understanding pressure sensor accuracy and sensor technology
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Understanding PressureSensor Accuracy
and Sensor Technology
T h e m a t e r i a l s i n c l u d e d i n t h i s c o m p i l a t i o n a r e f o r t h e u s e o f D w y e r I n s t r u m e n t s , I n c . p o t e n t i a l c u s t o m e r s a n d c u r r e n t e m p l o y e e s a s a r e s o u r c e o n l y . T h e y m a y n o t b e r e p r o d u c e d , p u b l i s h e d , o r t r a n s m i t t e d e l e c t r o n i c a l l y f o r c o m m e r c i a l p u r p o s e s .
F u r t h e r m o r e , t h e C o m p a n y β s n a m e , l i k e n e s s , p r o d u c t n a m e s , a n d l o g o s , i n c l u d e d w i t h i n t h e s e c o m p i l a t i o n s m a y n o t b e u s e d w i t h o u t s p e c i fi c , w r i t t e n p r i o r p e r m i s s i o n
f r o m D w y e r I n s t r u m e n t s , I n c . Β© C o p y r i g h t 2 0 1 4 D w y e r I n s t r u m e n t s , I n c .
Understanding Pressure Sensor Accuracy
New Accuracy Equation
1% RMS β 1% RSS β 1% SUM β 1% TEB
Why is Accuracy Important?E ffi c i e n c y a n d Q u a l i t y
E ffi c i e n c y I m p r o v e o p e r a t i o n s
R e d u c e o p e r a t i n g c o s t
Q u a l i t y R e d u c e s c r a p
I m p r o v e y i e l d s
Why is Accuracy Important?Ac c u r a c y v s . P r i c e
%
$
Accuracy StandardsW h o i s t h e I E C ?
F o u n d e d i n 1 9 0 6 , t h e I E C ( I n t e r n a t i o n a l E l e c t r o t e c h n i c a l
C o m m i s s i o n ) i s t h e w o r l d β s l e a d i n g o r g a n i z a t i o n f o r t h e
p r e p a r a t i o n a n d p u b l i c a t i o n o f I n t e r n a t i o n a l S t a n d a r d s f o r
a l l e l e c t r i c a l , e l e c t r o n i c a n d r e l a t e d t e c h n o l o g i e s .
T h e I E C i s t h e l e a d i n g g l o b a l o r g a n i z a t i o n t h a t p u b l i s h e s
c o n s e n s u s - b a s e d i n t e r n a t i o n a l s t a n d a r d s .
Accuracy StandardsI E C D e fi n i t i o n o f Ac c u r a c y( I n t e r n a t i o n a l E l e c t r o t e c h n i c a l C o m m i s s i o n )
A c c u r a c y i s m a x i m u m p o s i t i v e a n d n e g a t i v e d e v i a t i o n f r o m
t h e s p e c i fi e d c h a r a c t e r i s t i c c u r v e o b s e r v e d i n t e s t i n g a
d e v i c e u n d e r s p e c i fi e d c o n d i t i o n s a n d b y a s p e c i fi e d
p r o c e d u r e .
Accuracy StandardsI E C 6 1 2 9 8 - 2 S t a n d a rd
A c c u r a c y m u s t i n c l u d e H y s t e r e s i s ,
N o n - R e p e a t a b i l i t y a n d N o n - L i n e a r i t y.
Accuracy FactorsN o n - Re p e a t a b i l i t y
T h e m a x i m u m d i ff e r e n c e
i n o u t p u t w h e n t h e s a m e
p r e s s u r e i s a p p l i e d ,
c o n s e c u t i v e l y , u n d e r
t h e s a m e c o n d i t i o n s a n d
a p p r o a c h i n g f r o m t h e
s a m e d i r e c t i o n .
Accuracy FactorsH y s t e re s i s
T h e m a x i m u m d i ff e r e n c e i n
s e n s o r o u t p u t a t a p r e s s u r e
w h e n t h a t p r e s s u r e i s fi r s t
a p p r o a c h e d w i t h p r e s s u r e
i n c r e a s i n g a n d t h e n
a p p r o a c h e d w i t h p r e s s u r e
d e c r e a s i n g d u r i n g a f u l l
s p a n p r e s s u r e c y c l e .
Accuracy FactorsN o n - L i n e a r i t y
T h e m a x i m u m p o s i t i v e o r n e g a t i v e d e v i a t i o n b e t w e e n t h e
a v e r a g e c u r v e a n d t h e s e l e c t e d s t r a i g h t l i n e , e x p r e s s e d i n
p e r c e n t o f i d e a l o u t p u t s p a n a n d i s i n d e p e n d e n t o f n o n -
r e p e a t a b i l i t y a n d h y s t e r e s i s .
T h r e e N o n - L i n e a r i t y M e t h o d s ( d e fi n e d b y I E C ) Te r m i n a l P o i n t N o n - L i n e a r i t y
B e s t F i t S t r a i g h t L i n e N o n - L i n e a r i t y
Z e r o B a s e d N o n - L i n e a r i t y
Accuracy FactorsB e s t Fi t S t r a i g h t L i n e v s . Te rm i n a l Po i n t
Calculating AccuracyW h a t a re t h e d i ff e re n t m e t h o d s ?
R o o t o f t h e M e a n S q u a r e d
R o o t o f t h e S u m S q u a r e d
S u m o f Fa c t o r s
To t a l E r r o r B a n d ( @ 2 1 Β° C )
Calculating AccuracyRo o t o f t h e M e a n S q u a re d M e t h o d
πΉπ΄πΊ=β ( π΅ππβπ³ππππππππ )π+(π―πππππππππ )π+(π΅ππβπΉππππππππππππ )π
π
Calculating AccuracyRo o t o f t h e S u m S q u a re d M e t h o d
πΉπΊπΊ=β (π΅ππβπ³ππππππππ )π+(π―πππππππππ )π+( π΅ππβπΉππππππππππππ )π
Calculating AccuracyS u m o f t h e Fa c t o r s M e t h o d
πΊππ=π΅ππβπ³ππππππππ +π―πππππππππ+π΅ππβπΉππππππππππππ
Calculating AccuracyTo t a l E r ro r B a n d ( @ 2 1 Β° C )
Calculating AccuracyAc c u r a c y Va r i a n c e B a s e d o n M e t h o d
N o n - L i n e a r i t y β 0 . 5 % B F S L
N o n - R e p e a t a b i l i t y β 0 . 0 5 % F. S .
H y s t e r e s i s β 0 . 1 % F. S .
πΉπ΄πΊ=β ( π΅ππβπ³ππππππππ )π+(π―πππππππππ )π+(π΅ππβπΉππππππππππππ )π
π=π .ππ%
πΉπΊπΊ=β (π΅ππβπ³ππππππππ )π+(π―πππππππππ )π+( π΅ππβπΉππππππππππππ )π=π .ππ%
πΊππ=π΅ππβπ³ππππππππ +π―πππππππππ+π΅ππβπΉππππππππππππ=π .ππ%
Pressure Sensor Technology
Major Sensor Technologies
S t r a i n M e a s u r i n g E l e m e n t s B o n d e d ( S i l i c o n o r F o i l G a u g e s )
D e p o s i t e d ( T h i n o r T h i c k - fi l m )
S i l i c o n P i e z o r e s i s t i v e ( M o u n t e d o n s u b s t r a t e )
D i s p l a c e m e n t M e a s u r i n g E l e m e n t s H a l l - C e l l ( G r o s s M o t i o n )
C a p a c i t i v e ( F i n e M o t i o n )
Bonded Strain Gauges
S i l i c o n S t r a i n G a u g e β S i l i c o n s t r a i n g a u g e b o n e d t o m e t a l
s u b s t r a t e
F o i l S t r a i n G a u g e β F o i l s t r a i n g a u g e b o n e d t o m e t a l
s u b s t r a t e
B o n d e d S i l i c o n G a u g e
Deposited
T h i c k F i l m - F o r m e d b y t h e d e p o s i t i o n o f l a y e r s o f s p e c i a l
a d h e s i v e s o n t o a n i n s u l a t i n g s u b s t r a t e o n a d i a p h r a g m
T h i n F i l m - S t r a i n g a u g e s a r e a t t a c h e d t o a m e t a l l i c b a s e
e l e m e n t u s i n g a s p u t t e r i n g p r o c e s s .
T h i n F i l mT h i c k F i l m
Silicon Piezoresistive( M o u n t e d o n S u b s t r a t e )
S i l i c o n P i e z o r e s i s t i v e - R e s i s t a n c e e l e m e n t s d i ff u s e d i n
c r y s t a l l i n e o r p o l y c r y s t a l l i n e S i l i c o n
Silicon Piezoresistive
Capacitive( Fi n e M o t i o n )
C a p a c i t i v e β D i a p h r a g m m o v e m e n t b e t w e e n p l a t e s
d e t e r m i n e s c a p a c i t a n c e
d
h
a
Diaphragm
Substrate
Detect Electrode
Source Electrode
Guard Electrode
Glass
Ceramic CapacitiveMetal Capacitive
Hall Cell( G ro s s M o t i o n )
H a l l - C e l l - M a g n e t s t r e n g t h d e t e r m i n e s H a l l c u r r e n t
Pressure Sensor Ranges
B o n d e d S t r a i n G a u g e
0 1 B a r ( a ) 1 0 B a r ( a ) 6 0 B a r ( a )6 0 0 B a r ( a )
2 0 0 0 B a r ( a )
Pressure Range
T h i n - F i l m
C e r a m i c T h i c k F i l m
S i l i c o n P i e z o r e s i s t i v e
C e r a m i c C a p a c i t i v e