Elements of Data Acquisition System

ELEMENTS OF DATA ACQUISITION SYSTEM

The system used for data processing, data conversion, data transmission and data storage is called data Acquisition system

Objective of Data Acquisition system

(i) Monitor the operation of plant so that optimum and safe operation of plant

(ii) All the data efficiently inform to the operator about the state of plant

(iii) It must be able to collect and store data properly for diagnosis the plant and record purpose.

(iv) It should be reliable and should not have a blown time greater than 0.1%

(v) The data acquisition system must acquire the necessary data at correct speed and at the current time.

Generalized Data Acquisition System (or) Elements of Data Acquisition System

The figure.5.62 shows the generalized data acquisition system. The components

(i) Transducer

The transducers is a device used to convert the physical quantity into an electrical signal. The transducers such as strain gauge, thermocouples, piezoelectric devices, photosensitive are mostly used. The output of Transducer which is proportional to the physical quantity being measured.

(ii) Signal conditioner

It is the supporting circuit for the transducer It allows the output of transducer and convert to the desired level signal. That is accepted signal by next stage. The signal conditioning circuit, mostly consists of filter, amplifier, and level shifter etc.

 (iii) Multiplexers

It allows a single channel to share the more than one input quantity. The desired input quantity can be transmitted to the next stage by selecting the appropriate lines. By using multiplexer reduce the cost of installation and periodic replacement of channel if those are used for separate input signal.

(iv) Analog to digital converter

The output signal of multiplexer is sometimes to display in digital value (or) stored into the chart recorder (or) magnetic tape for that convert the signal into digital by using ADC.

PC Based Data Acquisition System

The figure 5.63 shows the PC Based data acquisition system. The output of transducer are interfaced to the personal computer through the PC-ADDON card. It is used for analysis the signal by software. This gives very powerful communication and analysis of multiple measurement data easily. The features of PC based data acquisition systems are.

(i) The Analysis data are plotted individually (or) simultaneously on the screen to show the characteristics this is useful for pointing out the variation occurs at different time.

(ii) These are useful in displaying the data measured at any location on the plant into the desired place. That is called man-machine interface (MMI)