Model 4200A-SCS Source-Measure Unit (SMU) User's Manual
Section 2: Connections and configuration
4200A-SMU-900-01 Rev. A December 2020
2-21
The Keithley Instruments
Low Level Measurements Handbook
provides an in-depth discussion on
guarding and other techniques that are useful for building quality test fixtures. See the Learning
Center on your 4200A-SCS for a copy of the
Handbook
.
The 4200A-SCS functions on all current ranges and up to ±20 V without the interlock being asserted.
Testing with more than ±20 V
Asserting the interlock allows the SMU and preamplifier terminals to become hazardous,
exposing the user to possible electrical shock that could result in personal injury or death.
SMU and preamplifier terminals should be considered hazardous even if the outputs are
programmed to be low voltage. Precautions must be taken to prevent a shock hazard by
surrounding the test device and any unprotected leads (wiring) with double insulation that is
rated for 250 V, Category O.
If voltages greater than ±20 V are required for testing, follow these practices:
•
Add an interlock switch to the fixture to ensure that hazardous voltages are not present when the
exterior enclosure of the test fixture is open.
The 4200A-SCS voltage output is higher when the exterior enclosure of the test fixture is closed.
•
Connect the exterior enclosure to COMMON or safety ground using #16 AWG wire or greater.
•
Ensure that the wiring (FORCE, GUARD, and SENSE) within the fixture does not electrically
contact the exterior enclosure.
Recommended connecting cables
To ensure accurate, reliable connections, use only quality, low-noise triaxial cables such as those
supplied with the SMU (4200-MTRX-
X
) and preamplifier (4200-TRX-
X
) for all source-measure signal
connections.
For optimum measurement accuracy, noise immunity, and settling time, keep cables as short
as possible.
