Data acquisition is the process of sampling signals that measure real world physical conditions
and converting the resulting samples into digital numeric values that can be manipulated
by a computer. Data acquisition systems typically convert analog waveforms into digital values
for processing. The components of data acquisition systems include:
Sensors that 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, which convert
conditioned sensor signals to digital values. Data acquisition applications are controlled
by software programs developed using various general purpose programming languages such
as LabVIEW, BASIC, C, Fortran, Java, Lisp, Pascal.
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 Maximum Integrated Data Acquisition
System can be easily tailored and is used in several physics experiments worldwide.
History In 1963, IBM produced computers which specialized
in data acquisition. These include the IBM 7700 Data Acquisition System and its successor,
the IBM 1800 Data Acquisition and Control System. These expensive specialized systems
were surpassed in 1974 by general purpose S-100 computers and data acquisitions cards
produced by Tecmar/Scientific Solutions Inc. In 1981 IBM introduced the IBM Personal Computer
and Scientific Solutions introduced the first PC data acquisition products.
Methodology Sources and systems
Data acquisition begins with the physical phenomenon or physical property to be measured.
Examples of 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. A sensor, which is a type of transducer, is
a device that converts a physical property into a corresponding electrical signal. 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. DAQ hardware
DAQ hardware is what usually interfaces between the signal and a PC. It could be in the form
of modules that can be connected to the computer's ports or cards connected to slots in the motherboard.
Usually the space on the back of a PCI card is too small for all the connections needed,
so an external breakout box is required. The cable between this box and the PC can be expensive
due to the many wires, and the required shielding. DAQ cards often contain multiple components.
These are accessible via a bus by a microcontroller, which can run small programs. A controller
is more flexible than a hard wired logic, yet cheaper than a CPU so that it is permissible
to block it with simple polling loops. For example: Waiting for a trigger, starting the
ADC, looking up the time, waiting for the ADC to finish, move value to RAM, switch multiplexer,
get TTL input, let DAC proceed with voltage ramp.
DAQ device drivers DAQ device drivers are needed in order for
the DAQ hardware to work with a PC. The device driver performs low-level register writes
and reads on the hardware, while exposing API for developing user applications in a
variety of programming environments. Input devices
3D scanner Analog-to-digital converter
Time-to-digital converter Hardware
CAMAC – Computer Automated Measurement and Control
Industrial Ethernet Industrial USB
LAN eXtensions for Instrumentation NIM
PowerLab PCI eXtensions for Instrumentation
VMEbus VXI
DAQ software Specialized DAQ software may be delivered
with the DAQ hardware. Software tools used for building large-scale data acquisition
systems include EPICS. Other programming environments that are used to build DAQ applications include
ladder logic, Visual C++, Visual Basic, and LabVIEW and MATLAB. See also:
LabChart MIDAS
References
Further reading Simon McBeath. Competition Car Data Logging:
A Practical Handbook. J. H. Haynes & Co. ISBN 1-85960-653-9. Simon S. Young. Computerized Data Acquisition
and Analysis for the Life Sciences. Cambridge University Press. ISBN 0-521-56570-7.
W. R. Leo. Techniques for Nuclear and Particle Physics Experiments. Springer. ISBN 3-540-57280-5.
Charles D. Spencer. Digital Design for Computer Data Acquisition. Cambridge University Press.
ISBN 0-521-37199-6. B.G. Thompson & A. F. Kuckes. IBM-PC in the
laboratory. Cambridge University Press. ISBN 0-521-32199-9. Buddy Fey. Data Power: Using Racecar Data
Acquisition. Towery Pub. ISBN 1-881096-01-7. Francesco Fornetti. Instrumentation Control,
Data Acquisition and Processing with MATLAB. Explore RF Ltd. ISBN 978-0957663503.
Tomaž Kos, Tomaž Kosar, and Marjan Mernik. Development of data acquisition systems by
using a domain-specific modeling language. Computers in Industry, 63(3):181–192, 2012.
[1] doi:10.1016/j.compind.2011.09.004 External links
Visual DAQ - An Analytics Platform for Connecting DAQ Systems
DAS DATA - Cloud Platform for Connecting Internet of Things