Xây dựng hệ đo điện trở đất đa cực đề tài NCKH QT 07 19 pdf

DAI HOC QUOC GIA HA NOI
TRlTonVG DAI HOC KHOA HOC TlT NHIEN
'k'k'k'k'krk'krk'k

XAY DlTNG HE DO DIEN TRO DAT DA CUC
MA SO: QT-07-19

CHII TRI DE TAI:
ThS. TRAN VINH THANG
CAC CAN BO THAM GIA:ThS. GIANG KIEN TRUNG
ThS. NGUYEN NGOC DINH
ThS. NGUYEN ANH DUG

HA NOI - 2007


I. Bao cao torn tat.
a. Ten de tai: Xay dung he do dien trd dat da cue. (Ma so: QT-07-19)
b. Chu tri de tai: Tran VTnh Thang
c. Cac can bp tham gia:
ThS. Giang Kien Trung
ThS. Nguyen Ngpc Dinh
ThS. Nguyen Anh Due
d. Muc tieu va npi dung nghien curu.
Nghien ciiu cac phuong phap do dien trd dat trong tham do dia vat ly,
cac giai phap ky thuat va qua d6 che tao thiet hi do dien trd dat da circ c6 su
dung may tinh lam cong cu do dac va xu ly so Heu. Vdi muc tieu la cai tien
va nang cao kha nang cua phep do, rut ngan thai gian va cong siic do dac khi
trien khai thirc te.
e. Cac ket qua dat duoc.
Khoa hpc:

Tiep can va nam bat duac phuang phap do dac trong
ITnh virc dia dien, qua do c6 duac cac giai phap cai tien
nang cao hieu qua cua phuong phap. Phuc vu dao tao va
nghien cuu trien khai thirc cac he do vat ly.
01 bai bao gui dang len tap chi DHQG Ha Npi
Thirc tien:
- Xay dung thanh cong he do dien trd dat da cue vdi cau true
phan bo, bao gom: 01 bp xu ly tap trung va 08 bp phan phan bo chiia cac
dien cue dupe dieu khien tir xa, phan mem nhung va phan mem do dac ca
ban tren may tinh vdi cac lira chpn hnh boat.
f. Tinh hinh kinh phi cua de tai.
T6ng kinh phi: 20.000.000 ddng
Trong do: Vat tu: 5.190.000 d
Thong tin: 1.578.500 d
Thue khoan chuyen mon: 11.631.500 d
Quan ly phi, dien nude: 1.600.000 d
KHOA QUAN LY
CHU TRI DE TAI
(Ky va ghi ro ho ten)
(Ky va ghi ro ho ten)

?^i^^^

[/-^IH^--^

PGS. TS. Nguyen The Binh

Tran VInh Thang

TRU^OTVG DAI HOC KHOA HOC TlT NHIEN

rtOf*

^:/ ^..M^

TC . /J-^-

UiHijMOAljWk.


n. Report
a. Project: Multi-electrode Earth Resistivity measurement. (Code: QT07-19)
b. Coordinator: Tran Vinh Thang
c. Co-operators: MSc. Giang Kien Trung
MSc. Nguyen Ngoc Dinh
MSc. Nguyen Anh Due
d. Objectives and scientific contents.
Methology research of the Earth resistivity measurement, design and
build a distributed resistivity measurement system by using computer and
microcontroller for measuring and data processing. Objective of the research
to develop a new measurement system, which has high performance, saving
acquisition time.
e. Results.
Scientific:
- To approach an application of computer and microcontroller
technology to design the new earth resistivity measurement system.
To opened out a R&D capacity for applying in education training, and
measurement science.
Real applications:
- 01 paper submits to VNU's journal of Science.

- Building sucessfuly a new distributed Earth Resistivity
Measurement system included: 01 Central Data Acquisition Unit, 08
distributed electrode with remote control. Firmware and software for basical
data acquisition.
f Budget.
Total: 20.000.000 VND
where:
Material: 5.190.000 VND
Scientific information: 1.578.500 VND
Employments: 11.631.500 VND
Official fee: 1.600.000 VND


MUC LUC
•

•

Ldi md dau
1. Co sd phuang phap do dien trd trai dat
2. Thiet ke tong qUan
3. Xay dung he do dien trd da cue ban tap trung
4. Ket qua va danh gia

5
5
8
11
16

Ketluan
Tai lieu tham khao

20
21


Loi md* dau.
Trong ITnh vuc tham do dien, phuang phap do dien trd thudng dupe
dung de ve lai ban do cau true dien cua be mat trai dat. Dieu nay nham xac
dinh cau true va/hoac tinh chat vat ly cua cac vat lieu tren be mat trai dat.
Trong phuang phap nay, dong dien di vao long dat thong qua cac dien cue
va dien the do dupe thong qua cac dien cue khac.
Thiet bi do theo phuang phap nay ca ban bao gom mot nguon phat va
mot may thu. Nguon phat cung cap mot dong dien c6 tan so thap (vao cac dien cue dong. Cong suat ciia nguon phat tiiy thupc vao phuang
phap do. Trong hau bet cac trudng hop tiiy vao each bo tri dien cue nhu
Schlumberger, Wenner can cong suat thap va nguon nuoi cd the la pin ha\'
Accu. Bp thu cd the la mot Von-met dan gian hay phuc tap nhu mot he do
CO ghep noi vdi may tinh nham nang cao hieu qua cua phep do vdi kha nang
luu trir va xu ly tin hieu so.
y

f

r

\

Ve nguyen tac, thiet bi do dac dudng nhu kha dan gian, chi can 4 dien

cue la ta cd the khao sat dupe be mat trai dat, Tuy nhien, trong thuc te, neu
vdi mot he do dan gian, cong viee thuc dja se trd nen rat kho khan do can trd
bdi thai gian va cong sue tien hanh. Chinh vi vay, he do da circ ra ddi va
hien nay cd rat nhieu san pham da dupe thuong mai hda nhu cac san pham
SARIS (Scintrex Ltd, Canada), RESECS/RESITOMO (DNT GmbH,
Germany) vdi 960 dien cue, SYSCAL Switch-48 (IRIS Instruments, France)
vdi 48 dien cue. Vdi cac che dp do da dang, kha nang phan tich manh boi
may tinh gan kem luon trong he. Cac he do c6 cau triic kieu tap chung va dat
tien.
Muc dich ciia nghien ciru trong de tai nay nham thiet ke va che tao
mot he do da cue cd cau true ban tap trung, su dung cap it spi, cd kha nang
*

'

t

y

ung dung trong khao sat thuc te trong dieu kien Viet nam, phuc vu thuc tap
va nghien cuu cho sinh vien nganh Vat ly Dja cau.
9

L Co-sd phuong phap do dien trd dat [1]
Phuang phap dien trd DC su dung nguon soay chieu AC c6 tan so rat
thSp lam ngudn tin hieu cho viee xac dinh phan bo dien trd. Nhu vay, thanh
phSn tu trudng c6 thi bd qua va ta cd phuang trinh Maxwell:

A X £ - 0, ( 1 )

Trong do E la vector dien trudng. e,^ la hang so dien moi cua chan
khong, q la mat dp dien tich.


Ky thuat dia dien nham dua ra dupe ban do 3D ve tinh chat vat ly cua
trai dat. Do do, phuang trinh tren ap dung trong he tpa dp khong gian x, y, z.
Mac du phuang trinh chi ap dung cho dong mot chieu lien tuc, nhung cd the
ap dung cho tin hieu AC d tan so rat thap bdi sir anh hudng cua dong cam
ung CO the bo qua. Truang tmh dien c6 the mo ta theo gradient ciia dien the
U:
E = -VV (2)
Tu do ta CO phuang trinh Poisson ca ban cho truang tinh dien:
^'-U{x,y,z) = - — q{x,y,z)

(3)

Phuang trinh lien tuc cho mot diem trong khong gian 3D theo ham
Dirac la:
V.y(.x,;;,z,/) = - M £ ^ l £ l i l ^ ( ; r ) J ( ^ ) j ( z ) (4)
Ot

Trong do, j la vector mat dp dong va t la thai gian. K^t hop (2) va
djnh luat Ohm:
r
r
r
y=c7£ = ^ (5)
P

Phuang trinh (4) cd the ^Mqz viet lai:

-V.[a(.V,V,z)V^(.V,>-,2)]..^^'^-f^-^^^(.Y-x)<?(>^->;)^(z-zJ
Ot

(6)

Trong do Xs, ys, z, la diem nguon tiem dien tich. Xet mot phan tu the
tich A V ta cd:
^-^^S^l^6{x-x^5{y-y^5{z~z^^-L^^
ot

(7)
AV

0 day, I la cap tai mot nguon diem, thuc te no chinh la dong phat qua
dien cue. The phuang trinh (7) vao (6) dan den phuang trinh vi phan tung
phan cho dien the trong mdi trudng 3D bat dong nhSt, dang hudng tao bdi
mot nguon diem la:
-'i^.[cT{x,y,z)VU{x,y.z)

= j^5{x-xJ5{y-yJS{z-zJ

(8)

Vdi moi trudng dong nhat va dang hudng, dien trudng gay gdi mot
nguon diem cd the dupe giai bang each tich phan phuang trinh lien tuc (4)
theo the tich va ap dung dinh ly phan ky Gauss dan d8n tich phan mat cua
mat dp dong j . The j tir (5) va tich phan theo mat cau vdi ban kinh r thu
duac:

Tir do de dang cd dupe:

t/(r) = - ^ ( 1 0 )
Anr

Phuang trinh (10) mo ta the tao bdi mot nguon diem trong khong
^

\

f

t

y

'

gian dong nhat tai mot diem each nguon mot khoang r. Tren thuc te, phep do
dien trd vdi cac dien cue duac thuc hien tren be mat trai dat. trong trudne
hop do phuang trinh (8) dugc tich phan tren nua mat cau thu dugc:
Ip (11)
U{r)
2nr

Ve ly thuyet, nguon diem can cd mot diem tuang irng dat tai vo cue
de cd dong qua mdi trudng. Viee xac dinh dien trd be mat can biet them su
phan bd ciia the. Su dung hai dien cue dat tai A va B (hinh 1) \a ap dung
phuang trinh 11, the tai mot diem tuy y M la:
UM

^[^-k

(12)

In r, r.
Trong do, ri la khoang each giua M va A, con xi la khoang each giua
MvaB.
B
A
M
N

V

V

current

equipotential
^ •^~- - J i n e

Hinh 1: Su' phan bo ciia cac dudng dong va the vdi hai dien cue tai be
mat cua mot ban cau done nhat.


De do hieu dien the phai can den hai dien cue. Ve mat ly thuyet, hai
cue c§p dong A va B cd tha diing luon dS do Xhk tuomg ung. Tuy nhien, dien
trd chuyen tiep giira cac dien cue va b6 mat se anh hudng den phep do. Do
vay, can diing them mot cap cue nira de do dien the, va nhin chung, phuang

phap do dien trd DC thudng diing bdn dien cue. Hieu dien the giua hai diem
M v a N l a At/ la:
LTZ r,

r,

r^

r^

A

trong do, r3 la khoang each giira N va A, va r4 la khoang each giua N
va B. Do vay, K la he so dac trung cho khoang each giira cac dien cue va gpi
la he sd hinh hoc. Tir dd ta thu duac:
'^ = ^ ^ ( 1 4 )
Vdi trai dat khong dong nhat, phuang trinh tren se cho cac gia trj bien
ddi theo sir sap xep ciia cac dien cue tren be mat. Cac gia tri thu dupe tir
r

y

r

phuang trinh (14) cho mot mat dat khong dong nhat dupe xem nhu la gia tri
bieu kien p^
2. Thiet ke tong quan
Nhin chung, cac dien cue A, B, M va N cd the dat tiiy y, Tuy nhien, mot
SO sir sap xep cac dien cue dac biet thudng dupe diing nhu tren hinh 2, tuang
ling la cac he sd hinh hpc K.

Mot trong nhung tham sd quan trpng ciia phuang phap do dien trd nay la
dp sau tham dd (Schlumberger, 1932), cac khao sat ciia Muskat, Evinger,
1941 cho thay dong xuyen sau chi phuc thupc vao khoang each giua hai cue
A va B, trong khi dp sau tham dd dupe xac djnh bdi tham so hinh hpc cua
ca bdn dien cue. Viee phan tich ve dp sau tham dd cung nhu la xu sd lieu la
rat phuc tap va khong phai la van de can giai quyet ciia de tai nay.
Thiet bi do dien trd DC ve ca ban la mot thiet bi cd gia thanh thap, cac bp
phan ca ban bao gom:
y

y

f

Mot nguon dong, trudng hap dan gian la mot nguon Pin dupe ndi
vdi mot chuyen mach dimg de dao chieu cue
Mot ampe ke do dong tiem xudng long dat
Mot Von ke do tin hieu the
04 thanh kim loai ddng vai trd cac dien cue
04 day ndi de noi cac dien cue vdi nguon va thiet bi do.
nhu anh minh hoa tren hinh 3.


Type

Electrode Arrangement

Geometric Factor

Wenner

K-2na
A

Ml

y ¥^\t

L a . —fiL-^

Schlumberger

K - n n(n+])a
n>3

*
M.5^
ItN
.
i
.
ja:ja_j
na ,

A"

.

Dipole-Dipole

K - n n(n+l)(n+2)a
'I

"B

y^^

\

Pole-Dipole

K - 2n n (n-»-1) a
n>3

Pole-Pole

K-2na

#
K-2n

Gradient

t.iM
A|

T

I

X

(Y' + ( i - x r ) *

' ^

J +x
+

(Y' + d + x)')'

y

(X.^Y^^)

AB/3^,

AB/3

^ /5/3

A > 10-a

Hinh 2: Sir sap xep cac dien cue hay diing trong phuang phap do dien trd
DC va cac he sd hinh hpc tuang ling.


^ " f i t

•.•!»*-.

I'.ii'O

-^•TT

t

V

M

S

^.'O-r ,^/ t.ecv.i

-•<•!

cu.-e'

Hinh 3: Thiet bi do dien trd dat ca ban diing 4 dien cue (Coruh, 1988)
Bang each diing 4 dien cue tren, viee thu thap sd lieu kha dan gian va
chiing ta cd the hoan toan thu dupe cac hinh anh 2D va 3D ciia be mat trai
dat.Tren thuc te, viee di chuyen cac dien cue va thiet bi do khong thich hop
cho viee khao sat mot dien tich rpng.
He do da cue ra ddi nham giai quyet bai toan tren, va rat nhieu tac gia da
nghien cihi va che tao he do tiiy theo dieu kien su dung va chi phi khac nhau
[2-9], ve CO ban he cd cau tao nhu tren hinh 4:
Cctcle C u n c + SA-tcfirp j-v.s
Mjitccfe,

lectfooe-c 1

Hinh 4: So dd minh hoa he do da cue (Griffiths, Barker, 1993)

0


Mot he da cue ca ban theo ki^n tnic tap trung gdm mot cap nhieu loi \a
mot he chuyen mach, sd lupng cue cang Idn thi kich thudc phan ciing cang
Idn va dd lai la mot ban che. Ngay nay, su phat tri^n ciia ky thuat dien tu va
vi dien tu cho phep chiing ta che tao dupe nhiing he do hien dai ban ddng
thai lam he thong minh ban nhd phan mem. Dij lieu do dupe chuyen vao
may tinh va dupe xu ly, luu trir ngay tren thuc dia.
Muc tieu de tai nay nham thiet ke va che tao mot he do dien trd dat da
cue theo kien tnic ban tap trung, tire la he cd cac bd phan chuyen mach nam
tai cac dien cue, dieu nay cho phep giam ket cau chi diing cap it spi (so vdi
kien tnic tap trung), chi phi thap (so vdi he cd kien tnic phan bd - thiet bj do
nam tai mdi dien cue).
3. Xay dung he dq dien trd da cue ban tap trung
Tren dieu kien cho phep, chiing tdi da thuc hien viee xay dung he do dien
trd dat da cue vdi cau tnic nhu tren hinh 5:

PC

CTR
DAQ

EU#1

1

Accu 12V

DC-DC

EU#2

1

El

EU#n

1

E2

Hinh 5: So dd cau tnic he do da cue
He bao gom cac bp phan cau thanh sau:
+ PC: may tinh'PC hoac Laptop
+ CTR-DAQ: bo thu thap sd lieu va dieu khien
+ EU#n: Bd dieu khien dien cue thu n (Electrode Unit)
+ DC-DC: bp chuyen ddi nguon dien
+ Accu: nguon dien mot chieu 12-24V
+ En : Dien cue sd n
3.1 Bo ddi nguon DC-DC.
Vdi dac thii cua phep do dupe thuc hien tai hien trudng rpng, dja hinh
phuc tap va khong cd nguon dien ludi, ddng thdi nguon kich ddng can phai
dam bao cd dien the cao mdi dap ung dupe yeu cau do vdi khoang each sau
va xa. Trong nhieu san pham thuong mai, nguon nay la mot may phat dien
chay bang xang dau. Tu}' nhien, muc dich ciia thiet bi trong de tai nay la chi

En


ap dung trong pham vi nhd. kich thudc va trpng lupng nho tien mang \ac
trong dieu kien thuc tap, do dd, ngudn kich na\ dupe ch^ tao theo ky thuat
bien ddi dien DC-DC diing ngudn nudi la accu 12V hoac 24V.
So dd khdi cua ngudn nhu tren hinh 6:
y

f

y

Accu 12V

Rectifier

• 4 OUT

+ Filter
/

N

.ôl.ô-taJ

lôW

ã**"

>*'^

PWM

Feedback

PWM
Generator

Controller

-y

V

*

/

1

\

Hinh 6: So dd khdi bd ddi ngudn DC-DC
Bp tao tin hieu PWM diing IC TL494 cd chuc nang dieu che dp rpng
xung PWM va dieu khien MOSFET cong suat d tan sd khoang 150KHz.
MOSFET ddng vai trd cua chuyen mach cong suat dieu khien bien the xung,
ldi ra ciia bien the xung se dupe chinh luu va Ipc de cd dupe dien ap trung
binh bien ddi trong khoang tir 50V den 350V. Mach phan hoi dua tin hieu

cua dien ap ra trd ve bp tao xung PWM de on dinh dien ap mong mudn.
Mach dieu khien PWM dupe ket bdi vdi bp CTR-DAQ cd tac dung dat
gia trj ciia the ldi ra. Qua bp nay, bp chuyen ngudn cd the boat dong nhu mot
ngudn the on ap dieu chinh dupe, ddng thdi cho phep chuyen chi'rc nang
thanh ngudn ddng.
Dien ap ra lai dupe dua vao mot ra-le de dao chieu ngudn dien khi ap
dung do d che dp phan cue cam ling.
/

•>

y.

r

y

F

-i

3.2 Bo dieu khien va thu nhan so lieu CTR-DAQ
Vdi vai trd quan trpng la dieu khien toan bd he thong, do dien ap va dong
y

t

r

^

dien tren cac dien cue. Bp dieu khien va thu nhan sd lieu CTR-DAQ can
dam nhan cac chuc nang sau:
Ket ndi vdi may tinh Laptop de nhan lenh va truyen dii lieu do dupe
ve may tinh.
Dieu khien xap xep cua cac dien cue tiiy theo mode do
Dieu khien gia tri dien ap cao ap dat len cac dien cue, tuang ling la
ddng can do.
12


Doc du lieu tu bo chuyin d6i tin hieu ADC I6-24bit mane thona tin
ve ddng va the tuong ung vdi cac niit cue.
De dam nhan cac chuc nang dd, bd diSu khien va thu nhan du lieu duac
thiet ke bao gdm cac khdi chuc nang nhu so dd hinh 7

/

CTR-DAQ

"

^

Relay

USB

CPU
(DSPic)

-^

^

XI

\^\

> 1

X2
V2

^

w

, 1 ,

X3
11

ADC
16-24bits

''

i k

X4
n
X5
+24
X6
GND
X7
A

I

USB

^
^

1

USB-RS485

1

V.
PWM ctr V- I ^
out

^

Vin

J

X8
B

Hinh 7: So do khoi bp dieu khien va thu nhan dir lieu CTR-DAQ
DSPie4013 la bp dieu khien tin hieu sd ciia Microchip dupe diins lam
CPU dieu khien toan bp khdi CTR-DAQ. Chip vi dieu khien nay c6 nhan
DSP 17xl7bit, 24kB bp nhd chuong trinh 2k RAM vdi bus du lieu 16 bit va
chay d toe dp xap xi 29MIPS, nhd dd, bd dieu khien cd the boat ddng vdi toe
dp cao, thuc hien nhieu phep tinh phuc tap, dac biet cd the boat ddng doc lap
theo chuong trinh da cai san ma khong can may tinh ngoai khi di da ngoai.
*

-1

r

t

Vi dieu khien cd chuc nang ket ndi may tinh qua bp RS232-USB converter.
dieu khien cac ro-le chuyen mach de bao dam cac che dp do ddng. the. dieu

13


khien bd ngudn va mode do DC, phan cue IP ddng thdi dieu khien mach
chuyen ddi tuong tu thanh sd ADC de dpc tin hieu cua dien ap.
Mach chuyen ddi tuong tu sd ADC diing AD7705 ciia Analog Device \ di
dp phan giai 16bit. Dien ap tham chieu 2.5V danh gia dp chinh xac cua tin

hieu do dupe diing MAX872 ciia Maxim vdi dp chinh xac 0.2% va dp troi
theo nhiet dp thap 40ppm/^C. Dai dien ap vao cd the chpn bang phan mem tir
±10mV den ±2.5V do ben trong chip ADC nay da chua bd khuyech dai lap
y

I

y

trinh dupe PGA dieu dd khien mach do trd nen linh boat vdi nhieu dai do
khac nhau. Khi do d che dp do ddng, ddng dien dupe do bang each do the
tren mot dien trd Shunt 0.1 ohm vdi dp chinh xac 0.1%.
Khdi dieu khien cac dien cue dupe thuc hien qua mang cdng nghiep
RS485 chi dung 2 dudng day cap xoan AB cho phep ket ndi tdi 31 dien cue
each nhau tdi 1200m max. Viee dieu khien duac thuc hien bang mav tinh
laptop ket ndi cdng USB qua bd chuyen ddi true tiep USB-RS485.
Cac ldi vao ra ciia modul CTR-DAQ bao gom 2 cdng ket noi USB vdi
may tinh, mot cdng ndi vdi bp doi ngudn va mot cong gom 8 dudng da> XIX8 ndi tdi cac bd dieu khien dien cue EU#n.
3.3 Bd dieu khien cac dien cue EU#n
Bd dieu khien cac dien cue EU//n cd nhiem vu chpn ket ndi hoac khong
ket ndi dien cue En vdi cac dudng tin hieu XI-X4 va dupe cung cap nguon
dien +24V tir bd CTR-DAQ, mdi dien cue la mot nut mang RS485 nhan tin
hieu di^u khien va phat tin hieu TEST OK cho may tinh de dam bao da nhan
va thuc hien lenh thanh cdng. So do khdi ciia bp nay nhu tren hinh 8

N

(v.
Euffn
X7

i^

^

w

^

X8
B

^

Relay
CPU
Tiny2313

w

^

^

w

w

X2
V2

^
w

X3
II

^

X4
12

^

X5

5V
Regulator

^

w

X6 ^
GND

J

\ ^

En

T

Hinh 8: Sa do khoi bo dieu khien dien cue EU#n

14

XI
VI


Chip vi dieu khien AVR Tiny2313 nhan tin hieu dieu khien qua mang
RS485 vdi dia chi mem xac dinh vj tri ciia dien cue va dieu khien su ddng
(active), cat (passive) ciia dien cue En vdi dudng tin hieu tiiy vao che dp do.
Mdi bd nay dupe bd tri thanh tirng hop rieng biet tren dd cd gan cac dien
cue, mdi hop cd 2 giac ndi de lap ndi tiep nhau chi qua mot cap 8 spi.
^

^

\

•>

3.3 Cac phan mem dieu khien
Toan bd he thong dupe dieu khien bdi phan mem tren may tinh dieu
khien viet bang Delphi vdi ehire nang don gian la thu thap sd lieu theo cac
mode do dac. Viee xu ly va hien thi la mot cdng viee rat phuc tap ciia
chuyen nganh xu ly va hien thi bang dd hpa cac sd lieu dja vat ly nen khong
the cd dupe mot phan mem hoan thien thuong mai hda. So dd thuat toan nhu

tren hinh 9.
START

r

STOP

Fault

^

Test En

i

OK

i

OK

Fault

Calib ADC

Set Mode

\

Set

POWER

Measuring

Save Data

Hinh 9: Chuong trinh dieu khien.
Hai phSn m^m nhiing dupe viet bang ngdn ngiJ C dupe bien dich va nap
vao bd nhd chuong trinh ciia hai vi dieu khien trong cac bp CTR-DAQ va
EU#n.'

15


4. Ket qua va danh gia
4.1 Cac hinh anh minh hoa ve he do
Cac hinh anh minh hoa he do dugc liet ke bai cac hinh duai day

Hinh 10: Hinh anh bo ngudn DC-DC va bo CTR-DAQ

16


Hinh 11: Bo di^u khien dien cue EU#n

- h o c

17

QUOC GIA HA NO,

Hinh 12: Hinh anh toan bd he do dien trd dat vdi 8 dien cue

SH

>:t Mutti electrode Earth resititjvify nraasurernenl

Electrode Arangement
A

B
Mode Sel,

M

Clear

N
Voltage
50V

100V

150V

• 200 V

250 V

300V

• IP
DC

Test

System message
System sell lest
Electrode self lest
System ready!
^Measuring....

Save
lyol. fmV)

Icur. (mA)

121.532
195.982
245.312

12.226
16.283
21.536

Start Meas,

pass
pass

Hinh 13: Giao dien phan mem dieu khien va thu thap so lieu

18


Phan mem giao dien cho he do boat ddng nhu sau:
Tmdc tien, he do va cac dien cue se dugc kiem tra xem cd boat ddng
binh thudng khong bang lenh kiem tra dupe gui tu may tinh den cac
dien cue.
Tiep dd la sir lira chpn vi tri cac dien cue, dien ap do tiiy vao muc
dich do va che dp do la DC hay IP. d che dp IP, dien ap se dupe ONOFF, dao chieu de do d che dp phan cue cam ung, sir phu thupc theo
thdi gian se dupe ghi lai sau thdi gian ngan nhat la 0.1s (do tdc dp
lay mau ciia ADC).
Bat dau do, nguon cao ap tu bd DC-DC se dupe bat, va no se tat tu
ddng sau khi phep do dupe lay mau 10 Ian, gia trj trung binh dupe
hien thj tren bang sd lieu.
4.2 Kiem tra danh gia he do
Do dieu kien khong cho phep, he do dugc danh gia thdng qua sir danh gia
ve dp chinh xac cua cac bp phan ciia he thdng. Hang muc quan trong nhat dd
la bd do dien ap diing ADC 16bit, ket qua dupe so sanh giua hai kenh vdi
nhau va vdi thiet bi do chuan. Ket qua dupe minh hpa tren hinh 14.

1.00.8-

-

•
•

0.61

0.4-

• • •

Sai so: %

#

0.20.0-0.2-

•

#

i'

• • •
•
JikAAAAA • AAA

i

••

-04-

A

l

t

•
•

A

-0.6-

DAQ
Keithley197ADMM

-0.8-1.00

500

1000

1500

2000

250(D

Dien ap vao: mV
Hinh 14: Ket qua so sanh vdi Keithlay 197A DMM. vdi cac gia tri dien
ap khac nhau va theo thdi gian.

19


Cac gia tri khao sat ung vdi cac dien ap tir 0-2400mV, sai sd ciia bd DAQ
so vdi thiat bi Autoranging Microvolt Digital Multi-Meter Keithley 197A
khong vugt qua 1% d gia trj dien ap nhd vai chuc mV.
Hinh 15 la k6t qua khao sat vdi thang do tu -1.25V d6n + 1.25V, qua dd
cho thay sai sd phan tin hieu be cai thien dang kL diSu nay cho phep chpn
thang do thich hop cho cac loai tin hieu khac nhau.
0.20

0.30

0.15
0.10

f
S
o

LJJ

0.25

I—•-Keithley 197A1
k-# DAQ data

0.20-

0.05

0.00-

^

Sfc.

0.15-

P 0.10

h-ôKeithlôy 197A
^ ã - OAQ dôta

u

liJ

0.05

-0.05

0.00

-0.10

-0.05

-0.15
I

ã0.20

200

I
400

I

600

'

I • — r

800

1000

'

I —

1200

T

0

•

I

200

• ' — 1 — '

400

I

600

'

T

800

'

I — '

1000

r'

1200

Input Voltage (mV)

Input Voltage (mV)

Hinh 15. K^t qua do vdi thang do tu-1.25V den + 1.25V
Ket luan.
\

r

r

Sau khi thuc hien de tai, chiing toi da dat dupe mot so ket qua va nhan
xet sau:
Tien hanh xay dung he do da cue theo kien triic ban tap trung, day la
ki6n tnic lai giiJa hai loai he tap trung va he cac dien cue phan bd.
Phuang thuc nay cd nhieu uu diem dd la: ha gia thanh, da cue, cap it
spi, gpn nhe va de mang vac do cac module c6 the thao lap dupe. He
dupe di^u khiln bdi phan mem linh boat vdi cac mode do DC va
phan cue IP.
Tuy nhien, do di8u kien khdng cho phep, he do chua dupe kiem
nghiem thuc \k va so sanh vdi mot he do chuan da dupe thuong mai
hda ma chi ^Mqc: danh gia thdng qua tiing bp phan rieng le, va cho
dp chinh xac cao. Viee danh gia toan bp he thong can them thdi gian
mdi cd th^ khang dinh chinh xac.
D^ hoan thien ph4n mem thanh san pham thuong mai. doi hoi nhieu
thdi gian va cdng sue bdi khi dd doi hoi mot lugng chat xam Idn cho
xu ly sd lieu.
20

1.
2.

3.

4.

5.

6.

7.

8.

9.

Tai lieu tham khao.
Peter Stummer, New developments in electrical resistivit\- imanging.
Doctor Dissertation, 2003.
Max A. MejuM. Montague, Basis for a flexible low-cost automated
resistivity data acquisition and analysis system, Computers &
Geosciences Volume 21 , Issue 8 (October 1995)
Werkema, D.D., Jr.; Atekwana, E.; Sauck, W.; Asumadu, J.A. A
generic
automated/semiautomated
digital
multielectrodeinstrument
for
field

resistivity
measurements,
Instrumentation and Measurement, IEEE Transactions on. Volume 49.
Issue 6, Dec 2000 Page(s):1249- 1253.
Shoui, F.H.; Georges, S.; Lagace, P.J.; Do, X.D., Fast processing of
resistivity sounding measurements in N-layersoii, Power
Engineering Society Summer Meeting. 2001. IEEE, Volume 3, Issue ,
2001 Page(s):1743- 1748 vol.3.
Hidalgo, H.; Gomez-Trevino, E.; Marroquin, J.L.; Esparza. F.J.
Piecewise continuous models for resistivity soundings, Geoscience
and Remote Sensing, IEEE Transactions on Volume 39, Issue 12. Dec
2001 Page(s):2725-2728.
Stummer, P.; Maurer, H.; Horstmeyer, H.; Green, A.G. Optimization
of DC resistivity data acquisition: real-time experimental design
and a new muitielectrode system, Geoscience and Remote Sensing,
IEEE
Transactions
on
Volume 40, Issue 12, Dec 2002 Page(s): 2727 - 2735.
F. H. Slaoui, a, S. Georgesb, P. J. Lagacea and X. D. Doc. The
inverse problem of Schlumberger resistivity
sounding
measurements by ridge regression. Electric Power S\ stems
Research, Volume 67, Issue 2, November 2003. Pages 109-114.
R. J. Owenl • , O. Gwavava2 • and P. Gwaze3. Multi-electrode
resistivity survey for groundwater exploration in the Harare
greenstone belt, Zimbabwe, Hydrogeology Journal, Volume 14,
Numbers 1-2 / January, 2006,
Jingping Zhe,l Stewart Greenhalgh,l and Laurent Marescot2,
Multichannel, full waveform and flexible electrode combination

resistivity-imaging system. Geophysics. Volume 72, Issue 2, pp.
F57-F64 (March-April 2007)


TOM TAT CAC CONG TRINH NCKH CUA CA NHAN
(bai bao, bao cao tai Hoi nghi khoa hoc....)
DONG TRONG BAO CAO CUA OE TAI

Nganh: Vat ly; Chuyen nganh: Vat ly ky thuat
1. Ho va ten cac tac gia cong trinh:
Tran VTnh Th5ng
Mr

Nguyen Ngoc Dinh
2. Nam: 2008
3. Ten bai bao:
LOW COST DATA ACQUISITION SYSTEM FOR PHYSICAL
EXPERIMENTS EDUCATION
4. Ten tap chi/ Sach/ Tuyin tap Hoi nghi/ So, trang:
VNU Journal of Science (to be submited)
'

y

f

5. Tom tat cdng trinh bang tieng Viet:
Bo thu thap sd lieu dung may tinh da dugc xay dung bao gdm chip vi
dieu khien dung de dpc dir lieu tu bp chuyen ddi tuong tu sd ADC 16 bit vdi
hai kenh vao, diJ lieu dudng truyen qua cdng USB de vao may tinh. Phan

mem nhiing dugc viet bang ngdn ngi> C, phan mem giao dien va dieu khien
tren may tinh dugc viet bang Delphi, cac ldi vao nam trong dai do tu -1.25 V
den 1.25V, vdi dp chinh xac cao < 0.3%, bd thu thap sd lieu nay la da nang
vdi nhieu thi nghiem vat ly.
A low cost data acquisition (DAQ) system using computer has been
built. A microcontroller based hardware control an 16 bits analog to digital
converter with two channel inputs and interface to the computer via USB
port. Firmware writen in C language and software writen in Delphi, which
controls all the system operation. The inputs is in voltage with high voltage
protection circuit in the range from -1.25V to +1.25V. This DAQ system is
useful for many kind of physical experiments education with high accuracy
(lower than 0.3% of error).
y

1

21

I

y


LOW COST DATA ACQUISITION SYSTEM FOR PHYSICAL EXPERIMENTS
EDUCATION
T r a n Vinh Thang, Nguyen Ngoc Dinh
Faculty

of Physics,

HaNoi

UniversUy

of Science

Abstract
A

low

cost

data

acquisition

(DAQ)

system

using

computer

has

been

built,

A

microcontroller b a s e d h a r d w a r e control an 16 bits analog to digital converter with two
c h a n n e l i n p u t s a n d interface to t h e c o m p u t e r via U S B port. F i r m w a r e writen in C
l a n g u a g e a n d software writen in Delphi, which controls all the system operation. The
i n p u t s is in voltage with high voltage protection circuit m the r a n g e from - 1 . 2 5 V to
+ 1.25V. T h i s DAQ system is useful for m a n y kind of physical e x p e r i m e n t s education
w i t h high accuracy (lower t h a n 0.3% of error).
I. I n t r o d u c t i o n
C o m p u t e r - b a s e d e q u i p m e n t s is becoming incorporated into more physical e x p e r i m e n t s courses.
In p a r t i c u l a r , c o m p u t e r s equipped with lowcost d a t a acquisition systems (sometimes known a s
d a t a l o g g e r s ) h a v e h a d t h e effect of increasing t h e level of hands-on e x p e r i m e n t a l activity in physics
l a b o r a t o r i e s a t both colledge and university. Supported by a variety of sensors such a s voltage.
c u r r e n t , light, force a n d t e m p e r a t u r e , t h e s e s y s t e m s have been shown to be pedagogically effective,
p a r t i c u l a r l y w h e r e h i g h e r level l e a r n i n g skills a r e concerned [1,2,3] with commercial expensive
h a r d w a r e [4,5], or r e m o t e teaching [6]. The most popular commercially available low-cost d a t a
acquisition s y s t e m s include those supplied by the US companies Vernier [7] antl PASCO [8| In this
paper, we will p r e s e n t our work in r e s e a r c h and development of an d a t a acquisition s y s t e m for
physical e x p e r i m e n t s at Physics Faculty of HaNoi University of Science. In our laboratory, we
i m p l e m e n t e d a h a r d w a r e , f i r m w a r e a n d Delphi language - based software to compete an DAQ
system.
II. D A Q i m p l e m e n t a t i o n
2,1 D A Q h a r d w a r e
Block d i a g r a m of t h e DAQ h a r d w a r e is shown in figure 1. Microchip's P I C 1 8 F 4 5 5 0
Microcontroller u n i t is u s e d to control Analog Device's AD7705 16bits analog to digital c o n v e r t e r
a n d interface to t h e c o m p u t e r via U S B port. Reference voltage using Maxim's MAX872 is t h e most
i m p o r t a n t p a r t of t h e m o d u l e with error of 0.2% a n d drift of SOppm/'^C.

^

USB

^1 MCU

L J

M

l^n

4550

' ^ ^ ^ — " ^

T

Ext.
Capture

•

AD7705
16bit ADC

z

2.5V Ref
[VIAX872

F i g . 1 Block d i a g r a m of t h e D a t a Acqusision module

Two inputs with IMohm impedance and a low-passed filter is connected in serial. Before
entered to the ADC, input signals passed through to the 3V overload protection circuit, this is very
important for measuring an unknown signal. The module has a low cost, low power consumption
and is supplied by the computer via USB cable. All of the hardware parts are closed in a box in
dimension of 150x95x50mm as shown in photo in figure 2.

-T6^rUSB-0AQ

Fig. 2 Photo of the DAQ module
2.2 DAQ firmware and software
The DAQ hardware is controlled by a firmware, which residents in the program memory of
microcontroller, and writen in C language. The software is writen by Delphi as shown in figure 2.
Functions and operation modes of the software are interested in most of practical activities in
physics. Functions include; Port configuration (USB CDC class). Save data to text file, Zero
calibrate, clear data and copy data to clipboard, this may be used to paste dnectly m any data
analysis software as Origin, Exel. Operation Modes included: Single data Capture, Timer capture
with variable interval, External Capture (or manual capture).

'jy J

^> 16 Bits Hf-^p^d DAQ5ys1em
File

Edit

Calibrate

Config

About

Pofl Contig

#

r

COM3 - 1

SingleCapfu.e

CLOSE

J

«

CHI (V)

1

.7-8294E-5; Z . - : : -

2

7 6294E-5

3 8147E-5

i3

0 00011444

38147E-5

14

0 00011444

5 8147E-5

1 CH2(V|

^ ^ l . . \
7fi7^4E-5

5
'•' Timelniefv^
Ext. Cap^ufe

1000

mc

START

|

r OpyData Ctrl-tC
'^

r lear

17E-5

7

•0 045319

3 8147E-5

Q

•0 04b73

3S147E-5

9

•0 040359

0 00049591

10

-0 D:f55695

3ei47E-5

11

•0 00M114

J8147E5

Fig.3 Software interface

^


III. Result and discussion
The inputs range is chosen at (-1.25V to +1.25V), it is equivalent with a O.OSSmVbit
resolution. The accuracy of the implemented DAQ system is compared with that of Autoranging
Microvolt Digital Multimeter Keithley 197A. The results as shown in figure 4 are very closed to
the results of the DMM 197A, the error is only 0.3% at maximum at near 0.2mV and smaller at
the range form lOmV to 1.25V, however, this is very good for the most of the experiments in
general physic lab.

0.20-1

0.30-

0.15

0.25-

Keithley 197 A
OAQ data

0.10

0.20-

I

0.05-1

S

0.00

SL\

.U.

0.155ô
w
O

Keithley 197A
DAQ data

E]
0.10-

i-

o

LU

UJ
0.05-

-0.05

0.00-

-0.10
-0.15-1
-0.20

El

I
200

I

400

'

1

600

T
800

-0.05-

r1
.
1
1000 1200

-|ôIôIFItI.|rIã

0

200

Input Voltage (mV)

400

600

800

1000 1200

Input Voltage (mV)

oltag

Fig.4 DAQ module vs. Keithley 197A

.>

0.6064-j
0.60630,60620.6061 0.6060C.60590.60580,60570.60560.60550.60540.60530.60520.60510.6050-

Voltage drop on the diode at room temperature

-I

0

1

1

500

>

1

•

1000

r

1500

'

1

2000

'

1

2500

Time (s)

Fig.5 Voltage drop on silicon diode at room temperature
Figure 5 is the mea-sured voltage drop on 1N4148 silicond silicon diode used as temperature
sensor with a V-T's coefficient about - 2 m V / T . The result shoun that our DAQ system can be used
for high accuracy experiments.
This work is supported by QT-07-19 project.