lab lecture3 intro to labview

8/7/2019 Lab Lecture3 Intro to LabView

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MCEN 371 Mechanical Engineering Lab

Chapter 6:Chapter 6:

LabVIEWLabVIEW

Part 1: Introduction


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Obje ctiv esObje ctiv es What i s Data Acqui sition and Why use it?

Overview of La bVIEW Develop an id ea of what La bVIEW r eally is Learn what grap hica l programming languag e and

dataf low mean Get a f eel for t he La bVIEW environm ent

Learning VI programming t hroug h examp le


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Wh at is Data Acqui sition and Why use it? Traditiona l Ex periments signa ls from sensor s ar e sent to

ana log or digita l meter s, r ead by the ex perimenter , andr ecord ed by handIn automat ed data acqui sition systems the sensor s tran smit avoltag e or curr ent signa l dir ectly to a comput er via a dataacqui sition board.

Softwar e such as La bVIEW contro ls the acqui sition and

proc ess ing of such data The benefits of automat ed sys tems ar e man y:

Improv ed accurac y of r ecording Incr eased fr equency with wh ich measur ements can be tak en Potentia l to automat e pr e and po st proc ess ing and build in qua lity contro l


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Overview of La bVIEW

La bVIEW La borator y Virtua l Instrum entEngin eering Work bench

Grap hica l programming languag e that a llows for

instrum ent contro l, data acqui sition , and pr e/ po st proc ess ing of acquir ed data


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Graphica l programming languag e& Data f low

La bVIEW r elies on grap hica l sym bols rather thantex tua l languag e to d escri be programming action s

The princip le of dataf low, in wh ich function s exe cute on ly after r eceiving t he necessar y data , gov erns exe cution in a straig htfor ward mann er.


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H ow does La bVIEW work?

La bVIEW program s ar e ca lled:

Virtual Instruments (VIs) becau se the ir app ear ence and op eration imitat e actua l instrum ents.

H owever , they ar e ana logou s to main program s, function s and su broutin es from popu lar languag e lik e C, Fortran , Pasca l,


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What does a VI look like?


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In La bVIEW you can cr eate or u se virtua l instrum ents (VI) for

data acqui sition. A VI a llows your comput er scr een to act a s anactua l la borator y instrum ent with charact eristics tai lor ed to your

particu lar needs.

You can a lso u se built-in examp les, or u se standard t emplates

for setting up your data acqui sition input c hann els .


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A VI has thr ee main part s:1. T he front panel:

an interactiv e user int erfac e of a VI, so nam ed becau se itcan simu lates the front pan el of a p hys ica l instrum ent.

2. T he block (or wiring) diagram:It is the VIs sourc e cod e, con struct ed in La bVIEWs grap hica l programming languag e, G. It i s the actua l

exe cuta ble program .Su broutin e in the block diagram of VI.

3. Icon/connector


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LabVIEWLabVIEW

Part 2: The La bVIEW Environm ent


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O bjectivesO bjectivesLearn how the thr ee main part s of t he La bVIEW environm ent the f ront panel , block diagram , and

icon/connector work tog ether.Learn t he diff er ence betwee n controls andindicators & Be a ble to r ecogniz e the ir block diagram terminals .

Learn a bout t he capa bilities and u ses of t he toolbar , tools palette , controls palette , f unctions

palette , and subpalettes .


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Front Pan elsSimp ly put , the f ront panel is the windo w throug h wh ich

the user int eract s with the program .

When you run a VI, you mu sthave the front pan el open sothat you can input data to t he exe cuting program.

The front pan el is whe r e yousee your program s output.


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Compon ents of a front pan el:

The f ront panel is primari ly acombination o f controls and indicators .


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Contro l? or Indicator?

Controls = Input s from t he user = Sourc e Termina ls

Indicators = Output s to t he user = D estination s


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M anipu lating Contro ls and Indicator s

R ight c lick on an indicator to Chang e to contro l Chang e format or pr ecision

R ight c lick on a contro l to

Chang e to indicator Chang e mechanica l action ( whe ther to latch open

or c losed, and what to u se as defau lt)


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Block Diagram sThe block diagram windo w holds the grap hica l sourc e

cod e of a La bVIEW VI it is the actua l exe cuta ble cod e

You con struct t he block diagram by wiring tog ether o bjects that p erform s pecific

function s. The variou s compon ents of a

block diagram ar e terminals , nodes and w ires.


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Te rmina lsWhe n you p lace a control (or indicator ) on t he

FRONT PA NEL

La bVIEW automatica lly

cr eates a corr es pondingcontrol (or indicator )terminal on t he BL OCK DIA GR AM


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Contro l or Indicator Te rmina l?

Control terminals havethick bord er s

Indicator terminals havethin bord er s


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Dele ting B lock Diagram Te rmina ls

By defau lt, you cannot d ele te a block diagram t ermina l that belong s to a control (or indicator ).

The terminal disapp ear s only whe n you d ele te its corr es ponding control (or indicator ) on t he FRONT PA NEL.


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Nodes Node is just a fanc y word for a program exe cution element Nodes ar e ana logou s to statements, operators, f unctions and

subroutines in standard programming languag e: The add and subtract functions r e pr ese nt on e type of node .

A structure is an ot her ty pe of node . Structur es can exe cut e cod e r e peatedly or conditiona lly, simi lar to loop s and ca se

statements in traditiona l programming languag es.La bVIEW has also s pecia l nodes , called formula nodes , wh ich ar e useful for evaluating mat hematica l formu las or ex pr ess ion s.


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Wir es

A La bVIEW VI is hel d tog ether by wires conn ecting nod es and t ermina ls; they deliver data from on e sourc e termina l toone or mor e destination t ermina ls.


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Basic wir es used in block diagram sand corr es ponding t y pes

Eac h wir e has diff er ent style or co lor , de pending on t he data

ty pe that f lows throug h the wir e:Scalar 1D arra y 2D arra y Color

Floating-pointnum ber

orang e

Integer num ber blue

Boo lean gr een

String pink


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Brok en wir esIf you conn ect mor e than

one sourc e or no sourc e

at a ll to a wir e,

La bVIEW DISAGR EES with what

your e doing , and t hewire will app ear broken


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Compon ents of a block diagram Review !

Nodes : program exe cution

elementsTerminals : Port s throug h wh ich data pa sses betwee n the block diagram and t he front pan el and betwee n nod es of t he block diagramWires : Data pat hs be twee ntermina ls


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Dataf low Programming Goingwith the f low

Stated simp ly, a nod e exe cut es on ly whe n dataarriv es at a ll its input t ermina ls; the nod es supp lies data to a ll of it s output t ermina ls whe n it fini shes exe cuting ; and t he data pa ss imm ediat ely from sourc e todestination t ermina ls.


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Icon s and Conn ector s

The icon is the grap hica l

r e pr ese ntation of t he VIin the block diagram.

&

the connector defines the input s and output s

more on this later

The icons and connectors s pecif y the pathw ays for data to f low into and out of VIs.


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Front Pan el & Wiring Diagram.It is often hel pfu l to vi ew both simultaneously using t he Windo ws-Tile Left and R ight command from t he pull down menu.A new (empt y) VI is shown below with the k ey pull-down m enu

pallets visi ble.


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Modif ying a VI

Only one of t he two windo ws (front pan el or wiring diagram)is activ e at an y point in tim e. To activat e one simp ly mov e the mou se over it and c lick a mou se button.

To di s play any of the pallets (too ls, contro ls, or function s)you can u se the Windo ws pull down m enu or simp ly left or right click your mou se.

When you fir st pu ll up a pa llet an imag e of a pu sh pin i s dis played in t he upp er left hand corn er. C lick on it to k ee p the

pa llet continuou sly dis played.


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Add /edit t ext

Wir e f eatur es tog ether tocontro l f low of data

Sele ct a f eatur e toedit or mov e

O perate a contro l

Pro be Data(trou blesh oot)


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Insert a digita l indicator or contro l

Insert a boolean contro l

( button or switch)


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Add a structur e such as for , wh ile, and ca se statements

Add a num ericoperator (+ ,-,)

File I/O

Add a booleanoperator (and , or)

Data Acqui sition

Signa l ana lysis

Compari son

M athematica l Function s

Timing /dia log


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Reord er o bjects

R un

Continuou s run

Pau seStop

Font ring

Alignm ent ring

Distri bution ring

Debugging f eatur esmore on this later


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LabVIEWLabVIEW

Part 3: E xamp les


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Examp le 1: Crap s

From t he function s num eric pan el insert a pair of dic eFrom t he Contro ls pan el insert a

num eric digita l indicator (on t he front pan el) Use the wiring too l to conn ect

the two (in t he wiring diagram)and c lick t he run buttonr e peatedly.

Num ber s from 0.00 to 1.00should be dis played in t he front

pan el


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Examp le 1: Crap s (continu ed)

Dele te the wir eAdd a mu ltiplication nod e and anum eric con stant to a llow multip lication by 5

Add an addition nod e andnum eric con stant to a llow addition of 1Add a mat hematica l R ound to Near est nod e.M ak e a second cop y of t his structur e to r e pr ese nt a seconddie and wir e them tog ether throug h an addition nod e with anoutput to a num eric con stant

This wiring diagram simu lates the rollingof 2 dic e and t heir addition to form a num ber

from 2 t hroug h 12.


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Examp le 2: Ana log & Digita l

Voltmeter (simulated signal)

Uniform noi se used as simu latedsigna l Function s Signa l

Proc ess ing Signa l GenerationmenuA bsolute value function fromfunction s num eric m enuM ean va lue of data series fromthe function s mat hematic s Pro ba bility and Stati stics menu

The 250 m s wait imp lementedfrom t he time and dia log m enuslows the f lutter of t he meter.


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Examp le 3: Reading an ana log input signa l Requires A/D board to implement

From t he function s menu sele ctdata acqui sition and t hen ana log

input. The n sele ct either Samp le Chann el or Samp le Chann els

This places the samp ling icon inyour wiring diagram

You t hen need to configur e the chann el(s) and wir e the output toother part s of your program.


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Examp le 4: Signa l Ana lys is (continu ed)


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Examp le 5: Cr eating Su b-VIsIn wiring diagram u se sele ction too l (mou se box) to sele ct a ll items to be in t he

Su bVI.From Edit m enusele ct Cr eate Su bVIDou ble click on n ew icon and save it a s ase parat e VI.Cut-and-pa ste it atwill or in sert it u singFunction s SelectVI menu

lab lecture3 intro to labview

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