Twilight DT4200, Инструкция по эксплуатации

Страница: 75 / 80

Appx.
1
Appendix
Appx. 1 RMS and Average
Difference between the RMS and Average
When converting AC to RMS, 2 methods are available, “True
RMS method (True RMS indication)” and “Average method
(Average rectifying RMS indication)”.
In the case of the sine wave where no skew is included, the same
values are indicated in both methods. However, if the waveform
is skewed, a difference occurs between the 2 methods.
The true RMS method is applied to this instrument.
In the true RMS method, the high frequency component is also
included and displayed.
In the average method, the input waveform is handled as a
sine wave where no skew is included (only single frequency).
The average of the AC signal is obtained, converted to the
RMS, and then displayed. If the waveform is skewed, a greater
measurement error occurs.
Measurement example True RMS Average rectifying
100 V sine wave 100 V 100 V
100 V square wave 100 V 111 V
Vm=Vavg=Vrms Vavg Vrms
t
V(t)
Vm
V(t)
t
T T
Sine wave
Vm: Maximum value, Vavg: Average value, Vrms: RMS, T: Time period
Square wave