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The materials included in this compilation are for the use of Dwyer Instruments, Inc. potential customers and current employees as a resource only. They may not be reproduced, published, or transmitted electronically for commercial purposes. Furthermore, the Company’s name, likeness, product names, and logos, included within these compilations may not be used without specific, written prior permission from Dwyer Instruments, Inc. ©Copyright 2014 Dwyer Instruments, Inc.
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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 ’ 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 . © 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 ≠ 1% RSS ≠ 1% SUM ≠ 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 ’ 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 ° 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
𝑹𝑴𝑺=√ ( 𝑵𝒐𝒏−𝑳𝒊𝒏𝒆𝒂𝒓𝒊𝒕𝒚 )𝟐+(𝑯𝒚𝒔𝒕𝒆𝒓𝒆𝒔𝒊𝒔 )𝟐+(𝑵𝒐𝒏−𝑹𝒆𝒑𝒆𝒂𝒕𝒂𝒃𝒊𝒍𝒊𝒕𝒚 )𝟐
𝟑
Calculating AccuracyRo o t o f t h e S u m S q u a re d M e t h o d
𝑹𝑺𝑺=√ (𝑵𝒐𝒏−𝑳𝒊𝒏𝒆𝒂𝒓𝒊𝒕𝒚 )𝟐+(𝑯𝒚𝒔𝒕𝒆𝒓𝒆𝒔𝒊𝒔 )𝟐+( 𝑵𝒐𝒏−𝑹𝒆𝒑𝒆𝒂𝒕𝒂𝒃𝒊𝒍𝒊𝒕𝒚 )𝟐
Calculating AccuracyS u m o f t h e Fa c t o r s M e t h o d
𝑺𝒖𝒎=𝑵𝒐𝒏−𝑳𝒊𝒏𝒆𝒂𝒓𝒊𝒕𝒚 +𝑯𝒚𝒔𝒕𝒆𝒓𝒆𝒔𝒊𝒔+𝑵𝒐𝒏−𝑹𝒆𝒑𝒆𝒂𝒕𝒂𝒃𝒊𝒍𝒊𝒕𝒚
Calculating AccuracyTo t a l E r ro r B a n d ( @ 2 1 ° 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 – 0 . 5 % B F S L
N o n - R e p e a t a b i l i t y – 0 . 0 5 % F. S .
H y s t e r e s i s – 0 . 1 % F. S .
𝑹𝑴𝑺=√ ( 𝑵𝒐𝒏−𝑳𝒊𝒏𝒆𝒂𝒓𝒊𝒕𝒚 )𝟐+(𝑯𝒚𝒔𝒕𝒆𝒓𝒆𝒔𝒊𝒔 )𝟐+(𝑵𝒐𝒏−𝑹𝒆𝒑𝒆𝒂𝒕𝒂𝒃𝒊𝒍𝒊𝒕𝒚 )𝟐
𝟑=𝟎 .𝟑𝟎%
𝑹𝑺𝑺=√ (𝑵𝒐𝒏−𝑳𝒊𝒏𝒆𝒂𝒓𝒊𝒕𝒚 )𝟐+(𝑯𝒚𝒔𝒕𝒆𝒓𝒆𝒔𝒊𝒔 )𝟐+( 𝑵𝒐𝒏−𝑹𝒆𝒑𝒆𝒂𝒕𝒂𝒃𝒊𝒍𝒊𝒕𝒚 )𝟐=𝟎 .𝟓𝟏%
𝑺𝒖𝒎=𝑵𝒐𝒏−𝑳𝒊𝒏𝒆𝒂𝒓𝒊𝒕𝒚 +𝑯𝒚𝒔𝒕𝒆𝒓𝒆𝒔𝒊𝒔+𝑵𝒐𝒏−𝑹𝒆𝒑𝒆𝒂𝒕𝒂𝒃𝒊𝒍𝒊𝒕𝒚=𝟎 .𝟔𝟓%
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 – 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 – 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 – 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
Recommended