Phase sensitive detector

A phase sensitive detector is a device which is used for the detection and measurement of the amplitude and phase of a periodic signal with respect to another reference signal of the same frequency. Phase sensitive detectors are also known as lock-in amplifiers and synchronous demodulators. These devices are widely used by electronics engineers and nanotechnology researchers. Instrumentation is a little bit complex here since both amplitude and phase of the signal carries information. In an ac bridge network, the excitation voltage of the bridge is acting as the reference signal and unknown impedance carries both amplitude and phase components. A phase sensitive detector consists of a signal generator, amplifier, reference signal generator, inverter, adder, low-pass filter and meter. Nowadays phase sensitive detectors have an additional provision for shifting the phase of the reference signal until a maximum or zero reading is obtained. For performing some special tasks, low-pass filter can be replaced by an integrator.