7.1. A/D - D/A CONVERTERS

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In Chapter 3.3.7 in the Example IX is shown principle of A/D conversion based on a method of measuring the sample an analog signal at regular intervals. In Chapter 3.5.6 mentioned D/A converter within the computer's graphics card.

Musical cards, today often an integral part of the common computer configuration, has incorporated both the two transducers to provide an analog recording of music on the disk in binary notation, and translate it into music. Common designation of such integrated circuit of A/D/A converter. Principles of professional converters are the same but the fundamental difference in the accuracy of the transformation. Further presentation therefore will refer to their basic principles of operation and performance, and not on the specific application.

In order to be an A/D or D/A conversion should first determine what quality conversion is to be achieved, and therefore choose the converter.

As the number of different combinations of binary number according to:

 Scope of code

proportional to the number of bit in the binary number (chapter about coding), the first conclusion is that the conversion will be better if it uses binary combinations with multiple bits. So:

Bits Combinations Purpose
24 No significance
416 Simpler devices
8256 Typical experimental measurements
16 65'536 Music and precise measurements
32 4'294'967'296 Very precise measurements

Certain numerical value obtained by measuring, for example, the voltage galvanic cell, the conversion can be divided into different DISCRETE levels. Measurement is more accurate if the same size uses more bits, because it is distributed to a larger number of levels. When taking the sample will be taken for the actual measured value will be made towards the nearest approximation level.

Another important factor in the transformation of the time period in which to convert it from one form to another. If changes are slow then it is not not very important time of sampling, like the time of conversion between the two samples, which will become cheaper electronic device performance. Faster changes will require electronic devices with faster components that will certainly affect their price.

The third factor of importance is converters for measuring range at the entrance or exit. If it does not need, for example, the size of which can measure very small, it needs to combine with the amplifier or get a converter that is able to work with multiple measurement ranges.

How transducers should not affect the measurement system of electronic components are designed so that the input resistance is very large (over 1 MΩ), and the output is very small (as close to zero), and sensors from which data are collected mainly designed as voltage sources with as low internal resistance.

So, for the effective use of transducers should know within what limits and with what tempo to watch for who wants investigated and studied and accordingly install a converter that will be able to perform the task assumed. When choosing a converter should choose some reputable companies that are expected to deliver quality care to program support, without which the application of the transducer is almost impossible. Attention should be given to whether the operating system of a computer to use a converter program support and whether the transducer is designed for the type of computer in which you want to set.

In measurement systems will generally precede the A/D converters, while in production systems lead the D/A converters.

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