Chapter 9
Data Acquisition
Measurement or generation of
physical signals.
What is MAX?
• MAX stands for Measurement & Automation Explorer.
• MAX configures and organizes all your National Instruments DAQ,
PCI/PXI instruments, GPIB, IMAQ, IVI, Motion, VISA, and VXI devices.
• Used for configuring and testing devices.
Icon Found on
Windows Desktop
Data Acquisition in LabVIEW
Traditional NI-DAQ
Specific VIs for
performing:
• Analog Input
• Analog Output
• Digital I/O
• Counter operations
NI-DAQmx
Next generation driver:
• VIs for performing a
task
• One set of VIs for all
measurement types
DAQ System Components
> Sensor/Transducer
> Signal Conditioning Unit
> DAQ PCI Interface Card
> Computer
> Software Analyze & Display
Phenomena & Transducers
Temperature
Thermocouple
Resistance Temperature Detectors (RTDs)
Integrated Circuit Sensor
Light
Vacuum Tube Photosensor
Photoconductive Cells
Sound
Microphone
Force & Pressure Strain Gauges
Piezoelectric Transducer
Load Cells
Position
Optical Encoder
Potentiometers
Fluid Flow
Head Meters
Rotational Flowmeters
pH
pH electrodes
Signal Conditioning Circuits
> Linearization
> Excitation
> Isolation
> Filtering
> Amplification
Data Acquisition
 Data
Acquisition (DAQ) Basics
 Connecting Signals
 Simple DAQ Application
DAQ Device
M-SERIES
Computer
Sensors
Cable
Terminal Block
NI USB-6009
14-bit Analog Inputs
Signal Types
Digital:
> On-Off
> Pulse Train
Analog:
> DC
> Time-Domain
> Frequency-Domain
Signal Information
> State
> Rate
> Level
> Shape
> Frequency
Signal Source Configuration
> Referenced Singled-Ended RSE
> Non-referenced Singled-Ended NRSE
> Differential
Analog I/O Conversion Issues
> Resolution
> Range
> Sampling Rate
ADC Resolution
> Number of bits used to represent an analog signal.
Range
Minimum & Maximum analog signal levels that the
ADC can handle.
Code Width
VCW = Range
Resolution
Gx2
The smallest detectable voltage change by
a data acquisition board with gain G.
Sampling Rate
Samples of an analog signal
Discrete points in time
Sampling frequency – number of samples
per second
Sampling Rate
Aliased Signal
Adequately Sampled Signal