Section 4: Sourcing and measuring
2470 High Voltage SourceMeter Instrument Reference Manual
4-10
2470-901-01 Rev. A /
May
2019
Four-wire remote sense connections
Using 4-wire remote sense connections provides the most accurate low resistance, voltage source,
and measurement accuracy. Specified accuracies for instrument source and measurement
capabilities are only guaranteed when you use 4-wire remote sensing.
By default, the 2470 instruments are configured to use 2-wire or local voltage sensing. If you choose
to enable 4-wire or remote voltage sensing, it is critical that you establish and maintain the proper
Kelvin connections between the corresponding force and sense leads to ensure the proper operation
of the instrument and to make accurate voltage measurements. Sense HI must be connected to
Force HI, and Sense LO must be connected to Force LO.
When sourcing voltage with remote sense, the instrument relies on the voltage detected with the
sense lines to provide the proper closed-loop control of its output voltage. If a sense line becomes
disconnected from its corresponding force line, an erroneous voltage is sensed and the output
voltage may be adjusted to a level that is radically different than the programmed voltage level
(possibly to hazardous levels, depending on the model).
When sourcing current with remote sense, the instrument relies on the voltage detected with the
sense lines to properly limit the voltage across the device-under-test. If a sense line becomes
disconnected from its corresponding force line, an erroneous voltage is sensed and the voltage
across the device may exceed the programmed source limit voltage, possibly causing damage to the
device or test fixture.
In both cases, the voltage is not measured correctly if a sense lead becomes disconnected from its
corresponding force lead.
Even with the overvoltage protection set to the lowest value (20 V), never touch anything
connected to the terminals of the 2470 when the
instrument
is on. Always assume that a
hazardous voltage (greater than 30 V
RMS
) is present when the
instrument
is on. To prevent
damage to the device under test or external circuitry, do not set the voltage source to levels
that exceed the value that is set for overvoltage protection.
To prevent unexpected voltages caused by a sense lead that becomes disconnected from its
corresponding force lead during remote sense operation, you can enable overvoltage protection
(OVP) to restrict the maximum output voltage level of the instrument when either voltage or current is
sourced. With OVP enabled, the voltage between the Force HI and the Force LO terminals will not
exceed the specified overvoltage limit value regardless of the voltage present on the sense leads.
(on page 4-34) for additional information.
To make 4-wire measurements, you must set the sense mode of the instrument to 4-wire, as
described in the following topics.
