Download What Is Data Acquisition? - Erasmus DWSPIT Polkowice

University of Pitesti
Dolnośląska Wyższa Szkoła Przedsiębiorczości i Techniki
w Polkowicach
Data Acquisition
Simedre Mirel-Adrian
Dr inż. ZDZISŁAW PÓLKOWSKI
Polkowice, 2015
Introduction
Data acquisition involves gathering signals from measurement sources
and digitizing the signals for storage, analysis, and presentation on a
PC. Data acquisition systems come in many different PC technology
forms to offer flexibility when choosing your system. You can choose
from PCI, PXI, PCI Express, PXI Express, PCMCIA, USB, wireless,
and Ethernet data acquisition for test, measurement, and automation
applications. Consider the following five components when building a
basic data acquisition system (Figure 1):
• Transducers and sensors
• Signals
• Signal conditioning
• DAQ hardware
• Driver and application software
http://www.ni.com/white-paper/3536/en/
What Is Data Acquisition?
• Data acquisition (DAQ) is the process of measuring an electrical or
physical phenomenon such as voltage, current, temperature,
pressure, or sound ,flow rate with a computer.
• Data acquisition systems, as the name implies, are products and/or
processes used to collect information to document or analyze some
phenomenon. In the simplest form, a technician logging the
temperature of an oven on a piece of paper is performing data
acquisition. As technology has progressed, this type of process has
been simplified and made more accurate, versatile, and reliable
through electronic equipment. Equipment ranges from simple
recorders to sophisticated computer systems. Data acquisition
products serve as a focal point in a system, tying together a wide
variety of products, such as sensors that indicate temperature, flow,
level, or pressure.
http://www.omega.com/techref/pdf/dasintro.pdf
Transducers
Data acquisition begins with the physical phenomenon to be measured.
This physical phenomenon could be the temperature of a room, the
intensity of a light source, the pressure inside a chamber, the force
applied to an object, or many other things. An effective data acquisition
system can measure all of these different phenomena.
A transducer is a device that converts a physical phenomenon into a
measurable electrical signal, such as voltage or current. The ability of a
data acquisition system to measure different phenomena depends on
the transducers to convert the physical phenomena into signals
measurable by the data acquisition hardware. Transducers are
synonymous with sensors in data acquisition systems. There are
specific transducers for many different applications, such as measuring
temperature, pressure, or fluid flow. Table 1 shows a short list of some
common phenomena and the transducers used to measure them
Signals
• The appropriate transducers convert physical phenomena into
measurable signals. However, different signals need to be
measured in different ways. For this reason, it is important to
understand the different types of signals and their corresponding
attributes. Signals can be categorized into two groups:
• Analog Signals
An analog signal can exist at any value with respect to time. A few
examples of analog signals include voltage, temperature, pressure,
sound, and load. The three primary characteristics of an analog
signal are level, shape, and frequency.
http://www.ni.com/white-paper/3536/en/
• Digital Signals
A digital signal cannot take on any value with respect to time.
Instead, a digital signal has two possible levels: high and low. Digital
signals generally conform to certain specifications that define the
characteristics of the signal. They are commonly referred to as
transistor-to-transistor logic (TTL). TTL specifications indicate a
digital signal to be low when the level falls within 0 to 0.8 V, and the
signal is high between 2 and 5 V. The useful information that you
can measure from a digital signal includes the state and the rate.
http://www.ni.com/white-paper/3536/en/
Data Acquisition System Block Diagram :
Data acquisition and control hardware :
http://www.slideshare.net/amoldude/data-acquisition-system-33836067
Types of Data Acquisition
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Three general usage types:
Laboratory
Distributed
Portable
Laboratory and distributed DAQ systems are normally put in a
permanent location as these are comprised of relatively large or
bulky hardware and connect to desktop PCs in some way. These
systems depend upon the PC to access, process, and analyze input
data and prepare it for some type of presentation. Portable DAQ
systems, on the other hand, are small, lightweight units that are
easily carried by hand and work with laptops or, even, no computer
at all when installed at a location or site to only record data.
http://www.industrial-electronics.com/DAQ/
• Laboratory and distributed data-acquisition systems typically adhere
to industry-based packaging standards. For instance, some
laboratory systems are mounted in standard 19-inch racks while
distributed systems often use track mountings. A subset of these
systems includes a host computer that accommodates dataacquisition plug-in boards. Portable systems, in contrast, have no
real standardized form -- they may come in various sizes and
shapes, but they are typically small and light. Further, portable
systems are additionally classified as either stand-alone units or
those which connect to a PC. Stand-alone units are self-contained
data loggers and don't need a PC connection to function.
• Most modern data-acquisition systems, regardless of form factor, do
their intended tasks very well; i.e., they acquire and process data. All
systems have several factors in common; they need signal
conditioners to convert sensor signals and other electrical inputs to a
form that a processor can handle.
http://www.industrial-electronics.com/DAQ/
COMPONENTS OF DAQ
The purpose of any data acquisition system is to gather useful
measurement data for characterization, monitoring, or control. The
specific parameters of your application will dictate the resolution,
accuracy, channel count, and speed requirements for a data acquisition
system.
•Each data acquisition system has unique functionality to serve
application-specific requirements, all systems share common
components that include,
•Signals & sensors
•signal conditioning
•DAQ hardware
•computer with software.
https://www.newark.com/wcsstore/ExtendedSitesCatalogAssetStore/cms/asset/images/americas/common/storefront/keysight-technologies/data-acquisition-system.pdf