Types of Data Acquisition

Types of Data Acquisition

HardwareData acquisition systems (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, etc.) or cards connected to slots in the motherboard.

Hardware• CAMAC

• Computer Automated Measurement Control is a standard bus and modular crate electronics standard for Data acquisition and control used in nuclear and particle physics experiment and in industry.

• The bus allows data exchange between plug-in modules (up to 24 in a single crate) and a crate controller, which then interfaces to PC or to a VME-CAMAC interface.

Hardware• Industrial Ethernet

• Refers to the use of standard Ethernet protocols with rugged connectors and extended temperature switches in an industrial environment, for automation or process control.• Components used in plant

process areas must be designed to work in harsh environments of temperature extremes, humidity, and vibration that exceed the ranges for information technology equipment intended for installation in controlled environments.

Hardware• Industrial USB 

• the name given to the use of the USB protocol in an industrial environment, for data

acquisition, automation, and production machine control.

• Until recently, USB has been thought of strictly as a consumer communication bus, commonly used

for PC peripherals. However, its popularity has caused increasing interest for USB in the industrial space. The introduction of USB 2.0, with a transfer rate of 480 Mbit/s, provides a solution for implementing a portable high speed diagnostic system.

Some of the advantages are:– High-speed transfer rates with USB 2.0 at 480 Mbit/s– Easy setup due to Plug-and-Play– Portability

The difficulties of Industrial USB include:– Connector strain relief– Maximum cable length of 5m (with commercially available USB

hubs and extenders, it is possible to extend USB up to 30 m or 500 m, respectively)

Hardware• LAN eXtensions for

Instrumentation (LXI)- is a standard developed by the LXI Consortium, an industry consortium that maintains the LXI specification, promotes the LXI Standard, and ensures interoperability. The LXI standard defines the communication protocols for instrumentation and data acquisition systems using Ethernet.

Hardware• Nuclear Instrumentation Module (NIM) -defines mechanical and electrical specifications for electronics modules used in experimental particle and nuclear physics. The concept of modules in electronic systems offers enormous advantages in flexibility, interchange of instruments, reduced design effort, ease in updating and maintaining the instruments.

The NIM standard also specifies cabling, connectors, impedances and levels for logic signals.

Hardware• PowerLab - is a data acquisition system developed by ADInstruments comprising hardware and software and designed for use in life science research and teaching applications. It is commonly used in physiology, pharmacology, biomedical engineering, sports/exercise studies and psychophysiology laboratories to record and analyse physiological signals from human or animal subjects or from isolated organs. The system consists of an input device connected to a Microsoft Windows or Mac OS computer using a USB cable and LabChart software which is supplied with the PowerLab and provides the recording, display and analysis functions.

Hardware• PCI eXtensions for

Instrumentation (PIX)-  is one of several modular electronic instrumentation platforms in current use. These platforms are used as a basis for building electronic test equipment, automation systems, modular laboratory instruments in science, and the like. PXI is based on industry-standard computer buses and permits flexibility in building equipment. Often modules are fitted with custom software to manage the system.

Hardware• VMEbus (Versa Module Europa

bus) -is a computer bus standard, originally developed for the Motorola 68000 line of CPUs, but later widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987. It is physically based on Eurocard sizes, mechanicals and connectors (DIN 41612), but uses its own signalling system, which Eurocard does not define. It was first developed in 1981 and continues to see widespread use today

Hardware• VME eXtensions for Instrumentation

- The VXI bus architecture is an open standard platform for automated test based upon VMEbus. VXI stands for VME eXtensions for Instrumentation, defining additional bus lines for timing and triggering as well as mechanical requirements and standard protocols for configuration, message-based communication, multi-chassis extension, and other features. 

- The basic building block of a VXI system is the mainframe or chassis. This contains up to 13 slots into which various modules (instruments) can be added. The mainframe also contains all the power supply requirements for the rack and the instruments it contains

Software

Software

QuickDAQ allows you to acquire and display from all Data Translation USB and Ethernet data acquisition devices that support analog input streaming. Combine QuickDAQ with Data Translation hardware to acquire data, record data to disk, display the results in both a plot and digital display, and read a recorded data file.  Data can be exported to other applications like Microsoft Excel® and The Mathworks MATLAB® for more advanced analysis. 

Software

VIBpoint Framework This application supports the DT9837 Series, DT9838, DT9839, DT9839E, DT9847, and DT8837 modules. Discover and select available hardware, configure and load/save configurations, acquire and display data, perform single channel and two-channel FFT operations, save data to disk, file, or open in Excel.

SoftwareSignal Processing Component Library for .NET  is a comprehensive library of .NET components ideal for developing signal processing applications.Each componentcontains properties and methods that can be used to perform single-channel and two-channel FFT operations, and to calculate signal metrics on time-domain data.  The open design architecture allows hardware-independent support.

Software

DAQ Adaptor for MATLABMATLAB® from The MathWorks is a software environment and programming language used for data acquisition, data analysis, measurement automation, and application development. Use MATLAB with the Data Acquisition Toolbox and the DAQ Adaptor for MATLAB to interface MATLAB with Data Translation hardware to access analog and digital I/O data.With these tools, a Data Translation module can be configured within MATLAB to access all the built-in features of the hardware device. All Data Translation's USB and PCI boards can be accessed for a full range of performance capabilities. Analysis and visualization features of MATLAB can be incorporated into the design to analyze data, save it for post-processing, and make changes based on analysis results.

Software

LV-Link 3.0 LV-Link™ is a library of VIs (Virtual Instruments) that enable LabVIEW® programmers to access the data acquisition features of DT-Open Layers-compliant USB and PCI devices. This library is consistent with the design and layout of the LabVIEW DAQmx VIs to speed development time and minimize learning curve issues.LV-Link provides the ability to measure and control analog I/O, digital I/O, quadrature decoders, and counter/timer signals, and stream data at full-speed. To get up and running quickly, numerous example programs are provided with the software. 

Software

DT-Open Layers for .NET DT-Open Layers® for .NET is a simple, yet powerful native .NET class library for developing test and measurement applications in Microsoft Visual Studio®. The library provides a standard environment for developing test and measurement applications and is compatible with all Data Translation USB and PCI data acquisition boards. This intuitive software library enables users to create flexible programs in Visual C#®. and Visual Basic.NET®, while protecting their hardware investment with complete compatibility to other Data Translation data acquisition boards.

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 a standard API for developing user applications in a

variety of programming environments.

Device Drivers

Device Drivers

Data Gathering Techniques

Data Gathering Techniques

Sampling Nyquist Theorem Transforming a signal from the time domain to the frequency domain requires the application of the Nyquist theorem. The Nyquist sampling theorem states that if a signal only contains frequencies less than cutoff frequency, fc, all the information in the signal can be captured by sampling it at a minimum frequency of 2fc. This means that capturing a signal with a maximum frequency component of fmax requires that it must be sampled at 2fmax or higher. However, common practice dictates that while working in the frequency domain, the sampling rate must be set more than twice and preferably between five and ten times the signal’s highest frequency component. Waveforms viewed in the time domain are usually sampled 10 times the frequency being measured to faithfully reproduce the original signal and retain accuracy of the signal’s highest frequency components.

Data Gathering Techniques

Aliasing and Fourier Transforms When input signals are sampled at less than the Nyquist rate, ambiguous signals that are much lower in frequency than the signal being sampled can appear in the time domain. This phenomenon is called aliasing.

Data Gathering Techniques

Discrete Fourier Transform When ac signals pass through a time-invariant, linear system, their amplitude and phase components can change but their frequencies remain intact. This is the process that occurs when the continuous time domain ac signal passes through the ADC to the discrete time domain. Sometimes, more useful information can be obtained from the sampled data by analyzing them in the discrete time domain with a Fourier Series rather than reconstructing the original signal in the time domain. The sampled data pass through a Fourier transform function to cull out the fundamental and harmonic frequency information. The amplitude of the signal is displayed in the vertical axis, and the frequencies measured are plotted on the horizontal axis.

Data Gathering Techniques

Fast Fourier Transforms The Fast Fourier Transform (FFT) is so common today that FFT has become an imprecise synonym for Fourier transforms in general. The FFT is a digital algorithm for computing Fourier transforms of data discretely sampled at a constant interval. The FFT’s simplest implementation requires 2n samples. Other implementations accept other special numbers of samples. If the data set to be transformed has a different number of samples than required by the FFT algorithm, it is often padded with zeros to meet the required number. Sometimes the results are inaccurate, but most often they are tolerable.

Data Gathering Techniques

Standard Fourier Transforms A Standard Fourier Transform (SFT) can be used in applications where the number of samples cannot be arranged to fall on one of the special numbers required by an FFT, or where it cannot tolerate the inaccuracies introduced by padding with zeros. The SFT is also suitable where the data are not sampled at evenly spaced intervals or where sample points are missing. Finally, the SFT can be used to provide more closely spaced points in the frequency domain than can be obtained with an FFT. In an FFT, adjacent points are separated by 1/T, the inverse of the time interval over which the measurement was made.