Fluke NORMA 6003, User Manual, Page: 95 / 98

Power Analyzer
Appendix
89
How to Make More Accurate Measurements
Measurement Error Caused by the Channel Resistance
By wiring a circuit to match the load, you can minimize the effects of power loss on measurement
accuracy. The wiring of the source and load is discussed in this section.
Connect the voltage measurement circuit near the load (as shown in
Appendix Figure 1
). The current
measurement circuit measures the sum of i
L
and i
V
. i
L
(desired current) is the current flowing through
the load of the circuit under measurement, and i
V
(error current) is the current flowing through the
voltage measurement circuit. Because the current flowing through the circuit under measurement is i
L
,
only i
V
reduces measurement accuracy. The input resistance of the voltage measurement circuit of
the Analyzer is approximately 2 MΩ. If the input voltage is 1000 V, i
V
is approximately 0.5 mA (1000
V/2 MΩ). Only when the load current i
L
is 0.5 A or more, the effect of i
V
on the measurement accuracy
is 0.1% or less.
Connect the voltage measurement circuit near the source (as shown in
Appendix Figure 2
). The
voltage measurement circuit measures the sum of e
L
and e
I
. e
L
(desired voltage) is the load voltage,
and e
I
(error voltage) is the voltage drop across the current measurement circuit. The input resistance
of the current measurement circuit of the Analyzer, I Rin is approximately 0.025Ω. If the input current
is 10A, the effect of e
I
on the measurement accuracy i s approximately 0.25V (10A×0.025Ω). Only