tireman9 Report post Posted July 7, 2018 I have a small Husky 750Watt "modified sine wave"inverter I use to occasionally run AC powered items. The AC items do not seem to be putting out their full power. Using a small digital multi-meter the inverter output shows 91V with load or no-load. Checking with a small AC analog gauge that I use to check the voltage at outlets in the RV when plugged into shore power the Inverter shows 128 V with no-load. Is the low reading to be expected as the meters are giving the RMS value? Share this post Link to post Share on other sites
kaypsmith Report post Posted July 7, 2018 Most Digital meters are designed to read PSW (pure sine wave), your inverter as you stated is MSW, therefore the analog will read the higher voltage as opposed to the digital. MSW is also referred to as square wave because of the abrupt change from positive to negative or vice versa. Some devices do not work well with MSW, thus showing degradation in performance, or in some cases will not work at all. The picture notes in red "True sine wave", because it represents a US standard grid, PSW in inverters is as close to this as can be produced electronically. Share this post Link to post Share on other sites
dickandlois Report post Posted July 8, 2018 Good Graphics Kay ! One can see the difference the Modified wave affect has on a 120 volt AC Clock. It sees the abrupt transitions as 4 pulses instead of 2 and that makes them run fast. Like one hour equals 2 when running on a modified sine wave. Older equipment does run fine,( except timing equipment) but with a lower RMS Present things can run a little slower, fans are a good example. RMS = Root Means Squared. Rich. Share this post Link to post Share on other sites
