2606B System SourceMeter® Instrument Reference Manual
Section 2: General operation
2606B-901-01 Rev. B / May 2018
2-37
Fundamental circuit configurations
The fundamental source-measure configurations for the 2606B are shown in the following figure.
When sourcing voltage, you can measure current or voltage (see A: Source V). When sourcing
current, you can measure voltage or current (see B: Source I). See
page 4-12) for detailed information.
Figure 22: Fundamental source-measure configurations
Operation considerations for the ADC
The following paragraphs discuss autozero and NPLC caching.
Autozero
The ADC of the 2606B uses a ratiometric A/D conversion technique. To ensure accuracy of readings,
the instrument must periodically obtain fresh measurements of its internal ground and voltage
reference. Separate reference and zero measurements are used for each aperture.
As summarized in the "Autozero settings" table, there are three different settings for autozero. By
default, the instrument automatically checks these reference measurements whenever a signal
measurement is made (AUTO). If the reference measurements are out of date when a signal
measurement is made, the instrument will automatically take two more A/D conversions, one for the
reference and one for the zero, before returning the result. Thus, occasionally, a measurement takes
longer than normal.
This extra time can cause problems in sweeps and other test sequences in which measurement
timing is critical. To avoid the extra time for the reference measurements in these situations, the OFF
selection can be used to disable the automatic reference measurements. Note that with automatic
reference measurements disabled, the instrument may gradually drift out of specification.