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Lesson 8Data Acquisition and Waveforms

A. About plug-in data acquisition (DAQ) boards

B. About the organization of the DAQ VIs

C. How to perform a single analog inputD. About the DAQ Wizards

E. About waveform analog input

F. How to write waveforms to file

G. How to scan multiple analog channelsH. How to output an analog signal

I. How to drive the digital I/O lines

J. About buffered data acquisition

You Will Learn:

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DAQ library supports allDAQ boards

LabVIEW uses the NI-DAQdriver-level software

DAQ boards for Analog I/O Digital I/O Counter/timer I/O

Data acquisition systemcomponents

Overview

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Analog Input Considerations

Single-Ended vs. Differential

Resolution

100 200150500

Time (ms)0

1.25

5.00

2.50

3.75

6.25

7.50

8.75

10.00

Amp

litude(volts)

16-Bit Versus 3-Bit Resolution(5kHz Sine Wave)

16-bit

3-bit

000

001

010

011

100

101

110

111

| ||||

Range

Gain

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Analog Input Considerations

Sampling Rate

Averaging

Adequately Sampled

Aliased due to undersampling

1 0

1 * 212 = 2 .4 mV

2 0

1 * 21 2 = 4 .8 mV Code Width

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DAQ Software Architecture Windows

LabVIEW for Windows

DAQ Library VIs

Win95 Device Manager

nidaq32.dll for

Windows

Windows Registry

DAQ Board

DAQ-STC

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DAQ Hardware Configuration

Measurement & Automation Explorer (MAX)

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The DAQ Signal Accessory

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Exercise 8-1 on page 8-10

Students examine MAX and the

DAQ Configuration Utility

Time to complete: 15 min.

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DAQ VI Organization

Analog Input

Analog Output

Digital I/O

Counter

Calibration andConfiguration

Signal Conditioning

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Analog Input VI Organization

Easy I/O VIs

Advanced VIsUtilitly VIs

Intermediate VIs

Single-point VIs

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DAQ Channel Name Control

Data type used tocommunicate with

DAQ boards

Enter channel names

by number or byvirtual channel name

defined in MAX

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Students build Voltmeter.vi*This VI will be used in a later exercise.


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Students modify Measurement Averaging.viTime to complete: 20 min.

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DAQ Wizards

DAQ Channel Wizard

DAQ Solution Wizard

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Students use the DAQ Solution Wizard


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Waveform Analog Input

AI Acquire Waveform

VI displays a dialog box if an error occurs

VI returns a waveform datatype

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Students Build Acquire Waveform.viTime to complete: 25 min.

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Writing Waveform Data to File

Waveform File I/O

subpalette of the

Waveform palette

Three VIs for writing

waveform data to file

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Students buildAcquire Waveform to File.viTime to complete: 15 min.

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Scanning Multiple Analog Input Channels

AI Acquire Waveforms VI accepts multiple

channel names as input

1D array of waveforms is returned

Order of the channels (in DAQ Channel Name)

determine the array order

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Scanned Waveforms and Graphs

Plot all waveforms on the same waveform graph

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Students examine and run Scan Example.viTime to complete: 15 min.

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(Optional)

Students build Scan Two Waveforms.viTime to complete: 20-25 min.

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Analog Output VIs

Single-point VI

Waveform Generation VI

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Students examine and runVoltage OutputExample.vi with Voltmeter.vi


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Digital Input and Output VIs

Line = single TTL signal

Port = collection of lines (4 or 8)

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Students examine and run Digital Example.viTime to complete: 20 min.

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Buffered Data Acquisition (Optional)

Intermediate VIs

- Highly recommended for most applications- Continuous acquisition with triggering

available

- Interval scanning

- Different gains for different channels- Streaming data to disk

- Error handling

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Analog Input Operations

SequenceAI Config Configure channels, gains, and

computer buffer

AI Start Set trigger conditions, program clocks,

and start DAQAI Read Read data from buffer(repeat if continuous)

AI Clear Stop DAQ, free board and computer

resources

General VI parameters

taskID to control execution order

Bold terminals

Default values

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Analog Input Intermediate VIs

Buffered Analog Input

Continuous Data Acquisition

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(Optional)

Students build Continuous Acquire with MIO.viTime to complete: 20-25 min.

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Summary

Use the Measurement & Automation Explorer to configure

DAQ boards and virtual channels DAQ VIs organized into five subpalettes Analog Input,

Analog Output, Digital I/O, Counter, Configuration and

Calibration, and Signal Conditioning

Analog Input and Output subpalettes are divided into

levels Easy I/O, Intermediate, Advanced, and Utility VIs

Easy I/O contains VIs for

Single-channel analog input and output

Single-channel waveform input and output

Multichannel waveform input and output

Digital input and output

Continuous DAQ can be performed using the intermediate

VIs of AI Config, AI Start, AI Read, and AI Clear

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Additional Exercises on page 8-56

8-12 -- Students build Temp Monitor with LED.viTime to complete: 25 min.

8-13 -- Students use the DAQ Solution Wizard toopen Simple Data Reader.vi


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Lesson 9Instrument Control

A. An overview of instrument control

B. About GPIB communication and configuration

C. About LabVIEW instrument drivers

D. How to use instrument driver VIs

E. About Virtual Instrument Software Architecture

F. How to use the VISA functions

G. About serial port communication

H. About waveform transfers

You Will Learn:

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Instrument Control Overview

Control 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 availableInstruments Computer

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GPIB Communication

1965 1987 1990 1992 19931975

GPIB Instrument

GPIB Cable

GPIB Interface

LV Instr 1-192

1999

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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

12

13

24

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

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GPIB Software Architecture Windows

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Configuring GPIB Board and Instruments

Measurement & Automation Explorer (MAX)

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Students use MAX to examine the GPIB board

settings and communicate with an instrumentTime to complete: 20-25 min.

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Instrument Drivers

More than 650 LabVIEW instrument drivers

Programming simplified to high-level API

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Installing and Finding Instrument Drivers

NI Web site orInstrument Driver CD

Install the instrument

driver VI Library into

LabVIEW\instr.libdirectory

Access drivers fromInstrument I/O

Instrument Driverssubpalette

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Students open the Getting Started InstrumentDriver VI for the NI Instrument Simulator

Time to complete: 20-25 min.

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Instrument Drivers

Instrument drivers have a similar hierarchy

Instrument Driver VI Tree

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Instrument Driver Inputs and Outputs

VISA Sessions

A connection or link to a specific instrument

Created after instrument is initialized

Used throughout VI whenever youcommunicate with that specific instrument

Error Clusters

NI DEVSIM Initialize.vi

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VISA Resource Name

Exact name and

location of the

instrument

Use the VISA

Resource Name

control (like the DAQChannel Name control)

You can specify the

full resource name

or the VISA Alias

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Putting It All Together

Initialize instrument

Do operation(s)

Close instrument

Check error status

VISA Sessions

Error Clusters

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Students build the Voltage Monitor.viTime to complete: 10 min.

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Virtual Instrument Software Architecture

Standard API for programming instruments Platform independent

Interface independent

Interface to Serial, GPIB, and VXI instruments

Uses VISA.DLL

NI-488.2OS Calls NI-VXI

GPIB VXISerial PXI

VISA

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VISA Terminology

ResourceInstrument, Serial Port, or Parallel PortSessionConnection to a Resource

Instrument DescriptorResource 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]::pr imary address[::INSTR]

VXI VXI[board]::VXI log ical add ress[::INSTR]

GPIB-VXI GPIB-VXI[board][::GPIB-VXI prim aryaddress]::VXI log ical add ress[::INSTR]

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VISA Functions

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Students build Read VISA Waveform.viTime to complete: 20-25 min.

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Serial Communication

RS-232 Instrument

RS-232 Cable

PC SerialPort

LV Instr 1-210

Popular means of communication betweencomputer 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

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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 softwarehandshaking options

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Serial Hardware Connection

RS-232

Most PCs DCE or DTE

configurations 9-pin or 25-pin Single-ended

RS-422 Macintosh 8-pin Differential

RS-485 Multidrop Industrial Automation

Pin DTE DCE

1 DCD Input Output2 RxD I O3 TxD O I4 DTR O I5 Com - -6 DSR I O

7 RTS O I8 CTS I O9 RI I O

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Serial VIs and Functions

Found in Serial

subpalette under

Instrument I/O

Based on VISA functions

Serial VIs and functionsalso work with parallel

port communication

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Serial I/O Example

Initialize the serial port settings

Write commands to the device

Read device response

Check for errors

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Students examine and run Serial Write & Read.viTime to complete: 15-20 min.

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Waveform Transfers (Optional)

ASCII Waveforms

Binary Waveforms

1-byte integers

2-byte integers

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Exercise 9-6 on page 9-45(Optional)

Students examine and run Waveform Example.viTime to complete: 20 min.

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(Optional)

Students build Binary Waveform.viTime to complete: 20-25 min.

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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

An instrument driver eliminates the need for your to have

detailed knowledge of the specific strings used by an

instrument Instrument Library more than 650 instruments supported

Instrument driver VIs share a common hierarchy and come

with an example to help you get started

VISA a standard protocol for using multiple types of I/O and

instrument driver development

Serial library contains functions for serial communication

You need to know the format of the returned data string in

order to convert it to the correct values

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Additional Exercises on page 9-51

9-8Students use the NI DEVSIM Getting

Started VI to communicate in serial mode with

a deviceTime to complete: 20-25 min.

9-9Students modify a previous VI and save it

as Voltage Data to File.viTime to complete: 20-25 min.

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Lesson 10

VI Customization

You Will Learn:

A. How to customize the panel windowB. How to create pop-up panels

C. How to use Key Navigation

D. How to edit VIs with disabled options

E. About customizing palettes

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Customizing VI Properties

Access VI Properties... by right-clicking on 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

Use Top-Level Application Window or Dialog

appearance types Create custom window appearance

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SubVI Node Setup

Access SubVI Node Setup by right-clickingon subVI icon on calling VIs diagram

Affects only that single instance of the subVI

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Students build Use Pop-Up Graph.viand

Pop-Up Graph.viTime to complete: 20-30 min.

K N i ti

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Key Navigation

Assigns keyboard strokes to front panel controls

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Students buildTemperature System.viTime to complete: 25-30 min.

C bi ti f VI P ti (O ti l)

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Combination of VI Properties (Optional)

Opens, runs, and closes LabVIEW

without user intervention

Save with Options to make backups

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Exercise 10-3 on page 10-19(Optional)

Students modifyEdit_Me.viTime to complete: 25-30 min.

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Customizing LabVIEW Palettes (Optional)

Access different palette setsfrom the Options button in

Control or Function palette

Display either icon or text

Control and Function palettes

Editi C t l & F ti P l tt

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Editing Control & Function Palettes

Modify the existing

palettes

Create your own

palettes

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S mmar

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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 You can fully customize the Control and Function

palettes from the Option button in the FunctionBrowser window

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