The "C" version for the 2400 series offers a Contact Check function.
The Contact Check function detects measurement error due to excessive
resistance in the force or sense leads WHILE performing 4 wire
measurements.
It is important to note the contact check function does not apply
current to the Device Under Test (DUT). A pulse is sent to the Hi
source and Hi sense and to the Lo source and Lo Sense terminals. The
resistance is then compared to a trip point resistance value. The
Trip point is configurable for either 50 ohm, 22 ohm or 2.1 ohm. If
the resistance of the DUT connections is higher than the Trip point
resistance, it is considered an "open lead" and the microprocessor is
notified. This notification can be communicated to your test system
on the front panel, over the GPIB bus, or with the instrument's
digital I/O.
The primary benefit of the Contact Check feature is the ability to
verify good connections with the DUT before the measurement is made.
This allows avoidance of false product failures by detection of
contact fatigue, loose or broken connections, or relay
failures.