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1

Lesson 9Data Acquisition and Waveforms

TOPICSPlug-in DAQ devices

Data Acquisition in LabVIEW Analog InputData Logging

Analog OutputCountersDigital I/O

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2

Overview and Configuration

Fundamental task of a DAQ system is tomeasure or generate real-world physicalsignals

DAQ system consists of:TransducersSignal ConditioningPlug-in DAQ deviceDriver Software

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MeasurementSoftwareFramework

NI-DAQ contains:Traditional NI-DAQNI-DAQmx

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4

DAQ Hardware Configuration

Measurement & Automation Explorer (MAX)

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Channels and Tasks

Signalsai 0ai 1

ai 2

Sine Wave 1

Sine Wave 2

Sine Wave 3

Channel names

TasksTiming and Triggering

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The DAQ Signal Accessory

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NI-DAQmx versus Traditional NI-DAQFeature NI-DAQmx Traditional NI-DAQ

Test Panels DAQ Assistant with code generation no

On-line diagnostics

Scaling to voltage and physical units

50 kS/s with single point I/O

Measurement multithreading Instant calibration

Automatic selection of optimal gains

Guaranteed lossless data

650 Alliance members

Integration with LabVIEW

Developer Exchange discussion forum

Compatible with Legacy ISA Boards no

Accuracy

Performance

Productivity

QualityBest

GoodFair Compatibility

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Data Acquisition in LabVIEW

Traditional NI-DAQSpecific VIs for

performing: Analog Input Analog Output Digital I/O Counter operations

NI-DAQmxNext generation driver: VIs for performing a

task One set of VIs for all

measurement types

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NI-DAQmx Data Acquisition

Single set of VIs used to perform analogI/O, digital I/O, and counter operations

DAQ Assistant Express VI Quickly and easily program the DAQ device Creates a local task Most applications can use the DAQ

Assistant Express VI

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NI-DAQmx Data Acquisition Task Types

Measurement typecan be: Analog Input Analog OutputCounter InputCounter Output

Digital I/O

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Analog Input

Analog Input taskis specific to the

measurement

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Analog Input Task Timing and Triggering

Configures the number of samples and sample rate for the task

Configures the start andreference triggers for the task

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Data Logging It is often necessary to permanently store data that is acquired

from the DAQ device LabVIEW includes the ability to read and write a LabVIEW

Measurement File

LabVIEW Measurement File is an ASCII text file

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Analog Output

Analog Output taskis specific to thegeneration type

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Analog Output Task Timing and Triggering

Configures the number of samples and sample rate for the task

Configures the start andreference triggers for the task

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Counters A counter is a digital timing device

Typical uses of a counter: Event counting Frequency measurement Period measurement Position measurement Pulse generation

Gate

Source

Output

Count Register

Count register Stores the current count of the counter

Source Input that causes the counter to increment each time it togglesGate Input that is used to enable or disable the function of the counter Output Signal that generates pulses or a series of pulses

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Digital Input and Output Digital I/O can

read from or writeto a line or anentire digital port

A digital port is acollection of digitallines

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Summary MAX is the primary configuration and testing utility that is

available for the DAQ device. The DAQ Assistant is used to configure the DAQ device and

perform data acquisition.

Most application can use the DAQ Assistant. For applicationsthat require advanced timing and synchronization use the VIsthat come with NI-DAQmx.

The DAQ Assistant can perform Analog Input, Analog Output,Digital I/O, and Counter operations.

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Lesson 10Instrument Control

TOPICSInstrument Control Overview

GPIB Communication and ConfigurationInstrument I/O AssistantVirtual Instrument Software Architecture (VISA)Instrument DriversSerial Port CommunicationWaveform Transfers

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Instrument Control OverviewControl any instrument if you know the following:

Type of connector on the instrument Type of cables needed Electrical properties involved Communication protocols used Software drivers available

Instruments Computer

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GPIB Communication

GPIB Instruments

GPIBCable

GPIB Interface

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Standards Introduction

1965

1987

1990

1992

1993

1975

HP designs HP-IB (Hewlett Packard Interface Bus)

HP-IB becomes IEEE 488

IEEE 488.2 adoptedIEEE 488 becomes IEEE 488.1

SCPI (Standard Commands for ProgrammableInstruments) added to IEEE 488.2

IEEE 488.2 revised

HS488 proposed

1999 HS488 approved

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GPIB Hardware Specifications

Max cable length betweendevices = 4 m (2 m average) Max cable length = 20 m Max number of devices =

15 (2/3 powered on)1

12

13

24

DIO5

DIO6

DIO7 DIO8 REN GND (TW PAIR W/DAV) GND (TW PAIR W/NRFD) GND (TW PAIR W/NDAC) GND (TW PAIR W/IFC) GND (TW PAIR W/SRQ)

GND (TW PAIR W/ATN)

SIGNAL GROUND

DIO1

DIO2

DIO3 DIO4 EOI DAV

NRFD NDAC

IFC SRQ

ATN

SHIELD

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GPIB Software Architecture Windows

Driver Software(*.DLL)

InstrumentDriver VIsNI-VISA

LabVIEW

Diagnostics Tools:

GPIB Diagnostic ToolNI-Spy

Configuration Tools:Measurement &Automation Explorer

Interface Board(GPIB, PXI,

VXI, computer based, etc.)

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Configuring GPIB Board and Instruments

Measurement & Automation Explorer (MAX)

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What is the Instrument I/O Assistant?

Accessed through a LabVIEWExpress VI Sets up device

communication and dataparsing step by step througha configuration interface

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Communicating with an Instrument

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Virtual Instrument Software Architecture

Platform independent VISA is the backbone of the

IVI and Plug & PlayInstrument Drivers

Interface independent Must know SCPI command

set to program directly withVISA

GPIB VXISerial PXI

VISA

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VISA Terminology

Resource Instrument, Serial Port, or Parallel Port Session Connection to a Resource Instrument Descriptor Resource location

Format: Interface Type::Address::INSTR

Examples:

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Instrument Descriptor Syntax Resource Name contains interface info VISA Aliases also work

Interface Resource Name Grammar

Serial ASRL[board][::INSTR]GPIB GPIB[board]:: primary address [::INSTR]

VXI VXI[board]:: VXI logical address [::INSTR]

GPIB-VXI GPIB-VXI[board][:: GPIB-VXI primary address ]:: VXI logical address [::INSTR]

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VISA Resource Name

Exact name and location of the instrument Use the VISA Resource Name control You can specify the full resource name of the VISA Alias

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Instrument Drivers

More than 1200 LabVIEW Instrument drivers Programming simplified to high-level API

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Installing and Finding Instrument Drivers Drivers available atni.com/idnet

Install the instrument driver VI Library intoLabVIEW 7.0\instr.lib directory

Access drivers fromFunctionsInputInstrument Driverssubpalette

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IDNET - Instrument Driver Network

Learn about drivers Get help with developing drivers Submit your driver to the network

Download drivers

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Instrument Driver Model

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Initialize

Configure

Action/Status

Data

Utility

Close

Instrument Driver VIs

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Instrument Driver Inputs and Outputs

Instrument Descriptor VISA Sessions- A connection or link to a specific instrument- Created after instrument is initialized

- Used throughout VI whenever you communicate with that specificinstrument Error cluster

HP34401A Initialize.vi

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Putting It All Together

Initialize instrument Do operation(s) Close instrument Check error status

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Serial Communication Popular means of communication between computer and

peripheral device Data sent one bit at a time across the cable

Used for low transfer rates or long distances

Only a cable is needed since most computers have at leastone available serial port

RS-232 Instrument

RS-232 Cable

PC SerialPort

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Serial Hardware Connection

RS-232 DCE or DTE

configurations

9-pin or 25-pin

RS-422

DCE or DTE

8-pin

RS-485 Multidrop

Pin DTE DCE

1 DCD Input Output2 RxD I O3 TxD O I4 DTR O I5 Com - -

6 DSR I O7 RTS O I8 CTS I O9 RI I O

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Serial Communication

Terminology Baud rate bits per second Data bits inverted logic and LSB first Parity optional error-checking bit Stop bits 1, 1.5, or 2 inverted bits at data end Flow control hardware and software handshaking options

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Using the Instrument I/O Assistant with Serial

Select COMX asthe instrumentaddress

Use the I/O Assistant as donewith GPIB

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Summary LabVIEW can communicate with any instrument that connects to

your computer if you know the interface type Use the Measurement & Automation Explorer (MAX) to detect,

configure, and test your GPIB interface and instruments Use the Instrument I/O Assistant for easy and fast GPIB and serial

programming. An instrument driver eliminates the need for your to have detailed

knowledge of the specific strings used by an instrument Instrument Library more than 2000 instruments supported

Instrument driver VIs share a common hierarchy and come with anexample to help you get started

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Lesson 11VI Customization

TOPICSConfiguring Appearance of Front PanelSubVI Front PanelsKeyboard ShortcutsVI PropertiesCustomizing Palettes

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Customizing VI Properties Access VI Properties by right-clicking the icon pane or selecting it

from the File menu Affects every instance of that VI in all applications

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Window AppearanceOnly affects VI panel while VI is running

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Window Size Set minimum and current panel size

Adjust size of panel relative to the monitor Scale objects on

panel as windowresizes

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Creating Pop-Up Panels Every Instance Use Top-Level Application Window or Dialog appearance types

Create custom window appearance

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Creating Pop-Up Panels Single Instance

Access SubVI Node Setup by right-clicking on subVI icon oncalling VIs diagram

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Key Navigation Assigns keyboard strokes tofront panel controls

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Preventing Editing of a VI Opens, runs, and closes LabVIEW without

user intervention Remove menus, Abort button, etc

Save with Options

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Summary Use VI Properties to set VI execution, window, and documentation

options Use SubVI Node Setup to set execution options for a single

instance of a subVI Use the Key Navigation option to assign front panel controls to a

keyboard key combination Use the Save with Options from the file menu to make backups of

your VIs You can often edit VIs by aborting them from the diagram of

another VI

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Technical Support Resources

Award-Winning Websitewww.ni.com/support Drivers & UpdatesProduct Manuals

KnowledgeBasesExample CodeTutorials Application NotesDiscussion Forums

http://www.ni.com/supporthttp://www.ni.com/support

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Info-LabVIEW ListserveUser-sponsored Internet mailing list

Send subscription messages to the Info-LabVIEW list processor listmanager@pica.army.mil

Send other administrative messages to the Info-LabVIEW listmaintainer at

info-labview-REQUEST@pica.army.mil

Post a message to subscribers atinfo-labview@pica.army.mil

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LabVIEW Publications

LabVIEW Technical Resourcequarterly newsletter by LTRPublishing LabVIEW Graphical Programming and LabVIEW Power

Programming by Gary W. Johnson, McGraw-Hill

LabVIEW for Everyoneby Lisa K. Wells and Jeffrey Travis,Prentice-Hall

LabVIEW Signal Processing by Mahesh Chugani, Abhay Samant,and Michael Cerna, Prentice-Hall

LabVIEW Applications and Solutionsby Rahman Jamal and HerbertPichlik, Prentice-Hall