Inverter putting out 98 volts
I'm using a power line cigarette lighter plugin style inverter for inside the cab, running my computer and periodically, for a 32 inch tv for tailgating. I have never checked the voltage until today ...
Forum Discussion
wa8yxm wrote:
I have both Peak and TRUE RMS meters (RMS is the area "under the curve" that is the area between the sine wave and the base line (0 volts) and that will be the same with your inverter as with mine (True Sine Wave)..
RMS is "root mean square" and is computed as the square root of the average (mean) of the square of the voltage (over time), rather than the average of the voltage over time. The latter is what average responding voltmeters measure, though they're usually calibrated to show RMS voltages for sine waves.
A good many multimeters are average responding as that's pretty easy to do electronically or electromechanically. The AC voltage is rectified and fed through an integrator (which, for an analog meter, may just be the meter mechanism itself). By contract, properly measuring RMS voltage is typically done by either measuring the power dissipation in a fixed resistance (typically thermally) or by sampling and digitizing the voltage and then computing it mathematically with a little computer (the standard approach today now that little computers are dirt cheap).
The reason RMS values are used, rather than peak or average voltages and currents, is that it allows the power equations for a resistive load to be the same for AC and DC: the power dissipated is computed as the current times the voltage, or the square of the current times the resistance, or the square of the voltage divided by the resistance. Similarly, Ohm's law continues to hold without needing additional fudge factors or resorting to calculus.
