The document discusses the integration of wireless measurements with wired data acquisition systems, highlighting the importance of a hybrid measurement system that balances measurement quality, bandwidth, latency, synchronization, I/O selection, distance, and power consumption. It details a five-layer architecture for designing these systems, emphasizing the modularity and reusability of software components. The presentation supports the case for mixed wired/wireless systems and concludes with a demonstration of a hybrid testing setup.

1. 1
Incorporating Wireless Measurements
with Wired Data Acquisition Systems
Charlie Stiernberg
Remote Data Acquisition Product Manager, National Instruments

2. 2
Agenda
• PC-based data acquisition technologies
• Making the case for mixed wired/wireless systems
• Designing hybrid measurement systems
• Demonstration

3. 3
Software
DAQ
Signal
Conditioning
Signal
Transducer
What is PC-Based Data Acquisition (DAQ)?

4. 4
DAQ System Technologies
PXI Portable/Handheld
Remote Desktop
IEEE 802.11, ZigBee,
802.15.4, etc.

5. 5
DAQ System Technologies
PXI Portable/Handheld
Remote Desktop
IEEE 802.11, ZigBee,
802.15.4, etc.

6. 6
Key DAQ System Requirements
• Measurement Quality
• Bandwidth
• Latency
• Synchronization
• I/O Selection / Availability
• Distance
• Power Consumption

7. 7
Measurement Quality
Important Factors to Consider
• Architecture – multiplexed versus simultaneous sampling
• Sampling rate – Nyquist theorem
• Accuracy
 Resolution
 Absolute accuracy
 Range and amplification
 Noise and filtering
• Calibration – certificates, traceability, interval

8. 9
Bandwidth versus Latency
Bandwidth: Measures the rate at which data is
sent across the bus, typically in Mbps
Latency: Measures the delay in the transmission
of data across a bus

9. 10
10000 1000 100 10 1 0.1
10000
1000
100
10
1
Increasing
(Improving)
Bandwidth
Decreasing (Improving) Latency
Approximate Latency (μs)
Max
Bandwidth
(MB/s)
Bandwidth versus Latency
IEEE 1394a
Gigabit Ethernet
USB 1.1 GPIB (488.1)
USB 2.0
Fast Ethernet
VME/VXI
PCI/PXI (32/33)
PCI Express (x4)
GPIB (HS 488)
IEEE 802.11g
802.15.4
Bluetooth
UWB IEEE 802.11n

10. 11
PXI
Multichassis
GPS
10-12 sec
Precision
sec
10-3 sec
10-6 sec
10-9 sec
10-2m 100m
Proximity
101m 102m 103m 104m 105m Global
<10-4m
Signal-Based
Time-Based
IRIG-B
Synchronization

11. 12
I/O Selection / Availability
• Wired Systems
 Decades of development
 High channel density
 Decoupled front-end signal conditioning
• Wireless Systems
 Years of development
 Low channel density
 Integrated signal conditioning

12. 13
Distance
RS-485, 1200 m
Ethernet, 100 m
GPIB, 20 m
Cabled PCIe, 7 m
USB, 5 m
>Wireless, ? m

13. 14
Power Consumption
Test Rack
100’s Watts
USB Power
<3 Watts
WSN
«1 Watt

14. 16
System Designer’s Dilemma
Measurement
Quality
Bandwidth
Latency
Synchronization
I/O Selection
Distance
Power
Consumption
Wired Systems
Measurement
Quality
Bandwidth
Latency
Synchronization
I/O Selection
Distance
Power
Consumption
Wireless Systems

15. 17
Hybrid Measurement Systems
Measurement
Quality
Bandwidth
Latency
Synchronization
I/O Selection
Distance
Power
Consumption

16. 19
USB
USB DAQ
Ethernet
PAC
Wi-Fi
WAP
Wireless DAQ Ethernet DAQ
PXI
PXI DAQ Wireless
Sensors
Gateway
Key Challenges: Standardization, Interoperability
Hybrid Measurement Systems

17. 20
Five Layer Architecture
Device I/O
Instruments, DAQ,
Distributed I/O
Bus
USB, PCI, PXI, Embedded,
Wireless
Measurement Services
NI-DAQmx, Instrument
Drivers, Modbus
Application
NI LabVIEW, ANSI C/C++,
C# VB 6, VB .NET
System Management
TestStand, DIAdem
Application
Management Services
Application
Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

18. 21
Device I/ O Layer
Choose Measurement Functionality
 Device(s) under test (DUT) drives measurement
requirements
 Measurement requirements drive DAQ selection
 Instrument selection drives may drive bus choices
 Optimize price/performance/functionality
DAQ Selection
Measurement
Requirements
DUT Bus
Optimize Price/Performance
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

19. 22
Computer / Bus Layer
• Application requirements dictate what level of wireless
functionality is necessary
• PC architecture
 Laptop or desktop PC, PXI or embedded controller, server or industrial PC
 Responsible for running measurements programs, configuring
hardware/software components, and connecting to the different buses
• Design this layer to account for connectivity needs
 Connect to a variety of wireless gateways or protocol translators
 Enables DAQ component reuse
• Advantages of a multiplatform system
 Extensibility, longevity, integration with latest technologies
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

20. 23
Measurement & Control Services
Measurement and Control
Services
Application Development Environments
Configuration
Manager
Diagnostic
Tools
Instrument
Drivers
Device APIs
Protocols
Benefits
• Separate hardware
and software when
debugging
• Aid in replacement
• Help in planning for
longevity
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

21. 24
Measurement & Control Services
• Example: Wireless Sensor Network
Instrument Drivers (ni.com/wireless)
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

22. 25
Application Layer
• Composed of individual programs
 Temperature measurement or vibration frequency
• Keeps applications and tests independent of bus
 Write modular test programs
 Avoid direct bus level calls in tests
 Use test-oriented abstractions
• Create GenerateWfm.vi instead of AWG4321_Start.vi
• Benefits of modular code
 Reusability: Modular code is usable in other test programs
 Replacement: Interchanging DAQ devices is simplified
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

23. 26
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes
DAQ Programs Using Device APIs
ZigBee
RS-232
DAQ Program
I/O
USB Driver
• DAQ programs
tied to driver API
• Increases
replacement time
and costs ISA100.11a
Ethernet

24. 27
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes
Hardware Abstraction Layer (HAL)
DAQ Program
Hardware Abstraction Layer
• HAL abstracts
test programs
from driver API
• Decreases
replacement time
and costs ZigBee
RS-232
I/O
USB Driver
ISA100.11a
Ethernet

25. 28
HAL Features and Benefits
• Features
 API translation
 Scaling
 Timing
 Formatting
 Error handling
 Fault insertion
 Simulation
• Benefits
 Improves interchangeability
 Enables “same answer”
 Higher software reuse
 Longer system life
 Reduces code revalidation
and documentation
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

26. 29
System Management Layer
• Framework to sequence test routines, log
data, generate reports, and manage
user privileges
• Benefits
 Improve code reuse
 Decrease development time
 Increase extensibility
 Accommodate software migration
Application Management
Services
Application Development
Driver or I/O Libraries
USB, PXI
DAQ Device
Gateway
Wireless Nodes

27. 30
Hybrid System Demonstration
USB Wi-Fi
Accelerometer
NI-DAQmx
LabVIEW ANSI C

28. 31
NI-DAQmx Hardware Abstraction Layer
Measurement Services Driver API

29. 32
Configure
Channel
Configure
Timing
Configure
Triggering
Start
Acquisition
Read
Data
Clear
Task
NI-DAQmx LabVIEW API

30. 33
DAQmxCreateAIVoltageChan( taskHandle, “Dev1/ai0”, “”, DAQmx_Val_Cfg_Default,
-10.0, 10.0, DAQmx_Val_Volts, NULL );
DAQmxCfgSampClkTiming( taskHandle, “”, 10000.0, DAQmx_Val_Rising,
DAQmx_Val_FiniteSamps, 1000 );
DAQmxCfgDigEdgeStartTrig( taskHandle, “/Dev1/PFI0”, DAQmx_Val_Rising );
DAQmxStartTask( taskHandle );
DAQmxReadAnalogF64( taskHandle, -1, 10.0, 0, data, 1000, &read, NULL );
printf( “Acquired %d samples. %d”, read );
DAQmxClearTask( taskHandle );
Read Data
Clear Task
Configure Channel
Configure Timing
Start Acquisition
Configure Triggering
NI-DAQmx C API

31. 34
Hybrid Test System Summary
Hybrid Systems
• Balance needs and maximize investment in ATE
• Use the five layer architecture
 Allow component reuse
 Carefully select or build new components
• Keep PCI and PXI in the center
 Best PC connectivity
 Best instrumentation connectivity

32. 35
Summary
• Wired and Wireless measurements have
advantages and disadvantages
• Hybrid measurement systems are a practical
approach to wireless
• Use the 5 Layer Architecture to separate
hardware and software components
• For more information, visit ni.com/wifi