Stanford Research Systems SR770 Data Sheet

· DC to 100 kHz bandwidth

· 90 dB dynamic range

· Low-distortion synthesized source
(SR770)

· Harmonic, band & sideband analysis

· 100 kHz real-time bandwidth

· Hardcopy output to printers and
plotters

· 3.5" DOS compatible disk drive

· GPIB and RS-232 interfaces

· SR760 ... $4950

(U.S. list)

· SR770 ... $6500 (U.S. list)

Stanford Research Systems phone: [phone]

www.thinkSRS.com

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. The SR770 additionally
includes a low-distortion, synthesized source allowing 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 distortion allow you to see signals that are 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. These
DSPs can perform 25 million, 24-bit multiplications and
additions each second. This enormous computing capability
allows the analyzers to operate at a real-time bandwidth of
100 kHz. In other words, the SR760 and SR770 process the

SR760/SR770 FFT Spectrum Analyzers

FFT Spectrum Analyzers

SR760 and SR770  100 kHz, single-channel FFT spectrum analyzers

www.thinkSRS.com

Available from:

Thurlby Thandar Instruments Ltd. Glebe Road, Huntingdon, Cambs.
PE29 7DR U.K. Tel: [phone] e-mail:[e-mail]

Web: www.tti-test.com or www.tti.co.uk

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 real-time bandwidths of about 10 kHz.

Easy To Use

The SR760 and SR770 are easy to use. The simple, menu­oriented 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 keystroke.

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 user­defined 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
sidelobes.

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.

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).

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, two­tone signals for intermodulation distortion (IMD) testing, pink
and white noise for audio and electronic applications, and
frequency chirps 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

SR760 and SR770 FFT Spectrum Analyzers

Stanford Research Systems phone: [phone]

www.thinkSRS.com

Spectrum analysis

Octave analysis

Transfer function (magnitude and phase)

source is synchronized with the instrument'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. The SR760's and SR770's data tables allow up
to 200 selected frequencies to be displayed in a tabular format

which can be printed or saved to disk. 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

SR760 and SR770 FFT Spectrum Analyzers

Stanford Research Systems phone: [phone]

www.thinkSRS.com

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 easily 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" disk drive. The drive uses standard DOS 1.44 Mbyte
disks which can be formatted on the analyzer or on your
personal computer. 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 view
data from the instruments. The screen can be dumped to a dot­matrix 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. Plotter output is available 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.

Limit and data tables

Harmonic distortion

Frequency

Measurement range 476 µHz to 100 kHz
Spans 191 mHz to 100 kHz in a binary

sequence

Center frequency Anywhere within the 0 to 100 kHz

measurement range
Accuracy 25 ppm from 20 °C to 40 °C
Resolution Span/400
Window functions Blackman-Harris, Hanning, Flat-Top

and Uniform
Real-time bandwidth 100 kHz

Signal Input

Number of channels 1
Input Single-ended or differential
Input impedance 1 MΩ, 15 pF
Coupling AC or DC
CMRR (at 1 kHz) 90 dB (input range < −6 dBV)

80 dB (input range <14 dBV)

50 dB (input range ≥14 dBV)
Noise

Typical 5 nVrms/√Hz at 1 kHz

(−166 dBVrms/√Hz)

Maximum 10 nVrms/√Hz

(−160 dBVrms/√Hz)

Amplitude

Full-scale input range −60 dBV (1.0 mVp) to +34 dBV

(50 Vp) in 2 dB steps
Dynamic range 90 dB (typ.)
Harmonic distortion No greater than −90 dB from DC to

50 kHz, no greater than −80 dB to

100 kHz (input range 0 dBV)
Spurious No greater than −85 dB below full

scale below 200 Hz. No greater than

−90 dB below full scale to 100 kHz.

(input range −50 dBV)
Input sampling 16-bit A/D at 256 kHz
Accuracy ±0.2 dB ± 0.005 % of full scale

(excluding windowing effects)
Averaging RMS, Vector and Peak Hold. Linear

and exponential averaging up to

64k scans.

Trigger Input

Modes Continuous, internal, external, TTL
Internal level Adjustable to ±100 % of input

scale. Positive or negative slope.
Min. trigger amplitude 10 % of input range
External level ±5 V in 40 mV steps. Positive or

negative slope, 10 kΩ impedance

Min. trigger amplitude 100 mV

SR760 and SR770 Specifications

Stanford Research Systems phone: [phone]

www.thinkSRS.com

External TTL Requires TTL level (low <0.7 V,

high >2 V)

Post-trigger Measurement record is delayed by

1 to 65,000 samples (1/512 to
127 time records) after the trigger.
Delay resolution is 1 sample
(1/512 of a record).

Pre-trigger Measurement record starts up to

51.953 ms prior to the trigger. Delay
resolution is 3.9062 ms.

Phase indeterminacy <2°

Display Functions

Display Real, imaginary, magnitude or phase
Measurements Spectrum, power spectral density,

time record and 1/3 octave

Analysis Band, sideband, total harmonic

distortion and trace math

Graphic expand Display expand up to ×50 about any

point
Harmonic marker Displays up to 400 harmonics
Data tables Lists Y values of up to 200 points
Limit tables Detects data exceeding up to 100

user-defined upper and lower limit

trace segments.

Source (SR770 only)

Amplitude range 0.1 mVp to 1.0 Vp
Amplitude resolution 1 mVp (output >100 mVp),

0.1 mVp (output <100 mVp)

DC offset <10.0 mV (typ.)
Output impedance <5 Ω, 50 mA peak output current

Sine Source

Frequency range DC to 100 kHz
Resolution 15.26 mHz
Amplitude accuracy ±1 % (0.09 dB) of setting
Spectral purity (Harmonics and sub-harmonics)

−80 dBc, f <10 kHz

−70 dBc, f >10 kHz

(Spurious)

< −100 dB full scale

Two-Tone Source

Frequency range DC to 100 kHz
Resolution 15.26 mHz
Amplitude accuracy ±1 % (0.09 dB) of setting
Spectral purity (Harmonics and sub-harmonics)

−80 dBc (f <10 kHz)

−70 dBc (f >10 kHz)

(Spurious)

< −100 dB full scale

White Noise Source

Frequency range DC to 100 kHz (all spans)
Flatness <1.0 dBpp (rms averaged spectra)

Pink Noise Source

Frequency range DC to 100 kHz (all spans)
Flatness <4.0 dBpp (using 1/3 oct. analysis)

Chirp Source

Output Equal amplitude sine waves at each

frequency bin of the current span.

Flatness <0.05 dBpp (typ.)

<0.2 dBpp (max.)

Phase AutoPhase function calibrates to

current phase spectrum.

General

Monitor Monochrome CRT. 640H by 480V

resolution. Adjustable brightness
and position.

Interfaces IEEE-488.2, RS-232 and Printer

interfaces standard. An XT
keyboard input is provided for
additional flexibility.

SR760 and SR770 Specifications

Stanford Research Systems phone: [phone]

www.thinkSRS.com

Hardcopy Screen dumps and table and setting

listings to dot matrix and LaserJet

compatible printers. Data plots to

HP-GL compatible plotters (RS-232

or IEEE-488.2).
Disk 3.5" DOS compatible format,

1.44 Mbyte (720 kbyte for the

SR760) capacity. Stores data and

instrument configurations.
Power 60 W, 100/120/220/240 VAC,

50/60 Hz
Dimensions 17" × 6.25" × 18.5" (WHD)
Weight 36 lbs.
Warranty One year parts and labor on defects

in materials and workmanship

Ordering Information

SR760 FFT spectrum analyzer $4950
SR770 FFT spectrum analyzer w/source $6500
O760H Carrying handle $100
O760RM Rack mount kit $85
CT100 SRS instrument cart $850

SR760 and SR770 rear panel

Available from:

Thurlby Thandar Instruments Ltd. Glebe Road, Huntingdon, Cambs.
PE29 7DR U.K. Tel: [phone] e-mail:[e-mail]

Web: www.tti-test.com or www.tti.co.uk