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The SR785 Two-Channel Dynamic Signal Analyzer is a precision, full-featured
signal analyzer that offers state-of-the-art performance at a price
that's less than half that of competitive analyzers. Building on
its predecessor, the SR780, the SR785 incorporates new firmware
and hardware that make it the ideal instrument for analyzing both
mechanical and electrical systems. For measurements involving servo
systems, control systems, acoustics, vibration testing, modal analysis,
or machinery diagnostics, the SR785 has the features and specifications
to get the job done.
Standard measurement groups include FFT, order tracking, octave,
swept-sine, correlation, time capture, and time/histogram. The SR785
brings the power of several instruments to your application: a spectrum
analyzer, network analyzer, vibration analyzer, octave analyzer
and oscilloscope.
A unique measurement architecture allows the SR785 to function
as a typical dual-channel analyzer with measurements like cross
spectrum, frequency response, coherence, etc. Alternatively, the
instrument can be configured so that each input channel functions
as a single-channel analyzer with its own span, center frequency,
resolution and averaging. This allows you to view a wide-band spectrum
and simultaneously zoom in on spectral details. The same advanced
architecture provides storage of all measurement building blocks
and averaging modes. Vector averaged, rms averaged, unaveraged,
and peak hold versions of all measurements are simultaneously acquired
and can be displayed without re-taking data.
Averaging
The SR785 comes equipped with a wide selection of averaging techniques
to improve your signal-to-noise ratio. RMS averaging reduces signal
fluctuations, while vector averaging minimizes noise from synchronous
signals. Peak hold averaging is also available. Both linear and
exponential averaging are provided for each mode.
Because the SR785 is so fast, there's no need for a separate "fast
averaging" mode. For instance, in a full-span FFT measurement
with a 4 ms time record, 1000 averages take exactly 4 seconds, during
which the SR785 still operates at its maximum display rate.
For impact testing, the average preview feature allows each time
record or spectrum to be accepted or rejected before adding it to
the measurement.
Order Tracking
Order tracking is used to evaluate the behavior of rotating machinery.
Measurement data is displayed as a function of multiples of the
shaft frequency (orders), rather than absolute frequency. Combined
with a waterfall plot, the SR785 provides a complete history or
"order map" of your data as a function of time or rpm.
Using the slice feature, the amplitude profile of specific orders
in the map can be analyzed.
In tracked order mode, the intensity of individual orders vs. rpm
is measured. Unlike other analyzers, there's no need to track a
limited number of orders to ensure full speed measurements. The
SR785's speed allows simultaneous tracking of up to 400 orders.
Run-up and run-down measurements are available in both polar and
magnitude/phase formats. RPM profiling is provided to monitor variations
of rpm as a function of time. A complete selection of time and rpm
triggering modes is included, allowing you to make virtually any
rotating machinery measurement.
Octave Analysis
Real-time 1/1, 1/3 and 1/12 octave analysis, at frequencies up
to 40 kHz (single channel) or 20 kHz (two channel), is a standard
feature of the SR785. Octave analysis is fully compliant with ANSI
S1.11-1986 (Order 3, type 1-D) and IEC 225-1966. Switchable analog
A-weighting filters, as well as A, B and C weighting math functions,
are included. Averaging choices include exponential time averaging,
linear time averaging, peak hold, and equal confidence averaging.
Broadband sound level is measured and displayed as the last band
in the octave graph. Total power, impulse, peak hold and Leq
are all available. Exponentially averaged sound power (Leq)
is calculated according to ANSI S1.4-1983, Type 0.
Octave displays can be plotted as waterfalls with a fast 4 ms storage
interval. Once data is stored in the waterfall buffer, the SR785
can display centile exceedance statistics for each 1/1, 1/3 or 1/12
octave band, as well as for Leq.
Swept-Sine Measurements
Swept-sine mode is ideal for signal analysis that involves high
dynamic range or wide frequency spans. Gain is optimized at each
point in the measurement, producing up to 145 dB of dynamic range.
A frequency resolution of up to 2000 points is also provided. Auto-ranging
can be used with source auto-leveling to maintain a constant input
or output level at the device under test (to test response at a
specific amplitude, for instance).
Auto-resolution ensures the fastest possible sweeps and adjusts
the frequency steps in the scan based on the DUT's response. Phase
and amplitude changes that exceed user-defined thresholds are measured
with high frequency resolution, while small changes are measured
using wider frequency steps between points. A choice of linear sweeps
with high resolution, or logarithmic sweeps with up to eight decades
of frequency range, is provided.
Time/Histogram
The time/histogram measurement group is used to analyze time-domain
data. A histogram of the time data vs. signal amplitude is provided
for accurate time domain signal characterization. Statistical analysis
capabilities include both probability density function (PDF) and
cumulative density function (CDF). The sample rate, number of samples,
and number of bins can all be adjusted.
Time Capture
The SR785 comes with 8 Mbytes of memory (32 Mbytes optional). Analog
waveforms can be captured at sampling rates of 262 kHz or any binary
sub-multiple, allowing you to optimize sampling rate and storage
for any application. For example, 8 Msamples of memory will capture
32 seconds of time domain data at the maximum 262 kHz sample rate,
or about 9 hours of data at a 256 Hz sample rate. Once captured,
any portion of the signal can be played back in any of the SR785's
measurement groups except swept-sine. The convenient Auto-Pan feature
lets you display measurement results synchronously with the corresponding
portion of the capture buffer to identify important features.
Transducer Units
Automatic unit conversion makes translating transducer data easy.
Enter your transducer conversion directly in V/EU, EU/V or dB (1V/EU).
The SR785 will display the result in units of meters, inches, m/sec2,
in/sec2, m/s, in/s, mil, g, kg,
lbs., N, dynes, pascals or bars. Built-in ICP power is provided
for accelerometers. Acoustic measurement results can be displayed
in dBSPL, while electrical units include V, V2,
dBV and dBm.
Source
The SR785 comes with six precision source types: low-distortion
(-80 dBc) single or two-tone sine waves, white noise, pink noise,
chirp, and arbitrary waveforms. The chirp and noise sources can
be bursted to provide activity over a selected portion of the time
record for FFT measurements, or to provide impulse noise for acoustic
measurements. The digitally-synthesized source produces output levels
from 0.1 mV to 5 V plus DC offset from 0 to ±5 V, and delivers
up to 100 mA of current.
Arbitrary waveform capability is standard with the SR785. Use the
arbitrary source to playback a section of a captured waveform, play
a selected FFT time record, or upload your own custom waveform from
your computer.
User Math
Custom measurements can be created in each of the SR785's measurement
groups using the math menu. Enter any equation involving rms averaged,
vector averaged or unaveraged time or frequency data, stored files,
constants, or a rich array of supplied operations including arithmetic
functions, FFT, inverse FFT, jΩ, d/dΩ, exp, ln x
and many others. All of the averaging modes are available as user
math operands. Unlike many other analyzers, the SR785's measurement
rate is virtually unaffected when user math is selected. For instance,
the function exp(ln(conj(FFT2/FFT1))) can be calculated with a 100
kHz real-time bandwidth.
Waterfall
Waterfall plots are a convenient way of viewing a time history
of your data. Each successive measurement record is plotted along
the z-axis making it easy to see trends in the data. All FFT, octave
and order tracking measurements can be stored in the SR785's waterfall
buffer memory. You can choose to save all measurements and averaging
modes, or just the current measurement to conserve memory. Waterfall
traces can be stored every n time records for FFT and order
tracking measurements. For order tracking measurements, new records
can be acquired at a specific time interval or change in rpm. In
octave measurements, the storage interval is in seconds (as fast
as every 4 ms). While displaying waterfall plots, you can adjust
the skew angle to reveal important features, or change the baseline
threshold to eliminate low-level clutter. Any z-axis slice or x-axis
record can be saved to disk or displayed separately for analysis.
Analysis
The SR785 includes a wide variety of built-in analysis features.
Marker analysis lets you easily measure the power contained in harmonics,
sidebands or within a given band of frequencies. Important information
such as THD, THD+N, sideband power relative to a carrier, or total
integrated power are calculated in real time and displayed on the
screen. The front/back display feature allows you to display live
data from both signal inputs on one graph. You can also simultaneously
display saved traces and live data. The peak-find marker allows
you to quickly locate frequency peaks with the click of a button.
The marker statistics feature calculates the maximum, minimum, mean
and standard deviation of data in any section of the display. For
modal analysis, the cursor can be configured to display the resonant
frequency and damping of a single selected mode.
Data tables are used to display up to 100 selected data points
in tabular format. Limit tables allow you to define up to 100 upper
and lower limit segments in each display for GO/NO-GO testing. Data
and limit table definitions can also be saved to and recalled from
disk for quick setup.
Curve Fit and Synthesis
The SR785 has a 20-pole, 20-zero curve fitter that can fit frequency-domain
data from both the FFT and swept-sine measurement groups. Curve
models can be displayed in pole/zero, pole/residue and polynomial
formats. Synthesis reverses the process; enter a model in any of
the above formats and the SR785 synthesizes the required curve.
The curve-fit/synthesis menu allows you to change gain, delay and
frequency scale, set pole and zero locations, and instantly see
the response of the modeled system.
Output
The SR785's built-in 3.5" disk drive, computer interfaces
(GPIB and RS-232), and printer port provide flexibility when saving,
printing and exporting data. Data can be saved in binary or ASCII
formats and displays can be printed/plotted to any of the ports
or the disk drive. Supported formats include PCX, GIF, PCL (LaserJet
and DeskJet), dot-matrix, postscript and HP-GL. An annotation
editor lets you add text, time, date and filenames to any portion
of the plot.
DataViewer
The SRS DataViewer is a Windows®
program that allows you to upload SR785 files into a graphical environment,
perform simple editing and copy into other applications. You can
add pointers and text, change scaling, and perform simple math operations.
Graphs can be saved in PCX, BMP or GIF formats.
Data Conversion Utilities
The SR785 comes with a complete suite of data conversion utilities
for both Windows and DOSoperating systems. SR785 files
can be converted to ASCII for use with spreadsheets, or Universal
File Format (UFF) and HP SDF for use with modal analysis programs.
SR785 files can also be converted to MAT file format for use with
MATLAB. Conversion from external file types is also supported. Both
HP SDF and SR780 files can be converted to SR785 format.
Instrument Modes
FFT, Time/Histogram, Correlation, Octave, Swept-Sine, Order Tracking
Frequency Domain Measurements
Frequency Response, Linear Spectrum, Cross Spectrum, Power Spectrum,
Coherence, Power Spectral Density
Time Domain Measurements
Time Record, Cross-Correlation, Auto-Correlation, Orbit
Amplitude Domain Measurements
Histogram, PDF, CDF
FFT Resolution
100, 200, 400, 800 lines
Views
Linear Magnitude, Log Magnitude, dB Magnitude, Magnitude Squared,
Real Part, Imaginary Part, Phase, Unwrapped Phase, Nichols, Nyquist,
Polar
Units
V, V2, V2/Hz,
V/√Hz, meters, meters/s, meters/s2,
inches, inches/s, inches/s2, mils,
g, kg, lbs., N, dynes, pascals, bars, SPL, user-defined engineering
units (EUs)
Displays
Single, Dual, Front/Back Overlay, Waterfall with Skew, Zoom and
Pan, Grid On/Off
Marker Functions
Trace Marker, Dual-Trace Linked Marker, Absolute and Relative Marker,
Peak Find, Harmonic Marker, Band and Sideband Marker, Waterfall
Marker, Frequency-Damping Marker
Averaging
RMS, Vector, Peak Hold, Linear, Exponential, Equal Confidence (Octave),
Preview Time Record, Percent Overlap Averaging, Overload Reject
Triggering
Continuous, Internal, External (Analog or TTL), Source, Auto/Manual
Arming, GPIB, RPM Step, Time Step, Pre/Post Trigger Delay
Source Outputs
Sine, Two-Tone, Swept-Sine, White/Pink Noise, Burst Noise, Chirp,
Burst Chirp, and Arbitrary
Windows
Hanning, Blackman-Harris, Flat-Top, Kaiser, Force/Exponential, User-Defined,
+/-T/2, +/-T/4, T/2, Uniform
User Math
+, -, ×, /, Conjugate, Magnitude/Phase, Real/Imaginary, Sqrt,
FFT, Inverse FFT, jΩ, Log, Exp, d/dx, Group Delay,
A-, B-, C-Weighting, x/x-1, Trace 1 to 4, Vector Average,
RMS Average, Peak Hold
Analysis
Harmonic, Band, Sideband, THD, THD + N, Limit Test with Pass/Fail,
Data Table, Exceedance, Statistics, Curve Fit and Synthesis
Time Capture
Captures time data for later analysis (FFT or Octave). Up to 2 Msamples
(8 Msamples optional) of data can be saved.
Storage
3.5", 1.44 Mbyte DOS formatted disk. Save data, setups and
hard copy data.
Hard Copy and Interfaces
Print to Dot Matrix or PCL (LaserJet and DeskJet) printers. Plot
to HP-GL or Postscript plotters. Print/Plot on-line (RS-232 serial,
Centronics parallel or IEEE-488.2) or to disk file. EPS, GIF, PCX
graphic formats also available for disk storage.
Data Conversion Utility
Data, waterfall and capture files can be converted to ASCII. Data
files can also be converted to Universal File Format, SDF format
or MATLAB MAT-File Format. SDF and SR780 files can be converted
to SR785 format.
DataViewer
Windows based graphics program for viewing SR785 files.
Graphs can be pasted to the clipboard or saved in PCX, BMP or GIF.
SR785 and Agilent 35670A Comparison
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