Open Leads Detection - Tektronix Keithley 2281 Series Reference Manual

Section 2: General operation

Open leads detection

When using four-wire sense connections, a missing or faulty connection with Sense HI, Sense LO,
Output HI, or Output LO results in improperly regulated voltage and inaccurate voltage measurements.
The voltage readback shown on the front panel is not equal to the real output voltage. The open leads
clamp circuit can limit the output voltage between Output HI and Output LO to less than V
V = V + V
total set
Where V is the voltage setting.
set
V is introduced from a clamp circuit, typically less than 7 V. Without the clamp circuit, the
clamp
instrument could output its maximum voltage when the open lead occurs.
Example
1. Connect a 300 Ω resistor to the rear-panel mating connector. For details, refer to
connections
2. Set the voltage to 3 V and current limit to 1 A.
3. Turn on the output.
The following figure shows the voltage readback and output voltage when you make a correct
four-wire sense connection.
4. Power off the instrument and remove one of the test leads.
To avoid damage to the device under test (DUT), you must power off the instrument before
making any changes on the connections. Otherwise, it may damage the device under test
(DUT).
2-66
Model 2281S-20-6 DC Power Supply and Battery Simulator Reference Manual
clamp
(on page 2-64).
Figure 40: Correct four-wire connections
.
total
Four-wire sense
077114601 / March 2019