Current Assembly (A7) - Fluke 5520A Service Manual

5520A
Service Manual
The dual-channel DDS (Direct Digital Synthesizer) generates finely stepped digital
waveforms that take the form of sine, triangular, and other waveforms.

2-5. Current Assembly (A7)

The Current assembly outputs six current ranges (330 A, 3.3 mA, 33 mA, 330 mA, 3 A,
and 20 A) and three voltage ranges (330 mV, 3.3 V, and 5V) to the AUX outputs. The
20 A outputs are sourced through the 20 A AUX binding posts.
The Current assembly works together with the DDS (A6) assembly. The Filter (A12)
assembly provides the high current power supplies.
The Current assembly (A7) contains the following blocks:
Operating power for the Current assembly is filtered by the Filter assembly (A12). Its
common is separated from SCOM by a shunt resistor.
Figure 2-4 is a block diagram of the current function. Note that the DDS assembly works
together with the Current assembly to generate current outputs.
IDAC
Ref
±
SCOM
2-6
A floating supply.
Several stages of transconductance amplifier.
Current-sensing shunts and shunt amplifier. (These are the accuracy-setting
elements.)
AUX voltage function.
DDS Assembly (A6)
IDAC Error
Amp
dc
ac
Figure 2-4. Current Function (AUX Out Ranges)
ac
DDS
Ch 1
dc
AC
Converter

Current Assembly (A7)

Current
Amp
SCOM
Shunt
SCOM
Amp
Shunt
ICOM
SCOM
AUX HI
AUX LO
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