Power Calculations; High Capacitance Operation; Enabling The High Capacitance Feature - Keithley 2450 Reference Manual

Model 2450 Interactive SourceMeter® Instrument Reference Manual

Power calculations

Power readings are calculated from the measured current and voltage as follows:
Where:
P is the calculated power
V is the measured voltage
I is the measured current

High capacitance operation

The Model 2450 high capacitance feature can prevent problems when you are measuring low current
and driving a capacitive load. In this situation, you may see overshoot, ringing, and instability. This
occurs because the pole formed by the load capacitance and the current range resistor can cause a
phase shift in the voltage-control loop of the instrument.
The actual operating conditions for a given capacitive load can vary. This is due to the large dynamic
range of the current measurement capability and wide range of internal resistors in the instrument.
Some test applications require capacitors larger than 100 nF. In these applications, you can use the
high-capacitance feature to minimize overshoot, ringing, and instability.

Enabling the high capacitance feature

Before enabling high-capacitance mode, note the following:
•
Test the DUT and the capacitor to determine the best current limit and range of output voltages.
•
The settling times can vary based on the DUT. It is important to test the limits of the DUT before
you use high-capacitance mode.
•
Failure to test the DUT for the appropriate current limit and output voltages can result in damage
to or destruction of the DUT.
•
For optimal performance, do not continuously switch between normal mode and high-capacitance
mode.
•
Before you charge the capacitor, start with 0 (zero) voltage across the capacitor.
•
When high-capacitance mode is enabled, a minimum load capacitance of 100 nF is
recommended. In the absence of this minimum load capacitance, overshoot and ringing may
occur.
Using the front panel:
1. Press the MENU key.
2. Under Source, select Settings.
3. Next to High Capacitance, select On.
4. Select HOME to return to the operating display.
2450-901-01 Rev. B/September 2013
Section 4: Source-measure considerations
4-21