Keysight Technologies 3458A Guide D'utilisation page 201

DCV Digitizing
Digitizing can be done simply by specifying DC voltage measurements with a
short integration time and a short interval between samples ("short" relative to the
frequency of the signal being digitized). This is considered digitizing although the
multimeter's track-and-hold circuit is not used. The advantages of DCV digitizing
over direct-sampling (discussed later) are a lower noise level, higher resolution
(up to 28 bits), and a maximum sampling rate of 100,000 samples per second
(versus 50,000 for direct-sampling). The disadvantages of DCV digitizing are a
greater amount of trigger jitter (see the
page 409), the inability to AC-couple the input signal, and a lower bandwidth
input path of 150 kHz (vs. 12 MHz for direct- or sub-sampling). Since the
track-and-hold circuit is not used for DCV digitizing, each sample is much wider
(a minimum of 500 nanoseconds versus 2 nanoseconds for direct- or
sub-sampling).
The PRESET DIG command configures the multimeter for DC voltage
measurements with a sampling rate of 50,000 samples per second. PRESET DIG
selects a 3 µs integration time and level triggering when the input signal crosses
zero volts on its positive slope. The primary commands executed by PRESET DIG
are:
TARM HOLD -- Suspends triggering
TRIG LEVEL -- LEVEL trigger event
LEVEL 0,AC -- Level trigger at 0% of range (0 V), AC-coupled
TIMER 20E-6 -- 20 µs interval between samples
NRDGS 256,TIMER -- 256 samples per trigger, TIMER sample event
DCV 10 -- DC voltage measurements, 10 V range
DELAY 0 -- No delay
APER 3E-6 -- 3 µs integration time
MFORMAT SINT -- Single integer memory format
OFORMAT SINT -- Single integer output format
AZERO OFF -- Disables the autozero function
DISP OFF -- Disables the display
After executing PRESET DIG, you can increase the sampling rate by decreasing
the TIMER interval and by reducing the integration time using the APER
command. The minimum integration time for DCV is 500 nanoseconds.
Keysight 3458A User's Guide
"Appendix A: Specifications"
Digitizing 5
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