Wireless Measurement Device Selection Guide

Publish Date: Nov 16, 2012 | 1 Ratings | 5.00 out of 5 |  PDF

Overview

Wireless measurement and monitoring systems provide an opportunity to reduce installation and system costs, increase flexibility, simplify system deployments, and address a new set of applications that were previously challenging or impossible with a wired approach. Implementing an NI wireless measurement solution allows you to enjoy these benefits without compromising system reliability or measurement quality. The NI platform also delivers the ability to integrate wireless devices with wired systems to create a complete measurement and control system.

NI offers two wireless measurement product lines that increase flexibility an reduce costs for many new applications: Wi-Fi data acquisition (DAQ), based on IEEE 802.11, and wireless sensor networks (WSNs), based on IEEE 802.15.4. The two product lines differ in specifications such as bandwidth, power, and security, but each delivers seamless NI LabVIEW integration as well as advanced customization options.

Table of Contents

  1. NI Wi-Fi Data Acquisition Devices
  2. NI Wireless Sensor Network Devices
  3. Additional Resources

1. NI Wi-Fi Data Acquisition Devices

Wi-Fi data acquisition is an extension of PC-based data acquisition to measurement applications where wiring is difficult or cost-prohibitive. Wi-Fi data acquisition (DAQ) devices combine IEEE 802.11 wireless or Ethernet communication, direct sensor connectivity, and the flexibility of NI-DAQmx software for remote monitoring of electrical, physical, mechanical, and acoustic signals. The NI cDAQ-9191 holds a single C Series module and is capable of streaming continuous waveform data on each channel at more than 50 kS/s with 24 bits of resolution.

 

Figure 1. The NI cDAQ-9191 streams continuous waveform data back to a host computer.

In addition, built-in NIST-approved 128-bit AES encryption and advanced IEEE 802.1X network authentication offer the highest commercially available network security (WPA2 Enterprise). With the flexibility of the NI software platform, including LabVIEW, and the ubiquity of 802.11 network infrastructure, it's easy to incorporate the NI cDAQ-9191 and wireless connectivity into new or existing PC-based measurement or control systems.

Learn more about NI Wi-Fi Data Acquisition

NI WLS-9163 and C Series Hardware

Each NI Wi-Fi DAQ device is a combination of an NI WLS-9163 wireless carrier and an NI C Series signal conditioning module. The WLS-9163 provides both IEEE 802.11b/g and Ethernet connectivity back to a host PC.

Figure 2. Each Wi-Fi NI CompactDAQ device combines an NI cDAQ-9191 chassis and an NI C Series module to provide wireless sensor measurements.

C Series modules offer direct sensor connections, NIST-traceable calibration, and built-in signal conditioning for a variety of measurements, including temperature, high-voltage digital I/O, strain, acceleration, current, and voltage. In addition to the NI cDAQ-9191 wireless chassis, you can use C Series modules interchangeably for measurement and control applications with different chassis, including 4- and 8-slot NI CompactDAQ chassis and CompactRIO, as well as the NI USB-9171 single module chassis and NI cDAQ-9181 Ethernet chassis. 

Secure Wireless Data Acquisition

Wi-Fi NI CompactDAQ devices implement the highest commercially available wireless network security standard, IEEE 802.11i (commonly known as WPA2 Enterprise), including IEEE 802.1X network authentication and 128-bit AES data encryption. Authentication ensures that only authorized devices have network access, and encryption prevents data packets from being intercepted. Accepted worldwide, IEEE 802.11i security standards build on more than 10 years of wireless innovation in the IT sector. By using standard security protocols, NI Wi-Fi DAQ devices make it easy to add wireless measurements to IT networks safely.

Streaming Wireless Measurements with NI-DAQmx Software

After more than 20 years of helping engineers and scientists achieve high-quality PC-based data acquisition, NI-DAQmx driver software continues to be the heart of the National Instruments data acquisition platform. Recognizing the diversity of measurement applications, NI approaches data acquisition independent of specific PC bus technologies. You can use the same NI-DAQmx API for communicating across PCI, PCI Express, PXI, PXI Express, USB, Ethernet, and Wi-Fi. This means you can use an application developed for a USB data acquisition device (even a high-speed application) with a wireless data acquisition device without making any changes to the software.

Figure 3. NI-DAQmx driver software abstracts data acquisition bus technology from the user and provides a consistent API across multiple programming languages.

NI Wi-Fi DAQ devices can stream continuous 24-bit waveform data at more than 50 kS/s from multiple measurement channels. Managing this amount of data over a wireless network is a nontrivial task, but NI-DAQmx abstracts the complexity associated with buffered transfers over TCP/IP from the user. With device-side intelligence, message-based communication, and an advanced streaming engine, NI-DAQmx and NI Wi-Fi DAQ provide all the benefits of wireless technology for test and measurement applications without sacrificing the performance or reliability of a wired solution.

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2. NI Wireless Sensor Network Devices

A wireless sensor network is a wireless network consisting of spatially distributed autonomous devices that use sensors to monitor physical or environmental conditions. These autonomous devices, or nodes, combine with routers and a gateway to create a typical WSN system. The distributed measurement nodes communicate wirelessly to a central gateway, which provides a connection to the wired world where you can collect, process, analyze, and present your measurement data. To extend distance and reliability in a wireless sensor network, you can use routers to gain an additional communication link between end nodes and the gateway. 

 

Figure 4. Common Wireless Sensor Network Architecture

National Instruments Wireless Sensor Networks offer reliable, low-power measurement nodes that operate for up to three years on 4 AA batteries and can be deployed for long-term, remote operation. The NI WSN protocol based on IEEE 802.15.4 technology provides a low-power communication standard that offers mesh routing capabilities to extend network distance and reliability. 

Learn more about NI Wireless Sensor Networks

Read this Instrumentation Newsletter article on wireless sensor networks

NI WSN Hardware

For most WSN applications, you can create a basic network architecture in which the distributed measurement nodes acquire data from the environment around them and transmit these measurements to a gateway. NI WSNs provide the flexibility to connect your Ethernet gateway to a Windows or LabVIEW Real-Time host controller.

Figure 5. NI WSN Gateway and measurement nodes form a distributed wireless sensor network.

The NI WSN Ethernet gateway coordinates communication between distributed measurement nodes and the host controller in your NI wireless sensor network.  The gateway has a 2.4 GHz, IEEE 802.15.4 radio to collect measurement data from the sensor network and a 10/100 Mbit/s Ethernet port to provide flexible connectivity to a Windows or LabVIEW Real-Time host controller.  The gateway can accommodate up to 8 end nodes, but can be extended to communicate with up to 36 nodes when router nodes are implemented in your network topology.

The high-accuracy NI WSN measurement nodes provide four analog input channels and four digital input/output channels for easy sensor connectivity, while four AA alkaline cells deliver up to a three-year lifetime. You can configure each digital channel as input, sinking output, or sourcing output. The WSN-3202 also offers an up to 12 V, 20 mA sensor power output line that draws from the battery or external power supply to drive external sensors. 

NI-WSN Software

By using LabVIEW software to design your wireless sensor network system, you benefit from the rapid development of graphical programming for your entire solution. With LabVIEW, you can use the same graphical programming approach to create the node intelligence; develop desktop or embedded real-time applications that perform data logging, processing, and alarming; and take advantage of Web services that provide access to your application from any Web-enabled device.

Figure 6. Use the LabVIEW graphical programming platform to enhance and customize your wireless sensor network.

Simply drag and drop I/O variables from the LabVIEW Project to a LabVIEW block diagram for data extraction, analysis, and presentation. You can also use I/O variables to monitor node attributes such as link quality and battery voltage and determine if a node is configured as an end device or mesh router. You can create a simple data extraction program or integrate your WSN LabVIEW code into a complete wired and wireless measurement and analysis program.

LabVIEW WSN Software

The LabVIEW Wireless Sensor Network Module extends the LabVIEW graphical programming environment to create and deploy embedded applications to programmable NI WSN measurement nodes. Use LabVIEW WSN Pioneer to extend battery life by optimizing node behavior, perform custom analysis, and embed decision making on programmable NI WSN measurement nodes.

Figure 7. The NI LabVIEW WSN Module deploys embedded LabVIEW applications to NI WSN measurement nodes.

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3. Additional Resources

View the NI WSN homepage
View the wireless NI CompactDAQ homepage

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