Data Acquisition System with Block Diagram


In industrial and instrumentation environment we come across signals of two types.

1. Signals obtained by direct measurement of electrical quantities. They are generally DC or AC voltages, frequency, resistance etc.
2. Signals obtained from the output of transducers.

The instrumentation systems are of two types the analog systems and the digital systems. Therefore we have the data or information available in the above two forms. The data available is to be collected processed, stored, displayed and transmitted depending on the requirements.

A data acquisition system consists of the following elements:

(a) Individual sensors
(b) Necessary signal conditioning system
(c) Data conversion equipment
(d) Data processing equipment
(e) Multiplexing equipment
(f) Data handling equipment
(g) Storage system
(h) Display system
(i) Data transmission system

Data Acquisition System Definition: 

A data acquisition system is a complex system that consists of all the required subsystems for collection, conditioning, conversion, processing, display, storage and transmission of data.

To obtain the best characteristics of the system in terms of performance handling capacity and economy, the subsystems of a data acquisition system can be clubbed together. Usually analog information [data] is converted into digital form for processing, display, storage and transmission.

The processing of data may involve different operations. They can be simple or complex mathematical manipulations. The data collected from various points is to be transformed into a useful format. It will be necessary that the data is to be transmitted. The transmission may be from one collection point to the other or may be from the collection point to a computer.

General Data Acquisition System: 

A block diagrammatic representation of data acquisition system in general is shown in Figure.

General Block Diagram of Data Acquisition System
It can be observed from the block diagram that the outputs of the different transducers are supplied to the signal conditioners. In the process of signal conditioning the outputs of the transducers may be amplified, attenuated, linearized as per requirement.

The outputs originated from the signal conditioners are given to the inputs of a multiplexer. From the output of the multiplexer the analog data can be supplied to recorders meters for indication or for a display device for display.

Multiplexers output will be converted into digital format. This digital signal will be used with printer, digital display, magnetic recorder [tape recorder] for printing a hard copy, monitoring and recording respectively. The output of the A/D converter can be supplied to a computer and can also be transmitted.

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