Stanford Research SR850
DSP Lock-In Amplifier, 1 mHz to 102.4 kHz

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• MSRP: $10,500 |Used starting at: $5,395
  
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Product Overview

RENT Stanford Research Systems SR850 DSP Lock-In Amplifier (call for availability)

The Stanford Research Systems SR850 is a digital lock-in amplifier based on an innovative Digital Signal Processing (DSP) architecture. Its significant performance advantages over traditional lock-in amplifiers include higher dynamic reserve, lower drift, lower distortion, and dramatically higher phase resolution. In addition, the CRT display and 65,536 point memory make it possible to display and process data in a variety of formats unavailable with conventional lock-ins.

Features and Specifications of the Stanford Research Systems SR850 DSP Lock-In Amplifier include:

• 1 mHz to 102.4 kHz frequency range
• >100 dB dynamic reserve
• 0.001 degree phase resolution
• Time constants from 10 µs to 30 ks
  (up to 24 dB/oct rolloff)
• Auto-gain, -phase, -reserve and -offset
• Data logging (up to 65k samples)
• Smoothing, curve fitting & statistics
• GPIB, RS-232 and 3.5" disk drive 
• Digital Precision: Replaces the analog demodulator (mixer), low-pass filters and DC amplifiers using:
  
  • 18-bit A/D Converter at input
  • High-Speed DSP Chip
    • Digitally synthesizes the reference oscillator
    • Implements precise mathematical calculations which eliminate the drift, offset, nonlinearity and aging 
• Digital Flexibility:  7" CRT display supports a large selection of display options
• Input Channel:
  
  • Differential input with 6 nV/vHz input noise
  • Input impedance is 10 MO, and minimum full-scale input voltage sensitivity is 2 nV
  • No tracking band-pass filter is needed at the input
• Reference Channel:
  • Reference Source can be an externally applied sine wave or square wave, or its own digitally synthesized reference source.
  • Because the Internal Reference Source is synthesized from the same digital signal that is used to multiply the input, there is virtually no reference phase noise when using the internal reference.
  • The Internal Reference Source can operate at a fixed frequency or can be swept linearly or logarithmically over the entire operating range of 1 mHz to 102.4 kHz.
• High Dynamic Reserve:
  
  • The SR850 has the highest dynamic reserve (100 dB) of any lock-in available.
  • In the SR850, the ultra-high dynamic reserve is obtained without any sacrifice in stability or accuracy and without the use of analog band pass filters, eliminating the noise and error that such filters introduce.
• Traces and Displays:
  
  • Acquired data is stored in up to four user-defined traces.
  • Common operations, such as ratioing, can be performed in real time by defining an appropriate trace.
  • Trace values can be displayed as a bar graph with an associated large numerical display, or as a strip chart showing the trace values as a function of time.
  • Polar plots can be displayed showing the phasor formed by the in-phase and quadrature components of the signal.
  • Displays can be easily scaled from the front panel or over the computer interfaces.
  • Autoscale feature is available to quickly optimize the display.
  • Screen can be configured as a single large display, or as two horizontally-split displays.
• Convenient Auto Measurements:
  • Common measurement parameters are available as single-key "auto" functions.
  • The gain, phase, dynamic reserve and display scaling can all be set with a single key press.
  • For many measurements, the instrument can be completely configured simply by using the auto functions.
• Auxiliary A/Ds and D/As:
  
  • Four rear-panel A/D inputs allow measurement of external signals with millivolt resolution and the measured values can be incorporated into one of the SR850's trace definitions, or can be displayed on the front panel, or read via either computer interface.
  • Four D/A outputs can provide either fixed output voltages or a voltage level which scans synchronously with the SR850's frequency scans.
  • Both the A/D inputs and the D/A outputs have a ±10 V range. 
• Analysis Features:
  • Multiple-range Savitsky-Golay smoothing can be applied to any of the trace arrays, and statistical information (mean, variance, sum) can be calculated for a selected trace region.
  • A curve fitting routine calculates best fits to lines, exponential curves, and Gaussian curves for any portion of your data.
  • A trace "calculator" lets you perform a variety of simple arithmetic and trigonometric operations on trace data.
• Interfaces and Hardcopies:
  • The SR850 comes standard with RS-232 and GPIB interfaces.
  • All instrument functions can be queried and controlled via the interfaces.
  • For convenient debugging, characters received and sent via the interfaces can be viewed on the front panel.
  • Several hardcopy options are available.
  • Screens can be dumped to a dot-matrix or LaserJet compatible printer through the standard Centronics printer interface.
  • Displays can also be plotted on any HP-GL compatible plotter via GPIB or RS-232.
• Signal Channel:
  • Voltage Inputs: Single-ended or differential
  • Sensitivity: 2 nV to 1 V
  • Current Input: 10⁶ or 10⁸ V/A
  • Input Impedance:
    • Voltage Input: 10 MO + 25 pF, AC or DC coupled
    • Current Input: 1 kO to virtual ground
  • Gain Accuracy: ±1 % (±0.2 % typ)
  • Noise:
    • 6 nV/vHz at 1 kHz
    • 0.13 pA/vHz at 1 kHz (10⁶ V/A)
    • 0.013 pA/vHz at 100 Hz (10⁸ V/A)
  • Line Filters: 50/60 Hz and 100/120 Hz (Q=5)
  • CMRR: 100 dB at 10 kHz, decreasing by 6 dB/oct above 10 kHz
  • Dynamic Reserve: >100 dB (without prefilters)
• Reference Channel:
  • Frequency Range: 0.001 Hz to 102.4 kHz
  • Reference Input: TTL or sine (400 mVpp min)
  • Input Impedance: 1 MO, 25 pF
  • Phase Resolution: 0.001°
  • Absolute Phase Error: <1°
  • Relative Phase Error: <0.001°
  • Orthogonality: 90° ± 0.001°
  • Phase Noise:
    • Internal Reference: <0.0001° rms at 1 kHz
    • External Reference: 0.005° rms at 1 kHz, 100 ms, 12 dB/oct
  • Phase Drift:
    
    • <0.01°/°C below 10 kHz
    • <0.1°/°C, 10 kHz to 100 kHz
  • Harmonic Detection: 2F, 3F, ... nF to 102.4 kHz
  • Acquisition Time: (2 cycles + 5 ms) or 40 ms, whichever is greater
• Demodulator:
  • Stability:
    • Digital Outputs: no drift
    • Analog Outputs:
  • Harmonic Rejection: -90 dB
  • Offset/Expand: ±100 % offset, expand up to 256×
  • Time Constants: 10 µs to 30 ks (6, 12, 18, 24 dB/oct rolloff). Synchronous filtering available below 200 Hz
• Internal Oscillator:
  • Range: 1 mHz to 102.4 kHz
  • Accuracy: 25 ppm + 30 µHz
  • Resolution: 0.01 % or 0.1 mHz (whichever is greater)
  • Distortion:
    
    • -80 dBc (f < 10 kHz)
    • -70 dBc (f > 10 kHz) at 1 Vrms
  • Amplitude: 0.004 to 5 Vrms into 10 kO (2 mV resolution)
  • Output Impedance: 50 O
  • Amplitude Accuracy: 1 %
  • Amplitude Stability: 50 ppm/°C
  • Outputs: Sine and TTL (both can be phase-locked to an external reference)
  • Sweeps: Linear and log
• Inputs and Outputs:
  • Interfaces:
    
    • IEEE-488.2, RS-232 and Centronics interfaces standard.
    • All instrument functions can be controlled and read though the interfaces.
  • X,Y Outputs: ±10 V, updated at 256 ksamples/s
  • CH1 Output: ±10 V output of X, R or Trace 1 to 4
  • CH2 Output: ±10 V output of Y, T or Trace 1 to 4
  • Aux A/D Inputs: 4 BNC inputs, 1 mV resolution, ±10 V
  • Aux D/A Outputs: 4 BNC outputs, 1 mV resolution, ±10 V (fixed or swept amplitude)
  • Sine Out: Internal oscillator analog output
  • TTL Out: Internal oscillator TTL output
  • Trigger In: TTL signal either starts internal oscillator sweeps or triggers instrument data taking (rates to 512 Hz).
  • Remote Pre-Amp: Provides power to the optional SR550, SR552 and SR554 preamps
• Displays:
  • Screen Format: Single or dual display
  • Displayed Quantities:
    
    • Each display shows one trace.
    • Traces are defined as A×B/C or A×B/C² where A, B, C are selected from X, Y, R, T, X noise, Y noise, R noise, Aux 1 to 4 or frequency.
  • Displayed Types:
    
    • Large numeric readout
    • bar graph
    • polar plot
    • strip chart
  • Data Buffer:
    
    • 64k data points
    • Can be configured as:
      • a single trace with 64k points
      • 2 traces with 32k points each
      • or 4 traces with 16k points each
  • Sample Rate: 0.0625 Hz to 512 Hz, external to 512 Hz
• Analysis Functions:
  • Smoothing: 5, 9, 17, 21, 25 pt. (Savitsky-Golay)
  • Curve Fitting:
    
    • Linear
    • Exponential
    • or Gaussian
  • Calculator: 
    • Arithmetic
    • Trigonometric
    • and Logarithmic Calculations
  • Statistics: 
    • Mean
    • Standard Deviation
• General:
  • Hardcopy:
    
    • Screen dumps to dot matrix or LaserJet printers
    • Plots to HP-GL plotters (RS-232 or GPIB)
  • Disk Drive:
    • 3.5" MS-DOS compatible format, 1.44 Mbyte
    • Storage of data and instrument setups (binary or ASCII)
    • Screens can be saved as PCX files
  • Power: 60 W, 100/120/220/240 VAC, 50/60 Hz