wa8yxm wrote:
BFL13 wrote:
If the inverter is MSW your ordinary voltmeter will read 97 or so it varies. You need a fancy meter (RMS something) to get the "real" voltage.
If the inverter is PSW then it should read the full 120, same as shore power.
I will second that. The fancy meter is called a "True RMS Meter" Rms means "Root, Mean, Square. and if you were to look at the curve of the power output on a scope it is the area "under" the curve (Between the line of power and the base or zero line)
All very confusing but many meters are "Peak reading" and due to the Flat Top of the Modified wave... The peak is lower for the same area.
virtually all analog meters as you point out are peak responding, RMS calibrated for a 50-60 Hz pure sine wave. any other signal gives you pretty inacurate results, like trying to measure a MSW inverter output.
While I have a couple of old simpson analog meters, most of the time I dig out my digital meter. more rugged, less likely to be damaged.
With the advent of decent low cost RMS converter circuits with bandwidth at least into the 10's of KHZ making a digital meter than is RMS responding, RMS calibrated is pretty easy to do and gives accurate enough results for most power line measurements RV'rs need to make.
Many also have features like min/max/average with a 1ms or so sampling window that will allow you to capture pretty narrow pulses and a delta function that will let you see change vs baseline.
But there are still cases where I like to look at a signal with an analog meter.
