Input Channel:

SIMTRUM'S Single-channel Lock-in Amplifier detects an input signal in a single-ended mode or a differential voltage mode. With an ultra low-noise pre-amplifier, the input noise is low. Besides, the device can be used for current measurement with gains of 10⁶ or 10⁸ V/A. Two line filters (50/60 Hz and 100/120 Hz) are designed to eliminate power frequency interference. A programmable gain amplifier is used to adjust the dynamic reserve of the system, so that LIA can keep a high dynamic reserve.

Reference Channel:

The reference signal can work in external mode or internal mode. In internal mode, a precise and stable internal oscillator generates sine wave as an internal reference that is multiplied by the input signal. This internal signal is without any phase noise. With the digital phase-shifting technique, the phase resolution of the reference signal can achieve high resolution accuracy. In external mode, the reference signal can be a sine wave or a TTL pulse or a square wave. The rising or falling edge of the external reference signal triggers the Phase Lock Loop (PLL) to lock the external signal. Based on the frequency of the reference signal, LIA can detect the harmonics of the input signal. The maximum harmonic signal frequency can reach 32,767 times the fundamental frequency. 

Features

• Low input noise
• Wide frequency range
• High dynamic reserve

Applications

• Scanning Microscope - AFM, STM, SPM
• Materials Science - Carrier mobility, Carrier density, Hall effect, Ultrasonic
• Transport Measurement - Conductivity measurement, Impedance measurement
• Noise Represents - Noise density, Cross-correlation measurement
• Optical Experiment - analysis, Spectral measurement, THz measurement, TDLAS
• Sensor Measuring - Gyroscope, Photoelectric sensor, Resonator, Accelerometer
• Magnetic Sensor - SQUIDs, NV color center, Atomic Magnetometer, VSM
• Biomedical - Microfluidic

Working Theory

A lock-in amplifier, also known as a phase-sensitive detector, extracts a weak signal buried in noise by using a reference signal to demodulate the input signal, isolating the component at the reference frequency and phase.

Lock-in amplifiers employ phase-sensitive detection, a technique that selectively extracts signal components at a specific frequency and phase. A reference signal, typically a sine wave, is used to demodulate the input signal. The input signal is multiplied with the reference signal. The product of the multiplication is then passed through a low-pass filter, which allows the low-frequency components (representing the signal) to pass through while rejecting the high-frequency components (representing the noise).

If the input signal and the reference signal are correlated (i.e., they have the same frequency and phase), their multiplication will result in a low-frequency signal that is not averaged to zero by the low-pass filter. Noise, which is random and uncorrelated with the reference signal, will result in a high-frequency signal that is averaged to zero by the low-pass filter.