What is data acqustion?

It is the process of converting measurements, such as temperature, pressure, relative humidity, light, resistance, current, power, speed and vibration, into digital numeric values that can be manipulated by a computer. During data acquisition physical measurements are converted into a voltage.

Acquiring parameters such as temperature ,flow,pressure from the field instruments such as sensor from a system .

Data acquisition (DAQ) is the process of measuring an electrical or physical phenomenon such as voltage, current, temperature, pressure, or sound with a computer. A DAQ system consists of sensors, DAQ measurement hardware, and a computer with programmable software.

collect some data to be stored or shown in a screen :)

 

Data acquisition begins with the physical phenomenon or physical property to be measured. This include temperature, light intensity, gas pressure, fluid flow, and force. Regardless of the type of physical property to be measured, the physical state that is to be measured must first be transformed into a unified form that can be sampled by a data acquisition system. The task of performing such transformations falls on devices called sensors. A data acquisition system is a collection of software and hardware that lets you measure or control physical characteristics of something in the real world.  

 

A complete data acquisition system consists of DAQ hardware, sensors and actuators, signal conditioning hardware, and a computer running DAQ software. 

 

The components of data acquisition systems include:

• Sensors, to convert physical parameters to electrical signals.

• Signal conditioning circuitry, to convert sensor signals into a form that can be converted to digital values.

• Analog-to-digital converters, to convert conditioned sensor signals to digital values.

   

  A sensor, which is a type of transducer, is a device that converts a physical property into a corresponding electrical signal (e.g., strain gauge, thermistor). An acquisition system to measure different properties depends on the sensors that are suited to detect those properties. Signal conditioning may be necessary if the signal from the transducer is not suitable for the DAQ hardware being used. The signal may need to be filtered or amplified in most cases. Various other examples of signal conditioning might be bridge completion, providing current or voltage excitation to the sensor, isolation, linearization. For transmission purposes, single ended analog signals, which are more susceptible to noise can be converted to differential signals. Once digitized, the signal can be encoded to reduce and correct transmission errors.

   

  Data acquisition applications are usually controlled by software programs developed using various general purpose programming languages such as Assembly, BASIC, C, C++, C#, Fortran, Java, LabVIEW, Lisp, Pascal, etc. Stand-alone data acquisition systems are often called data loggers.

  There are also open-source software packages providing all the necessary tools to acquire data from different hardware equipment. These tools come from the scientific community where complex experiment requires fast, flexible and adaptable software. Those packages are usually custom fit but more general DAQ package like the SCADA.

   

  The definition of SCADA is ‘Supervisory Control and Data Acquisition’. The major function of SCADA is for acquiring data from remote devices such as valves, pumps, transmitters etc. and providing overall control remotely from a SCADA Host software platform. This provides process control locally so that these devices turn on and off at the right time, supporting your control strategy and a remote method of capturing data and events (alarms) for monitoring these processes. SCADA Host platforms also provide functions for graphical displays, alarming, trending and historical storage of data.

  Looking at the overall structure of a SCADA system, there are four distinct levels within SCADA, these being;

 

• Field instrumentation,

• PLCs and / or RTUs,

• Communications networks and

• SCADA host software.

 

 

 

 “You can’t control what you don’t measure” is an old adage, meaning that instrumentation is a key component of a safe and optimised control system.

 

SCADA is not a specific technology, but a type of application. Any application that gets data about a system in order to control that system is a SCADA application.

 

 

 

 

 

A SCADA application has two elements:

 

• The process/system/machinery you want to monitor a control - this can be a power plant, a water system, a network, a conveyor, a bin, tails, prep plant, sample stations, weigh points, converters, stockpiles or anything else.

 

• A network of intelligent devices that interfaces with the first system through sensors and control outputs. This network, which is the SCADA system, gives you the ability to measure and control specific elements of the first system.

 

 

 

“Goal of data management is to create data files from various plant sources to prevent systematic and spurious error”Best practice requires minimising manual data handling so as to avoid manual errors and also to reduce the opportunities for tampering with the data.  Any system aiming to automate the data handling must take into account the large variety of data sources within a single site and the variations between sites.

 

 

 

Data Acquisition is the collection of data, from any peripheral connected to a SCADA system, for processing to execute certain actions as per the requirement.