How Do I Make Low-Current Measurements; Low-Current Connections - Keithley 2601 User Manual

Appendix B: Frequently Asked Questions

How do I make low-current measurements?

Reference

Low-current connections

Low-current measurements (<1μA) are subject to errors caused by leakage currents and leakage
resistances in the signal path For that reason, Model 2635 and 2636 SourceMeters 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 B-7
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
both a guard shield and a safety shield, which is necessary when hazardous voltages are used.
The inner shield (guard) of the HI triax cable is connected to the test fixture guard shield, and the
outer cable shield (chassis ground) is connected to the safety shield.
Figure B-7
Model 2635/2636 low-current connections
B-10
See Section 3 for more connection information, and Section 12 of the Series 2600
Reference Manual for command details.
shows typical connections for low-current measurements. The DUT in this example
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Series 2600 System SourceMeter
2600S-900-01 Rev. C / January 2008
®
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