Keithley 2601A, User Manual, Page: 87 / 94

2600AS-900-01 Rev. B / September 2008 Return to Section Topics A-9
Series 2600A System SourceMeter
®
Instruments User’s Manual Appendix A: Frequently Asked Questions
Figure A-6
Model 2635A/2636A contact check connections
How do I make low-current measurements?
Low-current connections
Low-current measurements (<1
μ
A) are subject to errors caused by leakage currents and leakage
resistances in the signal path For that reason, Models 2635A and 2636A are equipped with triax
connectors to minimize these problems. To assure accurate low-level measurements, the integrity
of the signal path must be maintained to the DUT, including using both low-noise triax cables and a
suitable test fixture.
Figure A-7 shows typical connections for low-current measurements. The DUT in this example
could be a low-current semiconductor device, a high-megohm resistor, or any other passive or
active electronic device requiring low-current measurements. Note that the DUT is enclosed in
smua.reset() -- Restore defaults.
smua.contact.speed = smua.CONTACT_FAST -- Set speed to fast.
smua.contact.threshold = 10 -- Set threshold to 10W.
if (not smua.contact.check()) then
--One/both contact resistances are not
--below the programmed threshold.
smua.contact.speed = smua.CONTACT_SLOW
rhi, rlo = smua.contact.r()
print(rhi, rlo)
exit()
end
--
--
--
--
--
--
Check contacts against threshold.
Set speed to slow.
Get resistance readings.
Return contact resistances to the
host.
Terminate execution.
smua.source.output = smua.OUTPUT_ON -- Turn on output and continue.
CHANNEL A
SENSE
LO LO
GUARD
SENSE
HI HI
Sense LO
LO
KEITHLEY Model 2635A/2636A
HI
Sense HI
DUT
R
S
R
S
R
S
R
S
R
C
R
C
R
C
R
C
Cable/Relay
Resistance
Contact
Resistance
Triax
Cables
Center
Conductors
Inner
Shield
Center
Conductor