Data acquisition

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, abbreviated by the acronyms DAS, DAQ, or DAU, typically convert analog
waveforms into digital values for processing. 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.

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,
typically specific, hardware equipment. Digital data acquisition system block diagram
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 packages like the Maximum Integrated Data Acquisition System can be easily tailored and are used
in several physics experiments.

History
In 1963, IBM produced computers that 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
acquisition 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.[1][2][3][4][5]

Methodology

Sources and systems

Data acquisition begins with the physical phenomenon or physical property to be measured. Examples of
this include temperature, vibration, 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 allows one to measure or control the 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. If timing is necessary (such as for event mode DAQ
systems), a separate compensated distributed timing system is required.

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, shaped, or amplified in most cases. Various other examples of signal conditioning might be bridge
completion, providing current or voltage excitation to the sensor, isolation, and 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 (parallel, serial, USB, etc.) or cards connected to slots (S-100
bus, AppleBus, ISA, MCA, PCI, PCI-E, etc.) in a PC motherboard or in a modular crate (CAMAC, NIM,
VME). Sometimes adapters are needed, in which case an external breakout box can be used.

DAQ cards often contain multiple components (multiplexer, ADC, DAC, TTL-IO, high-speed timers,
RAM). 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 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.

Today, signals from some sensors and Data Acquisition Systems can be streamed via Bluetooth.

DAQ device drivers

DAQ device drivers are needed 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 programs.

Input devices
3D scanner
Analog-to-digital converter
Time-to-digital converter

Hardware
Computer Automated Measurement and Control (CAMAC)
Industrial Ethernet
Industrial USB
 LAN eXtensions for Instrumentation
Network interface controller
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, LabVIEW, and MATLAB.

See also
Black box
Data logger
Data storage device
Data science
Sensor
Signal processing
Transducer

References
1. COMDEX Fall November 18, 1981 Las Vegas, NV, "Tecmar shows 20 IBM PC option card..
LabMaster, LabTender, DADIO, DeviceTender, IEEE-488"
2. PC Magazine Vol1 No.1, "Taking the Measure" by David Bunnell, "Tecmar deployed 20
option cards for the IBM PC"
3. PC Magazine Vol1 No.5, "Tecmar Triumph" by David Bunnell, Scientific Solutions releases
20 new products for the PC
4. BYTE Vol7 No.1 "Scientific Solutions – Advertisement for data acquisition boards, stepper
controllers, IEEE-488 products
5. Test&Measurement World Vol 11 No 10 Decade of Progress Award: Scientific Solutions –
LabMaster First in PC Data Acquisition

Further reading
Simon McBeath (2002). Competition Car Data Logging: A Practical Handbook. J. H. Haynes
& Co. ISBN 978-1-85960-653-7.
Simon S. Young (2001). Computerized Data Acquisition and Analysis for the Life Sciences.
Cambridge University Press. ISBN 978-0-521-56570-7.
W. R. Leo (1994). Techniques for Nuclear and Particle Physics Experiments. Springer.
ISBN 978-3-540-57280-0.
V. Gonzalez (2012). Data Acquisition in Particle Physics Experiments. InTech. ISBN 978-
953-51-0713-2.
Charles D. Spencer (1990). Digital Design for Computer Data Acquisition. Cambridge
University Press. ISBN 978-0-521-37199-5.
 B.G. Thompson & A. F. Kuckes (1989). IBM-PC in the laboratory (https://archive.org/details/ib
mpcinlaborator0000thom). Cambridge University Press. ISBN 978-0-521-32199-0.
Buddy Fey (1996). Data Power: Using Racecar Data Acquisition. Towery Pub. ISBN 978-1-
881096-01-6.
Francesco Fornetti (2013). 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] (https://dx.doi.org/10.1016/j.compind.2011.09.004) doi:10.1016/j.compind.2011.09.004 (ht
tps://doi.org/10.1016%2Fj.compind.2011.09.004)

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