Digitize Functions; Digitize Measurements - Keithley 2461 Reference Manual

Model 2461 Interactive SourceMeter® Instrument Reference Manual

Digitize functions

The Model 2461 digitize functions make fast, predictably spaced measurements. The speed,
sensitivity, and bandwidth of the digitize functions allows you to make accurate voltage and current
readings of fast signals, such as those associated with sensors, audio, medical devices, power line
issues, and industrial processes. The digitize functions can provide 1,000,000 readings per second at
4½ digits. Digitize voltage and digitize current have separate internal signal paths that are optimized
for fast response to signal changes.
The sample rate determines how often the readings are output by the digitize function. You can set it
from 1000 to 1,000,000 readings per second.
The aperture determines the reading conversion time. This is when data is gathered to create the
reading. You set the aperture time in 1 µs intervals. If the aperture is more than 1 µs, the consecutive
1 µs readings are averaged to produce the reading.
The sample rate affects the available aperture settings. The maximum aperture is determined by
1/sample rate (rounded down to the nearest integer). The instrument will automatically adjust the
aperture setting if the sample rate is changed to a rate that does not support the existing aperture
setting. When this occurs, a warning message is generated that reports the new aperture setting.
The count is the number of times to make readings with the selected sample rate and aperture after a
trigger is detected. In continuous mode, the instrument generates automatic triggers. In manual
mode, a trigger is defined by pushing the TRIGGER key on the front panel. You can also set up other
types of triggers. For more information on triggers, refer to
If you are using the TSP command language, the commands use a different syntax for measure and
digitize commands. For example, command to change the measure function range is:
smu.measure.range = 100
The command to change the digitize range is:
smu.digitize.range = 100
Digitize voltage and digitize current support the same ranges as DC voltage (7.35 V to 105 V) and DC
current (1.05 A to 7.35 A). Digitize functions do not support autorange, autozero, or auto delay.

Digitize measurements

The digitize current and voltage functions make accurate, predictably spaced current and voltage
measurements.
Do not apply more than 105 V
result in instrument damage.
2461-901-01 A/November 2015
between INPUT HI and LO. Failure to observe this caution may
peak
Section 2: General operation
Triggering (on page 3-99).
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