The Superior Precision HF2LI Lock-In Amplifier

The HF2LI (high-frequency, two inputs) from Zurich Instruments is a digital lock-in amplifier spanning the frequency ranging from DC to 50 MHz. The instrument has two physical input channels so that it can replace two devices in several measurement setups.

The 128-bit digital signal processing offers high accuracy, increasing the dynamic reserve and noise performance. With these exceptional capabilities, the HF2LI takes lock-in amplification to a new level and facilitates new applications in a frequency range that was earlier linked to analog instrumentation.

The computer is connected by a high-speed USB interface, which enables data acquisition at high rates. The HF2LI is provided with a fully featured graphical user interface and with an option of programming interfaces that significantly enhance the usability of the instrument.

Key Features

The main features of the HF2LI amplifier are as follows:

  • Operates at 210 MSa/s, DC - 50 MHz
  • Consists of two independent lock-in units, and two signal generators
  • Includes one fundamental and two harmonics per lock-in unit
  • Two auxiliary inputs, four auxiliary outputs
  • USB 2.0 high-speed, 480 Mbit/s
  • LabOne® toolset: Sweeper, Scope, Spectrum analyzer, etc.


The applications of the HF2LI amplifier are as follows:

  • Laser spectroscopy
  • Scanning probe microscopy (SPM), Atomic force microscopy (AFM)
  • Sensors and actuators, MEMS, e.g. gyroscopes and accelerometers
  • Industrial processing
  • Nondestructive testing (NDT)
  • Non-linear imaging (SRS, CARS, Terahertz, etc.)
  • Radiology, med-tech, and ultrasound
  • Astronomy

HF2LI Functional Diagram


The HF2LI combines the new analog front-end circuits for signal sampling, and high-performance digital signal processors.

High-Precision Inputs

The two input paths of the HF2LI are optimized for very low noise operation. The sampling rate of 210 MSa/s is four times the analog bandwidth to guarantee complete capture of the signal and to avoid aliasing.

Signal Outputs

The HF2LI generates two high-frequency outputs as a linear combination of up to six sinusoids ranging between DC and 50 MHz. When the HF2LI-MF multi-frequency option is enabled, the frequency, amplitude and the phase shift can be set for all the components.

The HF2LI provides six dual-phase demodulators. Each demodulator can be configured with its individual filter properties, which includes filter order from first to eighth, and time constant ranging between 1 μs and 500 s (corresponding to signal bandwidths from 80 μHz to 200 kHz).

The filters are employed in advanced 128-bit digital architecture. The benefits of HF2LLI over common analog instruments are zero drift, orthogonality, higher dynamic reserve, and precise phase shifts.

Integrated Toolset

An integrated oscilloscope with memory for 2048 samples offers direct signal-vs-time and spectral views of the input signal. Users obtain an overview of the incoming and produced signals at any time to rapidly find the exact settings. A frequency response analyzer offers accurate signal-vs-frequency plots.

The FFT spectrum analyzer provides a high-resolution spectral view of the signals that are demodulated by the lock-in amplifier.

Zurich Instruments/

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