Data acquisition

Last updated

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 or DAQ, typically convert analog waveforms into digital values for processing. The components of data acquisition systems include:

Contents

Digital Data Acquisition System Block Diagram DigitalDAQv2.pdf
Digital Data Acquisition System Block Diagram

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.

Assembly language low level programming language

An assemblylanguage, often abbreviated asm, is any low-level programming language in which there is a very strong correspondence between the program's statements and the architecture's machine code instructions.

BASIC programming language

BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use. In 1964, John G. Kemeny and Thomas E. Kurtz designed the original BASIC language at Dartmouth College. They wanted to enable students in fields other than science and mathematics to use computers. At the time, nearly all use of computers required writing custom software, which was something only scientists and mathematicians tended to learn.

C (programming language) general-purpose programming language

C is a general-purpose, imperative computer programming language, supporting structured programming, lexical variable scope and recursion, while a static type system prevents many unintended operations. By design, C provides constructs that map efficiently to typical machine instructions, and therefore it has found lasting use in applications that had formerly been coded in assembly language, including operating systems, as well as various application software for computers ranging from supercomputers to embedded systems.

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 packages like the Maximum Integrated Data Acquisition System can be easily tailored and is used in several physics experiments worldwide.

Maximum Integrated Data Acquisition System data acquisition software

MIDAS is a DAQ package developed at the Paul Scherrer Institute, Switzerland, and TRIUMF, Canada. It was designed for particle detectors using CAMAC and VMEbus hardware.

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. [1] [2] [3] [4] [5]

IBM 7700 Data Acquisition System

The IBM 7700 Data Acquisition System was announced by IBM on December 2, 1963.

The IBM 1800 Data Acquisition and Control System (DACS) was a process control variant of the IBM 1130 with two extra instructions, extra I/O capabilities, 'selector channel like' cycle-stealing capability and three hardware index registers.

S-100 bus

The S-100 bus or Altair bus, IEEE696-1983 (withdrawn), is an early computer bus designed in 1974 as a part of the Altair 8800. The S-100 bus was the first industry standard expansion bus for the microcomputer industry. S-100 computers, consisting of processor and peripheral cards, were produced by a number of manufacturers. The S-100 bus formed the basis for homebrew computers whose builders implemented drivers for CP/M and MP/M. These S-100 microcomputers ran the gamut from hobbyist toy to small business workstation and were common in early home computers until the advent of the IBM PC.

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 allows one to 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 physical property is any property that is measurable, whose value describes a state of a physical system. The changes in the physical properties of a system can be used to describe its changes between momentary states. Physical properties are often referred to as observables. They are not modal properties. Quantifiable physical property is called physical quantity.

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 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. Data acquisition involves gathering signals from measurement sources and digitizing the signals for storage, analysis, and presentation on a PC. Data acquisition systems (a.k.a. DAS or DAQ) convert analog waveforms into digital values for processing. The device we will be using utilizes this process. Once connected to the computer via the shielded cable, we will be able to either send analog signals into the device (using a Wavtek generator) which can then be viewed on the PC itself, or generate a signal from the device itself and manipulate the values through the use of the Measurement & Automation Explorer.

Sensor converter that measures a physical quantity and converts it into a signal

In the broadest definition, a sensor is a device, module, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. A sensor is always used with other electronics.

A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another.

Strain gauge electronic component

A strain gauge is a device used to measure strain on an object. Invented by Edward E. Simmons and Arthur C. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate. As the object is deformed, the foil is deformed, causing its electrical resistance to change. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.

DAQ hardware

DAQ hardware is what usually interfaces between the signal and a PC. [6] 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 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.

Parallel port an interface for connecting peripherals to computers

A parallel port is a type of interface found on computers for connecting peripherals. The name refers to the way the data is sent; parallel ports send multiple bits of data at once, in parallel communication, as opposed to serial interfaces that send bits one at a time. To do this, parallel ports require multiple data lines in their cables and port connectors, and tend to be larger than contemporary serial ports which only require one data line.

Serial port communication interface socket/plug

In computing, a serial port is a serial communication interface through which information transfers in or out one bit at a time. Throughout most of the history of personal computers, data was transferred through serial ports to devices such as modems, terminals, and various peripherals.

Micro Channel architecture

Micro Channel architecture, or the Micro Channel bus, was a proprietary 16- or 32-bit parallel computer bus introduced by IBM in 1987 which was used on PS/2 and other computers until the mid-1990s. Its name is commonly abbreviated as "MCA", although not by IBM. In IBM products, it superseded the ISA bus and was itself subsequently superseded by the PCI bus architecture.

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 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 programs.

Input devices

Hardware

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:

Related Research Articles

Bus (computing) communication system that transfers data between components inside a computer

In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components and software, including communication protocols.

Industry Standard Architecture 16-bit internal bus of IBM PC/AT

Industry Standard Architecture (ISA) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088-based IBM PC, including the IBM PC/XT as well as IBM PC compatibles.

Sound card internal computer expansion card that facilitates the input and output of audio signals

A sound card is an internal expansion card that provides input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces used for professional audio applications.

Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory, independent of the central processing unit (CPU).

Expansion card a printed circuit board that can be inserted into an electrical connector, or expansion slot on a computer motherboard, backplane or riser card to add functionality to a computer system via the expansion bus

In computing, the expansion card, expansion board, adapter card or accessory card is a printed circuit board that can be inserted into an electrical connector, or expansion slot, on a computer motherboard, backplane or riser card to add functionality to a computer system via the expansion bus.

In computing, a plug and play (PnP) device or computer bus, is one with a specification that facilitates the discovery of a hardware component in a system without the need for physical device configuration or user intervention in resolving resource conflicts. The term "plug and play" has since been expanded to a wide variety of applications to which the same lack of user setup applies.

Signal varying physical quantity that conveys information

In communication systems, signal processing, and electrical engineering, a signal is a function that "conveys information about the behavior or attributes of some phenomenon". In its most common usage, in electronics and telecommunication, this is a time varying voltage, current or electromagnetic wave used to carry information. A signal may also be defined as an "observable change in a quantifiable entity". In the physical world, any quantity exhibiting variation in time or variation in space is potentially a signal that might provide information on the status of a physical system, or convey a message between observers, among other possibilities. The IEEE Transactions on Signal Processing states that the term "signal" includes audio, video, speech, image, communication, geophysical, sonar, radar, medical and musical signals. In a later effort of redefining a signal, anything that is only a function of space, such as an image, is excluded from the category of signals. Also, it is stated that a signal may or may not contain any information.

Hardware abstractions are sets of routines in software that emulate some platform-specific details, giving programs direct access to the hardware resources.

TV tuner card kind of television tuner that allows television signals to be received by a computer

A TV tuner card is a kind of television tuner that allows television signals to be received by a computer. Most TV tuners also function as video capture cards, allowing them to record television programs onto a hard disk much like the digital video recorder (DVR) does.

Data logger recording device

A data logger is an electronic device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they are based on a digital processor. They generally are small, battery powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors. Some data loggers interface with a personal computer, and use software to activate the data logger and view and analyze the collected data, while others have a local interface device and can be used as a stand-alone device.

Tecmar was an American manufacturer of PC enhancement products based in Solon, OH. The company was founded in 1974 by Dr. Martin and Carolyn Alpert and their first products were data acquisition boards for the first generation of microcomputers. Popular products included the Scientific Solutions LabMaster series of boards for S-100 and Apple computers.

Biopac student lab

The Biopac Student Lab is a proprietary teaching device and method introduced in 1995 as a digital replacement for aging chart recorders and oscilloscopes that were widely used in undergraduate teaching laboratories prior to that time. It is manufactured by BIOPAC Systems, Inc., of Goleta, California. The advent of low cost personal computers meant that older analog technologies could be replaced with powerful and less expensive computerized alternatives.

This is a glossary of terms relating to computer hardware – physical computer hardware, architectural issues, and peripherals.

The Event Driven Executive (EDX) is a computer operating system originally developed by IBM for the control of research laboratory devices and experiments. It included an application programming language known as EDL and HCF, a Host Communication Facility.

CompactDAQ

CompactDAQ is a data acquisition platform built by National Instruments that includes a broad set of compatible hardware and software. CompactDAQ integrates hardware for data I/O with LabVIEW software to enable engineers to collect, process and analyse sensor data. CompactDAQ systems are less expensive than equivalent systems within the NI PXI Platform.

Pico Technology manufacturer of PC-based oscilloscopes

Pico Technology is a UK-based manufacturer of high-precision PC-based oscilloscopes and automotive diagnostics equipment, founded in 1991. Their product range includes the PicoScope line of PC-based oscilloscopes, data loggers, automotive equipment, and most recently, handheld USB-based oscilloscopes. Since their inception in 1991, Pico Tech has been researching and developing PC-based oscilloscopes, when the market standard was analogue storage oscilloscopes. Pico Technology is one of two European scope manufacturers, and competes in the low to middle end of the instrumentation market.

PicoScope (software) oscilloscope software application

PicoScope is computer software for real-time signal acquisition of Pico Technology oscilloscopes. PicoScope is supported on Microsoft Windows, Mac OS X, Debian and Ubuntu platforms. PicoScope is primarily used to view and analyze real-time signals from PicoScope oscilloscopes and data loggers. PicoScope software enables analysis using FFT, a spectrum analyser, voltage-based triggers, and the ability to save/load waveforms to disk. PicoScope is compatible with parallel port oscilloscopes and the newer USB oscilloscopes.

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 SolutionsLabMaster First in PC Data Acquisition
  6. Data logger, Recorder, Data Acquisition – Background informatihttp://localhost:1613/Source/UPDESCO/StaticPages/RTI2-hi.aspxon Byte Paradigm – explains the differences between data logging and data acquisition.
  7. PowerChrom - Chromatography Data System (CDS) Software manufactured by EDAQ

Further reading

See also