SIGNAL RECOVERY

Model 7265
DSP Lock-in Amplifier

FEATURES DESCRIPTION

0.001 Hz to 250 kHz The SIGNAL RECOVERY model 7265 uses the latest digital signal processing (DSP)
operation technology to extend the operating capabilities of the lock-in amplifier to provide the
researcher with a very versatile unit suitable both for measurement and control of

Voltage and current mode experiments. At the same time due consideration has been given to the needs of those
inputs users wishing only to make a simple measurement quickly and easily.

Direct digital demodulation Operating over a frequency range of 1 mHz to 250 kHz, the model 7265 offers full-scale
without down-conversion voltage sensitivities down to 2 nV and current sensitivities to 2 fA. The instrument has a
choice of operating modes, signal recovery or vector voltmeter, for optimum

10 µs to 100 ks output time measurement accuracy under different conditions, and the use of DSP techniques
constants ensures exceptional performance.

Quartz crystal stabilized The instrument performs all of the normal measurements of a dual phase lock-in
internal oscillator amplifier, measuring the in-phase and quadrature components, vector magnitude, phase
angle and noise of the input signal.

Synchronous oscillator
output for input offset Several novel modes of operation are also include to give greater levels of versatility
reduction than ever before, for example:

Harmonic measurements to

Virtual Reference™
65,536F Under suitable conditions, this mode allows measurements to be made in the absence

Dual reference, Dual of a reference signal
Harmonic and Virtual

Dual Reference
Reference modes In this mode the instrument can make simultaneous measurements on two signals at

Spectral display mode different reference frequencies, which is ideal, for example, for use in source
compensated optical experiments

Built-in experiments

Spectral Display
This allows the spectrum of the
signals present at the input to be
APPLICATIONS calculated and displayed, which can

Scanned probe microscopy help when choosing the reference
frequency
Spectral Display

Optical measurements

Transient Recorder

Audio studies In this mode, the auxiliary ADC inputs can be used as a 40 kSa/s (25 µs/point) transient
recorder, with the captured transient being displayed graphically

AC impedance studies

Frequency Response

Atomic force microscopy This built-in experiment allows the internal oscillator frequency to be swept between
preset frequencies, while simultaneously measuring the input signal magnitude and
phase. The mode is ideal for determining the frequency and phase response of external
networks

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 Lock-in Amplifiers

Harmonic Analysis
Most lock-in amplifiers will measure signals at the applied
reference frequency or its second harmonic. In the 7265,
operation is possible at harmonics up the 65,536th, and in Dual
Harmonic mode, simultaneous measurements can be made on
two harmonics

Three auxiliary ADC inputs, one of which is a special integrating Pop-up Keypad to set Controls
converter, four DAC outputs and eight output logic lines are
provided. These can be used to record the magnitude of external used when setting controls that need adjusting to a large number
signals associated with the experiment, such as temperature or of significant figures.
pressure, or to generate voltages to control or switch other
equipment. Information from the ADCs together with the lock-in Control selection and adjustment is aided by the logical structure
amplifier's output data can be stored in the 32k point buffer of on-screen menus and sub-menus, supported by a series of
memory, and even displayed graphically on screen. context-sensitive help screens. A number of built-in automatic
functions are also provided to simplify instrument operation.

External control of the unit is via either the RS232 or GPIB

interfaces, using simple mnemonic-type ASCII commands. A
second RS232 port allows up to sixteen 7265 or compatible
instruments to be operated from a single RS232 computer port
by connecting them in a “daisy-chain” configuration.
Graphical Display
Compatible software is available in the form of a LabVIEW driver
The model 7265 is extremely easy to use. All instrument controls supporting all instrument functions, and the Acquire lock-in
are adjusted using soft-touch, front panel push-buttons, with the amplifier applications software. The driver and a free
present settings and measured outputs being displayed on the demonstration version of the software, DemoAcquire, are
centrally located, cold fluorescent backlit dot-matrix LCD. A available for download from our website at
particularly convenient feature is the pop-up keypad which is www.signalrecovery.com

Specifications
General Spectral Display
Dual-phase DSP lock-in amplifier operating Gives a visual indication of the spectral Frequency Response 0.001 Hz to 250 kHz
over a reference frequency range of 0.001 Hz power distribution of the input signal in a Gain Accuracy ±0.2% typ
to 250 kHz. user-selected frequency range lying Distortion -90 dB THD (60 dB
between 1 Hz and 60 kHz. Note that AC gain, 1 kHz)
Wide range of extended measuring modes and although the display is calibrated in terms Line Filter attenuates 50, 60,
auxiliary inputs and outputs. of frequency, it is not calibrated for 100, 120 Hz
amplitude. Hence it is only intended to Grounding BNC shields can be
User-upgradeable firmware. assist in choosing the optimum reference grounded or floated
frequency via 1 kΩ to ground
Measurement Modes
The instrument can simultaneously show any Display Current Input
four of these outputs on the front panel display: 240 × 64 pixel cold fluorescent backlit Mode Low Noise or Wide
X In-phase LCD panel giving digital, analog bar-graph Bandwidth
Y Quadrature and graphical indication of measured Full-scale Sensitivity
R Magnitude signals. Menu system with dynamic key Low Noise 2 fA to 10 nA in a
θ Phase Angle function allocation. On-screen context 1-2-5 sequence
Noise sensitive help Wide Bandwidth 2 fA to 1 µA in a
Harmonic nF, n ≤ 65,536 1-2-5 sequence
Dual Harmonic Signal Channel Max. Dynamic Reserve > 100 dB
Simultaneously measures the signal at Voltage Input Frequency Response (-3 dB)
two different harmonics F1 and F2 of the Modes A only, -B only or Low Noise ≥ 500 Hz
reference frequency Differential (A-B) Wide Bandwidth ≥ 50 kHz
Dual Reference Full-scale Sensitivity 2 nV to 1 V in a Impedance
Simultaneously measures the signal at two 1-2-5 sequence Low Noise < 2.5 kΩ @ 100 Hz
different reference frequencies, F1 and F2 Max. Dynamic Reserve > 100 dB Wide Bandwidth < 250 Ω @ 1 kHz
where F1 is the external and F2 the internal Impedance Noise
reference FET Input 10 MΩ // 30 pF Low Noise 13 fA/√Hz @ 500 Hz
Frequency Range for Dual Harmonic and Dual Bipolar Input 10 kΩ // 30 pF Wide Bandwidth 1.3 pA/√Hz @ 1 kHz
Reference Modes: F1 and F2 ≤ 20 kHz Maximum Safe Input 20 V pk-pk Gain Accuracy ± 0.6% typ, midband
Virtual Reference Voltage Noise Line Filter attenuates 50, 60,
Locks to and detects a signal without a FET Input 5 nV/√Hz @ 1 kHz 100, 120 Hz
reference (100 Hz ≤ F ≤ 250 kHz) Bipolar Input 2 nV/√Hz @ 1 kHz Grounding BNC shield can be
Noise C.M.R.R. > 100 dB @ 1 kHz grounded or floated
Measures noise in a given bandwidth via 1 kΩ to ground
centered at the reference frequency F

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Lock-in Amplifiers

Model 7265 Specifications Amplitude (rms) Auxiliary D/A Outputs 1, 2, 3 and 4

Range 1 µV to 5 V rms Maximum Output ±10 V
(continued) Setting Resolution Resolution 1 mV
Reference Channel 1 µV to 4 mV 1 µV Accuracy ±10 mV
TTL Input (rear panel) 4 mV to 500 mV 125 µV Output Impedance 1 kΩ
Frequency Range 0.001 Hz to 250 kHz 500 mV to 2 V 500 µV 8-bit Digital Output Port
Analog Input (front panel) 2 V to 5 V 1.25 mV 8 TTL-compatible lines that can be
Impedance 1 MΩ // 30 pF Accuracy independently set high or low to activate
Sinusoidal Input > 1 mV ±0.3%, F ≤ 60 kHz, external equipment
Level 1.0 V rms* ±0.5%, F > 60 kHz Reference Output
Frequency Range 0.3 Hz to 250 kHz 100 µV - 1 mV ±1%, F ≤ 60 kHz Waveform 0 to 5 V rectangular
Squarewave Input ±3%, F > 60 kHz wave
Level 250 mV rms* Stability 50 ppm/°C Impedance TTL-compatible
Frequency Range 2 Hz to 250 kHz Output Impedance 50 Ω Power - Low Voltage ±15 V at 100 mA rear
Sweep panel 5-pin 180° DIN
*Note: Lower levels can be used with the Amplitude Sweep connector for
analog input at the expense of increased Output Range 0.000 to 5.000 V rms powering
phase errors Law Linear SIGNAL RECOVERY
Step Rate 20 Hz maximum preamplifiers
Phase Set Resolution 0.001° increments (50 ms/step)
Phase Noise at 100 ms TC, 12 dB/octave slope Frequency Sweep Data Storage Buffer
Internal Reference < 0.0001° rms Output Range 0.001 Hz to 250 kHz Size 32k × 16-bit data
External Reference < 0.01° rms @ 1 kHz Law Linear or Logarithmic points, may be
Orthogonality 90° ±0.0001° Step Rate 20 Hz maximum organized as 1×32k,
Acquisition Time (50 ms/step) 2×16k, 3×10.6k, 4×8k,
Internal Reference instantaneous etc.
acquisition Auxiliary Inputs Max Storage Rate
External Reference 2 cycles + 50 ms ADC 1 & 2 From LIA up to 1000 16-bit
Reference Frequency Meter Resolution Maximum Input ±10 V values per second
1 ppm or 1 mHz, Resolution 1 mV From ADC1 up to 40,000 16-bit
whichever is the Accuracy ±20 mV values per second
greater Input Impedance 1 MΩ // 30 pF
Sample Rate User Settings
Demodulator and Output Processing ADC 1 only 40 kHz max. Up to 8 complete instrument settings
Output Zero Stability ADC 1 and 2 17.8 kHz max. can be saved or recalled from
Digital Outputs No zero drift on all Trigger Mode Internal, External or non-volatile memory
settings burst
Displays No zero drift on all Trigger Input TTL compatible Interfaces
settings ADC 3 RS232 and GPIB (IEEE-488). A second
Analog Outputs < 5 ppm/°C Maximum Input ±10 V RS232 port is provided to allow “daisy-
Harmonic Rejection -90 dB Resolution 12 to 20 bit, chain” connection and control of up to 16
Output Filters depending on compatible instruments from a single
X, Y and R outputs only sampling time RS232 computer port
Time Constant 10 µs to 640 µs in a Input Impedance 1 MΩ // 30 pF
binary sequence Sampling Time 10 ms to 2 s, variable General
Slope (roll-off) 6 dB/octave Power Requirements
All outputs Outputs Voltage 110/120/220/240 VAC
Time Constant 5 msto 100 ks in a Fast Outputs Frequency 50/60 Hz
1-2-5 sequence Function X and Y or X and Mag Power 40 VA max
Slope 6, 12, 18 and 24 dB/ Amplitude ±2.5 V full-scale; Dimensions
octave linear to ±300% full- Width 13¼" (350 mm)
Synchronous Filter Available for F < scale Depth 16½" (415 mm)
20 Hz Impedance 1 kΩ Height
Offset Auto and Manual on X Update Rate 166 kHz With feet 4¼" (105 mm)
and/or Y: ±300% full- Main Analog (CH1 and CH2) Outputs Without feet 3½" (90mm)
scale Function X, Y, R, θ, Noise, Weight 18 lb (8.1 kg)
Absolute Phase Measurement Accuracy Ratio, Log Ratio and
≤ 0.01° User Equations 1 & 2.
Amplitude ±10.0 V full-scale;
Oscillator linear to ±120% full-
Frequency scale
Range 0.001 Hz to 250 kHz Impedance 1 kΩ
Setting Resolution Update Rate 200 Hz
1 mHz ≤ F ≤ 900 Hz 1 mHz Signal Monitor
F > 900 Hz 4 mHz Amplitude ±10 V FS
Absolute Accuracy ± 50 ppm Impedance 1 kΩ
Distortion (THD) -80 dB @ 1 kHz and
100 mV rms

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 Lock-in Amplifiers

LabVIEW Driver Software SIGNAL RECOVERY Acquire Software

A LabVIEW driver for the instrument is available from the (see page 56)
www.signalrecovery.com website, offering example VIs for all Users who do not wish to write their own control code but who
its controls and outputs, as well as the usual Getting Started and still want to record the instrument’s outputs to a computer file will
Utility VIs. It also includes example soft-front panels built using find the SIGNAL RECOVERY Instruments Acquire Lock-in
these VIs, demonstrating how you can incorporate them in more Amplifier Applications Software, available at a small extra cost,
complex LabVIEW programs. useful. This 32-bit package, suitable for Windows XP/Vista,
extends the capabilities of the instrument by, for example,
adding the ability to record swept frequency measurements. It
also supports the internal curve buffer, allowing acquisition
rates of up to 1000 points per second independent of the
computer's processor speed.

SRInstComms Software
(see page 59)
Control up to ten SIGNAL RECOVERY instruments directly from Visual Basic, Visual
C++, LabVIEW, Visual Basic for Applications (included in Word, Excel, Outlook,
Access and other Microsoft products) and VBScript (supported by Internet Explorer 3
and later) without having to worry about low-level communications routines. The
SRInstComms control handles all the communications between your software and the
instrument(s) via the RS232 and/or GPIB interfaces, leaving you free to develop the
code to run your experiment.

Ordering Information
Each model 7265 is supplied complete with a comprehensive instruction manual. Users may download the instrument's LabVIEW
driver software and a free demonstration copy, DemoAcquire, of the SIGNAL RECOVERY lock-in amplifier applications software
package, from the www.signalrecovery.com website.

Optional Accessories

Model K02003 Rack mount to mount one model

7265 in a 19" rack

Model K02003 Rack Mount Kit

Model 7265 Rear Panel Layout

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