4: Sourcing and measuring 2470 High Voltage SourceMeter Instrument Reference
4-42 2470-901-01 Rev. A / May 2019
Determining upper limits when automatic measurement range is used
For resistance measurements, you can define the upper limit that can be selected when the
measurement range is set automatically. For voltage and current measurements, you can retrieve the
value of the upper limit.
Using a remote interface:
SCPI commands: Refer to [:SENSe[1]]:<function>:RANGe:AUTO:ULIMit (on page 12-52
).
TSP commands: Refer to smu.measure.autorangehigh (on page 14-111).
Automatic reference measurements
To ensure the accuracy of readings, the instrument must periodically get new measurements of its
internal ground and voltage reference. The time interval between updates to these reference
measurements is determined by the integration aperture that is being used for measurements. The
2470 uses separate reference and zero measurements for each aperture.
By default, the instrument automatically checks the reference measurements whenever a signal
measurement is made. If the reference measurements have expired when a signal measurement is
made, the instrument automatically makes two more readings, one for the internal ground and one for
the voltage reference, before returning the result. This can cause some measurements to take longer
than normal.
This additional time can cause problems in sweeps and other test sequences in which measurement
timing is critical. To avoid the time that is needed for the reference measurements, you can disable
the automatic reference measurements.
When automatic reference measurements are turned off, the instrument may gradually drift out of
specification. To prevent inaccurate readings, you can use autozero once to update the autozero
information.
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