It comes with the vendor's cryogen-free bottom-loading cryostat (the OptistatDry BLV), an MFLI lock-in amplifier
from Zurich Instruments, a specially designed ESD break-out box, and high-quality cables.
We have significantly enhanced the detection sensitivity of the eddy current method by detecting and demodulating the differential signal of the two coils induced by rail defects, using a digital lock-in amplifier
The block diagram of a typical lock-in amplifier
is shown in Figure 2.
The reflected scattered signal is diverted to a wideband homodyne quadrature mixer and the in-phase and quadrature IF (10 to 100 kHz) voltages are detected by a lock-in amplifier
. The signal levels from the in-phase and quadrature channels of the mixer for a typical microwave circuit with 10 dBm input power range from 10 [[micro]volt] to 10 mV when measured with a lock-in amplifier
with a 10 dB gain preamplifier.
A lock-in amplifier
with two detectors--a dual-phase lock-in--has two references in quadrature and determines both the cosine of the phase difference as well as a separate sine term.
The photodiode signal is analyzed by a dual-channel lock-in amplifier
, referenced by the driving frequency of the rf coils produced by a voltage controlled oscillator (VCO).
The FLL functional blocks consist of an RF generator, lock-in amplifier
and the rubidium physics package.
The system is based an RF comb-generator that modulates laser light at 2.46 GHz and mixes the detected power to a 123 MHz frequency measurable by a low-phase-noise RF lock-in amplifier
. The PMD resolution of the system appears to be limited by the phase noise of the lock-in amplifier
In spite of the high performance lock-in amplifier
used as a second stage signal-amplifier, the signal-to-noise ratio must be optimized for the output of the photocurrent measuring preamplifier.