Sensors and Actuators Sensor Physics

Transcription

1 Snsors and Atuators Snsor Physis Sandr Stuijk Dpartmnt of ltrial ninrin ltroni Systms

2 PN-JUNCON SNSOS (Chaptr 6.5)

3 3 mpratur snsors plamnt xitation physial fft matrial thrmal snsor ontat passiv thrmal xpansion mtal bimtal ontat ativ rsistiv fft mtal D ontat ativ rsistiv fft smiondutor silion rsistiv ontat ativ rsistiv fft polymr or rami thrmistor ontat passiv thrmoltri fft ondutor thrmooupl ontat ativ PN juntion smiondutor silion bandap non-ontat passiv pyroltri fft pyroltri pyroltri non-ontat ativ ultrasound - aousti

4 4 Smiondutor P-N juntion snsor smiondutor matrial dopd with P and N matrial P dopin N dopin ltrons dplt from N to P matrial P N intrnal fild dvlops aross PN juntion whih stops rombination pla lar nouh (and opposit) xtrnal fild aross PN juntion rombination pross an ontinu urrnt flows throuh PN juntion P N i

5 5 Smiondutor P-N juntion snsor smiondutor p-n juntion in diods hav tmpratur dpndny p-n juntion onntd to urrnt sour forward biasd (-m/ C) volta dpnds on tmpratur urrnt

6 6 Smiondutor P-N juntion snsor smiondutor p-n juntion in diods hav tmpratur dpndny p-n juntion onntd to urrnt sour volta aross th P-N juntion k ln k Boltzmann s onstant ( /K) ltron har ( ) saturation urrnt B 3 k band ap nry B matrial dpndnt onstant

7 7 Smiondutor P-N juntion snsor volta aross th P-N juntion k ln saturation urrnt has stron tmpratur dpndny B k 3 tmpratur snsitivity d d ln k k ln k B aurat snsor ruirs onstant urrnt B ln 3k k ln 3 P-N juntion has non-linar tmpratur dpndny 3 ln non-linarity is limitd in opratin ran (-5 to +5 C) k k B ln 3

8 8 Smiondutor P-N juntion snsor disadvantas of usin diods for tmpratur masurmnt stabl, tmpratur indpndnt urrnt sour ndd buildin diods in smiondutor with littl variation is diffiult both issus impat snsitivity and rpatability of dvi solution for sond problm: bipolar transistor olltor urrnt v vb k k s onnt bas to olltor (v b = ) v k k v ln whn forward biasd ( ~ - A hn >> ) v k ln b b

9 9 Smiondutor P-N juntion snsor disadvantas of usin diods for tmpratur masurmnt stabl, tmpratur indpndnt urrnt sour ndd buildin diods in smiondutor with littl variation is diffiult both issus impat snsitivity and rpatability of dvi solution for sond problm: bipolar transistor dvi havs as a diod usin sam approah as with diod w find v B dpnds on k omtry ln B ln 3 dopin onntration liminat B throuh on alibration point b b

10 Smiondutor P-N juntion snsor alibration: rfrn output ( ) with olltor urrnt C at output has non-linar rlation with tmpratur output dpnds on urrnt b 3 ln C B k v v v 3 3 ln ln C B k B k B k B k C 3 3 ln ln B B k C 3 3 ln k C 3 ln

11 Smiondutor P-N juntion snsor snsitivity of th transistor (assum onstant olltor urrnt) dv d k 3 ln 3 snsitivity typial valus for silion snsitivity: -.m/ C non-linarity:.34m/ C non-linarity b

12 Smiondutor P-N juntion snsor xampl diod onntd transistor v =.595 at 5 C and snsitivity of -.65m/ C olltor urrnt = μa dsin th iruit to obtain an output from to ovr th tmpratur ran from C to C - + b - + v o

13 3 Smiondutor P-N juntion snsor xampl diod onntd transistor v =.595 at 5 C and snsitivity of -.65m/ C olltor urrnt = μa dsin th iruit to obtain an output from to ovr th tmpratur ran from C to C output volta v o bas-mittr volta v two onstraints v m C 5 C m C C 5 C b.65m C C 5 C v o

14 4 Smiondutor P-N juntion snsor xampl diod onntd transistor v =.595 at 5 C and snsitivity of -.65m/ C olltor urrnt = μa dsin th iruit to obtain an output from to ovr th tmpratur ran from C to C substitut all valus (A) (A) solvin ths onstraints ivs = 637Ω, / = 44.5 (.656 ) (.45 ) hoos = kω, thn = 44.kΩ

15 5 Smiondutor P-N juntion snsor two issus nd to onsidrd whn usin a P-N juntion snsor bas-mittr volta has non-linar tmpratur dpndny olltor urrnt must onstant with tim and tmpratur solution: us two idntial transistors kpt at th sam tmpratur mittr urrnts hav onstant ratio ( / onstant) diffrn in bas-mittr voltas v d v k C v ln ln saturation urrnts ar ual output (v d ) proportional to tmpratur whn ratio / is onstant Q non-linar tmpratur dpndny rmovd k vd ln C C k C b b Q v d - + -v v o instrumntation amplifir

16 6 Smiondutor P-N-juntion snsor olltor urrnts an ombind into a sinl urrnt sour ombin two transistors with diffrnt mittr aras vry simpl, but aurat tmpratur snsor Q 3 and Q 4 ar ual and form urrnt mirror Q onsists of 8 transistors in paralll urrnt dnsity in Q is 8 tims larr than Q Q 3 Q 4 Q Q 3 Q 4... Q 8 paralll transistors Q Q

17 7 Smiondutor P-N-juntion snsor olltor urrnts an ombind into a sinl urrnt sour ombin two transistors with diffrnt mittr aras vry simpl, but aurat tmpratur snsor Q 3 and Q 4 ar ual and form urrnt mirror Q onsists of 8 transistors in paralll urrnt dnsity in Q is 8 tims larr than Q volta diffrn twn v Q and v Q similar to solution on prvious slid hn v v ln ln k k 8 k ln ln ln8 79 k k K Q 3 Q 4 Q Q + 8 -

18 8 Smiondutor P-N-juntion snsor olltor urrnts an ombind into a sinl urrnt sour ombin two transistors with diffrnt mittr aras vry simpl, but aurat tmpratur snsor volta diffrn twn v Q and v Q k input urrnt k 8 k ln ln ln8 79 an fixd durin manufaturin (.. 358Ω) ivs followin urrnt-tmpratur rlation A K K Q 3 Q 4 Q Q + 8 -

19 9 Smiondutor P-N juntion snsor tmpratur snsor is plad in sris with lar rsistor (.. kω) urrnt throuh snsor is tmpratur dpndnt rsistor translats urrnt to volta volta aross rsistor is masur for tmpratur urrnt-to-volta ur for diffrnt tmpraturs output urrnt v o r tmp snsor output volta

20 Smiondutor P-N juntion snsors xampl - LM35Z from national smiondutors snsor output out snsitivity a a m idal snsor would hav no offst volta part-to-part variations aus m offst rror C C non-linarity rror a [ 9.9 m C,.m C]. C