1-6
IM 253710-01E
• Umn, Imn (rectified mean value calibrated to the rms value)
This function rectifies one period of the voltage or current signal, determines the
average, and multiplies the result by a coefficient. The coefficient is the number
that when applied to a sinusoidal input signal, gives the true rms value. When the
input signal is a distorted or is a DC waveform, these values will differ from the true
rms values. Let f(t) represent the input signal as a function of time and let T be the
period of the signal.
Umn or Imn =
π
2
2
•
1
T
0
T
f(t) dt
• Udc, Idc (simple average)
These are the average values over one period of the voltage and current signal.
This function is useful when determining the average value of a DC input signal or
a DC component that is superimposed on an AC input signal.
Udc or Idc =
1
T
0
T
f(t)
dt
• Uac, Iac (AC component)
These are the AC components of the voltage and current. They are the rms values
of the difference of the square of the true rms values of the input signal and the
square of the DC component.
Uac =
Urms
2
– Udc
2
, or Iac =
Irms
2
– Idc
2
Element number
When an input module is installed in a slot that is located on the rear side of the main
unit, the slot combined with the input module is referred to as an element. The main
unit can contain up to four elements which are numbered from one to four. On power
measurement modules, one voltage and current pair can be input to each element.
The element number is appended to the symbols that were defined in the earlier
section, “Measurement function on each power measurement module” so that the
correspondence can be seen. For example, “Urms1” represents the true rms value of
the voltage of element 1.
Wiring method
The wiring method is the method by which the signals that are input to each element
are combined. Different selections are possible depending on the number of
elements that have power measurement modules installed. In some cases, only one
type of wiring method can be selected, while in other cases, two types of wiring
methods can be selected. When two types of wiring methods are selected, “A” or “B”
is appended to the symbols that were defined in the earlier section “Measurement
function of the average or sum of multiple measurement modules
(
Σ
function)” so that
the correspondence can be seen.
For example, “Urms
Σ
A” represents the true rms value of the average of the voltage of
the power measurement modules that are combined using wiring method A.
Efficiency
The
η
(efficiency 1) is determined by (P
Σ
B)/(P
Σ
A), and 1/
η
(efficiency 2) is determined
by (P
Σ
A)/(P
Σ
B).
η
is the efficiency of wiring B with respect to wiring A. 1/
η
is the
efficiency of wiring A with respect to wiring B.
1.2 Measurement Modes and Measurement/Computation Periods