Signal Recovery 7265

The Signal Recovery 7265 Dual Phase DSP Lock-In Amplifier 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 Signal Recovery 7265 Dual Phase DSP Lock-In Amplifier offers full-scale voltage sensitivities down to 2 nV and cur sensitivities to 2 fA. The instrument has a choice of operating modes, signal recovery or vector voltmeter, for optimum measurement accuracy under diffe 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.

Three auxiliary ADC inputs, one of which is a special integrating converter, four DAC outputs and eight output logic lines are provided. These can be used to record the magnitude of external signals associated with the experiment, such as temperature or pressure, or to generate voltages to control or switch other equipment. Information from the ADCs together with the lock-in amplifier's output data can be stored in the 32k point buffer memory, and even displayed graphically on screen.

The Signal Recovery 7265 DSP Lock-In Amplifier is extremely easy to use. All instrument controls are adjusted using soft-touch, front panel push-buttons, with the present settings and measured outputs being displayed on the centrally located, cold fluorescent backlit dot-matrix LCD. A particularly convenient new feature is the pop-up keypad which is used when setting controls that need adjusting to a large number of significant figures.

Control selection and adjustment is aided by the logical structure of on-screen menus and sub-menus, supported by a series of 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.

Features and Specifications of the Signal Recovery 7265 Dual Phase DSP Lock-In Amplifier include:

• Frequency Range:   1 mHz to 250 kHz
• 0.001 Hz to 250 kHz operation
• Voltage and cur mode inputs
• Direct digital demodulation without down-conversion
• 10 μs to 100 ks output time constants
• Quartz crystal stabilized internal oscillator
• Synchronous oscillator output for input offset reduction
• Harmonic measurements to 65,536F
• Dual reference, Dual Harmonic and Virtual Reference modes
• Spectral display mode
• Built-in experiments
• Several novel modes of operation give greater levels of versatility:
  • Virtual Reference ™:   Allows measurements to be made in the absence of a reference signal
  • Dual Reference: Allows simultaneous measurements on two signals at diffe reference frequencies
  • Spectral Display:   Allows the spectrum of the signals present at the input to be calculated and displayed
  • Transient Recorder:   Allows the auxiliary ADC inputs to be used as a 40 kSa/s (25 μs/point) transient recorder, with the captured transient being displayed graphical
  • Frequency Response:   Allows the internal oscillator frequency to be swept between preset frequencies while simultaneously measuring the input signal magnitude and phase
  • 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 taken on two harmonics
• Applications:
  • Scanned probe microscopy
  • Optical measurements
  • Audio studies
  • AC impedance studies
  • Atomic force microscopy