User`s guide

Agilent 16440A User’s Guide, Edition 4 5
User's Guide
Operation
The following figure shows a simple circuit diagram of the selector (selector
expander).
The CH 1 and CH 3 circuits are different from the CH 2 and CH 4 circuits. Each
channel has one mechanical relay for SMU and one mechanical relay for PGU, but
the CH 1 and CH 3 circuits also have a semiconductor relay for PGU. The relays are
controlled by the 4155/4156 via the control circuit.
The semiconductor relay is useful when you need to perform a lot of switching (for
example, read/write tests of flash ROM) because the semiconductor relay is more
durable than mechanical relays.
CH 1 and CH 3 can have four switching states: all open, SMU on, PGU on, and
PGU open. CH 2 and CH 4 can have three switching states: all open, SMU on, and
PGU on.