS output voltage is lower than expectation
There are three tools to measure AC voltage, true RMS, average sensing digital meters and oscilloscope. Digital meters show the AC voltage is RMS (Root Mean Square), and it’s calculated after measurement. Both true RMS and average sensing meters show the same value for pure sine wave power. However, some UPS’s supply pure sine wave and some simulated sine wave output. For the UPS’s with simulated sine wave output, average sensing digital meters will show a significantly lower voltage.