Specifications

Since each supply can output
maximum of 50 A, it can
produce enough current for
B&K Precision's 8510 DC load
to draw at its maximum range
(0-120 A). A handful of shunt
resistors rated at 5 W 0.22 ΩJ
are connected in parallel and
are connected to a BNC-to-
binding post adapter. A larger
shunt can also be used to
simplify the same setup and
reduce the temperature from
heat dissipation. Since high
current will be drawn, it is
important to note here that
heavy gauge wires should be
used to connect the power
supplies to each other and to
the load. Connect the power
supply to the DC load and
shunt resistors as illustrated in
Figure 11. Connect the BNC
to binding post adapter into a
B&K Precision's 2542
oscilloscope. Follow the setup
below for the DC load and
oscilloscope.
DC Load Setup
1. Setup transient mode
with current levels from
0 A for 0.5 ms to 120 A
for 1000 ms in pulse
mode.
2. Set load to CC mode
3. Turn on input for a
short moment. Turn off
once oscilloscope setup
is complete.
Oscilloscope Setup
1. Set to single run.
2. Adjust trigger level
until waveform trace is
captured.
3. Adjust vertical and
horizontal scale and the
trigger level and run
once again.
4. Repeat steps 2 and 3
until a good sampled
trace is captured.
Results
Observe the trace on the
oscilloscope and compare it to
Figure 10. Use the scope's
cursors to approximate the
10% and 90 % mark.
Observe the steepest slope in
between the cursor lines. A
rough estimate can be made
by taking the difference of the
two cursor lines. Since this
setup tests a current transition
from 0 A to 120 A, slew rate
can be calculated by dividing
the change in current over the
11 of 17
Figure 10. Slew Rate Measurement Graph
Figure 11. Slew Rate Test Setup
Power supply
+ -
Power supply
+ -
Power supply
+ -
DC Load
Mode: CC
Transient: 0 A to 120 A
+ -
Oscilloscope
Mode: Single Trigger
Shunt
Resistance