5: Source-measure considerations 2470 High Voltage SourceMeter Instrument
5-2 2470-901-01 Rev. A / May 2019
Source current
When you configure the instrument to source current, the instrument functions as a high-impedance
current source that can limit voltage and can measure current or voltage.
As shown in the figure below, if you set the instrument to 2-wire sense, voltage is measured at the
FORCE HI and FORCE LO terminals of the instrument. If you set the instrument to 4-wire sense,
voltage is measured directly at the device under test using the sense terminals. Four-wire sense
eliminates any voltage drops that may be in the test leads or in the connections between the
instrument and the device under test.
Figure 88: Current source configuration
The current source does not use the sense leads to enhance current source accuracy. However, if
the instrument is in 4-wire sense, the instrument may reach limit levels if you disconnect the sense
leads. When 4-wire sense is selected, you must connect the sense leads. If the sense leads are not
connected, incorrect operation will result.
If you are sourcing and measuring the same function (for example, sourcing current and measuring
current), the measurement range is the same as the source range. This feature is valuable if you are
operating when the source limit has been exceeded. When the source limit has been exceeded, the
programmed source value is not reached. Thus, measuring the source lets you measure the actual
output level. You can also use the source readback function to measure the source. See
Source
readback (on page 4-44) for information.
You can set overvoltage protection if there is potential for disconnection of the sense leads. For more
information on overvoltage protection, see Overvoltage protection (on page 4-34
).
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