S dng FC105 x l tn hiu tn hiu module Analog Hm Scale FC105 c chc
nng c gi tr nguyn ( IN) v chuyn i n sang dng gi tr thc nm trong
khong gia gi tr gii hn di v gi tr di hn trn ( LO_LIM v HI_LIM). Kt
qu c vit vo u ra OUT. Hm Scale s dng cng thc sau:OUT = [ ( (FLOAT
(IN) K1)/(K2K1)) * (HI_LIMLO_LIM) ] + LO_LIMHng s K1 v K2 c thit lp
da trn gi tr u vo l gi tr lng cc (BIPOLAR) hay n cc
(UNBIPOLAR)BIPOLAR: Gi tr s nguyn u vo nm trong khong t -27648 n
27658, nh vy K1=-27648, K2=27648UNBIPOLAR: Gi tr s nguyn u vo nm
trong khong t 0 n 27648, nh vy K1=0; K2=27648Nu gi tr nguyn u vo ln
hn K2, u ra OUT s c gn bng HI_LIM v s bo li li. Nu s nguyn u vo nh
hn K1 th u ra s c gn bng LO_LIM v s bo li li
Tham s hm FC105:
Trng hp bo liNu s nguyn u vo c gi tr ln hn K2 , u ra (OUT) s c
gn bng HI_LIM, Nu gi tr u vo nh hn K1 th u ra c gn bng LO_LIM. C 2
trng hp trn u tr v Li. ENO s c logic 0 v RET_VAL c gi tr bng
W#16#0008
V D:
- Mt cn tnh s dng Loadcell c ti trng nm trong khong [0-100kg],
vi tn hiu u ra ca Loadcell l [0-20mV], - Tn hiu loadcell qua b
khuch i in p thnh tn hiu [0-10V],- Sau tn hiu c khuch i c a ti
module AI ca PLC S7-300.
Trong V d ta s dung module AI tch hp cng CPU313C gm 5 knh vo
Analog, phn gii 12 bit. a ch l 752...761
Ta ni tn hiu cm bin c u ni ti knh 1, gi tr chuyn i ca module AI
s c lu vo thanh ghi c a ch PIW752, Nu ni ti knh 2 th s c a ch
PIW756. Trong v d ny ta s dng knh 1, PIW752
Gi tr ca PIW752 l gi tr nguyn khng du (do tn hiu o l 0..10V) nm
trong di t 0-27648.
Lu :: Tt c cc module AI phn gii t 12bit n 16bit u lu gi tr chuyn
i vo 1 a ch PIW, c di 1 t. Cng c gi tr trong khong ( -27648 n
27648) . Gi tr nm ngoi khong trn c quy nh l trn.
Ta s lp trnh trong OB1 s dng FC105 nh sau:
Bc 1: Gi FC105 theo ng dn: Libraries\Standard Library\TI_S7
Converting Block\ FC105 SCALE
Bc 2: Khai bo cc tham s:
- IN: PIW752- Tn hiu cm bin l tn hiu khng du nn BIPOLAR =0 =>
M0.0 =0- HI_LIM =100.0 ( kg) - LO_LIM= 0 (kg)- OUT: MD20 ( gi tr cn
thc t )- RETVAL: MW10
Bc 3: Save, Download OB1 v FC105 xung CPU. Chy th nghim hm
trn
