Keithley 2651A Reference Manual page 56

Section 2: General operation
I
Sense selection
Front panel sense selection
To select sensing mode:
1. Press the CONFIG key, and then press the MEAS key. Choose V-MEAS, and then press the
ENTER key or the navigation wheel
2. Select SENSE-MODE, then press the ENTER key.
3. Select 2-WIRE or 4-WIRE, as desired, and then press the ENTER key or the navigation wheel
.
Remote sense selection
Use the smua.sense command to control sense selection by remote. The programming example
below illustrates how to enable 4-wire sensing:
smua.sense = smua.SENSE_REMOTE
See Remote source-measure procedure
details.
Remote ohms programming
The following paragraphs summarize basic commands necessary for remote ohms programming and
also give a programming example for a typical ohms measurement situation.
2-34
Model 2651A High Power System SourceMeter® Instrument Reference Manual
Figure 9: 4-wire resistance sensing
Model 2651A
Input/Output HI
4-wire Sense HI
V
M
4-wire Sense LO
Input/Output LO
Because sense current is negligible,
and measured resistance =
R
R
Lead
V
M
Resistances
R
R
I
= Current sourced by SourceMeter
V = Voltage measured by SourceMeter
M
V
= Voltage across resistor
R
.
(on page 2-25) and
Test Current (I)
LEAD
Sense Current (pA)
LEAD
V R
R S
LEAD
LEAD
V = V
M R
V V
M = R
R
=
S
I
I
Remote Commands (on page 5-1) for
2651A-901-01 Rev. A / March 2011
Resistance
Under Test