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Dynamic Current Measurement Control
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 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.
For static (or dc) measurement applications this measurement method yields accurate
measurements. However, due to the output capacitor C0, when there is a significant and rapid change
in output voltage, the additional output current does not all flow into load RL; 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, with the power analyzer's scope and data
logging functions, which capture thousands of measurement samples per second, this inaccuracy
becomes evident.
Dynamic current correction compensates for the current flowing into the output capacitor. The 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.
Keysight N6705C User's Guide
6 Advanced Source, Measurement, and Control
223
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