Keithley 2651A Reference Manual page 212

Model 2651A High Power System SourceMeter® Instrument Reference Manual
Source V
When configured to source voltage (V-source) as shown in the figure below, the High Power System
SourceMeter
and can measure current (I-meter) or voltage (V-meter).
Sense circuitry is used to monitor the output voltage continuously and make adjustments to the V-
source as needed. The V-meter senses the voltage at the input/output terminals (2-wire local sense)
or at the device under test (DUT) (4-wire remote sense using the sense terminals) and compares it to
the programmed voltage level. If the sensed level and the programmed value are not the same, the
V-source is adjusted accordingly. Remote sense eliminates the effect of voltage drops in the test
leads, ensuring that the exact programmed voltage appears at the DUT.
The voltage error feedback to the V-source is an analog function. The source error amplifier is used to
compensate for IR drop in the test leads.
V-source
Measure only (V or I)
The figure below shows the configurations for using the High Power System SourceMeter
exclusively as a voltmeter or ammeter. As shown in the figure, the instrument is configured to
measure voltage only by setting it to source 0 A and measure voltage.
2651A-901-01 Rev. A / March 2011
®
Instrument functions as a low-impedance voltage source with current limit capability,
Figure 78: Source V configuration
I-meter
A
+
Sense Output
-
Adjust V-Source
(Feedback)
NOTES: 1.
+
x1
–
Local
Remote
V
V-meter
Remote
Local
This represents a protection circuit that is very
high impedance until the voltage across it exceeds
approximately 3 V. Above 3 V, the protection turns
on and allows current to flow through it.
2. Approximately 13 kΩ.
Section 4: Theory of operation
GUARD
IN/OUT HI
1
2
SENSE HI
2
SENSE LO
1
IN/OUT LO
®
Instrument
4-15