Which device converts an analog signal into a series of digital binary numbers?

The device that converts an analog signal into a series of digital binary numbers is the A/D converter, or analog-to-digital converter. Its primary function is to take continuous analog signals, which can vary in amplitude and time, and sample them at discrete intervals to produce corresponding binary values that represent those amplitudes. This process involves quantization, where the analog signal is divided into a finite number of levels, and then encoding these levels into binary numbers.

A/D converters are essential in modern digital systems because they enable the processing, storage, and transmission of analog signals in digital form. This is crucial in various applications, including audio recording, digital imaging, and instrumentation, where analog signals need to be analyzed or manipulated by digital systems.

The other devices listed have different functions that do not involve converting analog signals to digital binary numbers. For instance, a Fast Fourier transform is used for signal processing to convert signals from the time domain to the frequency domain, while a differential amplifier amplifies the difference between two input signals without converting them to digital form. Similarly, an impedance meter measures the impedance of a circuit but does not convert analog signals into binary data.