SR865A – 4 MHz lock-in amplifier


  • 4 MHz lock-in amplifier


SR865A – 4 MHz lock-in amplifier


The SR865A Lock-In Amplifier offers superb performance and outstanding value. With 4 MHz frequency range, time constants from 1 µs to 30 ks, very low noise front-end amplifiers, and a modern, intuitive user interface, the SR865A is the ideal choice for any synchronous detection application.


• 1 mHz to 4 MHz
• Low noise voltage & current inputs
• 1 µs to 30 ks time constants
• High bandwidth outputs
• Touchscreen data display
• 10 MHz timebase input and output
• GPIB, RS-232, Ethernet and USB
• HDMI video output


Technical Specifications

Signal Channel
Voltage inputs: Single-ended (A) or differential (A-B)
Sensitivity (output scale): 1 nV to 1 V (voltage input)
1 fA to 1 ?A (current input)
Voltage Input range: 10 mV to 1 V (peak).
Current input range: 1 ?A or 10 nA (peak)
Max input: 1 V (peak) or 1 ?A (peak)
Input impedance
Voltage input: 10 M? + 25 pF, AC (>1 Hz) or DC coupled
Current input: 1 k? or 100 ? to virtual ground
Gain accuracy: ?1 % (<200 kHz), ?2 % (to 4 MHz). Signal amplitude must be less than 30% of input range.
Noise: 2.5 nV/?Hz at 1 kHz (10 mV input range, typ.)
Harmonic distortion: -80 dB (100 kHz)
CMRR: 90 dB at 1 kHz (DC coupled, 10 mV to 100 mV input range)
Dynamic reserve: 120 dB (typ)

Reference Channel
Frequency range: 0.001 Hz to 4 MHz, specified.
Timebase: 10 MHz In/Out (phase locks the internal frequency to other SR865As.)
Input impedance: 1 M? or 50 ?
Phase setting resolution: (360/232) degrees
Phase noise
Int. reference: <0.0001? rms at 1 kHz (100 ms, 12 dB/oct)
Ext. reference: (typ) <0.001? rms at 1 kHz (100 ms, 12 dB/oct)
Phase drift (typ): Sine Out to signal In (200 mVrms)
<0.002?/?C below 20 kHz (DC coupled)
<0.02?/?C below 200 kHz
<0.2?/?C below 4 MHz
Harmonic detection: Detect at N ? fref where N<99 and (N ? fref ) < 4 MHz
Dual F reference: Detect at fdual =?fint – fext?
All frequencies must be less than 4 MHz
Chopper reference: SR865A drives SR540 Chopper (via Aux Out 4) to lock the chopper to fint

DC stability: Digital output values have no offset drift
Time constants: 1 ?s to 30 ks
Low pass filters: Typical RC-type filters or advanced Gaussian/Phase-Linear filters
Filter slope: 6, 12, 18 or 24 dB/oct rolloff
Synchronous filter: Available below 4 kHz
Harmonic rejection: -80 dB
Low latency output: Rear-panel BlazeX output with <2 ?s delay (plus LPF rise/fall times).

Internal Oscillator
Frequency: 1 mHz to 4 MHz, specified
Frequency accuracy: 25 ppm + 30 ?Hz (with internal timebase)
External timebase: 10 MHz timebase input/output on rear panel
Frequency resolution: 6 digits or 0.1 mHz (whichever is greater)

Sine Output
Outputs: Differential or single-ended
Output impedance: 50 ? source
Amplitude: 1 nVrms to 2 Vrms (specified amplitude is differential into 50 ? loads)
Output amplitude is halved when used single-ended
Output amplitude is doubled into a high impedance load
Amplitude resolution: 3 digits or 1 nV, whichever is greater
DC offset: ?5 V, differential or common mode
Offset resolution: 3 digits or 0.1 mV, whichever is greater
Output limit: ?6 V, sum of DC offset and peak amplitude
Sync: Logic level sync on rear panel (via BlazeX output)

Data channels: 4 data channels are displayed and graphed (green, blue, yellow, orange)
Data sources: Each data channel can be assigned any of these data sources:
X, Y, R, ?, Aux In 1 to 4, Aux Out 1 to 2, X noise, Y noise, Sine Out Amplitude,
Sine Out DC Level, Reference Phase, or Reference Frequency
Data history: All data sources are continually stored at all chart display time scales.
The complete stored history of any data source can be displayed at any time.
Offset: X, Y and R may be offset up to ?999 % of the output scale
Expand: X, Y and R may be expanded by ?10 or ?100
Ratio: X and Y may be ratioed by Aux In 3. R may be ratioed by Aux In 4
Capture buffer: 1 Mpoints internal data storage. Store (X), (X and Y), (R and ?) or (X, Y, R and ?)
at sample rates up to 1.25 MHz. This is in addition to the data histories for the chart display.
Data streaming: Realtime streaming of data, either (X), (X and Y), (R and ?), or (X, Y, R and ?) at sample rate to 1.25 MHz over Ethernet interface
Scanning: One of the following parameters may be scanned:
fint, Sine Out Amplitude, Sine Out DC Level, Aux Out 1 or 2.
Source: Input ADC, demodulator output, or filter output
Record length: 1024 bins
Averaging: Exponential rms

Inputs and Outputs
CH1 output: Proportional to X or R, ?10 V full scale thru 50 ?
CH2 output: Proportional to Y or ?, ?10 V full scale thru 50 ?
X & Y rear-panel outputs: Proportional to X and Y, ?10 V full scale thru 50 ?
BlazeX: Low latency output of X, ?2.0 V full scale or logic level reference sync output, either thru 50 ?
Aux outputs: 4 BNC D/A outputs, ?10.5 V thru 50 ?, 1 mV resolution
Aux inputs: 4 BNC A/D inputs, ?10.5 V, 1 mV resolution, 1 M? input
Trigger input: TTL input triggers storage into the internal capture buffer
Monitor output: Analog output of the signal amplifier
HDMI: Video output to external monitor or TV, 640 ? 480, 60 Hz
Timebase I/O: 1 Vrms, 10 MHz clock to synchronize internal reference frequency to other units

Interfaces: IEEE488.2, RS-232, USB device and Ethernet.
USB flash: Front-panel slot for USB flash storage of screen shots and data
Preamp power: 9-pin D connector to power SRS preamps
Power: 60 W, 100/120/220/240 VAC, 50/60 Hz
Dimensions: 17″” ? 5.25″” ? 17″” (WHL)
Weight: 22 lbs.
Warranty: One year parts and labor on defects in materials and workmanship