It's not really a "special" type of meter, but it has to use the RMS (Root Mean Square) method of calculating voltage rather than calculating it from the peak voltage, which is much lower on a modified sine inverter. Inexpensive digital meters tend to use the peak calculation and thus give low readings on Modified Sine, while mid-better quality units use RMS. Old fashioned analog meters generally give accurate readings on Modified Sine.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL