SIGNAL RECOVERY

Model 7280
Wide Bandwidth DSP Lock-in Amplifier

FEATURES DESCRIPTION

0.5 Hz to 2 MHz operation The model 7280 DSP Lock-in Amplifier is an exceptionally versatile instrument with
outstanding performance. With direct digital demodulation over an operating frequency

Voltage and current mode extending up to 2.0 MHz, output filter time constants down to 1 µs and a main ADC
inputs sampling rate of 7.5 MHz it is ideal for recovering fast changing signals. But unlike some
other high frequency lock-ins, it also works in the traditional audio frequency band.

Direct digital demodulation
without down-conversion In addition to its excellent technical specifications, it is also very easy to use. The front
panel is dominated by a large electroluminescent display panel, used both to show the

7.5 MHz main ADC sampling instrument's outputs and for adjusting its controls via a series of menus. Controls are set
rate by a combination of the use of the keys surrounding the display and the numeric
keypad, while four cursor-movement keys

1 µs to 100 ks output time
simplify use of the graphic display menus.
constants

Quartz crystal stabilized Users of the SIGNAL RECOVERY models
7260 and 7265 will find switching to the
internal oscillator
7280 very easy, since we've designed it

Harmonic measurements to with a similar menu structure. The only
32F significant changes are in some of the
control menus, where the better resolution

Dual reference, Dual of the display allows both the controls and
Harmonic and Virtual the instrument outputs to be shown
Reference modes simultaneously, for even faster feedback
on the effects of control adjustments. Main Display

Spectral display mode
Naturally, the instrument includes the extended operating modes like dual reference,
dual harmonic and virtual reference made popular by the 7260 and 7265, as well as the
spectral display mode used to aid reference frequency selection. It also includes GPIB
APPLICATIONS and RS232 interfaces for remote computer control and a range of auxiliary analog and
digital inputs and outputs. Compatible software is available in the form of a LabVIEW

Scanned probe microscopy driver supporting all instrument functions,

Optical measurements and the Acquire lock-in amplifier
applications software. The driver and a

Audio studies free demonstration version of the
software, DemoAcquire, are available for

AC impedance studies download from our website at
www.signalrecovery.com

Atomic force microscopy
In summary, if you need a lock-in capable
of working beyond the traditional audio
frequency band but still want the drift-free
performance that only digital demodulation
Auto Functions Menu brings, then look no further - you have
found it in the SIGNAL RECOVERY Model
7280.

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 Lock-in Amplifiers

Specifications Voltage Noise 5 nV/√Hz @ 1 kHz Reference Frequency Meter Resolution

General C.M.R.R. > 100 dB @ 1 kHz 1 ppm or 1 mHz,
Dual-phase DSP lock-in amplifier operating Frequency Response 0.5 Hz to 2.0 MHz whichever is the
over a reference frequency range of 0.5 Hz to Gain Accuracy ±0.3% typ, ±0.6% greater
2.0 MHz. Direct digital demodulation using a max. (full bandwidth)
main ADC sampling rate of 7.5 MHz. Distortion -90 dB THD (60 dB Demodulator and Output Processing
AC gain, 1 kHz) Output Zero Stability
Wide range of extended measuring modes and Line Filter attenuates 50, 60, Digital Outputs No zero drift on all
auxiliary inputs and outputs. User-upgradeable 100, 120 Hz settings
firmware. Grounding BNC shields can be Displays No zero drift on all
grounded or floated settings
Measurement Modes via 1 kΩ to ground Analog Outputs < 5 ppm/°C
The instrument can simultaneously show any Current Input Harmonic Rejection -90 dB
four of these outputs on the front panel display: Mode Low Noise, Normal or Output Filters
X In-phase Wide Bandwidth X, Y and R outputs only
Y Quadrature Full-scale Sensitivity Time Constant 1 µs to 1 ms in a 1-2-5
R Magnitude Low Noise 10 fA to 10 nA in a sequence, and 4 ms
θ Phase Angle 1-2-5 sequence Slope (roll-off) 6 and 12 dB/octave
Noise Normal 10 fA to 1 µA in a All outputs
Harmonic nF, n ≤ 32 1-2-5 sequence Time Constant 5 ms to 100 ks in a
Dual Harmonic Wide Bandwidth 1-2-5 sequence
Simultaneously measures the signal at F ≤ 250 kHz 1 pA to 100 µA in a Slope 6, 12, 18 and 24 dB/
two different harmonics F1 and F2 of the 1-2-5 sequence octave
reference frequency F > 250 kHz 10 pA to 100 µA in a Synchronous Filter Available for
Dual Reference 1-2-5 sequence F < 20 Hz
Simultaneously measures the signal Max. Dynamic Reserve > 100 dB Offset Auto and Manual on X
at two different reference frequencies, Frequency Response (-3 dB) and/or Y: ±300% full-
F1 and F2 where F1 is the external and F2 Low Noise ≥ 500 Hz scale
the internal reference Normal ≥ 50 kHz Absolute Phase Measurement Accuracy
Frequency Ranges for Dual Harmonic and Dual Wide Bandwidth ≥ 1 MHz ≤ 0.01°
Reference Modes: Impedance
Standard Unit F1 and F2 ≤ 20 kHz Low Noise < 2.5 kΩ @ 100 Hz Oscillator
With option -/99 F1 and F2 ≤ 800 kHz Normal < 250 Ω @ 1 kHz Frequency
With option -/98 F1 and F2 ≤ 2.0 MHz Wide Bandwidth < 25 Ω @ 10 kHz Range 0.5 Hz to 2.0 MHz
Virtual Reference Noise Setting Resolution 1 mHz
Locks to and detects a signal without a Low Noise 13 fA/√Hz @ 500 Hz Absolute Accuracy ± 50 ppm
reference (100 Hz ≤ F ≤ 2.0 MHz) Normal 130 fA/√Hz @ 1 kHz Distortion (THD) -80 dB @ 1 kHz and
Noise Wide Bandwidth 1.3 pA/√Hz @ 1 kHz 100 mV rms
Measures noise in a given bandwidth Gain Accuracy ± 0.6% typ, midband Amplitude (rms)
centered at the reference frequency F Line Filter attenuates 50, 60, Range 1 mV to 1 V
Spectral Display 100, 120 Hz Setting Resolution 1 mV
Gives a visual indication of the spectral Grounding BNC shield can be Accuracy ±0.2%
power distribution of the input signal in a grounded or floated Stability 50 ppm/°C
user-selected frequency range lying via 1 kΩ to ground Output Impedance 50 Ω
between 1 Hz and 2.0 MHz. Note that Sweep
although the display is calibrated in terms Reference Channel Amplitude Sweep
of frequency, it is not calibrated for TTL Input (rear panel) Output Range 0.000 to 1.000 V rms
amplitude. Hence it is only intended to Frequency Range 0.5 Hz to 2.0 MHz Law Linear
assist in choosing the optimum reference Analog Input (front panel) Step Rate 20 Hz maximum
frequency Impedance 1 MΩ // 30 pF (50 ms/step)
Sinusoidal Input Frequency Sweep
Display Level 1.0 V rms* Output Range 0.5 Hz to 2.0 MHz
320 × 240 pixel (¼ VGA) Frequency Range 0.5 Hz to 2.0 MHz Law Linear or Logarithmic
electroluminescent panel giving digital, Squarewave Input Step Rate 20 Hz maximum
analog bar-graph and graphical indication Level 250 mV rms* (50 ms/step)
of measured signals. Menu system with Frequency Range 2 Hz to 2 MHz
dynamic key function allocation. On- Auxiliary Inputs
screen context sensitive help *Note: Lower levels can be used with the ADC 1, 2, 3 and 4
analog input at the expense of increased Maximum Input ±10 V
Signal Channel phase errors Resolution 1 mV
Voltage Input Accuracy ±20 mV
Modes A only, -B only or Phase Set Resolution 0.001° increments Input Impedance 1 MΩ // 30 pF
Differential (A-B) Phase Noise at 100 ms TC, 12 dB/octave slope Sample Rate
Full-scale Sensitivity Internal Reference < 0.0001° rms ADC 1 only 40 kHz max.
0.5 Hz ≤ F ≤ 250 kHz 10 nV to 1 V in a External Reference < 0.01° rms @ 1 kHz ADC 1 and 2 17.8 kHz max.
1-2-5 sequence Orthogonality 90° ±0.0001° Trigger Mode Internal, External or
250 kHz < F ≤ 2.0 MHz 100 nV to 1 V in a Acquisition Time burst
1-2-5 sequence Internal Reference instantaneous Trigger Input TTL compatible
Max. Dynamic Reserve > 100 dB acquisition
Impedance 100 MΩ // 25 pF External Reference 2 cycles + 50 ms
Maximum Safe Input 20 V pk-pk

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Lock-in Amplifiers

Model 7280 Specifications Power - Low Voltage ±15 V at 100 mA rear Interfaces
Outputs panel 5-pin 180° DIN RS232 and GPIB (IEEE-488). A second
Main Analog (CH1 and CH2) Outputs connector for RS232 port is provided to allow “daisy-
Function X, Y, R, θ, Noise, powering chain” connection and control of up to 16
Ratio, Log Ratio and SIGNAL RECOVERY units from a single RS232 computer port
User Equations 1 & 2. preamplifiers
Amplitude ±2.5 V full-scale; Data Storage Buffer General
linear to ±300% full- Size 32k × 16-bit data Power Requirements
scale points, may be Voltage 110/120/220/240 VAC
Impedance 1 kΩ organized as 1×32k, Frequency 50/60 Hz
Update Rate: 2×16k, 3×10.6k, 4×8k, Power 200 VA max
X, Y or R @ TC ≤4 ms 7.5 MHz etc. Dimensions
All outputs @ TC ≥5 ms 1 kHz Max Storage Rate Width 17¼" (435 mm)
Signal Monitor From LIA up to 1000 16-bit Depth 19" (485 mm)
Amplitude ±1 V FS values per second Height
Impedance 1 kΩ From ADC1 up to 40,000 16-bit With feet 6" (150 mm)
Auxiliary D/A Output 1 and 2 values per second Without feet 5¼" (130mm)
Maximum Output ±10 V User Settings Weight 25.4 lb (11.5 kg)
Resolution 1 mV Up to 8 complete instrument settings
Accuracy ±10 mV can be saved or recalled at will from
Output Impedance 1 kΩ non-volatile memory
8-bit Digital Port
0 to 8 lines can be configured as inputs,
with the remainder being outputs. Each
output line can be set high or low and
each input line read to allow interaction
with external equipment. Extra line acts
as trigger input
Reference Output
Waveform 0 to 3 V rectangular
wave
Impedance TTL-compatible

Model 7280 Rear Panel

SIGNAL RECOVERY Acquire LabVIEW Driver Software

Software (see page 56) A LabVIEW driver for the instrument is
Users who do not wish to write their own available from the
control code but who still want to record www.signalrecovery.com website,
the instrument’s outputs to a computer file offering example VIs for all its controls and
will find the SIGNAL RECOVERY Acquire outputs, as well as the usual Getting
Lock-in Amplifier Applications Software, Started and Utility VIs. It also includes
available at a small extra cost, useful. This example soft-front panels built using these
32-bit package, suitable for Windows XP/ VIs, demonstrating how you can
Vista, extends the capabilities of the incorporate them in more complex
instrument by, for example, adding the LabVIEW programs.
ability to record swept frequency
measurements. It also supports the Ordering Information
internal curve buffer, allowing acquisition Each model 7280 is supplied complete with a comprehensive instruction manual. Users
rates of up to 1000 points per second may download the instrument's LabVIEW driver software and a free demonstration
independent of the computer's processor copy, DemoAcquire, of the SIGNAL RECOVERY lock-in amplifier applications software
speed. package, from the www.signalrecovery.com website.

Optional Accessories
Model 7280/99 Extended frequency range (800 kHz) for Dual Reference and
Dual Harmonic Modes

Model 7280/98 Extended frequency range (2.0 MHz) for Dual Reference and
Dual Harmonic Modes

Acquire™ 32-bit lock-in amplifier applications software for use with

Windows XP/Vista operating systems

Model K02004 Rack mount to mount one model 7280 in a 19" rack

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Lock-in Amplifiers

Why should you choose SIGNAL RECOVERY products?

Models 7280 and 7280BFP Wide Bandwidth DSP Lock-in Amplifiers
SIGNAL RECOVERY Product Features Benefit to you

They are the only commercially available 2 MHz genuine Allows use in systems requiring short output time constants
DSP lock-in amplifiers without problems caused by an insufficient number of samples
per signal cycle

Analog outputs updated at 7.5 MHz for use Ideal for scanned probe microscopy feedback control loops
with time constants down to 1 µs

Spectral Display (Model 7280 only) See in the frequency domain where interfering signals are and
choose a quiet region for your reference frequency

Dual Reference Measure two signals at two different frequencies simultaneously,

without the expense involved in buying two instruments

Dual Harmonic Measure two signals at two different harmonics simultaneously,

without the expense involved in buying two instruments

Curve Buffer Graphical Display Strip chart mode display is invaluable for monitoring during
manual adjustment of experiments

Virtual Reference Recover signals even without a reference

Large high resolution electroluminescent display Excellent viewing angle for good visibility even across a
(Model 7280 only) crowded laboratory

Easy to set controls with keypad and Enter the exact setting you need without having to fiddle with a
cursor movement keys (Model 7280 only) sensitive rotary knob. Move the cursors on the graphical display
with ease

User upgradeable firmware Benefit from future firmware upgrades without having to send the
instrument to a service facility

2-input multiplexing using A and -B inputs Measure two signals sequentially under computer control using
- even under computer control the same lock-in without having to switch connections

8 User Settings Memory (Model 7280 only) Several users can share an instrument but keep their own
personalized settings

Internal Oscillator can be used independently Set OSC OUT to a different frequency to the reference e.g. Use
of rest of instrument it to control a SIGNAL RECOVERY chopper at f and then
connect the lock-in's reference input to the chopper's f/10 SYNC
output

Auxiliary Digital Input and Output port Eliminate the need for separate digital I/O cards when building
complex computer controlled experiments

Excellent LabVIEW driver Saves programming time

Compatible with Acquire software Eliminates the need to develop programs

Compatible with SRInstComms Control the instrument from any ActiveX enabled programming
language, such as Visual Basic, VBA (Excel, Word, Access)
and VBScript (Internet Explorer)

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