Source Voltage - Keithley 2450 Reference Manual

Model 2450 Interactive SourceMeter® Instrument Reference Manual Section 4: Source-measure considerations

Source voltage

When you configure the instrument to source voltage, it functions like a low-impedance voltage
source that can limit current. The instrument can measure current or voltage. This configuration is
shown in the figure below.
Sense circuitry continuously monitors the output voltage and makes adjustments to the voltage
source as needed. The voltmeter senses the voltage and compares it to the programmed voltage
level. If the sensed level and the programmed value are not the same, the source voltage is adjusted
accordingly.
If you set the instrument to 2-wire sense, the voltmeter senses the voltage at the FORCE HI and
FORCE LO terminals. If it is set to 4-wire sense, the voltmeter sense the voltage at the device under
test. Four-wire sense eliminates the effect of voltage drops in the test leads, ensuring that the exact
programmed voltage is applied to the device under test.
If you are sourcing and measuring the same function (for example, sourcing voltage and measuring
voltage), the measurement range is the same as the source range. You can use this feature when
operating when source limits have been exceeded. When the source limits have been exceeded, the
programmed source value is not reached. Thus, measuring the source lets you measure the actual
output level. You can also use the source readback function to measure the actual output level. See
Source readback (on page 2-110) for information.
Figure 108: Voltage source configuration
2450-901-01 Rev. B/September 2013 4-3