YOKOGAWA DL850E, Руководство пользователя

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2-16
IM DL850E-01EN
RMS Measurement
When the selected channel belongs to the 701267 (HV (with RMS)), you can observe the RMS values of the
input signal.
AC-RMS
Use this setting when you only want to observe the RMS values of the input signal without the DC component.
Example
When you measure the RMS values of a 2 Vpeak sine wave, an approximately 1.4 VDC signal appears, as
shown in the figure on the right.
2 V
peak
Approx. 1.4 V
RMS values are calculated using the following equation.
u(t)
2
dt
1
T
0
T
u(t): Input signal, T: One cycle of the input signal
Given u(t) = Vmsinωt (where Vm is the peak value and ω is the angular velocity of 2πf, with f being the
frequency of the sine wave signal), the RMS value Vrms is:
V
rms
=
Average of u(t)
2
over one cycle
=
=
1
2π
0
2π
(V
m
sinwt)
2
dwt
V
m
2
As shown in the example above, if Vm is 2 V, the RMS value Vrms is approximately 1.4 V.
DC-RMS
Use this setting when you want to observe the RMS values of the entire signal, including both the DC and AC
components.
Example
When you measure the RMS values of a 2 Vpeak sine wave with a 1 VDC component superimposed on it, an
approximately 1.7 VDC signal appears, as shown in the figure on the right.
Approx. 1.7 V
2 V
peak
+ 1 V
dc
Given DC component Vdc and AC component u(t) = Vmsinωt, the RMS value Vrms (+ DC) of a sine wave
signal with a DC component superimposed on it is:
V
rms
(+DC) = =
1
2π
0
2π
(V
m
sinwt + V
dc
)
2
dwt
V
m
2
2
+ (V
dc
)
2
As shown in the example above, if Vdc is 1 V and Vm is 2 V, the RMS value Vrms (+DC) is approximately 1.7 V.
In RMS measurement mode, when a signal with an AC component below 40 Hz is acquired, because of the
characteristics of the RMS circuit, a ripple component is displayed, and the RMS values are not displayed
properly. DC signals are measured properly.
2 Vertical Axis