Signal Recovery 7124 Precision Lock-In Amplifier

The Signal Recovery 7124 Precision Lock-In Amplifier is engineered for superior performance in signal detection, utilizing a distinctive analog fiber optic link that interconnects a Remote Connection Unit (RCU) with the main instrument console. This innovative design ensures a noise-free operation, as the RCU operates without digital clock signals, enabling all the benefits of advanced DSP technology coupled with a user-friendly interface and exceptional low-noise performance.

During standard operation, signal and reference connections are established at the RCU. The amplifier's input configurations allow for versatile operation in either single-ended or differential voltage modes, as well as in current mode with selectable transimpedance settings. Users can effortlessly switch between two single-ended voltage signals for sequential measurements under computer control. Additionally, for applications requiring further preamplification, external Signal Recovery preamplifiers can be connected to enhance performance.

The RCU features general-purpose analog and TTL logic reference inputs, along with an output for a precise Direct Digital Synthesis (DDS) oscillator that generates sine wave signals with adjustable frequency and amplitude. The setup optimizes the connection to various experimental configurations.

Main Console Features

The main console of the Signal Recovery 7124 is a compact benchtop unit equipped with a color display, dedicated control keys for navigation through menus, and straightforward numeric entry. The console efficiently processes signals received from the RCU module using sophisticated DSP algorithms operating within a dedicated field programmable gate array (FPGA) and is supported by a ColdFire processor. With an operating frequency range of 0.5 Hz to 150 kHz and an ADC sampling rate paired with an analog output DAC update rate of 1 MHz, the amplifier is optimized for time constants as short as 10 µs.

The main display is instrumental for routine operation, featuring customizable views for instrument controls on the left and output data, offset status, and reference frequency on the right. Output display selections include both digital and bar-graph formats. Clear error information, such as overload indicators and reference unlock messages, is prominently displayed, while soft keys facilitate control selection and numeric data entry.

Key Features and Specifications

• Extended Operating Modes:
  • Single Reference Mode: Perform harmonic analysis on harmonics up to 127 x F.
  • Dual Harmonic Mode:
    • Simultaneously measure signals at two harmonics of the reference signal.
    • Measure both the fundamental frequency and one of its harmonics concurrently.
  • Dual Reference Mode:
    • Facilitates simultaneous measurement of two signals at unrelated frequencies.
    • Ideal for optical experiments where signals through different paths are modulated at distinct frequencies.
  • Spectral Display: Displays the spectrum of input signals, assisting in selecting the reference frequency.
  • Tandem Demodulation Mode: Process an amplitude-modulated signal by first demodulating at a carrier frequency and subsequently processing it at a lower frequency.
• Synchronous Oscillator Output: Delivers an analog sinusoidal signal representative of the in-phase demodulator, available in both internal and external reference modes.
• Inputs and Outputs:
  • The RCU unit includes connections for signal, reference channels, and an oscillator output.
  • An 8-way digital output port for peripheral control is also available.
  • The main console features another oscillator output, an auxiliary signal channel input, four auxiliary ADC inputs, and four DAC outputs.
  • DAC outputs can serve as analog outputs for signal measurements (e.g. X, Y, Magnitude, Phase) or as general-purpose programmable analog outputs.
• Computer Control: External control is facilitated through USB, RS232, or Ethernet interfaces utilizing simple mnemonic ASCII commands.