The difference between analog quantity and switch quantity and the principle of mutual conversion

The detectors we usually use are connected to active signals, which are analog quantities. The analog quantity is the output active signal. The switch value is the passive signal output.
1. Analog quantity refers to the quantity that the variable changes continuously in a certain range; that is, it can take any value (within the value range) within a certain range (definition domain). The digital quantity is a discrete quantity, not a continuous change quantity, and can only take several discrete values, such as a binary digital variable can only take two values.
2. The switch value refers to the collection and output of discontinuous signals, including remote signal collection and remote control output. It has two states, 1 and 0. This is the nature of switching in digital circuits, and electricity refers to the on and off of the circuit or the on and off of contacts. Principles of mutual conversion between
analog quantity and switch quantity
1. A digital-to-analog converter is a system that converts a digital signal into an analog signal, which can generally be realized by low-pass filtering. The digital signal is decoded first, that is, the digital code is converted into a corresponding level to form a ladder signal, and then low-pass filtering is performed.
According to the theory of signals and systems, a digital stepped signal can be regarded as the convolution of an ideal impulse sampling signal and a rectangular pulse signal. Then according to the convolution theorem, the frequency spectrum of a digital signal is the frequency spectrum of the impulse sampling signal and the rectangular pulse spectrum (ie Sa function). In this way, using the reciprocal of the Sa function as compensation for the spectral characteristics, the digital signal can be restored to a sampled signal. According to the sampling theorem, the frequency spectrum of the sampled signal is filtered through ideal low-pass filtering to obtain the frequency spectrum of the original analog signal.
In general implementation, it is not directly based on these principles, because sharp sampling signals are difficult to obtain. Therefore, the two filtering (Sa function and ideal low-pass) can be combined (cascaded), and because the filtering characteristics of each system are physical Unrealizable, so it can only be approximated in a real system.
2. The analog-to-digital converter is a system that converts analog signals into digital signals. It is a process of filtering, sampling and holding, and encoding. The analog signal is band-limited filtered, sample-and-hold circuit, into a ladder-shaped signal, and then through the encoder, so that each level in the ladder-shaped signal into a binary code. Chengdu Yuanxiang Electronics Co., Ltd., analog switch value collector TO-I/O-210 provides multi-channel digital (switch value) input and output, 4-20ma or 0-5V/20V analog quantity acquisition port, built-in relay switch (support DC and 220V power supply on-off control), with collection and wireless transmission functions. It is a very good product.