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load voltage e
is 250 V or more, the effect on the measurement accuracy is less than 0.1 %. In
L
summary, when measuring low voltage and large current, it is recommended to use the wiring method
of the figure above; when measuring high voltage and small current, it is recommended to use the
wiring method of the figure below.
Effects of Leakage Capacitance
Each measurement channel of the Analyzer is isolated from each other. However, these isolated
channels still have a leakage capacitance C
capacitance of the instrument itself, the isolation capacitance of the power adapter, and the anti-
interference capacitance inside the instrument. In general, the test object of the Analyzer has a higher
voltage relative to the earth, and we call this voltage common mode voltage V
voltage can generate a current i
certain impact on the measurement results of the Analyzer.
As shown in
Figure
A3, during voltage measurement, the current i
circuit through R
, R
s+
measurement and R
in
measurement voltage is:
the power supply under measurement R
terminal (black terminal) of the measurement circuit.
Figure A3. Effects of Leakage Current on Voltage Measurement
During current measurement, the current i
resistance of the test resistance and the common terminal of the measurement circuit R
voltage, that is coupled into the measurement circuit. The effect on the measurement
ΔI
[
(
=
i
R
current:
cs
Shunt
can cause measurement errors.
through the leakage capacitance C
cs
and R
. R
and R
s-
in
s+
is the test internal resistance of the power analyzer. The effect on the
ΔU
[
=
i
R
//(R
cs
S-
s-
Rs+
U
Rs-
Ics
cs
) R
⁄
]
+
R
, the voltage drop of i
S-
Shunt
relative to the earth, which consists of the distributed
s
are internal resistances of the power supply under
s-
)
]
+
R
. Because R
S+
in
has the main impact. R
Rin
2M Ohm
Cs
Vcom
∆U= Ics[Rs-//(Rs+ + Rin)]
flows through the test resistance R
cs
Power Analyzers
. The common mode
com
. This current i
s
cs
is coupled to the measurement
cs
is larger, internal resistance of
in
is connected to the common
s-
, and the internal
shunt
in R
and internal resistance R
Shunt
Appendix A
will have a
and forms a
s-
s -
81
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