5790B
Operators Manual
4-28
Current Measurements with an A40, A40A, or Custom Current Shunt
Overview
The Fluke A40/A40A allows for relative ac/dc current transfer measurements
from 2.5 mA to 20 A with a frequency range of 10 Hz to 100 kHz. All connections
are made to INPUT 1 or the AUX Input using the special Fluke adapters noted in
the subsequent sections.
Connect an A40/A40A or Custom Shunt to INPUT 1
Use accessory 792A-7004 to connect the Fluke A40/A40A Current Shunts to
INPUT 1 and make current measurements, see Figure 4-4. The 792A-7004 has
an internal 90 Ω resistor for direct connection to the A40/A40A current shunts for
relative current measurements.
Note
The A40/A40A can only provide relative current measurements
relative to a reference input (either dc or ac). For direct absolute
current measurements, use a Fluke A40B.
90 Ω
A40
90 Ω
792A-7004
5790B
FM
Type
N
INPUT1
10 MΩ
AUX
Input
A45-4004
A40A output
Cable
1” Spacing
FF
M
UHF
A40A
hvi012.eps
Figure 4-4. Measuring Relative Current Using 792A-7004
If the uncertainty of the A40 or A40A shunt and the Product are insufficient for
your application, obtain better uncertainties by calibrating the A40/A40A Current
Shunt (with the 792A-7004 adapter) for ac/dc current difference together with the
Product as a system. This system calibration (where the Product/Shunt/Adapter
are calibrated as a system) can be done at our Fluke Electrical Laboratory. The
Fluke Laboratory does this system calibration at specific currents and
frequencies up to 30 kHz with uncertainties as low as 25 ppm. Since the 792A-
7004 Adapter is shunting part of the current, it must be sent in and characterized
with the A40 or A40A Current Shunts and the Product.
To use the INPUT 1 and the 792A-7004 the adapter, see Figure 4-4:
1. Connect the 792A-7004 adapter to the INPUT 1 Type "N" connector.
2. Connect a Model A40 (not A40A) Current Shunt to the adapter.
3. Push INPUT1 so that “INPUT 1” is shown in the upper corner of the display.
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