SR760 and SR770 FFT Spectrum Analyzers
- DC to 100 kHz bandwidth
- 90 dB dynamic range
- 16-bit A/D conversion
- Low distortion synthesized source (SR770)
- Harmonic, band and sideband analysis
- 100 kHz real time bandwidth
- Internal and external triggering
- Linear and exponential averaging
- Hardcopy output to printers and plotters
- 3.5 inch MS-DOS compatible disk drive
- GPIB and RS-232 interfaces included
The SR760 and SR770 are single channel, 100 kHz FFT Spectrum Analyzerswith a dynamic range of 90 dB and a real-time bandwidth of 100 kHz. TheSR770 additionally includes a low distortion synthesized source allowingyou to measure the transfer functions of electronic and mechanicalsystems. The speed and dynamic range of these instruments, coupled withtheir flexibility and many analysis modes, make them the ideal choice fora variety of applications including acoustics, vibration, noisemeasurement, and general electronic use.
High Dynamic Range
The SR760 and SR770 have a true dynamic range of 90 dB. This means thatfor a full scale input signal the instruments have no spurious responseslarger 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 endnoise and low harmonic distortion allow you to see signals that are buriedin the noise of other analyzers.
At the Speed Limit
The SR760 and SR770 use a pair of high-speed 24-bit digital signalprocessors (DSP's) to filter, heterodyne, and transform sampled data fromits 16-bit analog-to-digital converter. These DSP's can perform 25 million24-bit multiplications and additions each second. This enormous computingcapability allows the analyzers to operate at a real-time bandwidth of 100kHz. Iin other words, the SR760 and SR770 process the input signal with nodead time. Your measurements will be done in as little as a tenth of thetime of other analyzers, which may typically have real time bandwidths ofonly 10 kHz.
Easy To Use
The enormous power of the SR760 and SR770 does not come at the expense ofease of use. The simple menu-oriented interface logically groups relatedinstrument functions. Context-sensitive help is available for all keys andmenus., and entire instrument setups can be saved to disk and recalled in a single keystroke.
The spectrum, power spectral density, and input time record can bedisplayed in a variety of convenient linear and logarithmic unitsincluding Volts, Vrms, dBV, dBVrms, or user-defined 'Engineering Units'(EU's). The magnitude, phase, and real and imaginary parts of complexsignals can all be displayed. Several window functions including Hanning,flattop, uniform, or Blackman-Harris can be chosen to optimize in-bandamplitude accuracy or minimize out-of-band sidelobes.
The SR760 also computes both the 15 and 30 band 1/3 octave spectracommonly used in acoustics and noise measurement applications. A-weightingcompensation is available for octave measurements. Amplitudes are computedfor band -2 (630 mHz) through band 49 (80 kHz).
Triggering and Averaging
Flexible triggering and averaging modes let you see signals as low as 114dB below full scale. RMS averaging provides an excellent estimate of thetrue signal and noise levels in the input signal, while vector averagingcan be used with a triggered input signal to actually reduce the measurednoise level. Both RMS and vector averaging can be performed exponentially,where the analyzer computes a running average (weighting new data moreheavily than older data), or linearly, where the analyzer computes anequally weighted average of a specified number of records. Triggering canbe used to capture transient events or to preserve spectral phaseinformation. Both internal and external triggering are available withadjustable pre and post-trigger delays.
The SR770 includes a very low distortion (-80 dB) synthesized source whichcan be used to make frequency response measurements. It generates singlefrequency sine waves, two-tone signals for intermodulation distortion(IMD) testing, pink and white noise for audio and electronic applications,and frequency chirps for transfer function analysis. This direct digitalsynthesis (DDS) source provides an output level from 100 mV to 1 V, anddelivers up to 50 mA of current.
Frequency Response Measurements
With its low distortion DDS source, the SR770 is capable of performingaccurate frequency response measurements. The source is synchronized withthe insturment's input allowing transfer functions to be measured with0.05 dB precision. The SR770 measures the magnitude and phase response ofcontrol systems, amplifiers, and electro-mechanical systems and displaysthe resulting Bode plot.
Limit and Data Tables
Sometimes, it's important to keep track of a few key portions of aspectrum. The SR760's and SR770's data tables allow up to 200 selectedfrequencies to be displayed in a tabular format which can be printed orsaved to disk. Automated entry makes it easy to set up data tables forharmonic or sideband analysis. Convenient limit tables allow the entry ofup to 100 separate upper or lower limit segments for pass-fail testing. Onexceeding a limit, the analyzers can be configured to generate a screenmessage, an audio alarm, or a GPIB service request.
Three built-in analysis modes simplify common measurements. Harmonicanalysis computes both harmonic power and THD (Total Harmonic Distortion)relative to a specified fundamental. Sideband analysis lets you computepower in a set of sidebands relative to the carrier power. And finally,band analysis lets you easily integrate the power in a selected frequencyband. All three analysis modes provide clear on-screen markers which makeit easy to pick out frequencies of special interest such as harmonics orsidebands.
Too many analyzers have markers that go too slow or too fast, but neverseem to end up where you want them. The SR760 and SR770 have a marker thatwas designed to be fast, responsive, and flexible. The marker can beconfigured to read the maximum, minimum, or mean of a selected width ofdisplay, or can be set to tracking mode to lock on to a moving peak.Delta-mode readouts let you easily view frequency or amplitude differencesbetween two peaks. Automated peak-find lets you quickly move between thepeaks in a spectrum. And the markers for the upper and lower displays canbe linked to easily display similarities or differences in the two spectra.
Data taken with the SR760 and SR770 can be processed with the built-intrace calculator. Basic arithmetic functions such as addition,subtraction, multiplication, division, square roots and logarithms can beperformed on traces. Traces can be combined with other on-screen traces,or with traces stored on disks. These calculator functions are quiteuseful for performing background subtraction or normalization of data.
Flexible Storage and Output
All traces, data tables and limit tables can be stored on the analyzers'3.5 inch disk drive. The drive uses standard DOS 1.44M floppy disks whichcan be formatted on the analyzer or on your personal computer. Data can besaved in a space-saving binary format, or an easy-to-access ASCII formatfor off-line analysis. A variety of hardcopy options let you easily viewdata from the instruments. The screen can be dumped to a dot-matrixprinter or a LaserJet compatible laser printer via the standard rear-panelCentronics printer interface. Complete limit and data tables, as well as asummary of the instrument settings can be printed as well. Plotter outputis available to any HPGL compatible plotter with an RS-232 or GPIBinterface.
Easy to Interface
All functions of the analyzers can be queried and set via the standardRS-232 and GPIB interfaces. A comprehensive set of commands allowsflexible control and data transfer to your computer. Data can be quicklytransferred in binary format, or more conveniently as ASCII coded numbers.The complete, documented command list is available as a help screen in theinstruments for convenient reference while programming.
The Competitive Choice
Spectrum analyzer specifications can be confusing. Is the stated frequencyrange the real-time bandwidth, or simply the maximum operating frequency?Is the stated dynamic range the spurious-free dynamic range, or simply theA-D converter's resolution? The SR760 and SR770 have 100kHz real-timebandwidth, as well as 90dB of spurious free dynamic range. Other featuresare important as well. What is the input range? Does the unit provide adisk for easy storage? Is it easy to get hardcopy output? The SR760 andSR770 give you superior specifications and a broad array of convenientfeatures at an affordable price.