A square wave looks like two adjacent squares. One of the squares is above the zero volt line, the other is below it. As with a sine wave, for half of the cycle the voltage is positive, and for the other half of the cycle it is negative. Square-wave inverters can handle all heat devices, such as electric resistance heaters, and hair dryers. Modified or quasi sine-wave inverters will run almost any piece of equipment except those most sensitive to harmonics, such as laser printers and computers.
Harmonics are the amount of distortion or variation that occurs in a pure or perfect waveform.
Pure sine wave inverters produce an electric waveform that emulates the sine wave produced by a utility s electricity. Pure sine-wave inverters are typically used to run equipment that is very sensitive to harmonics. Contact the manufacturer to determine what tools and appliances their inverter can and cannot handle. Frequency and Voltage Equipment that is sensitive to the purity of the waveform is often sensitive to the inverter s ability to maintain a frequency of 60 cycles. Timing devices, such as clocks, are particularly affected by a change in frequency, and may also require voltage regulation.