Atec Stanford-Research-Systems-SR785 - Manual (Page 2)

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 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 (dual 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
L
eq
are all available. Exponentially averaged sound power
(L
eq
) 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 L
eq
.
Swept-Sine Measurements
Swept-sine mode is ideal for signal analysis that involves high
dynamic range or wide frequency spans. Gain is optimized at
SR785 Dynamic Signal Analyzer
Stanford Research Systems phone: (408)744-9040
www.thinkSRS.com
Order map (top), tracked order (bottom)
Octave analysis
Narrow band FFT (top), wide band FFT (bottom)