SR780 – 100 kHz 2-ch. FFT analyzer


  • 100 kHz 2-ch. FFT analyzer


SR780 – 100 kHz 2-ch. FFT analyzer


The SR780 Dynamic Signal Analyzer combines high performance and low cost in a full-featured package. It offers 102.4 kHz dual-channel FFTs with 90 dB dynamic range, swept-sine measurements, ANSI standard octave analysis, waterfall displays and transient capture for less than half the cost of other similarly equipped analyzers.


• DC to 102.4 kHz bandwidth
• 90 dB dynamic range
• Low-distortion synthesized source
• 145 dB dynamic range (swept-sine)
• Real-time octave analysis
• Up to 32 Mbyte memory
• GPIB and RS-232 interfaces


Technical Specifications

Measurement Groups
Groups: FFT, Octave Analysis, Swept-Sine

Range: 102.4 kHz or 100 kHz (both displays have the same range)
FFT spans: 195.3 mHz to 102.4 kHz or 191 mHz to 100 kHz. The two displays can have different spans and start frequencies.
FFT resolution: 100, 200, 400 or 800 lines
Real-time bandwidth: 102.4 kHz (highest FFT span with continuous data acquisition and averaging)
Accuracy: 25 ppm from 20 ?C to 40 ?C

Dynamic Range
Dynamic range:
FFT and Octave:
Swept-Sine: 90 dB typical, 80 dB guaranteed.
145 dB
Includes spurs, harmonic and intermodulation distortion and alias products. Excludes alias responses at extremes of span.
Harmonic distortion: <-80 dB (single tone in band)
Intermod. Distortion: <-80 dB (two tones in band, each less than -6.02 dBfs)
Spurious: <-80 dBfs
Alias responses: <-80 dBfs (single tone outside of span, -30 dBV, Hanning window, 64 rms averages)
Residual DC response: <-30 dBfs (FFT with Auto-Cal on)

Amplitude Accuracy
Single channel: ?0.2 dB (excluding windowing)
Cross channel: ?0.05 dB (DC to 102.4 kHz)
(transfer function measurement, both inputs on the same range, rms averaged)

Phase Accuracy
Single channel: ?3.0 deg. relative to external TTL trigger (-50 dBfs to 0 dBfs, frequency <10.24 kHz, center of frequency bin, DC coupled).
For Blackman-Harris, Hanning, Flat-Top and Kaiser windows, phase is relative to a cosine wave at the center of the time record. For Uniform, Force and Exponential windows, phase is relative to a cosine wave at the beginning of the time record.
Cross channel: ?0.5 deg. (DC to 51.2 kHz)
?1.0 deg. (DC to 102.4 kHz)
(transfer function measurement, both inputs on the same input range, vector averaged)

Signal Inputs
Number of inputs: 2
Full-scale input range: -50 dBV (3.16 mVp) to +34 dBV (50 Vp) in 2 dB steps
Maximum input level: 57 Vp
Input configuration: Single-ended (A) or differential (A-B)
Input impedance: 1 M? + 50 pF
Shield to chassis: Floating mode: 1 M? + 0.01 ?F. Grounded mode: 50 ?. Shields grounded in (A-B) mode
Max. shield voltage: 4 Vp
AC coupling: 0.16 Hz cutoff frequency
CMRR: 90 dB at 1 kHz (input range <0 dBV)
80 dB at 1 kHz (input range <10 dBV)
50 dB at 1 kHz (input range ?10 dBV)
ICP signal conditioning: Current source: 4.8 mA
Open circuit voltage: +26 V
A-weight filter: Type 0 tolerance, ANSI standard S1.4-1983 (10 Hz to 25.6 kHz)
Crosstalk: <-145 dB below signal (input to input and source to inputs, 50 ? receiving input source impedance)
Input noise: <10 nVrms/?Hz above 200 Hz (<-160 dBVrms/?Hz)

Trigger Input
Modes: Free run, Internal, External, or External TTL
Internal: Level adjustable to ?100 % of input scale, positive or negative slope. Min. trigger level: 5 % of input range
External: Level adjustable to ?5 V in 40 mV steps, positive or negative slope.
Input impedance: 1 M?
Max. input: ?5 V
Min. trigger amplitude: 100 mV
External TTL: Requires TTL level to trigger (low 3.0 V)
Post-trigger: Measurement record is delayed up to 8192 samples after the trigger.
Pre-trigger: Measurement record starts up to 8192 samples prior to the trigger.

Transient Capture
Mode: Continuous data recording
Maximum rate: 262,144 samples/s for both inputs
Maximum capture Length: 2 Msamples (single input)
8 Msamples with optional memory

Octave Analysis
Standards: Conforms to ANSI standard S1.11- 1986, Order 3, Type 1-D and IEC 225-1966
Frequency range: Single channel
1/1 Octave 0.125 Hz to 32 kHz
1/3 Octave 0.100 Hz to 40 kHz
1/12 Octave 0.091 Hz to 12.3 kHz
Two channels
1/1 Octave 0.125 Hz to 16 kHz
1/3 Octave 0.100 Hz to 20 kHz
1/12 Octave 0.091 Hz to 6.17 kHz
Accuracy: <0.2 dB (1 second stable average, single tone at band center)
Dynamic range: 80 dB (1/3 Octave, 2 second stable average) per ANSI S1.11-1986
Sound level: Impulse, Peak, Fast, Slow and Leq per ANSI S1.4-1983 Type 0 and IEC 651-1979 Type 0

Source Output
Amplitude range: 0.1 mVp to 5 Vp
Amplitude resolution: 0.1 mVp (output >500 mVp)
DC offset: <10.0 mV (typ.)
Offset adjust: ?5 VDC (sine, two-tone)
Output impedance: <5 ?, ?100 mA peak output current
Sine Source:
Amplitude accuracy: ?1 % of setting, 0 Hz to 102.4 kHz
0.1 Vp to 5.0 Vp, High-Z load
Harmonics, sub-harm. & spurious 0.1 Vp to 5 Vp
<-80 dBc (fundamental <30 kHz)
<-75 dBc (fundamental <102 kHz)

Two-Tone Source
Amplitude accuracy: ?1 % of setting, 0 Hz to 102.4 kHz
0.1 Vp to 5 Vp, High-Z load
Harmonics, sub-harm.: <-80 dBc, 0.1 Vp to 2.5 Vp

White Noise Source
Time record: Continuous or burst
Bandwidth: DC to 102.4 kHz or limited to span
Flatness: <0.25 dBpp (typ.), <1.0 dBpp (max.), 5000 rms averages

Pink Noise Source
Bandwidth: DC to 102.4 kHz
Flatness: <2.0 dBpp, 20 Hz to 20 kHz (using averaged 1/3 Octave Analysis)

Chirp Source
Time record: Continuous or Burst
Output: Sine sweep across the FFT span
Flatness: ?0.25 dB (amplitude: 1.0 Vp)

Swept-Sine Source
Auto functions: Source level, input range and frequency resolution
Dynamic range: 145 dB

Arbitrary Source
Amplitude range: ?5 V
Record length: 2 Msamples (playback from arbitrary waveform memory or capture buffer). Variable output sample rate.

CRT monitor: Monochrome, 800H by 600V resolution
Interfaces: IEEE-488.2, RS-232 and printer interfaces standard. All instrument functions can be controlled through computer interfaces. A PC (XT) keyboard input is provided for additional flexibility.
Hardcopy: Print to dot matrix and PCL compatible printers. Plot to HP-GL or postscript plotters. Print/plot to RS-232 or IEEE-488.2 interfaces or to disk file. Additional file formats include GIF, PCX and EPS.
Data storage: USB drive
Preamp power: Power connector for SRS preamps
Power: 70 W, 100/120/220/240 VAC, 50/60 Hz
Dimensions: 17″” ? 8.25″” ? 24″” (WHL)
Weight: 56 lbs.
Warranty: One year parts and labor on defects in materials and workmanship