HP 54522A - Page 258

Specifications and Characteristics
Operating Characteristics
Effective Resolution The maximum sample rate and the number of
bits in an oscilloscope’s digitizer are too often used for comparing
oscilloscopes. These specifications, however, do not describe
performance under dynamic signal conditions. Effective Resolution is a
figure of merit that describes the digitizing oscilloscope’s performance
under dynamic conditions, and is measured using the sinewave curve fit
test. This method considers:
e Quantization error
e Non-linearities (including preamp and ADC)
e System noise
e Frequency of input signal
All of these affect the effective resolution of the instrument. Some
manufacturers specify effective bits using half-scale sinewaves. While the
effective bits performance using half-scale testing is overstated when
compared to full-scale testing, Hewlett-Packard publishes both sets of
numbers for the oscilloscope so that, when comparing effective bits
performance between digitizing oscilloscopes, a fair comparison can be made.
The oscilloscope’s typical performance for a single acquisition is shown below:
Frequency 50kHz 1MHz 20MHz 50MHz 100MHz 250MHz 500MHz
Full scale 75 74 6.6 5.8 5.8 5.2 5.2
Halfscale 7.6 74 7.0 6.5 65 5.8 55
For more information about effective resolution, please contact your
Hewlett-Packard sales office, and ask for Product Note 5180A-2, Dynamic
Performance Testing of A to D Converters, (pub # 02-5952-7629).
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