YOKOGAWA 701210, Руководство пользователя, Страница: 50 / 747

2-12
IM 701210-05E
2.2 Setting the Horizontal and Vertical Axes
RMS Measurement <Section 5.15>
If the module of the selected channel is a High-Voltage 100 kS/s, 16-Bit Isolation Module
(with RMS), the rms value of the input signal can be observed.
AC-RMS
This setting is used when you want to observe only the rms values of the AC signal,
eliminating the DC components from the input signal.
Example
When the rms value of a 2-V
peak
sinusoid input signal is measured, a DC waveform at
approximately 1.4 V is displayed (see right figure).
2V
peak
Approx. 1.4 V
The rms value is derived from the following equation:
u(t)
2
dt
1
T
0
T
Where u(t) is the input signal and T is one period of the input signal.
If u(t) = V
m
sin
ω
t (where V
m
is the peak value and
ω
is the angular velocity (= 2
π
f, where f
is the frequency of the sinusoid signal)), the rms value, V
rms
, is derived from
V
rms
=
The average of u(t)
2
over one cycle
= =
1
2
π
0
(V
m
sinwt)
2
dwt
V
m
2
2
π
As in the above example, when V
m
is 2 V, the rms value, V
rms
, is approximately 1.4 V.
DC-RMS
This setting is used when you want to observe the rms values of both the DC and AC
components of the input signal.
Example
When the rms value of a 2-V
peak
sinusoid input signal riding on top of a 1-V DC component
is measured, a DC waveform at approximately 1.7 V is displayed (see right figure).
2V
peak
+1V
dc
Approx. 1.7 V
If the DC component is expressed as V
dc
and the AC component as u(t) = V
m
sin
ω
t, the
rms value, V
rms
(+DC), of the sinusoid input signal riding on top of the DC component is
derived from the following equation:
V
rms(+DC)
= =
1
2
π
0
(V
m
sinwt+V
dc
)
2
dwt
V
m
2
2
+ (V
dc
)
2
2
π
As in the above example, when V
dc
is 1 V and V
m
is 2 V, the rms value, V
rms
(+DC), is
approximately 1.7 V.