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Measurement Considerations
F-9
To minimize the effects of dielectric absorption on current measurements, avoid applying
voltages greater than a few volts to insulators being used for sensitive current measurements. In
cases where this practice is unavoidable, it may take minutes or even hours in some cases for
the current caused by dielectric absorption to dissipate.
Voltage burden
The input resistance of the ammeter causes a small voltage drop across the input terminals.
This voltage is known as the voltage burden. If the voltage burden is large in relation to the
voltage of the measured circuit, then signi
fi
cant measurement errors will occur.
Refer to Figure F-3 to see how voltage burden affects current measurements. Assume V
S
is
set to output 5mV and R
L
is 5k
Ω
. An ideal ammeter with zero voltage burden would measure
the current source as follows:
I
M
= V
S
/R
S
= 5mV/5k
Ω
= 1
In practice however, every ammeter has a voltage burden. If the voltage burden (V
B
) is lmV,
the current will be measured as follows:
I
M
= (V
S
+
V
B
)
/ R
S
= (5mV + 1mV) / 5k
Ω
= 1.2
The lmV voltage burden caused a 20% measurement error. The voltage burden of Model
6430 is <1mV.
R
L
I
L
= <1mV
6430
I
M
V
S
V
B
I
M
=
V
S
–
V
B
R
L
Figure F-3
Voltage burden
Содержание 6430
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Страница 78: ...2 14 Connections ...
Страница 98: ...3 20 Basic Source Measure Operation ...
Страница 138: ...5 30 Source Measure Concepts ...
Страница 156: ...6 18 Range Digits Speed and Filters ...
Страница 168: ...7 12 Relative and Math ...
Страница 176: ...8 8 Data Store ...
Страница 202: ...9 26 Sweep Operation ...
Страница 248: ...11 22 Limit Testing ...
Страница 310: ...16 6 SCPI Signal Oriented Measurement Commands ...
Страница 418: ...17 108 SCPI Command Reference ...
Страница 450: ...18 32 Performance Verification ...
Страница 477: ...A Specifications ...
Страница 489: ...B StatusandErrorMessages ...
Страница 498: ...B 10 Status and Error Messages ...
Страница 499: ...C DataFlow ...
Страница 503: ...D IEEE 488BusOverview ...
Страница 518: ...D 16 IEEE 488 Bus Overview ...
Страница 519: ...E IEEE 488andSCPI ConformanceInformation ...
Страница 523: ...F MeasurementConsiderations ...
Страница 539: ...G GPIB488 1Protocol ...
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