labview basics course slides

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Lesson 9Data Acquisition and Waveforms

TOPICSPlug-in DAQ devicesData Acquisition in LabVIEWAnalog InputData LoggingAnalog OutputCountersDigital I/O

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Overview and Configuration

Fundamental task of a DAQ system is to measure or generate real-world physical signals

DAQ system consists of:•Transducers•Signal Conditioning•Plug-in DAQ device•Driver•Software

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Measurement Software Framework

NI-DAQ contains:•Traditional NI-DAQ•NI-DAQmx

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DAQ Hardware Configuration

Measurement & Automation Explorer (MAX)

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Channels and Tasks

Signalsai 0ai 1ai 2

Sine Wave 1

Sine Wave 2

Sine Wave 3

Channel names

TasksTiming and Triggering

The DAQ Signal Accessory

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NI-DAQmx versus Traditional NI-DAQFeature NI-DAQmx Traditional NI-DAQTest Panels DAQ Assistant with code generation noOn-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

Integration with LabVIEWDeveloper Exchange discussion forumCompatible with Legacy ISA Boards no

650 Alliance members

Productivity

Performance

Accuracy

QualityBest

GoodFairCompatibility

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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 analog I/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 type can be:•Analog Input•Analog Output•Counter Input•Counter Output•Digital I/O

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Analog Input

Analog Input task is 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 and reference 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 task is specific to the generation 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 and reference triggers for the task

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CountersA counter is a digital timing deviceTypical 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 counterSource – Input that causes the counter to increment each time it togglesGate – Input that is used to enable or disable the function of the counterOutput – Signal that generates pulses or a series of pulses

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Digital Input and Output• Digital I/O can

read from or write to a line or an entire digital port

• A digital port is a collection of digital lines

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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 applications

that require advanced timing and synchronization use the VIs that 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

GPIB Communication

GPIB Cable

GPIB Interface

GPIB Instruments

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Standards IntroductionHP designs HP-IB (Hewlett Packard Interface Bus)1965HP-IB becomes IEEE 4881975

1987 IEEE 488.2 adoptedIEEE 488 becomes IEEE 488.1

1990 SCPI (Standard Commands for Programmable Instruments) added to IEEE 488.2

1992 IEEE 488.2 revised

HS488 proposed1993

HS488 approved1999

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GPIB Hardware Specifications• Max cable length between

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

15 (2/3 powered on)1

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DIO5DIO6DIO7DIO8RENGND (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

DIO1DIO2DIO3DIO4EOIDAV

NRFDNDAC

IFCSRQATN

SHIELD

GPIB Software Architecture — Windows

Driver Software(*.DLL)

Instrument Driver VIsNI-VISA

LabVIEW

Diagnostics Tools:GPIB Diagnostic Tool

NI-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 LabVIEW Express VI

• Sets up device communication and data parsing step by step through a configuration interface

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Communicating with an Instrument

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Virtual Instrument Software Architecture

GPIB VXISerial PXI

VISA

• Platform independent• VISA is the backbone of the

IVI and Plug & Play Instrument Drivers

• Interface independent• Must know SCPI command

set to program directly with 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 at ni.com/idnet

• Install the instrument driver VI Library into LabVIEW 7.0\instr.lib directory

• Access drivers from Functions»Input»Instrument Drivers subpalette

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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

HP34401A Initialize.vi

• 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 specific

instrument• Error cluster

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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 least

one 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 as the instrument address

• Use the I/O Assistant as done with 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 an

example to help you get started

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Lesson 11VI Customization

TOPICSConfiguring Appearance of Front Panel SubVI 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 window resizes

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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 InstanceAccess SubVI Node Setup by right-clicking on subVI icon on calling VI’s diagram

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Key NavigationAssigns keyboard strokes to front 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 Website www.ni.com/support• Drivers & Updates• Product Manuals• KnowledgeBases• Example Code• Tutorials• Application Notes• Discussion Forums

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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 list maintainer atinfo-labview-REQUEST@pica.army.mil

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

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LabVIEW Publications• LabVIEW Technical Resource quarterly newsletter by LTR

Publishing • LabVIEW Graphical Programming and LabVIEW Power

Programming by Gary W. Johnson, McGraw-Hill• LabVIEW for Everyone by Lisa K. Wells and Jeffrey Travis,

Prentice-Hall• LabVIEW Signal Processing by Mahesh Chugani, Abhay Samant,

and Michael Cerna, Prentice-Hall• LabVIEW Applications and Solutions by Rahman Jamal and Herbert

Pichlik, Prentice-Hall