The widespread use of microprocessor and computer techniques in systems of automatic control and process control requires conversion devices information. Control signals are formed corresponding analog voltage level, and information processing is carried out digitally in binary notation.

Unit of digital information— one bit — it odnorodno binary number, which takes the value 1 (the availability of information) or 0 (the lack of information). The totality of bits is the word, which is processed by a digital device. The length of the data words is fixed and is characterized by the bit width, what visicalc the number of bits in a word. Typical are the words of length 4, 8, 12 and 16 discharges. Vasiliva the word is called a byte.

 For example, the structure of the 16-bit binary word is as follows:, as shown in figure. 79:

The division of words into bytes allows you represented by a binary word information to be written in another notation, for example, hexadecimal. Write number in different systems are given in table. 6.

That's why, in practice, there are two types of data converters — analog to digital converters (ADC) and digital-to-analog converters (DAC).

ANALOG-TO-DIGITAL CONVERTERS

ADCS implemented with different principles of operation. The main point is the quantization of a signal, that is the representation of analog values through discrete values (rice. 80), and then the entry in the binary system. For the greater adequacy of the quantization time sampling choose the lowest.

The most common ADC, functional diagram of which contains a comparator, digital machine (CA) and the DAC chip, depicted in figure. 81.

During startup, the CA scheme generates the sequence of digits in binary code, served on the input of the DAC, the output signal of which is changed according. The value of this signal is compared by a comparator with the analog signal Uвх, which is supplied to the second input of the comparator. If these stresses are the same, the comparator produces a signal on a stop CA, at the output of which is fixed and the value of the input signal in binary code write.

DIGITAL-TO-ANALOG CONVERTERS

The main components of the DAC is the matrix of resistances, the device I / o operational amplifier. In figure. 82 shows a diagram of a simple DAC, which converts the incoming digital information to an analog signal based on the change in the gain OU. The inputs to a DAC corresponds to the number chotiritisyachnogo 2⁰, 2¹, 2², 2³ and for each input we obtain the transmission coefficients

Input op amp is fed the reference voltage IEP using the keys S₀ ÷S₃ and depending on their situation (closed or open) is determined by the voltage at the output of the amplifier

 

 

Undoubtedly, to reduce the transformation error, you need to increase the bit width of the DAC input.

Size called voltage, which corresponds to "weight" the lowest-value bit.

In the General case when the input word of the DAC output voltage is determined by the expression  signal to the corresponding discharge S = 0 in his absence.

 

Currently manufactured DAC chips series 301НРЗ-301НР6 with a division ratio of 1/2048 (rice. 83).