Module 2
Basic Measurement
2-32
Two SMUs can be operated in parallel.
The trick is to not use any SMU as COMMON.
HRSMU and MPSMU can only sink 100 mA.
Use GNDU (ground unit) or the chassis to sink the 200 mA of current. Chassis noise level will not
affect the measurement. There is a shorting bar in the back of the instrument which connects SMU
common to the chassis. The shorting bar must be connected as shown above. Use the connector on
the shorting bar to make an easy chassis connection to your circuit. The chassis connection is also
provided if you use a packaged part test fixture, such as the 16442A/B.
Note
The only time you would ever want to remove the shorting bar, is the case of floating the instrument
circuit common when using other instruments. An example might be a connection to a RF Network
Analyzer. You may want to remove chassis ground loops by connecting the circuit common directly
to the NWA chassis.
Note
Never use the chassis ground for low current measurements. It is noisy. Use the GNDU or an SMU
set to 0 volts or COMMON mode.
Note
If the GNDU is used, connect the 16493L GNDU cable between the GNDU and the test fixture. Do
not connect the triaxial cable. The GNDU is rated for up to 4.2 A, while the maximum current rating
of the triaxial cable is 1 A.
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