Tap chl Khoa hpc Tru'dng Dai hoc Can Thd website

Tgp chi Kboa bgc Tnrdng Dgi hgc Cdn Tho Phdn A: Kboa hgc Tv nhiin. Cong nghf vd Mdi tru&ng: 31 (2014): 26-35

Tap chl Khoa hpc Tru'dng Dai hoc Can Thd website: sj.ctu.edu.vn

M A C H K H U E C H DAI STRAIN G A U G E DUNG V I M A C H C H U Y E N D U N G 1B31AN Vo Minh Tri'

'Bd mdn Tu ddng hda, Khoa Cdng nghi, Trudng Dgi hgc Cdn Tha Thong tin chung:

Ngdy nhgn: 31/10/2013 Ngdy chdp nhdn: 28/04/2014 Title:

Design ofa strain gauge amplifier using integrated circuit 1B3IAN Tir khda:

Cdm bien biin dgng, khuech dgi strain gauge, cdm bien trpng lugng

Keywords:

Strain gauge measurement, strain gauge signal conditioning, amplifier

ABSTRACT

Output signals directly from strain gauges have small amplitude expressed in microstrains; therefore, amplijying and processing these signals has always been considered in precise measurement. The aim of this paper is to survey and implement a special integrated circuit designed for strain gauge amplification, namely 1B31AN (Analog Devices), in order to support research and teaching activities at Measurement and Sensors Laboratory. Department of Automation Technology, College oj Engineering Technology. Can Tho University. The study results show that this integrated circuit is highly jiinctionable, being suitable for training on the principles and configuration, amplification, and signal processing oj strain gauges. This integrated circuit is compatible with strain-gauge configurations of quarter-bridge, half-bridge, and full-bridge circuits.

Besides, the amplitude and quality of the output signal from the amplifier can be adjusted depending on the requirements of low pass filtering and gain adjustment.

TOM TAT

Tin hi?u ngo ra true tiep tit cdc cdm biin biin dgng strain gauge cd biin dg rdt nhd tinh bdng micro strain, vi vgy vi^c khuich dgi vd xir ly lin hi4u do tit cdc train gauge ludn Id vdn di dugc quan tdm trong do ludng chinh xdc. Di tdi nay nhdm khdo sdt vd ung dung mgch khuich dgi tin hiiu cho cdm bien biin dgng dimg vi mgch 1B31AN ciia hdng Analog Device di phuc vw cho nghien cuu vd gidng day d phong thi nghiem Do ludng vd cdm biin, bg mdn Tif dgng hda, Khoa Cdng nghi, Truang Dgi hgc Cdn Tha. Kit qud cho thdy IBS IAN dugc thiit ki cd tinh md dun hda rdt cao, rdt phii hgp diing cho gidng dgy ve nguyen ly vd kit ndi strain gauge, khuech dgi, vd xu ly tin hiiu do. Vi mgch ndy dugc thiit kd di tuong thich vdi cdc logi cdu hinh cdu nhu dan. hai nua. hay todn cdu. Bin cgnh do, bien dg vd chdt lugng cua tin hieu ngo ra cd thi thay ddi dugc tity theo yeu cdu dtra vdo tinh ndng lgc hg thdng vd diiu chinh h? sd khuich dgi.

1 G i d l T H I f U

Sfrain gauge linhiing phin Hi cdra biin dugc chl tgo bdng bdn din faay kim loai mi diln trd ciia no tiiay ddi khi cd tdc dpng ciia ngoai lyc. Ciu tao cua Sfrain gauge li mdt doan ddy ddn kim loai dugc ddn frln rapt radng mdng tiiudng Ii plastic theo hinh zigzag. Khi bj keo hay nin tiieo chiiu tich cyc

thi diln fro cda sfrain gauge thay doi. Sfrain gauge dugc sii dung nfaiiu frong chl tgo loadcell, cim bien do moment, ap suit, luu lugng nhu Ii nhthig phdn tir so cip.

Sy thay ddi diln trd ctia sfrain gauge Id rat nhd vi cdc biln dang chi tinfa bing micro-strain. Ylu

Tgp chi Khoa hgc Tru&ng Dgi hgc Cdn Tlio Phdn A: Khoa hgc Tu nhien, Cong nghf vd Mdi Iru&ng: 31 (2014): 26-35 ciu dit ra kfai tfaiit kl macfa kfauich dai tin hieu cfao

sfrain gauge Id pfadi dim bio dugc cic yen cdu:

Dieu cfainfa fae so kfauicfa dai tiieo ylu cau Cho pfaep loai bd cic tfaanh phdn nfaiiu Ho trg cac logi cdu Iiinfa ragcfa ciu Thiet ki ragch kfauicfa dgi cd tiii sti dyng cdc Iinfa kiln dien tii tfadng dung nfau BJT, OPAMP vd kit fagp vdi cdc linh kiln thy dpng R, L, C, Tuy nfaien dp chinh xdc khdng cao do chat lugng linh kiln va khd nang kfaii nhilu khi khulch dgi. Vi the viec sir dyng cdc vi ragcfa cfauyin dyng dl thilt ke mgch kfauicfa dgi cho sfrain gauge Id xu faudng radi hien nay. Texas Instrurnent dd phdt friin vi ragch INAI25 cd the diing de kfauech dai strain gauge.

Tuy nhiin vi mgch nay cdn nhieu ban chl vl kfad ndng ciu hinh can v i chdng nhilu.

De tdi nay nham rayc dich khdo sat cfaiic nang vd thiet ke ragch kfauich dgi tin hieu cho sfrain gauge tiling vl mgch 1B31AN dl phyc vu cho hoc tap vd gidng dgy mdn Do ludng vd Cdra biln d Bp radn Ty dpng hda.

2 PHU'ONG PHAP THlTC HIEN 2.1 Tdng quan

Nhu da gidi thi|u sfrain gauge dugc diing nhu nhiing phin tii so cap dl chi tao load cell, edm biin do moment, dp suit, luu lugng,,., vi hiu hit cic cam biln ndy deu sii dyng sfrain gauge d dgng ciu Wheatstone.

Cdu Wheatstone la mpt mach diln dugc sir dung di do mdt diln frd chua biit bang cdch cdn bdng hai nhdnh cua mdt ragch edu, ttong dd cd radt nhdnh chiia cac thdnh phdn chua biit Hogt ddng ciia nd tuang ty nhu mpt cdu phdn thi. Nd dugc phit minh bdi Samuel Hunter Christie vio nam 1833 vd dugc cdi thien vd phd biin bdi Charles Wlieatstone vdo nam 1843. Mot trong nhiing myc dich sii dyng ban ddu ciia cdu Wheatstone Id diing vdo vile phdn ticfa vd so sinfa (Ekeloi; 2001).

Mdt cdch tdng qudt, cdu Wheatstone cd dang nhu Hinfa 1, cic thdnh pfain frd khang Ri, R;, R5, R4 Id cdc diln frd thudn. Ciu dugc kich bang ngudn dien ap VEX, ngo ra Vo la dien thi chenh lecfa giua faai mil a v i b. Diln tfai Vo dugc tinh:

"o-

_R+R. ^{'EX (1)}

Rl, R2, R3, R4 dugc chpn sao cho khi d trgng thii can bdng thi Vo cd gid tri OV.

Thdng tiiucmg khi tiiilt kl ngudi ta thudng cfapn cdc gid tri dien frd sao cfao d trgng tfaii cdn bdng R2 = R3, R[ = kl, hodc Ri = R2 = R3 = R4.

Trong cic mgch cira bien, cdu Wheatstone dugc su dung bing cich thay till cic dien frd Ri, R2, R3, R4 fren Hinfa I bang cdc strain gauge, tiiy trudng hgp mi so sfrain gauge dugc mdc vdo cdu cd tfal la I, 2 hoac 4. Do do tir dang mach ciu Wheatstone tdng qudt ta cd cae dgng biln till sau:

u. Quarter-Bridge

G-'AR

Hinh 2: Quarter-Bridge Ci dgng mach cdu nay, chi cd rapt sfrain gauge dugc sir dung, so dd nguyen Iy nhu Hinh 2. Do Ri

= R2 = R3 = RG = R, vdi RG Id diln frd cua sfrain gauge khi chua bj bien dgng. Khi cd tac ddng vdo vdt chiing, diln ttd cua strain gauge se thay ddi mdt lugng AR. Kfai do, Vo dugc tinh:

R

IR-i-AR 2 EX ⁽²⁾

Anh hudng cua nhi^t dg

Tfayc tl, yeu td nhiet dp bin ngoii inh hudng tryc tiep lln diln ttd ciia strain gauge ldm giira dp chinh xdc cua kit qud do. Trong trudng hgp ndy dl hgn chi infa faudng eiia nfaiet dp ngudi ta sii dung them mpt dummy gauge dl din vio vat chiing nhung d ttgng tfaii kfadng hoat ddng.

Hinh 1: Mgch cin ban ciia cau Wheatstone

Tap chl Khoa hgc Tru&ng Dgi hgc Can Tha

Hinh 3: Sir diing dummy gauge dl tranfa anh hirdng cua nhilt do

PhdnA- Khoahgc Tunhiin, Cong nghf vd Moi iruang: 31 (2014): 26-35 Nfau frln Hinh 3 Iiic niy straui gauge A la strain gauge dugc din lln vat efaiu biin dgng, cdn sfrain gauge D khdng dugc dan true tiip lln vit efaiu biln dgng md dan lln v^t kfadng cfaju biin dgng d gdn dd. Liic ndy ca 2 sfrain gauge ciing cfaju tdc dpng ciia cimg mpt dilu kiln nhi^t d$ nen dnh faudng ciia nfaiet dp dugc bd qua. Tuong ting cic sfrain gauge A vd D frln Hinfa 3 vd RG va Ri frln Hinh 2 vdi nhau thi cdng tfaiic tinh diln thi Vo van dugc tinh nhu cdng thiic (2).

Anh hudng cOa diin tra ddy ddn

Hinh 4: Anh hudng ciia dien trd day dan a mgch do dang Quarter-

Bridge

b) Three-Wire Connection Do mach do vi vit chju biln dgng dgt xa nhau

d mpt klioing cich nhdt djnh nen can cd ddy ndi giQa sfrain gauge vd mgch do. Chinh cdc doan day din nay lim xuit hi|n tfalm tiiinh phdn dipn frd RL nhu fren Hinh 4a.

Thanh phin diln frd nay lam cho ciu bi rail cin bing ngay ea khi kliong cd tie ddng lim strain gauge thay doi diln frd. Mat khdc, dien ttd cua ddy dan cung chiu tdc dpng cua nhiet dp bin ngoai nen khi nhilt dp tfaay ddi RL ciing tfaay dii tfaeo lira

cho cau bj mat dn djnh han.

Dl hgn chl inh hudng ciia dien frd day dan va nhilt dp ngudi ta cai tiln bang each thay ddi cich ddu ddy ddn nhu Hinh 4b. Liic niy cd 2 dogn Aa vd aB deu dugc bii dien frd ddy dan vd ciing chju tic dpng ciia nhiet dp nin cau sl cdn bdng khi khdng cd tac dpng. Dogn ddy ddn cd dien frd RL2 mang ddng diln rit nhd ve mach do nin di|n thi roi tren ddy dan ndy rat nhd v i cd the bd qua.

b. Half-Bridge Gauge in

tension

Gauge in compression

( R G - A R )

R G + A R (compression)

Hinh 5: Half-Bridge 28

I op cbi Khoa hgc Tru&ng Dgi hgc Cdn Tho PhdnA: Khoa hgc Tv nbien, Cdng nghf vd Moi Iru&ng. 31 (2014): 26-35 So do nguyin ly vd iing dyng ciia mach do

dgng Half-Bridge dugc gioi tfailu d Huih 5. Mach do Half-Bridge su dung 2 sfrain gauge d ttgng thai tich cyc nfaung ttong dd cd I sttain gauge efaiu nen vi I sttain gauge efaiu keo, dp nhgy tdng gip ddi so vol dgng Half-Bridge. Mgch thiit ki dang nay da logi bd dnh hudng cua nhipt dd. Di|n ip lecfa Vo dugc tinh theo cdng thiic (3):

R-AR IR

c Full-Bridge

0)

Macfa Full-Bridge sii dyng 4 strain gauge, frong dd cd 2 sfrain gauge chiu nen vd 2 strain gauge chiu keo. So dd mach FuU-Bndge nhu Hinh 6.

R G - A R

Hinh 6: Full-Bridge Di^n thi Vo dugc tinh theo cdng thiic (4);

''0= '

IR 2R (4)

Nfau dd diim qua d frln, dl ciu Wfaeatstone hogt dpng can phai cap mpt diln ip nudi VEX (excitation voltage). Ngudn di|n ip ndy thudng cd gii tri trong khodng 3V - 15 V. Niu dipn dp nay Idn thi diln dong diln chay qua cdc sfrain gauge trong cdc nhdnh ciing Idn vi the sl ldm dnh hucmg den diln frd cua sfrain gauge do infa faudng cua nfaiet dp bdn tiiin cic sfrain gauge sinh ra (self- heating).

Di$n dp kich thich VEX ciing irtii faudng din dien ip l?ch Vo cua ciu (tfal hi|n frong cdc cdng tinic (I), (2), (3)), niu VEX khdng duge giii i n djnh thi Vo cung sl khdng dn dinh vd lira dnh faudng den kit qud do. VI tfae ragcfa nguon nudi cfao cim biin dugc thiit ke tiilm chiic ndng remote sensing.

Chirc ndng niy cho phip mach kiem tra diln dp VEX tten mgch cdu bing dudng hdi tilp diln thi diing 2 diy dSn sense higfa vd sense low tgi diim ndi day cip di|n tfae kicfa tfaich cho cam biln.

Dudng hii tiip dipn the ndy dua vi bp nguon di so

sdnfa yi bii them lugng di$n dp roi frln day dan.

Vi the nhiing cam biln loai ndy ttd nin cd 6 diy (Hinh 7).

+Sen 1

j

^ \ ' \ /

+EH _+Sig -Exl -Sen -.Sig Hinh 7: Sadd nguyen Iy ciia can 6 day 2.2 Ndi dung

2.2.1 IC khuich dai tin hi^u 1B31AN a Chuc ndng

- IC dugc thilt kl chuyin diing dk khuech dai tin hieu cho cic cira biln, ragch do c6 dgng cdu vd nira edu.

Dien thi kich thich cho cdm biin thay ddi dugc vi chiic nang remote sensing hd ttg cho cac cdm bien 6 ddy, 4 day, nira ciu.

• Bp Ipc tin failu (10 Hz - 20 kHz), cfao phep tuy chinh.

- HI so kfauech dai thay ddi duoc frong khoing 2 mVN - 5.000 mVlW.

FUNCTIONAL BLOCK DIAGRAM

Hinh 8: So do khii chiic ndng cua IC 1B31AN

Tgp chi Khoa hgc Tru&ng Dgi bgc Cdn Tho Phdn A- Khoa hgc Tv nhien, Cdng nghi vd Moi truong: 31 (2014): 26-35 b. Kit ndi vdi cdm biin

IC IB31 ho trg cic logi cim biin logi 6 ddy, 4

day vd mgch do dang nua cdu cd frd klidng 120 fi hoic ldn hon (Analog Devices, 1996).

a. Cam biln 6 day b. Do niia cdu Hinh 9: Sff dd nguyen ly kit noi vdi cam bien vi strain gauge c. Diiu chinh dien dp cdp ngudn cho cdm

biin VEXC

Di|n dp cap nguin cho cam biln (di|n dp kich) VEXC dugc ddt frudc 10 V khi ndi chin 19 (RBF OUT) vdi chin 20 (REF IN). Dl tang diln dp VEXC cdn mdc them dien frd RE.\T tir chdn 21 (EXC ADJ) tdi chin 26 (HALF-BRIDGE COMPL) nfau Hinh 10a.

Gia fri di|n ttd REXT dupe tinh theo cdng

thiic (5), (6):

\OknxV, _{REF_OUT} -V

*^ EXC '^ REF_om VREF_OUT = 6,8V

20feQxJg^

RpYT — "

20An - Rr

(5)

(6)

a. VE.XC 10 V - 15 V b. VE.VC 4 V - 10 V Hinfa 10: fiiln the cap nguon cam bien VEXC Dl giira di|n till VEXC thi raic rapt biln trd 20

kfl giiia chdn 19 (REF OUT) vd chin 20 (REF IN) vi rapt ty 4.7 pF tir chan 20 tdi cfain 16 (COMMON) nhu Hinfa I Ob, liic nay VEXC tiiay dii dugc frong kfaodng 4 V - 10 V.

d. Dieu chinh h4 sd khuech dgi HI sd khuich dgi G duoc tinh theo cdng thuc:

SOAQ

^

(7)

Trong dd Ro la diln frd ndi giiia chdn 3 yd chin 4. Dya vdo cdng thiic (7) niu rauin tiiay ddi fae sd kfauicfa dai thi chi cin thay ddi gii fri di|n frd RG, vi tili nen sii dung RG li mdt biin frd di dl dang dieu chinh kfai sii dung,

e. Diiu chinh tdn sd edt ciia bg lgc hg thdng (Low pass filter)

Tdn sd cit ciia bd lpc fag tiidng dugc tiiiit ke mac dinh d 1 kHz. Dl tiiay dii tin sd cit tiidp hon I kHz cdn mdc tiiem 2 tu diln giiia chin 12 voi chin 16 vd chin 13 vdi chin 14 nfau Hinh I la. Gia tri ciia cdc tu di$n dupe tinh tiieo cdng tiiitc;

Tgp chi Khoa hgc Truang Dgi hgc Can Tha

'(f-)

PhdnA: Khoahgc Tv nhien, Cdng nghf vd Moi Iru&ng- 31 (2014). 26-35 Vdi f^ Id tin sd raong mudn (fi: <l kHz).

C5£t2 = 0 . 0 0 2 2 ^ F l — - 1

(8)

(9)

Ddi vdi tin sd cit Idn hon I kHz thi radc thera 3 diln frd RsELuRsEL2.RsEL3 nhu Hinli lib.

a. Tan so dudi 1 kHz b. Tan so trin 1 kHz Hinh 11: Thay ddi tan so bp Ipc tin hieu Gii fri cua cdc dien frd nay dugc tinh theo cdng

tiiuc(I0),(ll),(12): R.

Rs^,,=\6ka

V _/ V _/

r^-ii

_{IkHz J}

r^-,]

l\kHz J

•--^°*"/[4-'

⁽¹²⁾

(10)

(11)

2.2.2 Thiet ki mgch khuich dgi

Chiic ndng ciia cua timg khoi dugc tnnh bay cy thi dudi diy:

Hinh 12: Sff do nguyen ly mach khuech dai

Tgp chi Khoa hgc Trucmg Dgi hge Cdn Tho Phan A. Khoa hgc Tv nhien, Cong nghf vd Moi tru&ng: 31 (2014): 2&35

Hinh 13: Khii mgch kilm tra diln dp dting Voltmeter

SWl-l: -(-VS) SWl-2; +VS SWl-3: UNUSED SWl-4: OFF SWl-5: V_EXC1 (CHI) SWl-5: V EXC2 (CH2)

Xoay SWl dl thay ddi cic vi fri kit noi ciia chin (+) vi chin (-) ciia Voltmeter vdi cdc diem can do diln dp (Hinh 13).

Vi tti I: do di|n ip -VS Vj tri 2: do dien ip +VS

INPUT * BRIDGE EXCITATION

Vj tti 3: khdng dung Vj tti 4: khong diing Vi fri 5: do VEXC cua kinfa 1 Vi fri 6: do VEXC ciia kinfa 2

•

L

A

"0—a

HNPUT([

JNRJT (A) V_EXC (C)

Jl

,

I (*WPU(P—'

...JPF

^

3 = L

GHD * SENSE LOW (B-E)

OUTPUT ( F I L T E S E D )

1

Tl

Hinh 14: ChQn kilu liet ndi cam bien Load cell ket n6i voi mach khuSch dai

Ihong qua diu ndi 16S-1. Tiiy theo loai cam biSn ma xoay SW2 dl chgn ciu hmh kjt ndi cho thich hgrp(Hinh 14).

Vi tri 1: ket n6i vdri cam biln 6 day

Vi tri 2: ket noi voi cam bien 4 day Vi tri 3: n6i tit ng6 vao INPUT+ va INPUT- cua IC dl dilu chinh input of&et

Vi tri 4: kit nii voi mach niia cau

P chi Khoahgc Tmong Dgi hgc Cdn Ttia Phdn A: Khoa hgc Tu nhiin. Cdng ngftp v<i Moi tmang: 31 (2014): 26-35

<S) O U T P U T ( F I L T E R E D )

S K 3 - 1 : F = 10 Hz S K 3 - 2 : F = 90 Hs S H 3 - 3 : F = ISO Hz S H 3 - 4 : F = 500 Hz

Hinb 15: Dieu chinh tan so Tdn sd cat ciia macfa Igc faa tfadng cd tfal tfaay ddi ttong kfaodng tii 10 Hz din I kHz bang cdch kit hgp cac ty hay diln ttd ben ngodi. Tan sd cit ciia macfa loc ha thdng dugc tfaay ddi bdi SW3 (Hinfa 15), khi xoay SW3 tfai cdc chdn chiic ndng cua mach Igc dugc thay ddi vi tri de ghep ndi vdi cdc gii tri ty diln kfadc nhau, tir do tin sd cat dugc thay ddi.

Vjtri I: tdnsdcdt lOHz Vj tri 2: tin sd cit 90 Hz Vj fri 3: tdnsdcdt 180 Hz Vj tri 4: tdn sd cit 500 Hz Vj fri 5: tdn so edt 1000 Hz

Hinh 16: Dieu chinh hf so kfaech dai

cat cua b9 Ipc ha thfing

Do Igi cua mach kfauicfa dai dugc dilu cfainh thdng qua SW4 vd mpt bien frd tinh chinh (Hinh 16). Dilu cfainh SW4 sl lim thay ddi cic gid tri diln trd cd gid tri cd djnfa (10 i l - 280 Q) vi cac di|n frd ndy dugc mdc ndi tilp vdi biln trd tinh chinfa cd gid frj tiiay ddi tii 0 H - 100 n .

Nfau vay ddi vdi m^ch khulch dai ndy d^ lgi cd till dieu cfainh frong kfaodng:

80*0

(13) lOfi + OO

SOJtfi

I-—_—

2800 + lOOa = 212 (14) 3 KET QUA VA DANH GIA

De kiem fra ho^t ddng va ddnfa gid chit lugng cua thiet hi ta lien fadnh mdt sd thi nghiim de kiem tra:

3.1 Thi nghiim 1: Kfaao sit dap iing tan sd ciia mach kfauech d^i

Ndi cdc ddy ciia loaded! vao ngd vdo cua m^cfa kfauich dai

- Xoay niim cfainh de dat do khulch dai mong mudn

Dieu cfainfa VEXC sao cfao gid fri bdng 10 V - Sii dyng Card NI myDAQ dl xem tin hieu ngdra

Thay ddi niim chinh tin sd cat ciia bg Ipc vd luu 1^ kit qua.

Kit qua tfai ngfailm cfao tfady kfai dilu cfainfa mira cfainfa tin sd cat ciia mach lgc gidm dan thi cdc thdnh phin tin sd nhieu hi triet tieu dan vd bien dp sdng nfaieu ciing gidm din. Cy the:

Tgp chi Khoa hgc Tnrdng Dgi hgc Cdn Tho Phdn A: Khoa hoc Tv nhiin, Cong nghf vd Mdi truane- 31 (20I4)- 26-35 Khi fc = 1000 Hz, frong sdng nhilu cd cac

thdnfa pfain:

- Chu ki 20 ms: tin so 50 Hz, biln dp khoing 100 mV

Chu ki 2.5 ms: tin sd 400 Hz

Chu ki 2 ms; tin sd 500 Hz Chu ki 1 ms : tin sd 1000 Hz Khi fc = J 0 Hz, tin hieu ngd ra chi cdn Iai tiidnh phdn nhilu cd tin sd 50 Hz nfaung bien dp da suy gidm cdn rdt nhd (kfaodng 5 mV).

IjH^^H

l^^^^^^^l

^^^^^^^H

I^^^^^^^^H

^^^^^^^^1

W^^^

a.f<=IkHz

"z::.^^ ^^ ''

*SL - I S .S- _ j _ J '.j^

'"— --..

:j

"y~ r*_ •_ ff

~;2:£,

•^

u . .

IIBLJ^^^^^^H

1 ™

^^^^^^1 ^ —"' -'.

^^^^^^1

^ ^ ^ B .•^- '''•->. ->

- - • " S V T T - J r

e. i i = I 0 H 2

Hinh 17: Tin hi|u nga ra quan sat tren oscilloscope (myDAQ)

3.2 Thi nghijm 2: Khulch dai load cell Lln luot dSt cac tai bilt tnroc ffpng lircmg D§u day load cell vao m^ch khulch d^i '^" ' ° ^ ^^^ ^3 ghi lai gid tri dpe dirge tren

MyDAQ. Kit qua thu dupe nhtf Bang I.

Tgp chi Khoa bgc Tmang Dgi bgc Can Tha Phdn.4. Khoa hgc Tv nhiin. Cdng nghf vd Moi Intong. 31 (2014): 26-35

Sii d u n g M A T L A B d i v l Im cdc gid tti fren vd tim dang faam md td mdi quan fae giiia kfadi lugng vd diln till (Hutii 18).

Hinh 18: Dd tb| moi quan fai giira di|n thi va khdi iugng |

Bang 1: Cdc c^p gia tri khoi lugng, diln the thu dirge tfr thi nghidm

Tu kit qui tinh toin ta dugc phuong trinh bilu diln quan he v-m nhu sau:

V (mV) = 3,885 m + 8,022

Khoi Itrgmg m (gram) Bien thi v 0 180 280 360 385 540 560 665 720 945 1000 1280 1665 1945 2445 2665 3000

milivolt) 0 705 1108 1408 1480 2110 2190 2565 2805 3660 3910 5010 6480 7585 9520 10380 11610

4 K £ T LU^N VA D t XUAT

Bdng each sir dyng IC chuyin dung IB31AN de tfaiit ki mach khuich d^i tin failu cho cdm bien vdi cac tiidng so kT tiiudt tiieo dk nghj cOa nha sin

xuit dd giim bdt sy phiic tap trong b'nii loan va thilt ke phdn ciii^, ddng thdi dp tin cdy vi dp chinfa xic ciing cao hon so vdi mach thilt kl bdng nfaihig Iinfa kiln rdi. Ket qud cua cac thi nghiim cho thay mach sau khi thilt ki cfai tao ddp iing dugc nfaiing yeu cdu ddt ra cho mpt bai thyc hinh ve bin chit va ky thudt xii Iy tin failu tir mpt sfrain gauge. Tiiilt bi da dugc frien khai giing day rapt each rat failu qud cho thyc hdnh hpc phdn Cdm biln cfauyen ndng tai phong thi nghiim Do ludng va Cdm biln, thudc Bo mon Ty dong fadzi, Kfaoa Cong nghe.

TAI LI$U THAM KHAO 1. EkeIof,S.,200I.Tfaegenesisoftiie

Wheatstone bridge. Engineering Science and Education Journal, ISSN: 0963-7346.

2. John P. Bentley, 2005. Principles of Meauremenl Systems. NXB Pearson Prentic Hall.

3. Analog Devices, 1996. Wide Bandwidth Sfrain Gauge Signal Conditioner - 1B3I.USA.

4. National Instrument, 2013. Measuring strain with sfrain gauge, http://www.ni.com/white- paper/3642/en/ tiny cap ngdy 10/10/2013.