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2 Installing the Instrument
Model
S
resistor
Model
S
resistor
protect
protect
PV8921A, PV8922A
198 kΩ
PV8931A, PV8932A
198 kΩ
If the remote sense wires open during normal CV operation (with output current present), the change
in output voltage at the load will depend on the load current and the load wire resistances involved.
When the sense leads open, the unit automatically reverts to local sensing. The voltage at the previous
remote sense point (usually at the load) will change by an amount given by the following equation:
Δ V= K(V
) - I
x (total resistance of load leads)
set
out
K = 1% for 1 kV models, 1.2% for 1.5 kV models, and 1.65% for 2 kV models
I
= positive when the unit sourcing current; negative when the unit is sinking current
out
Shorted sense leads are detected by the over-voltage protection function. This function 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 results in the output being disabled due to a negative
over-voltage fault (OV). Refer to
Additional Load Considerations
for information about lead inductance
when using remote sensing with load capacitance and lead inductance.
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.
Note that due to the voltage drop in the load leads, the voltage at the output of the power supply could
be higher than the voltage being regulated at the load. The voltage at the output terminals of the
power supply should never exceed the unit's voltage rating.
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 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.
Keysight PV8900 Series Operating and Service Guide
67
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