Data acquisition is defined as the process of measuring phenomena and physical world conditions such as pressure, temperature, sound, and electricity. This is achieved through the use of sensors that sample analog signals in the environment and then transforms them to digital signals using analog-to-digital converters. The resultant digital numeric values are then capable of being manipulated by a computer thus allowing for the presentation, storage, and analysis of these data.
The data acquisition process is primarily done using a combination of tools and instruments that form what is commonly referred to as a Data Acquisition System (DAS or DAQ). The DAQ system samples available environmental signals and transforms them into machine-readable signals as the software processes these acquired data for presentation or storage.
Basic data acquisition in action using NI.com’s data acquisition tools.
Composition of a DAQ system
A DAQ system comprises a computer with programmable software, DAQ measurement hardware, and sensors. Compared to previous traditional measurement systems, computer-based DAQ systems exploit the connectivity capabilities, productivity display, and the processing power of industry-standard PCs providing a more cost-effective, flexible, and powerful measurement solution.
DAQ System parts
Measuring physical phenomena, such as the intensity of light, the temperature of a room, or the force applied to an object usually starts with a sensor. Variously referred to as a transducer, a sensor is responsible for converting physical phenomenon into measurable electrical signals. Depending on the type of sensor being used, its electrical output can be resistance, current, voltage, or any other electrical attribute that varies from time to time. Some sensors may require additional circuitry and components in order to properly produce signals that can be safely and accurately deciphered by a DAQ device. Some common sensors and the phenomena that they measure include Accelerometer (Acceleration), Microphone (sound), Photo Sensor (light), Thermocouple (temperature) etc.
- DAQ Devices and Boards (DAQ Hardware)
DAQ hardware is the interface between signals from the outside world and a computer. It primarily acts as a device that digitizes analog signals so that a PC can interpret them. Here, the 3 key components that are used to measure signals are the computer bus, analog-to-digital converter (ADC), and the signal conditioning circuitry. However, many DAQ devices also come equipped with other functions for automating measurement processes and systems e.g. counter/timers generate and count digital pulses, digital I/O lines output and input digital signals, and digital-to-analog converters output analog signals.
- Computer and software
Computers with programmable software control the operations of DAQ devices and are used for visualizing, processing, and storing measurement data. Different types of PCs are used to carry out different types of applications. For instance, laptops may be used in the field for their portability, desktops may be used in labs for their processing power, or industrial computers may be used in manufacturing plants for their ruggedness.
Image via www.daqifi.com
Specific Data Acquisition devices are often created to address specific physical properties e.g. there are dedicated systems that are tasked with only measuring pressure or temperature. However, smaller dedicated DAQ systems can be integrated into larger systems through software by simply taking data gathered by individual systems and presenting these to the user.