Chapter Frequency Response Measurements With Logarithmic Resolution 1; Logarithmic Resolution In The Hp 3562A; The Log Resolution Preset Measurement; Single Decade Measurement - HP 3562A Operating Manual

3:
Chapter
Frequency Response Measurements with Logarithmic Resolution

Logarithmic Resolution in the HP 3562A

The Log Resolution Preset Measurement

Single Decade Measurement

Analysis via Display Selections

I ntroduction
Logarithmic resolution is a measurement technique which uses linear resolution FFT
measurements to create results similar to a log swept sine test. Linear resolution
points are combined, rather than redistributed, to produce frequency response or
power spectrum measurements with a true logarithmic frequency scale.
The key contribution of this technique is the combination of fast, high resolution FFT
analysis with the proportional resolution of a log sweep measurement. Further, when
applied to broad band testing of mechanical or electronic resonances, the log
resolution technique provides reduced measurement variance (compared to linear
resolution) and can save significant test time (when compared to log sweep tests with
equal resolution) .
Logarithmic Resolution in the H P 3562A
The Log Resolution mode in the HP 3562A provides 80-point-per-decade resolution
over one to five integer decades. Available start and stop frequencies and combina­
tions thereof are shown in Table 3-1. Frequency response magnitude and phase can
be measured using stationary (i.e., non-transient) stimuli such as random noise or
fixed sine signals from the built-in signal source. Input and output power spectra can
also be measured and observed. For complete analysis of results, measurements can
be manipulated with the built-in Waveform Math and Curve Fitting capabilities.
The following sections of this chapter introduce the basics of frequency response
measurements with the Log Resolution mode. T he 3-decade preset measurement
and a second 1-decade measurement, with averaging, will be shown.
Start Frequency Stop Frequencies
(in Hz) (inHz)
..
Table 3-/.
Log Resolution Start and Stop Frequencies
12
Frequency Response Measurements with Log arithmic Resolution
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