SR850 – 100 kHz DSP lock-in amplifier


  • 100 kHz DSP lock-in amplifier


SR850 – 100 kHz DSP lock-in amplifier


The SR850 is a digital lock-in amplifier based on an innovative DSP (Digital Signal Processing) architecture. The SR850 boasts a number of significant performance advantages over traditional lock-in amplifiers—higher dynamic reserve, lower drift, lower distortion, and dramatically higher phase resolution.


• 1 mHz to 102.4 kHz 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)


Technical Specifications

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 M? + 25 pF, AC or DC coupled
Current input: 1 k? to virtual ground
Gain accuracy: ?1 % (?0.2 % typ.)
Noise: 6 nV/?Hz at 1 kHz
0.13 pA/?Hz at 1 kHz (106 V/A)
0.013 pA/?Hz 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 M?, 25 pF
Phase resolution: 0.001?
Absolute phase error: <1?
Relative phase error: <0.001?
Orthogonality: 90? ? 0.001?
Phase noise
Int. reference: <0.0001? rms at 1 kHz
Ext. 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

Digital outputs: no drift
Analog outputs: <5 ppm/?C for all dynamic reserves
Harmonic rejection: -90 dB
Offset/expand: ?100 % offset, expand up to 256?
Time constants: 10 ?s 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 ?Hz
Resolution: 0.01 % or 0.1 mHz (whichever is greater)
Distortion: -80 dBc (f 10 kHz) at 1 Vrms
Amplitude: 0.004 to 5 Vrms into 10 k? (2 mV resolution)
Output impedance: 50 ?
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, ? 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

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, ?, X noise, Y noise, R noise, Aux 1 to 4 or frequency.
Display types: Large numeric readout, bar graph, polar plot or strip chart
Data buffer: 64k data points. The buffer 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 and standard deviation

Hardcopy: Screen dumps to dot matrix or LaserJet printers. Plots to HP-GL plotters (RS-232 or GPIB).
Data storage: USB drive. 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
Dimensions: 17″ ? 6.25″ ? 19.5″ (WHL)
Weight: 40 lbs.
Warranty: One year parts and labor on defects in materials and workmanship