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Lesson 9 Data Acquisition and Waveforms TOPICS

Plug-in DAQ devices Data Acquisition in LabVIEW Analog Input Data Logging Analog Output Counters Digital 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

DAQ Hardware Configuration

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Measurement & Automation Explorer (MAX)

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Channels and Tasks Channel names Sine Wave 1 Signals ai 0 ai 1 ai 2 Sine Wave 2 Sine Wave 3 Tasks Timing and Triggering

The DAQ Signal Accessory

NI-DAQmx versus Traditional NI-DAQ Productivity Performance Accuracy Quality Compatibility Feature

Test Panels DAQ Assistant with code generation 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

NI-DAQmx

            no

Traditional NI-DAQ

 no             Best  Good  Fair

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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

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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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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 toggles Gate – 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 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 10 Instrument Control TOPICS

Instrument Control Overview GPIB Communication and Configuration Instrument I/O Assistant Virtual Instrument Software Architecture (VISA) Instrument Drivers Serial Port Communication Waveform Transfers

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Instrument Control Overview

Control any instrument if you know the following: – Type of connector on the instrument – Electrical properties involved – Software drivers available − Type of cables needed − Communication protocols used

Instruments Computer

GPIB Communication GPIB Interface GPIB Instruments GPIB Cable

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Standards Introduction 1965 1975 1987 1990 1992 1993 HP designs HP-IB (Hewlett Packard Interface Bus) HP-IB becomes IEEE 488 IEEE 488.2 adopted IEEE 488 becomes IEEE 488.1

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

IEEE 488.2 revised HS488 proposed 1999 HS488 approved

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GPIB Hardware Specifications

DIO1 DIO2 DIO3 DIO4 EOI DAV NRFD NDAC IFC SRQ ATN SHIELD 1 13 12 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 • Max cable length between devices = 4 m (2 m average) • Max cable length = 20 m • Max number of devices = 15 (2/3 powered on)

GPIB Software Architecture — Windows Diagnostics Tools: GPIB Diagnostic Tool NI-Spy Interface Board (GPIB, PXI, VXI, computer based, etc.) Driver Software (*.DLL) NI-VISA Instrument Driver VIs LabVIEW Configuration Tools: Measurement & Automation Explorer

Configuring GPIB Board and Instruments

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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

VISA

Serial GPIB VXI PXI

• 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 Serial GPIB VXI GPIB-VXI Resource Name Grammar ASRL[board][::INSTR] GPIB[board]::primary address[::INSTR] VXI[board]::VXI logical address[::INSTR] 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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Instrument Driver VIs

• Initialize • • • • Configure • • • • • • • • • Action/Status • • • • • • • • • • • • • Data • • • • • • • • • • • • • • • • • • • • • • • • • • • Utility • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Close • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

•

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

PC Serial Port RS-232 Cable RS-232 Instrument

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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 1 DCD 2 RxD 3 TxD 4 DTR 5 Com 6 DSR 7 RTS 8 CTS 9 RI DTE DCE Input Output I O O O I I I O I I I O O O

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

Lesson 11 VI Customization

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TOPICS

Configuring Appearance of Front Panel SubVI Front Panels Keyboard Shortcuts VI Properties Customizing 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 Appearance

Only 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 Instance

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

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Key Navigation

Assigns 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

Info-LabVIEW Listserve

User-sponsored Internet mailing list • Send subscription messages to the Info-LabVIEW list processor

[email protected]

• Send other administrative messages to the Info-LabVIEW list maintainer at

[email protected]

• Post a message to subscribers at

[email protected]

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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