ly thuyet analog

BI 5: S DNG MODULE ANALOG1. GII THIU CHUNG V MODULE ANALOG. Trc ht bn hy so snh vic cng hai tn hiu tng t (analog) vi vic cng hai tn hiu s (digital), cng vic no n gin hn khi m k thut s pht trin nh hin nay? Hay ta ly mt v d n gin nh sau : Ta cn iu khin nhit ca mt l nung sao cho t c cht lng no . Lm th no o nhit v v x l nhit nh th no trong bi ton iu khin? Mt trong nhng cng c c s dng l module analog. - Vy Module analog l g? - Cc bn bit c nhng g v module analog ? - Bn tng s dng cha ? - Nguyn l hot ng chung ca module analog l g ? 1.1 Khi nim v module analog. Module analog l mt cng c x l cc tn hiu tng t thng qua vic x l cc tn hiu s. 1.2 Analog input Thc cht n l mt b bin i tng t - s (A/D). N chuyn tn hiu tng t u vo thnh cc con s u ra. Dng kt ni cc thit b o vi b iu khin: chng hn nh o nhit . 1.3 Analog output Analog output cng l mt phn ca module analog. Thc cht n l mt b bin i s - tng t (D/A). N chuyn tn hiu s u vo thnh tn hiu tng t u ra. Dng iu khin cc thit b vi di o tng t. Chng hn nh iu khin Van m vi gc t 0-100%, hay iu khin tc bin tn 0-50Hz. 1.4 Nguyn l hot ng chung ca cc cm bin v cc tn hiu o chun trong cng nghip. Thng thng u vo ca cc module analog l cc tn hiu in p hoc dng in. Trong khi cc tn hiu tng t cn x l li thng l cc tn hiu khng in nh nhit , m, p sut, lu lng, khi lng . . . V vy ngi ta cn phi c mt thit b trung gian chuyn cc tn hiu ny v tn hiu in p hoc tn hiu dng in thit b ny c gi l cc u o hay cm bin. tin dng v n gin cc tn hiu vo ca module Analog Input v tn hiu ra ca module Analog Output tun theo chun tn hiu ca cng nghip.C 2 loi chun ph bin l chun in p v chun dng in. - in p : 0 10V, 0-5V, 5V - Dng in : 4 20 mA, 0-20mA, 10mA. Trong khi tn hiu t cc cm bin a ra li khng ng theo chun . V vy ngi ta cn phi dng thm mt thit chuyn i a chng v chun cng nghip. Kt hp cc u cm bin v cc thit b chuyn i ny thnh mt b cm bin hon chnh , thng gi tt l thit b cm bin, hay ng hn l thit o v chuyn i o ( b transducer).

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Bi 5: S dng Module Analog - Trang 99 -

Module analog Thit b cm bin Thit b chuyn i 0 10V Analog Input ( A/D) Cc con s

u o Tn hiu vo khng in

4-20 mA Tn hiu ra tng t 0 10 V 4 20 mA

Analog Output ( D/A) Cc con s

2.

GII THIU V MODULE ANALOG EM235. EM 235 l mt module tng t gm c 4AI v 1AO 12bit (c tch hp cc b chuyn i A/D v D/A 12bit bn trong).

2.1 Cc thnh phn ca module analog EM235.

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Thnh phn 4 u vo tng t A+ , A- , RA c k hiu bi cc B+ , B- , RB ch ci A,B,C,D C+ , C- , RC D+ , D- , RD 1 u ra tng t (MO,VO,IO) Gain Offset Switch cu hnh S khi ca u vo Analog.

M t Cc u ni ca u vo A Cc u ni ca u vo B Cc u ni ca u vo C Cc u ni ca u vo D Cc u ni ca u ra Chnh h s khuch i Chnh tri im khng Cho php chn di u vo v phn gii

S khi u ra Analog

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2.2 nh dng d liu a/ D liu u vo: - K hiu vng nh : AIWxx (V d AIW0, AIW2) - nh dng: + i vi di tn hiu o khng i xng (v d 0-10V,0-20mA): MSB LSB 15 14 3 2 1 0 0 D liu 12 bit 0 0 0 Modul Analog Input ca S7-200 chuyn di tn hiu o u vo (p, dng) thnh gi tr s t 0 32000. + i vi di tn hiu o i xng (V d 10V, 10mA,): MSB LSB 15 4 3 2 1 0 D liu 12 bit 0 0 0 0 Modul Analog Input ca S7-200 chuyn di tn hiu o u vo p, dng) thnh gi tr s t -32000 32000. b/ D liu u ra: - K hiu vung nh AQWxx (V d AQW0, AQW2) - nh dng d liu + i vi di tn hiu o khng i xng (v d 0-10V,4-20mA): MSB LSB 15 14 4 3 2 1 0 0 D liu 11 bit 0 0 0 0 Modul Analog output ca S7-200 chuyn i con s 0 32000 thnh tn hiu in p u ra 0 10V.

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+ i vi di tn hiu o i xng (V d 10V, 10mA,): Kiu ny cc module Analog output ca S7-200 khng h tr. MSB 15 D liu 12 bit c/ Bng tng hp : nh dng d liu Kiu tn hiu i xng ( 10V, 10mA,) Tn hiu khng i xng (0 10V, 4 20mA) 2.3 Cch ni dy a/ u vo tng t: - Vi thit b o u ra kiu in p: Gi tr chuyn i - 32000 n +32000 0 n +32000 4 3 0 2 0 LSB 1 0 0 0

RA A+ A+ in p

-

Vi thit b o tn hiu u ra dng in: Hoc :

RA RA A+ A+ AA++ -M PS L+ PS M

4-20 mA 4-20 mA

b/ u ra tng t:

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MO VO IO Ti in p Ti dng in

c/ Cp ngun cho Module:

M L+

Ngun 24 VDC

Tng qut cch ni dy:

2.4 Ci t di tn hiu vo.

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Module EM 235 cho php ci t di tn hiu v phn gii ca u vo bng switch:

On OffSau y l bng cu hnh : Di khng i xng SW1 SW2 SW3 ON OFF OFF OFF ON OFF ON OFF OFF OFF ON OFF ON OFF OFF ON OFF OFF OFF ON OFF Di i xng SW1 SW2 SW3 ON OFF OFF OFF ON OFF OFF OFF ON ON OFF OFF OFF ON OFF OFF OFF ON ON OFF OFF OFF ON OFF OFF OFF ON Di u vo SW4 ON ON OFF OFF OFF OFF OFF SW4 ON ON ON OFF OFF OFF OFF OFF OFF SW5 OFF OFF ON ON OFF OFF OFF SW5 OFF OFF OFF ON ON ON OFF OFF OFF SW6 ON ON ON ON ON ON ON SW6 OFF OFF OFF OFF OFF OFF OFF OFF OFF 0 50 mV 0 100 mV 0 500 mV 01V 05V 0 20 mA 0 10 V Di u vo 25 mV 50 mV 100 mV 250 mV 500 mV 1V 2.5 V 5V 10 V phan gii 12.5 uV 25 uV 125 uV 250 uV 1.25 mV 5 uA 2.5 mV phn gii 12.5 uV 25 uV 50 uV 125 uV 250 uV 500 uV 1.25 mV 2.5 mV 5 mV

2.5 Trnh t thit lp v cn chnh cho module analog . a/ Cn chnh u vo cho module analog - Hy tt ngun cung cp cho module - Gt switch chn di o u vo - Bt ngun cho CPU v module. module n nh trong vng 15 pht. - S dng cc b truyn, ngun p, hoc ngun dng, cp gi tr 0 n mt trong nhng u vo. - c gi tr nhn c trong CPU. - Cn c vo gi tr hy chnh OFFSET a gi tr v 0 (cn chnh im khng) , hoc gi tr s cn thit k. - Sau ni mt trong nhng u vo vi gi tr ln nht ca di o. - c gi tr nhn c trong CPU. - Cn c vo gi tr hy chnh GAIN c c gi tr l 32000, hoc gi tr s cn thit k.

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Lp li cc bc chnh OFFSET v GAIN nu cn thit. Ch : Phi chc chn ngun cung cp cho cm bin phi c loi b nhiu v phi n nh. Dy dn tn hiu phi c lp bo v chng nhiu. Cc u vo analog khng s dng phi c ni ngn mch (v d A+ ni vi A-)

3. MT S NG DNG . 3.1 Vit chng trnh con tnh ton gi tr in p o t chit p. a/Hy lp mch theo s sau : . b/ Xy dng cng thc tnh ton: Di in p u ra ca chit p : 0 10V Vi di in p ny module analog s chuyn i sang di gi tr t 0 32000. Vy nu ta c c gi tr trn CPU l 24000 th gi tr analog u vo l bao nhiu Volt ?

u vo analog (y)-V 10 ?V u ra s (x) 0 24000 32000

0

S bin i t gi tr tng t u vo sang cc con s l s bin i 1-1 , v hon ton tuyn tnh. V vy mi quan h gia u vo v u ra l mi quan h tuyn tnh c dng ng thng n gin y = ax + b. C th thy ngay phng trnh trn c dng y = x/3200. Do nu bit c gi tr s l 24000 ta tnh c ngay u ra l 7.5 V. Ta hy tng qut ha cng thc tnh ton c th xy dng chng trnh con:

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24000 0 32000 0.0 (V) 10.0 (V) Chng trnh con tnh ton y = x/3200 7.5 (V)

Tng qut ha

D_Out D_Min D_Max A_Min A_Max Chng trnh con tnh ton y = ax + b A_In

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Cc k hiu : A_In : Gi tr analog u vo cn xc nh. A_Min : Gi tr gii hn di ca gi tr u vo tng t. A_Max : Gi tr gii hn trn ca gi tr u vo tng t. D_out : Gi tr chuyn i bng s ca A_In. D_Min : Gi tr chuyn i bng s ca A_Min. D_Max : Gi tr chuyn i bng s ca A_Max. T y ta xc nh c cng thc tnh ton cho gi tr u vo.A _ In = A _ Max A _ Min ( D _ Out D _ Min) + A _ Min D _ Max D _ Min

c/ Tin hnh vit chng trnh : + Chng trnh con : Khai bo cc bin vo ra v bin tm thi

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Cc ch thch :

Chng trnh con :

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+ Trong chng trnh chnh ta gi chng trnh con ny

+ Tin hnh bin dch, download, v debug chng trnh 3.2 Vit chng trnh con xut d liu ra u ra Analog. - Vi di gi tr t 0 32000, module analog s bin i u ra tn hiu tng t t 0 10V - Vy nu ta cn in p u ra l 8 V th gi tr bng s cn a ra l bao nhiu ?

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Gi tr bng s cn a ra (y) 32000 ? u ra tng t (x) - V 0 8 10

0

S bin i t gi tr s sang tn hiu tng t u ra l s bin i 1-1 . V vy mi quan h gia u vo v u ra l mi quan h tuyn tnh c dng ng thng n gin y = ax + b. C th thy ngay phng trnh trn c dng y = 3200.x. Do nu gi tr u ra l 8 V ta tnh c ngay con s cn a vo bin i l 25600. Ta hy tng qut ha cng thc tnh ton c th xy dng chng trnh con:

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8.0 V 0.0 10.0 V 0 32000 Chng trnh con tnh ton y = x/3200 25600

Tng qut ha

A_Out A_Min A_Max D_Min D_Max Chng trnh con tnh ton y = ax + b D_In

-

Cc k hiu : A_Out : Gi tr analog u ra mong mun A_Min : Gi tr gii hn di ca tn hiu ra tng t. A_Max : Gi tr gii hn trn ca tn hiu ra tng t. D_In : Gi tr bng s tng ng vi A_Out. D_Min : Gi tr bng s tng ng vi A_Min. D_Max : Gi tr bng s tng ng vi A_Max. T y ta xc nh c cng thc tnh ton cho gi tr u vo.D _ In = D _ Max D _ Min ( A _ Out A _ Min) + D _ Min A _ Max A _ Min

c/ Tin hnh vit chng trnh : + Khai bo cc bin vo ra v bin tm trong chng trnh con.

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+ Ch thch :

+ Chng trnh con :

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+ Chng trnh chnh gi chng trnh con :

+ Tin hnh bin dch, download v debug. 3.3 ng dng o nhit mi trng. - Di tn hiu o 0-150oC

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-

u ra 0-10V Cn tnh nhit thc t mi trng l bao nhiu.

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ly thuyet analog

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