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6 Advanced Source and Measurement Functions
Dynamic Current Correction Control
NOTE
NOTE
172
This control is used when making dynamic current measurements; it is not
required for static (or dc) measurements. On Models N678xA SMU, N6753A -
N6756A, and N6763A - N6766A, the designs are such that dynamic current
correction is not needed and the control is therefore unavailable.
The DC Power Analyzer measures the output current across an
internal current monitor. For most power modules this current
monitor is located on the inboard side of the output capacitor.
current
monitor
current
For static (or dc) measurement applications this measurement
method yields accurate measurements. However, due to the output
capacitor C
, when there is a significant and rapid change in output
0
voltage, the additional output current does not all flow into load R
some of it flows through the output capacitor. In this momentary
situation the measurement circuit is not only measuring the output
current going into the load, but also the output current flowing
through the output capacitor. Since the load never sees the additional
current, this results in an inaccurate output current measurement.
When the output current is measured and averaged over a number of
samples as in the case of static measurements, the inaccuracy is
insignificant. However, because the DC Power Analyzer has built-in
scope and data logging functions, which can sample the output
current at up to about 50 kHz, this inaccuracy becomes evident.
Dynamic current correction compensates for the current flowing into
the output capacitor. The DC Power Analyzer calculates what the
additional current is and subtracts it from the current measurement,
thus providing accurate output current measurements. This feature is
turned on by default and only applies to the high current range.
Dynamic current correction increases the peak to peak noise in current
measurements on some power modules. It may also limit the measurement
bandwidth as explained in the next section. If either condition is a significant
factor in your application, you should turn dynamic current correction off.
To turn dynamic current correction on or off, press Scope View or
Data Logger , then press Properties . In the current range dropdown
box, select the range labeled "CComp On" to turn current correction
on. Un-select the "CComp On" range to turn current correction off.
+ output
output
load
capacitor
R
C
L
O
- output
Model N6705 User's Guide
;
L
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