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6 Advanced Source and Measurement Functions
160
tracking enabled, the negative voltage limit tracks the positive voltage
limit setting. With tracking disabled, you can set different values for
the positive and negative voltage limits.
The following figure shows the current priority operating locus of the
power modules. The area in the white quadrants shows the output as
a source (sourcing power). The area in the shaded quadrants shows
the output as a load (sinking power).
+V limit
OC
-1 A /
-3 A
− Voltage
-V limit
operation
applies to
N6784A
only
Key
Sourcing power
Sinking power
Programmable
The heavy solid line illustrates the locus of possible operating points
as a function of the output load. As shown by the vertical portion of
the line, the output current remains regulated at its programmed
setting as long as the output voltage remains within the positive or
negative voltage limit setting. A CC (constant current) status flag
indicates when the output voltage is within the limit settings.
If the output voltage reaches either the positive or negative voltage
limit, the unit no longer operates in constant current mode and the
output current is no longer held constant. Instead, the power supply
will now regulate the output voltage at its voltage limit setting. Either
a VL+ (positive voltage limit) or VL− (negative voltage limit) status
flag is set to indicate that either the positive or negative voltage limit
has been reached.
As shown by the horizontal portions of the load line, when the unit is
sinking power, the output current may continue to increase in the
positive or negative direction as more current is forced into the unit.
Once the current is exceeds 12% of the rated current of the range
(1.12 A on the 1 A range; 3.36 A on the 3 A range), the output will
shut down, the output relays will open, and the OC and PROT status
bits will be set.
+ Voltage
+20 V /
+6 V
I setting
-20 V /
-6 V
Model N6705 User's Guide
+ Current
+1 A /
+3 A
OC
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