Appendix A Specifications 295
7 / Digitizing Specifications
General Information
The 3458A supports three independent methods for signal digitizing. Each method is discussed below to aid in
selecting the appropriate setup best suited to your specific application.
Summary of Digitizing Capabilities
Standard DC Volts Digitizing (DCV Function)
DC Performance
0.005% of Reading + Offset
1
Maximum Sample Rate (See DCV for more data)
DCV Standard DCV function.
This mode of digitizing allows signal acquisition at rates from 0.2 readings / sec at
28 bits resolution to 100k readings / sec at 16 bits. Arbitrary sample apertures from
500 ns to 1 sec are selectable with 100 ns resolution. Input voltage ranges cover
100 mV to 1000 V full scale. Input bandwidth varies from 30 kHz to 150 kHz
depending on the measurement range.
DSDC Direct Sampling DC Coupled measurement technique.
DSAC Direct Sampling AC Coupled measurement technique.
In these modes the input is sampled through a track / hold with a fixed 2 ns aperture
which yields a 16 bit resolution result. The sample rate is selectable from 6000 sec
/ sample to 20 µs / sample with 100 ns resolution. Input voltage ranges cover 10
mV peak to 1000 V peak full scale. The input bandwidth is limited to 12 MHz.
SSDC Sub-Sampling ( Effective time sampling ) DC Coupled.
SSAC Sub-Sampling ( Effective time sampling ) AC Coupled.
These techniques implement synchronous sub-sampling of a repetitive input signal
through a track / hold with a 2 ns sample aperture which yields a 16 bit resolution
result. The effective sample rate is settable from 6000 sec / sample to 10 ns /
sample with 10 ns resolution. Sampled data can be time ordered by the instrument
and output to the GPIB. Input voltage ranges cover 10 mV peak to 1000 V peak full
scale. The input bandwidth is limited to 12 MHz.
Technique Function Input Bandwidth Best Accuracy Sample Rate
Standard DCV DC – 150 kHz 0.00005 – 0.01% 100 k/sec
Direct-sampled DSDC / DSAC DC – 12 MHz 0.02% 50 k/sec
Sub-sampled SSDC / SSAC DC – 12 MHz 0.02% 100 M / sec (effective)
Range
Input
Impedance
Offset
Voltage
1
Typical
Bandwidth
Settling Time
to 0.01% of Step
100 mV
>10
10
W
<5 µV 80 kHz 50 µs
1V
>10
10
W
<5 µV 150 kHz 20 µs
10 V
>10
10
W
<5 µV 150 kHz 20 µs
100 V 10 MW <500 µV 30 kHz 200 µs
1000 V 10 MW <500 µV 30 kHz 200 µs
Readings / sec Resolution Aperture
100 k 15 bits 0.8 µs
100 k 16 bits 1.4 µs
50 k 18 bits 6.0 µs
1. ±1° C of an AZERO or
within
24 hours and ±1°C of last
ACAL.
2. <125 ns variability between
multiple 3458As
Sample Timebase
Accuracy: 0.01 %
Jitter: < 100 ps rms
External Trigger
Latency: < 175 ns
2
Jitter: < 50 ns rms
Level Trigger
Latency: < 700 ns
Jitter: < 50 ns rms
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