Open/Shorted/Reverse Sense Lead Detection
The sense leads are part of the output's feedback path. Connect them in such a way so that they do
not inadvertently become open circuited. When an open sense lead is detected prior to output turn-on
or while the output is on, the instrument responds with a sense fault (SF) status indication on the front
panel. The response time is about 50 microseconds. You can use the Advanced Signal Routing
capability to turn this fault into an output protection feature. Otherwise, the power supply returns to
local sensing mode, with the voltage at the output terminals approximately 1% higher than the
programmed value. Once the sense wires are reconnected, instrument status and operation returns
to normal.
You can disable this feature if it creates objectionable disruptions at the DUT or if the lead
configuration or load dynamics cause the system to falsely trip.
Front Panel Menu Reference SCPI Command
Select Protect\SFD
Check Enable sense fault detection to enable; uncheck
to disable. Then press Select.
To enable/disable sense fault detection:
SENS:FAUL:STAT ON|OFF
Shorted sense leads are detected by the over-voltage protection function. This function is not
programmable and results in the output being disabled due to an over-voltage fault (OV).
Reversed sense leads are detected by the negative over-voltage protection function. This function is
not programmable and results in the output being disabled due to a negative over-voltage fault (OV-).
It is very important to make sure the sense wires are connected properly. This is
because the over-voltage protection cannot detect sense lead mis-wiring without
enabling the output, thereby briefly subjecting the load to unintended voltages.
Over-voltage Protection
Over-voltage protection (OVP) provides a configurable over-voltage protection based on sense lead
voltage. Having the OVP circuit monitor the sense lead voltage rather than the output terminal
voltage allows for more precise voltage monitoring directly at the load. Since incorrect sense wiring
could defeat this feature, there is also a backup local OVP function. Refer to Programming Output
Protection for further information.
The backup local OVP function tracks the programmed OVP setting and trips if the voltage at the + and
- output terminals rises more than 1V + 10% of the unit's voltage rating above the programmed OVP
setting.
Output Noise
Any noise picked up on the sense leads will appear at the output terminals and may adversely affect
CV load regulation. Twist the sense leads or use a ribbon cable to minimize the pickup of external
noise. In extremely noisy environments it may be necessary to shield the sense leads. Ground the
shield at the power supply end only; do not use the shield as one of the sensing conductors.
2 Installing the Instrument
74 Keysight N6900/N7900 Series Operating and Service Guide
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