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Theory of Operation
Overall Functional Description
4
4-9
4-12. Description of the In-Guard Lines
The following list describes the 11 5725A in-guard lines:
• B-RCL
High-quality analog line from the 5725A which carries critical signals to be
measured by the 5700A adc during either 5725A calibration or 5725A self
diagnostics. During calibration, these signals are ICAL (output of the current
calibration amplifier), HVSENSE (DC output of the sense amplifier during dc gain
ac characterization), AC/AC (buffered output of the 5725A thermal rms sensor that
does frequency characterization).
• B-OUT HI
High voltage output from the 5725A step-up transformers, to be routed to either the
5700A front or rear panel terminals.
• B-SENSE HI
High voltage sense line from the 5700A output terminals. This signal is then
attenuated -100:1 by the High Voltage Sense assembly.
• BOOST IN
During normal 5725A ac operation, carries the 5700A DAC outputs, which in turn
drives either the High Voltage Amplifier or Current Amplifier. During 5725A
calibration, BOOST IN drives the High Voltage Sense assembly with up to -260V
from the 5700A Power Amplifier.
• B-CURRENT
Analog line that carries the current high output from the 5700A. When the user sets
the current output location to "5725A" in a 5700A menu, this signal is routed to the
5725A binding posts. Under this operating condition, all 5700A/5725A current
ranges are available from the same binding posts. Line B-CURRENT carries up to
2.2A in normal operation. During current calibration, this line carries 1.3A to
measure the value of the 0.02Ω 5725A current shunt.
• B-IRTN
Current return for B-CURRENT; carries up to 2.2A. Line B-IRTN eventually ties to
the same node as SCOM on the 5700A.
• B-IGRD
Current guard voltage from the 5700A; enables internal guarding within the 5725A
only.
• B-VGRD
5700A guard. Enables discrete guarding/shielding within the 5725A.
• B-PACOM
System common from the 5700A. Once inside the 5725A, it becomes VCOM,
HVCOM, DCOM, and KCOM. B-PACOM is the current return for signals from the
5700A, including source current for driving the 5725A in the ac voltage function.
Current output from the 5700A, when "5725A" is selected as the current output
location, returns via B-IRTN.
• B-SENSE LO
High quality ground from the 5700A that is the reference point for the 5700A DAC
and Oscillator assemblies.