Data acquisition systems (DAQ) are getting a lot of engineers’ attention lately. Pondering minds would like to know what is a DAQ? To clarify, it is simpler to explain what a DAQ “does” than to answer, “What it is”.
The DAQ was invented circa 1964, with the purpose of doing something with software. Initially, DAQ’s were designed to monitor, control and analyze a system, while storing the information on a disk. IBM was first to introduce this type of system with its 1800 data acquisition and control system. The 1800 data acquisition and control system could be linked into IBM’s System/360. Since 1964, computer systems have dramatically changed, and therefore, how information is processed and stored changed with it.
Most recently, the invention of the PC has contributed to software changes. Because of these software changes, DAQ’s are now used to transform physical properties into signals. A DAQ catches or captures data about an actual system and stores that information in a format that can be easily retrievable for purposes of engineering or scientific review and analysis. It is expected for DAQs to capture information programmatically or automatically in other words, without any hands-on human intervention or guidance.
Before a computer-based measurement system can measure a physical signal, such as temperature, a sensor or transducer must convert the physical signal into an electrical one, such as voltage or current. DAQ systems also tie various products together. Terms that are analogous with DAQ’s are the following: Analog-to-digital converter (ADC), digital-to-analog converter (D/A), Digital Input/Output (DIO), Differential Input, General Purpose Interface Bus (GPIB), Resolution, RS232, RS485, Sample Rate, Single-ended Input (SE).
There are a wide variety of interfaces used to connect data acquisition hardware to computers. Do not misconstrue the plug-in DAQ device to be the entire measurement system. It is actually only one system component. You cannot always directly connect signals to a plug-in DAQ device. In these cases, you must use signal-conditioning accessories to condition the signals before the plug-in DAQ device converts them to digital information. The software controls the DAQ system by acquiring the raw data, analyzing, and presenting the results.