Sunday, November 20, 2011

What Is Data Acquisition?

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. PC-based data acquisition uses a combination of modular hardware and flexible software to transform your standard laptop or desktop computer into a user- defined measurement or control system.  Learn more about each of these components in the sections below.
While 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, and a computer with software.
 Signal Conditioning  
 DAQ Hardware  


A sensor (or transducer) is a device that converts a physical phenomenon into a measurable electrical signal, such as voltage or current. The following table shows a short list of some common phenomena and the transducers used to measure them.
TemperatureThermocouple, RTD, Thermistor
LightPhoto Sensor
Force and PressureStrain Gage, Piezoelectric Transducer
Position and DisplacementPotentiometer, LVDT, Optical Encoder
pHpH Electrode
Table 1. Phenomena and Existing Transducers
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 and digital.

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.

Because analog signals can take on any value, the level gives vital information about the measured analog signal. The intensity of a light source, the temperature in a room, and the pressure inside a chamber are all examples that demonstrate the importance of the level of a signal.


Some signals are named after their specific shapes - sine, square, sawtooth, and triangle. The shape of an analog signal can be as important as the level because you can further analyze the signal, including peak values, DC values, and slope. The analysis of heartbeats, video signals, sounds, vibrations, and circuit responses are some applications involving shape measurements.

All analog signals can be categorized by their frequencies. Unlike the level or shape of the signal, you cannot directly measure frequency. You must analyze the signal using software to determine the frequency information. This analysis is usually done using an algorithm known as the Fourier transform.

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. The useful information that you can measure from a digital signal includes the state and the rate.


The state of a digital signal is essentially the level of the signal - on or off, high or low. Monitoring the state of a switch - open or closed - is a common application showing the importance of knowing the state of a digital signal.

The rate of a digital signal defines how the digital signal changes state with respect to time. An example of measuring the rate of a digital signal includes determining how fast a motor shaft spins. Unlike frequency, the rate of a digital signal measures how often a portion of a signal occurs.

Advantages of NI DAQ

Designed for performance, NI data acquisition devices provide high-performance I/O, industry-leading technologies, and software-driven productivity gains for your application. With patented hardware and software technologies, National Instruments offers a wide-spectrum of PC-based measurement and control solutions that deliver the flexibility and performance that your application demands. For more than 25 years, National Instruments has served as more than just an instrument vendor, but as a trusted advisor to engineers and scientists around the world.

High-Performance I/O

Measurement accuracy is arguably one of the most important considerations in designing any data acquisition application. Yet equally important is the overall performance of the system, including I/O sampling rates, throughput, and latency. For most engineers and scientists, sacrificing accuracy for throughput performance or sampling rate for resolution is not an option. National Instruments wide selection of PC-based data acquisition devices have set the standard for accuracy, performance, and ease-of-use from PCI to PXI and USB to wireless.

"National Instruments is a well-known supplier of data acquisition systems, and…it is important that we work with companies with proven track records that will be around for years to come."Rick Bradshaw (Halliburton)

High-Accuracy Designs

Many scientists and engineers mistakenly evaluate DAQ device error by just considering the bit resolution of the DAQ device. However, the error dictated by the device resolution, or quantization error, might account for only a very small amount of the total error in your measurement result. Other types of errors, such as temperature drift, offset, gain, and non-linearity can vary drastically by hardware design. Through years of experience, NI has developed several key technologies to minimize these errors and maximize the absolute accuracy of your measurements.

Easy Sensor Connectivity with Integrated Signal Conditioning

Traditionally, measuring sensors required separate front-end signal conditioning systems cabled to a data acquisition system. New technologies and miniaturization have enabled the integration of sensor-specific signal conditioning and analog to digital conversion on the same device. NI DAQ devices with integrated signal conditioning deliver higher-accuracy measurements by eliminating error-prone cabling and connectors and reduce the number of components in a measurement system. NI has also partnered leading sensor vendors to provide easy, tool-free sensor connectivity and automatic sensor configuration with TEDS technology.

I/O for Any Sensor, Any Bus

The breadth and depth of National Instruments product offering is not available from any other vendor. NI DAQ devices are offered on a variety of common PC-busses including USB, PCI, PCI Express, PXI, PXI Express, Wi-Fi (IEEE 802.11), and Ethernet, with a wide spectrum of measurement types. NI’s modular form factors provide interchangeability to meet your specific application’s needs and the flexibility for future expansion.

NI Data Acquisition Technologies   

Over the past 25 years, National Instruments has continually innovated to provide the industry’s most advanced data acquisition devices and help you to get the most out of standard PC technologies. NI engineers have developed patented hardware and software technologies to create a data acquisition platform that surpasses the performance and productivity of traditional devices.


The NI-STC3 chip is the core component of NI DAQ devices and was designed by NI engineers to address the needs of the most demanding test, measurement, and control applications. It provides a native PCI Express interface, four counters, and advanced timing and synchronization capabilities.

Learn more

NI Signal Streaming 

National Instruments patented NI Signal Streaming technology helps you get more performance out of your PC bus. NI Signal Streaming combines three innovative hardware- and software-level design elements to enable sustained high-speed and bidirectional data streams over USB, Ethernet, and Wi-Fi (IEEE 802.11).


National Instruments introduced the Technical Data Management Streaming (TDMS) open file format as a result of the deficiencies of other data storage options. The binary TDMS file format is an easily exchangeable, inherently structured, high-speed-streaming-capable file format that is quickly searchable without the need for complicated and expensive database design, architecture, or maintenance.

Learn More 


Many data acquisition vendors overlook the fact that an ADC is a nonlinear system. Failing to account for this can introduce significant errors in a measurement. NI-MCal is a software-based calibration algorithm that generates a third-order polynomial to correct for the three most common sources of measurement error: offset, gain, and nonlinearity.


A programmable gain instrumentation amplifier (PGIA) delivers a scaled voltage signal to the ADC using different gain settings to maximize the resolution of the data acquisition device. Most off-the-shelf PGIAs are not optimized for data acquisition applications, because their settling times are too long. NI-PGIA 2 technology improves accuracy and increases performance by minimizing settling time and maintaining the specified resolution even at the maximum sampling rate of the device.

NI InstantDAQ Technology

NI InstantDAQ technology offers a simple approach to taking measurements with your PC. NI DAQ devices with NI InstantDAQ automatically load built-in software for viewing logging data upon connecting the device to your PC. No prior driver installation is necessary.

Learn More

TEDS (IEEE 1451.4) - Sensor Plug & Play

Transducer electronic datasheet technology (TEDS) brings plug-and-play capabilities to sensors. TEDS-compatible sensors internally store an electronic datasheet with the sensor’s configuration information. National Instruments TEDS measurement systems can automatically configure these “smart sensors” for measurement, reducing setup time and eliminating transcription errors that commonly occur during sensor configuration.

Improved Productivity through Software

One of the biggest benefits of using a PC-based data acquisition device is that you can use software to customize the functionality and visualization of your measurement system to meet your application needs.  When examining the cost of building a data acquisition system, software development often accounts for 25 percent of total system cost. Obtaining easy-to-use driver software with an intuitive application programming interface makes a big impact on completing a project on time and under budget. National Instruments provides a wide array of software tools that make you more productive at accomplishing your measurement or automation tasks.
  • NI-DAQmx Driver Software
  • NI LabVIEW Graphical Programming
  • NI DIAdem Visualization and Reporting Tools

NI-DAQmx Driver Software

NI-DAQmx driver software goes far beyond a basic DAQ driver to deliver increased productivity and performance and is one of the main reasons National Instruments continues to be the leader in virtual instrumentation and PC-based data acquisition.

One Interface, Many Programming LanguagesNI-DAQmx provides the same interface for many popular programming languages including NI LabVIEW, Visual Studio .NET languages, C, and C++. The functions and properties, as well as the order of the functions you use, are the same across all languages.
One Interface, Hundreds of Data Acquisition DevicesWhether you are developing with a PCI, PCI Express, PXI, PXI Express, USB, Ethernet, or Wireless data acquisition device, the basic NI-DAQmx code is the same across all devices. With a single programming interface, you can easily upgrade or switch hardware without changing your code.
Easy and Powerful Data Acquisition SoftwareNI-DAQmx includes intuitive features to make taking measurements easier, as well as powerful features to give you higher performance and more flexibility.

NI LabVIEW Graphical Programming

NI LabVIEW is a graphical programming environment that makes it easy to take any measurement from any sensor on any bus. You can automate measurements from several devices, analyze data in parallel with acquisition, and create custom reports all in a matter of minutes with this industry-standard tool. From acquiring one simple measurement to capturing data from a complex 10,000-channel system, LabVIEW can help you acquire, analyze, and log data in less time.

Work Faster with a Graphical Approach
With LabVIEW, you develop data acquisition applications using drag-and-drop graphical icons instead of writing lines of text. You can complete programs that take weeks to write with traditional programming languages in hours using LabVIEW, even if you have no programming experience. An intuitive flowchart representation displays your code in a manner that is easy to develop, maintain, and understand.
Get Started Immediately with Open-and-Run Examples
There is no need to create your entire data acquisition system from scratch. LabVIEW includes several shipping examples for every common measurement task. Hit the ground running with open-and-run programs for virtually any setup, ranging from a simple single-channel measurement to a high-performance multichannel system featuring advanced timing, triggering, and synchronization across multiple devices.
Create a Professional User Interface in Seconds
LabVIEW helps you quickly create a graphical user interface using hundreds of drag-and-drop controls, graphs, and 3D visualization tools. You can customize the position, size, alignment, scale, and color of these built-in controls in a matter of seconds from a right-click menu. LabVIEW also helps you create your own controls or incorporate custom imagery and logos.


DIAdem is a single software tool that you can use to quickly locate, load, visualize, analyze, and report measurement data that is collected during data acquisition and/or generated during simulations. DIAdem is designed to help you move beyond Microsoft Excel for data analysis and meet the demands of today’s testing environments that require you to quickly access, process, and report on large volumes of scattered data in multiple custom formats to make informed decisions. DIAdem is a component of the NI Technical Data Management (TDM) solution.

NI DAQ Setup and Support

Getting Started with NI DAQ

Getting Started with NI Products
Follow the steps below to install, set up, and configure your NI data acquisition (DAQ) hardware and learn the basics of NI LabVIEW software.
Basic Programming with NI-DAQmx
See how MAX and the DAQ Assistant can help you configure your data acquisition system.
DAQ Video Demos
Watch short videos on performing common tasks using NI data acquisition devices and LabVIEW.
DAQ Training Options
Learn recommended techniques to reduce development time and improve application performance and scalability. See your options for online and instructor-led courses.


NI-DAQmx Support Overview
Ask an NI engineer your application questions or search online resources for answers.
DAQ Discussion Forums
Join the latest conversation threads in the DAQ community or post your own question.

Drivers and Code 

Download NI-DAQmx
Download the latest version of the NI-DAQmx driver.
Driver & Operating System Compatibility Chart
Find the recommended driver your NI DAQ device and operating system (OS).
Example Code
Share and download example programs and IP with other users.

Other Resources

How-To Guide for Most Common Measurements
Learn about the operating principles of common sensor types and how use NI data acquisition devices to take sensor measurements.
Field Wiring and Noise Considerations
Explore the common issues and solutions when connecting signals to your data acquisition device.
Advanced Programming with NI-DAQmx
Learn how to take advantage of advanced NI-DAQmx functionality including property nodes, synchronization, and high-speed streaming.


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