Section 4: Theory of operation
Model 2651A High Power System SourceMeter® Instrument Reference Manual
4-14
2651A-901-01 Rev. A / March 2011
Basic circuit configurations
Source I
When configured to source current (I-source) as shown in the figure below, the High Power System
SourceMeter
®
Instrument functions as a high-impedance current source with voltage limit capability
and can measure current (I-meter) or voltage (V-meter).
For 2-wire local sensing, voltage is measured at the input/output terminals of the System
SourceMeter instrument. For 4-wire remote sensing, voltage is measured directly at the device under
test (DUT) using the sense terminals. This eliminates any voltage drops that may be in the test leads
or connections between the System SourceMeter instrument and the DUT.
The current source does not require or use the sense leads to enhance current source accuracy. With
4-wire remote sensing selected, the sense leads must be connected or incorrect operation will result.
Figure 77: Source I configuration
Remote
SENSE HI
IN/OUT HI
Remote
IN/OUT LO
I-source
x1
V-meter
SENSE LO
Local
Local
GUARD
+
–
I-meter
1
2
2
1
Feedback
NOTES: 1.
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 k
Ω
.
A
V
