Data Acquisition System (DAQ or DAS)

instrumentation

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What is Data Acquisition?

The Data Acquisition is the process of sampling signal that measures real-world physical conditions and converting the resulting samples into digital numeric value that can be manipulated by a computer.

The microprocessor-based personal computers are extensively used to implement direct digital control. For such PCs, special Printed Circuit boards are used called as Data Acquisition systems in process control. These system work are developed for providing input and output analog data, these are used when the PC is used in control system. Just like other peripheral devices such as scanner, printer, game board etc…

Components of a DAQ system:

Sensors:

Sensors convert the physical quantity such as temperature, pressure, flow etc, into a readable voltage or current signal for easy signal processing.

The sensor sends the measured valve directly to the signal conditioning device or to data acquisition board.

Signal conditioning:

The sensor output may contain noise signal as well may not in the range to be detected by the computer system. A signal conditioning unit filters the signal and thus improve the quality of the signal pass through the DAQ.

The common signal conditioning includes the amplification, linearization, filtering, attenuation, common mode rejection etc.

Analog to Digital converter:

An A/D converter converts the analog signal to digital readable signal to the computer system. The conversion is necessary to enable the computer to process or store the signal.

Advantages:

  • Reduced data reduntancy

  • Improved data security

  • Improved data access to user through use of host and query language

  • Reduced updating error and increased consistency

  • Reduced data entry and storage

Disadvantages:

  • Database system is complex, difficult and time-consuming

  • Damage to database affect all application program

  • Hardware and Software start-up cost

  • Initial training required for all programmers and users