Signal Recovery- Dual Phase DSP Lock-in Amplifier (Model: 7265)

Overview

The SIGNAL RECOVERY model 7265 uses the latest digital signal processing (DSP) 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 experiments. At the same time due consideration has been given to the needs of those users wishing only to make a simple measurement quickly and easily.

Operating over a frequency range of 1 mHz to 250 kHz, the model 7265 offers full-scale
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 measurement accuracy under different conditions, and the use of DSP techniques ensures exceptional performance.

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

Several novel modes of operation are also include to give greater levels of versatility than ever before, for example:

Virtual Reference
Under suitable conditions, this mode allows measurements to be made in the absence of a reference signal

Dual Reference
In this mode the instrument can make simultaneous measurements on two signals at different reference frequencies, which is ideal, for example, for use in source compensated optical experiments

Spectral Display
This allows the spectrum of the signals present at the input to be calculated and displayed, which can help when choosing the reference frequency

Transient Recorder
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

Frequency Response
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.

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.

• 1m Hz to 250 kHz operation
• Direct digital demodulation without down-conversion
• 10 µs to 100 ks output time constants
• Synchronous oscillator output for input offset reduction
• Dual Reference, Dual Harmonic and Virtual Reference modes
• Spectral display mode
• Scanned probe microscopy
• Optical measurements
• Audio studies
• AC impedance studies
• Atomic force microscopy

The SIGNAL RECOVERY model 7265 uses the latest digital signal processing (DSP) 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 experiments.

Specifications outGeneral Dual-phase DSP lock-in amplifier operating over a reference frequency range of 0.001 Hz to 250 kHz. Wide range of extended measuring modes and auxiliary inputs and outputs. User-upgradeable firmware.   Measurements Modes The instrument can simultaneously show any four of these outputs on the front panel display:    X        In-phase    Y        Quadrature    R        Magnitude    ø        Phase Angle    Noise Harmonic nF, n ≤ 65, 536 Dual Harmonic    Simultaneously measures the signal at    two different harmonics F1 and F2 of the    reference frequency Dual Reference    Simultaneously measures the signal at    two different reference frequencies, F1    F2 where F1 is the external and F2 the    internal reference Frequency Range for Dual Harmonic and Dual Reference Modes F1 and F2 ≤ 20 kHz Virtual Reference    Locks to and detects a signal without a    reference (100 Hz ≤ F ≤ 250 kHz) Noise    Measures noise in a given bandwidth    centered at the reference frequency F Spectral Display    Gives a visual indication of the spectral    power distribution of the input signal in a    user-selected frequency range lying    between 1 Hz and 60 kHz.  Note that    although the display is calibrated in    terms  of frequency, it is not calibrated    for amplitude.  Hence it is only intended    to assist in choosing the optimum    reference frequency Display    240 x 64 pixel cold fluorescent backlit    LCD panel giving digital, analog bar-    graph and graphical indication of    measured signals.  Menu system with    dynamic key function allocation.  On-    screen context sensitive help Signal Channel Voltage Input    Modes A only, -B only or Differential (A-B)    Full-scale Sensitivity 2 nV to 1 V in a 1-2-5 sequence    Max. Dynamic Reserve > 100 dB    Impedance      FET Input      Bipolar Input 10 MΩ // 30 pF 10 kΩ // 30 pF    Maximum Safe Input 20 V pk-pk    Voltage Noise      FET Input      Bipolar Input 5 nV/√Hz @ 1 kHz 2 nV/√Hz @ 1 khZ    C.M.R.R. > 100 dB @ 1 kHz Frequency Response 0.001 Hz to 250 kHz Gain Accuracy ±0.2% typ Distortion -90 dB THD (60 dB AC gain, 1 khZ) Line Filter attenuates 50, 60, 100, 120 Hz Grounding BNC shields can be grounded or floated via 1 kΩ to ground Current Input    Mode Low Noise or Wide Bandwidth    Full-scale Sensitivity      Low Noise      Wide Bandwidth 2fA to 10 nA in a 1-2-5 sequence 2 fA to 1 µA in a 1-2-5 sequence    Max. Dynamic Reserve > 100 dB    Frequency Response (-3 dB)       Low Noise       Wide Bandwidth > 500 Hz ≥ 50 kHz    Impedance       Low Noise       Wide Bandwidth < 2.5 kΩ ! 100 Hz <250 Ω @ 1 kHz    Noise       Low Noise       Wide Bandwidth 13 fA/√Hz @ 500 Hz 1.3 pA/√Hz @ 1 kHz    Gain Accuracy ± 0.6% typ, midband    Line Filter attenuates 50, 60, 100, 120 Hz    Grounding BNC shield can be grounded or floated via 1 kΩ to ground- Reference Channel TTL input (rear panel)    Frequency Range 0.001 Hz to 250 kHz Analog Input (front panel)    Impedance    Sinusoidal input      Level      Frequency Range    Squarewave input      Level    Frequency Range 1 MΩ // 30 pF 1.0 V rms* 0.3 Hz to 250 kHz 250 mV rms* 2 Hz to 250 kHz *Note: Lower levels can be used with the analog input at the expense of increased phase errors Phase Set Resolution 0.001º increments Phase Noise at 100 ms TC, 12 dB/octave slope    Internal Reference    External Reference < 0.001º rms <0.01º rms @ 1 kHz Orthogonality 90º ±0.001º Acquistion Time    Internal Reference instantaneous acquisition    External Reference 2 cycles + 50 ms Reference Frequency Meter Resolution 1 ppm or 1 mHz, whichever is the greater Demodulator and Output Processing Output Zero Stability    Digital Outputs    Displays    Analog Outputs No zero drift on all settings No zero drift on all settings < 5 ppm/ºC Harmonic Rejection -90 dB Output Filters    X, Y and R outputs only      Time Constant      Slope (roll-off)    All outputs      Time Constant      Slope 10 µs to 640 µs in a binary sequence 6 dB/octave 5 ms to 100 ks in a 1-2-5 sequence 6, 12, 18 and 24 dB/octave Synchronous Filter Available for F < 20 Hz Offset Auto and Manual on X and/or Y: ±300% full-scale Absolute Phase Measurement Accuracy ≤0.01º Oscillator Frequency    Range    Setting Resolution      1 mHz ≤ F ≤ 900 Hz      F . 900 Hz    Absolute Accuracy 0.001 Hz to 250 kHz 1 mHz 4 mHz ± 50 ppm Distortion (THD) -80 dB @ 1 kHz and 100 mV rms Amplitude (rms)    Range      1µV to 4 mV      4 mV to 500 mV      500 mV to 2 V      2 V to 5 V    Accuracy      > 1 mV      100 µV – 1 mV      Stability 1 µV to 5 V rms 1µV 125 µV 500 µV 1.25 mV ±0.3%, F ≤ 60 kHz, ±0.5%, F > 60 kHz ±1%, F ≤ 60 kHz, ±3%, F > 60 kHz 50 ppm/ºC Output Impedance Sweep    Amplitude Sweep      Output Range      Law      Step Rate 0.001 to 5.000 V rms Linear 20 Hz maximum (50 ms/step) Frequency Sweep    Output Range    Law    Step Rate 0.001 Hz to 250 kHz Linear or Logarithmic 20 Hz maximum (50 ms/step) Auxiliary Inputs ADC 1 & 2    Maximum input    Resolution    Accuracy    Input Impedance    Smple Rate      ADC 1 only      ADC 1 and 2    Trigger Mode    Trigger Input ±10 V 1 mV ±20 mV 1 MΩ // 30 pF 40 kHz max. 17.8 kHz max. Internal, External or burst TTL compatible ADC 3    Maximum input    Resolution    Input Impedance    Sampling Time ±10 V 12 to 20 bit, depending on sampling time 1 MΩ // 30 pF 10 ms to 2 s, variable Outputs Fast Outputs    Function    Amplitude       Impedance    Update Rate X and Y or X and Mag ±2.5 V full-scale; linear to ±300% full-scale 1 kΩ 166 kHz Main Analog (CH1 and CH2) Outputs    Function    Amplitude    Impedance    Update Rate X, Y, R, ø, Noise, Ratio, Log Ratio and User Equations 1 & 2. ±10.0 V full-scale; linear to ±120% full-scale 1 kΩ 200 Hz Signal Monitor    Amplitude    Impedance ±10 V FS 1 kΩ Auxiliary D/A Outputs 1, 2, 3 and 4    Maximum Output    Resolution    Accuracy    Output Impedance ±10 V 1 mV ±10 mV 1 kΩ 8-bit Digital Output Port    8 TTL-compatible lines that can be independently    set high or low to activate exteranl equipment Reference Output    Waveform    Impedance 0 to 5 V rectangluar wave TTL-campatible Power – Low Voltage ±15 V at 100 mA rear panel 5-pin 180º DIN connector for powering SIGNAL RECOVERY preamplifiers Data Storage Buffer    Size    Max Storage Rate           From LIA      From ADC1 32k x 16-bit data points, may be organized as 1x32k, 2x16k, 3×10.6k, 4x8k, etc. up to 1000 16-bit values per second up to 40,000 16-bit values per second User Settings    Up to 8 complete instrument settings can    be saved or recalled from non-volatile    memory Interfaces    RS232 and GPIB (IEEE-488).  A second    RS232 port is provided to allow "daisy-    chain" connection and control of up to 16    compatible instruments from a single    RS232 computer port General Power Requirements    Voltage    Frequency    Power 110/120/220/240 VAC 50/60 Hz 40 VA max Dimensions    Width    Depth    Height      With feet      Without feet 13¼" (350 mm) 16½" (415 mm) 4¼" (105 mm) 3½" (90 mm) Weight 18 lb (8.1 kg)