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The SR760 and SR770 are single-channel 100 kHz FFT spectrum analyzers
with a dynamic range of 90 dB and a real-time bandwidth of 100 kHz.
Additionally, the SR770 includes a low-distortion source which allows
you to measure the transfer functions of electronic and mechanical
systems. The speed and dynamic range of these instruments, coupled
with their flexibility and many analysis modes, makes them the ideal
choice for a variety of applications including acoustics, vibration,
noise measurement and general electronic use.
High Dynamic Range
The SR760 and SR770 have a dynamic range of 90 dB. This means that
for a full-scale input signal, the instruments have no spurious
responses larger than -90 dBc (1 part in 30,000). Even signals as
small as -114 dBc (1 part in 500,000) may be observed by using averaging.
The low front-end noise and low harmonic distortionof the SR760
and SR770 allow you to see signals that would be buried in the noise
of other analyzers.
Powerful Processing
The SR760 and SR770 use a pair of high-speed, 24-bit digital signal
processors (DSPs) to filter, heterodyne and transform sampled data
from its 16-bit analog-to-digital converter. This computing capability
allows the analyzers to operate at a real-time bandwidth of 100
kHz. In other words, the SR760 and SR770 process the input signal
with no dead time. Your measurements will be done in as little as
a tenth of the time of other analyzers, which typically have a real-time
bandwidth of about 10 kHz.
Easy To Use
The SR760 and SR770 are very easy to use. The simple, menu-oriented
interface logically groups related instrument functions. Context-sensitive
help is available for all keys and menus, and entire instrument
setups can be saved to disk and recalled with a single key stroke.
Spectrum Measurements
The spectrum, power spectral density, and input time record can
be displayed in a variety of convenient linear and logarithmic units
including Vp, Vrms, dBVp, dBVrms or user-defined engineering units
(EUs). The magnitude, phase and real and imaginary parts of complex
signals can all be displayed. Several window functions including
Hanning, Flat-Top, Uniform and Blackman-Harris can be chosen to
optimize in-band amplitude accuracy or minimize out-of-band side
lobes.
Octave Measurements
The SR760 and SR770 also compute both the 15 and 30 band 1/3 octave
spectra, commonly used in acoustics and noise measurement applications.
A-weighting compensation is available for octave measurements. Amplitudes
are computed for band -2 (630 mHz) through band 49 (80 kHz).
Triggering and Averaging
Flexible triggering and averaging modes let you see signals as
low as 114 dB below full scale. RMS averaging provides an excellent
estimate of the true signal and noise levels in the input signal,
while vector averaging can be used with a triggered input signal
to actually reduce the measured noise level. Both rms and vector
averaging can be performed exponentially, where the analyzer computes
a running average (weighting new data more heavily than older data),
or linearly, where the analyzer computes an equally weighted average
of a specified number of records. Triggering can be used to capture
transient events or to preserve spectral phase information. Both
internal and external triggering are available with adjustable pre-trigger
and post-trigger delays.
Synthesized Source
The SR770 includes a low-distortion (-80 dB), synthesized source
which can be used to make frequency response measurements. It generates
single frequency sine waves, two-tone signals for intermodulation
distortion (IMD) testing, pink and white noise for audio and electronic
applications, and frequency chirp for transfer function analysis.
This direct digital synthesis (DDS) source provides an output level
from 100 µV to 1 V, and delivers up to 50 mA of current.
Frequency Response Measurements
With its low-distortion DDS source, the SR770 is capable of performing
accurate frequency response measurements. The source is synchronized
with the insturment's input allowing transfer functions to be measured
with 0.05 dB precision. The SR770 measures the magnitude and phase
response of control systems, amplifiers, and electro-mechanical
systems and displays the resulting Bode plot.
Limit and Data Tables
Sometimes it is important to keep track of a few key portions of
a spectrum. Data tables allow up to 200 selected frequencies to
be displayed in tabular format. Automated entry makes it easy to
set up data tables for harmonic or sideband analysis. Convenient
limit tables allow the entry of up to 100 separate upper or lower
limit segments for pass-fail testing. On exceeding a limit, the
analyzers can be configured to generate a screen message, an audio
alarm, or a GPIB service request.
Analysis Modes
Three built-in analysis modes simplify common measurements. Harmonic
analysis computes both harmonic power and THD (Total Harmonic Distortion)
relative to a specified fundamental. Sideband analysis lets you
compute power in a set of sidebands relative to the carrier power.
And band analysis lets you easily integrate the power in a selected
frequency band. All three analysis modes provide clear, on-screen
markers which make it easy to pick out frequencies of special interest,
such as harmonics or sidebands.
Markers
The SR760 and SR770 have a marker that is designed to be fast,
responsive and flexible. The marker can be configured to read the
maximum, minimum or mean of a selected width of display, or can
be set to tracking mode to lock on to a moving peak. Delta-mode
readouts let you easily view frequency or amplitude differences
between two peaks. Automated peak-find lets you quickly move between
the peaks in a spectrum. And the markers for the upper and lower
displays can be linked to display similarities or differences in
the two spectra.
Math Functions
Data taken with the SR760 and SR770 can be processed with the built-in
trace calculator. Basic arithmetic functions such as addition, subtraction,
multiplication, division, square roots and logarithms can be performed
on traces. Traces can be combined with other on-screen traces, or
with traces stored on disks. These calculator functions are quite
useful for performing background subtraction or normalization of
data.
Flexible Storage and Output
All traces, data tables and limit tables can be stored using the
3.5" DOS disk drive. The drive uses standard DOS 1.44 Mbyte
disks (720 kbyte for SR760) which can be formatted on the analyzer
or on your PC. Data can be saved in a space-saving binary format,
or an easy-to-access ASCII format for off-line analysis. A variety
of hardcopy options let you easily print data from the instruments.
The screen can be dumped to a dot-matrix printer or a LaserJet compatible
laser printer via the standard rear-panel Centronics printer interface.
Complete limit and data tables, as well as a summary of the instrument
settings, can be printed. Data can be plotted to any HP-GL compatible
plotter with an RS-232 or GPIB interface.
Easy to Interface
All functions of the analyzers can be queried and set via the standard
RS-232 and GPIB interfaces. A comprehensive set of commands allows
complete control of your analyzer from a computer. Data can be quickly
transferred in binary format, or more conveniently in ASCII format.
The complete command list is available as a help screen in the instruments
for convenient reference while programming.
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