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CHO MNG NGY THNH LP TRNG (01/04/1956-01/04/2010)

Tp ch Khoa hc Cng ngh Hng hi S 22 04/2010

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NGHIN CU CH TO TH NGHIM OSILLOSCOPE S MANUFACTURING RESEARCH TRIALS OF DIGITAL OSILLOSCOPE

TS. TRN SINH BIN; V NGC IP

Khoa in - in t tu bin, Trng HHH

Tm tt

Bi bo gm 3 phn: Tng quan v oscilloscope s; Xy dng cc s nguyn l mch in; Xy dng giao din trn my tnh cho oscilloscope s.

Abstract

The article is of three parts: Overview of the Digital Oscilloscope; Design principle circuit diagram; Designing interfaces on the computer for the Digital Oscilloscope.

1. M u

Trong k thut o lng v iu khin th vic quan st dng tn hiu in l mt vn rt quan trng. V th vic nghin cu ch to ra cc cc my hin sng (dao ng k hay oscilloscope) c u tin pht trin. Nu nh trc y cc oscilloscope ch l cc oscilloscope tng t c kch thc ln v ch dng li vic o cc tn hiu c tn s nh khong vi Mhz th ngy ny vi s pht trin ca cng ngh bn dn, cc oscilloscope tng t c th o c cc tn hiu in c tn s ti vi trm Mhz thm ch l ti c Ghz. Bn cnh s pht trin ca oscilloscope tng t cc nh sn xut cn cho ra i mt loi oscilloscope mi l oscilloscope s, oscilloscope s vi s tch hp ca cc b ADC, b vi x l tc cao kt hp cng ngh mch in nhiu lp lm cho cc oscilloscope s ny c kch thc nh gn tch hp nhiu chc nng v c kh nng o cc tn hiu in c tn s ln ti hng Ghz.

T nhng thc t bi bo ny nghin cu v oscilloscope s v bc u ch to th nghim thnh cng oscilloscope s.

2. Tng quan v oscilloscope s 2.1. Khi nim v oscilloscope s

tm hiu khi nim v Osilloscope s ta cn phi hiu c th no l mt Osilloscope c nh.

Osilloscope c nh l loi Osilloscope dng kho st cc loi tn hiu tc thi, tun hon chm, hay tn hiu ngn, tn hiu qu ... Di tn s c th n 150MHz. Di tn hiu t hng chc mV n hng trm vn.

Osilloscope s l loi dao ng k c nh s. Nguyn l lm vic da trn vic s ha tn hiu kho st nh b chuyn i A /D gi l qu trnh ly mu v chuyn i. Cc mu c ghi vo b nh, sau c bin i tr li thnh tng t phc v cho mc nh hin th.

2.2. Cu trc oscilloscope s

Hnh 1. Cu trc oscilloscope s.

Mch o: Ty thuc vo loi tn hiu u vo m mch o s tng t nh l mch khuch i v chuyn i tn hiu. Mch khuch i thng l mch c h s khuch i >0. Mch chuyn i ng vai tr chuyn i t tn hiu sau mch khuch i v loi tn hiu ph hp vi loi tn hiu u vo ca b ADC. Thng thng tn hiu m cc oscilloscope o thng l cc tn hiu dng hoc tn hiu p. V vy mch khuch i thng l cc mch gim dng hoc mch phn p s dng cc phn t nh bin dng, bin p, linh kin bn dn, mch in tr, in cm, in dung

B ADC: L b chuyn i tn hiu tng t thnh tn hiu s. Tn hiu o sau khi i qua mch o s c a vo b ADC. B ADC s chuyn i dng tn hiu ny t tn hiu tng



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t thnh tn hiu s a n b vi x l. Trn thc t b ADC c phn gii khc nhau: 8bit, 10bit, 12bit, 16bit, 24bit... phn gii cng ln th tn hiu u ra s s cng gn vi tn hiu u vo tng t. u ra s ca b ADC c th l bus song song hoc ni tip.

B vi x l: B vi x l ng vai tr x l trung tm, n nhn kt qu o t b ADC gia cng v x l trc khi gi v my tnh hin th. B vi x l c s dng ph bin hin nay l cc h vi iu khin nh 8051, AVR, PIC, PSOC, ARM... vi tc x l ph hp. Ngy nay cc vi iu khin c tch hp thm trong n cc b ADC c kh nng trch mu tc cao, ngoi ra n cn c kh nng ghp ni vi my tnh theo cc chun ghp ni. Ngoi cc kh nng trn mt u im ln na ca b vi x l l kh nng lu tr thng tin, kh nng ny ph hp cho cc cho cc osilloscope tc cao.

My tnh hin th kt qu o: My tnh s nhn cc thng tin t b vi x l sau gia cng v hin th. Vic truyn nhn thng tin t vi x l n my tnh v ngc li s c thc hin qua cc chun ghp ni nh RS232, LPT, USB, khe cm m rng

3. S nguyn l mch x l trung tm trong oscilloscope s 3.1. S nguyn l (trang sau) 3.2. Nguyn l hot ng

Mch x l trung tm c kh nhn 2 knh tn hiu tng t a ti b chuyn i ADC tch hp sn trong vi iu khin Pic18f4550. B ADC ny c phn gii 10bit, in p u vo t 0V 5V. Chc nng ca khi ADC l chuyn i tn hiu t dng tng t thnh tn hiu dng s lu tr v x l.

B vi iu khin pic18f4550 ca Microchip c tch hp sn b ADC, vi dung lng b nh chng trnh Flash 32k, SRAM 2048 byte, EEPROM 256 byte. Tn s xung nhp c th ln ti 48MHz, c 5 Port I/O, cc modul truyn thng tc cao, h tr cc chun giao tip I2C, SPI. Ngoi ra pic18f4550 cn c tch hp modul USB cho php giao tip trc tip vi thit b ngoi vi qua chun USB 2.0. S dng trnh bin dch CCSC vit chng trnh cho pic18f4550. Khi vi x l nhn d liu c s ha t b ADC s x l v lu tr trc khi gi v my tnh hin th.

Mch x l trung tm c thit k c kh nng ghp ni vi my tnh thng qua cng LPT v cng COM (RS 232) truyn d liu t my b vi x l v my tnh v ngc li.



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U1

pic18f 4550

1

234567

11

1413

15161718

19

12202122

23242526

2728

89

10

2930

32

31

3334353637383940

MCLR/VPP/RE3

RA0/AN0RA1/AN1RA2/AN2/VREF-/CVREFRA3/AN3/VREF+RA4/T0CKI/C1OUT/RCVRA5/SS/AN4/C2OUT

VDD1

OSC2/CLKO/RA6OSC1/CLKIN

RCO/T1OSO/T13CK1RC1/T1OSI/CCP2/UOE

RC2/CCP1/P1AVusb

RD0/SPP0

Vss1RD1/SPP1RD2/SPP2RD3/SPP3

RC4/D-/VMRC5/D+/VPRC6/TX/CK

RC7/RX/DT/SDO

RD4/SPP4RD5/SPP5/P1B

RE0/AN5/CK1SPPRE1/AN6/CK2SPPRE2/AN7/OESPP

RD6/SPP6/P1CRD7/SPP7/P1D

VDD2

Vss2

RB0/AN12/INT0/FLT0/SDI/SDARB1/AN10/INT1/SCK/SCL

RB2/AN8/INT2/VMORB3/AN9/CCP2/VPO

RB4/AN11/KBI0/CSSPPRB5/KBI1/PGMRB6/KB12/PGCRB7/KB13/PGD

Nguon DC

123456

0

R2

10K

J6

nguon tham chieu chuan

12

PGC/RB6

PGC/RB6

0

SW1

+12v

0

D1

LED

C133pf

0

PGM/RB3

vdd

AN2J3

Mach ghep noi may tinh qua cong COM

1234

5V_Chuan

vdd

0

HI

J10

Vao Vi dieu khien

1234

HI

J8

Cong Nap ICSP

123456

C3104p

mclr

J1

Chi Bao

123

AN4

Vss/Gnd

HI

12MHZ

CRYSTAL

HI

mclr

AN1

5V_Chuan

C233pf

R1220 C20

104

AN3

Vss/Gnd

Mach ghep noi may tinh qua cong LPT

PGM/RB3

0

HI

PGD/RB7

PGD/RB7

Dat

Hnh 2. S nguyn l mch x l trung tm oscilloscope s.

3.3. Thut ton cho vi x l



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Hnh 3. Thut ton khi vi x l.

4. Xy dng giao din trn my tnh v kt qu 4.1. Xy dng giao din trn my tnh

Trn thc t c rt nhiu ngn ng lp trnh c th s dng xy dng giao din iu khin ph hp vi yu cu cng ngh, trong bi bo ny ngn ng lp trnh visual basic phin bn 6.0 c s dng xy dng giao din trn my tnh cho m hnh oscilloscope s.

Lu thut ton trn my tnh:



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Hnh 4. Lu thut ton trn my tnh.

4.2. Gii thiu cc thng s chnh ca oscilloscope s

Cc thng s ca oscilloscope s: - in p ngun cp: 220 VAC. - C hai knh o c th o c tn hiu in p v dng in. - Vin: 55 V - Iin: 1000 mA - Di tn o c: 20 Hz 10 KHz. (tng ng vi tc ly mu 10 Ksps). - Ghp ni vi my tnh qua cng RS232. 4.3. Kt qu Hnh nh Osilloscope khi o hai knh vi in p 24 VAC i xng tn s 50 Hz.

a. in p c tn s 50 Hz b. in p c tn s 5 kHz

Hnh 5. Hnh nh Osilloscope khi o in p.



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- Hnh nh Osilloscope khi o tn hiu dng in c tn s 50 Hz.

Hnh 6. Hnh nh Osilloscope khi o dng in tn s 50Hz. 5. Kt lun

Bi bo nghin cu v oscilloscope s, phn tch v xut phng n ph hp thit k modul phn cng cho oscilloscope s. Trn c s tin hnh xy dng cc s mch, ch to th nghim thnh cng modul phn cng v thit k phn mm giao din trn my tnh cho oscilloscope s. Kt qu thu c l oscilloscope s ghp ni vi my tnh, hot ng n nh v chnh xc vi giao din trn my tnh d s dng. TI LIU THAM KHO [1] Ng Din Tp, o lng v iu khin bng my tnh, NXB Khoa hc k thut, H Ni 1997. [2] Ng Din Tp, K thut ghp ni my tnh, NXB Khoa hc k thut, H Ni 2001. [3] PGS V Qu im, C s k thut o lng in t, NXB Khoa hc k thut. [4] Nguyn Th Ngc Mai, Lp trnh c s d liu Visual Basic 6.0, NXB Lao ng. [5] Phm Thng Hn, K thut o lng cc i lng vt l T1, T2, NXB Gio dc, 1997. [6] Datasheet, PIC18F Family, Microchip. [7] Datasheet, PIC18F4550, Microchip. [8] Help CCSC, Microchip. [9] Datasheet LM324, TL084, 74LS00, MAX232CPE. [10] www.microchip.com.

Ngi phn bin: ThS. V Ngc Minh