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Motorola Sensor Device Data
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LINEARITY
Linearity refers to how well a transducer’s output follows
the equation: Vout = Voff + sensitivity x P over the operating
pressure range. There are two basic methods for calculating
nonlinearity: (1) end point straight line fit (see Figure 2) or (2)
a least squares best line fit. While a least squares fit gives
the “best case” linearity error (lower numerical value), the
calculations required are burdensome.
Conversely, an end point fit will give the “worst case” error
(often more desirable in error budget calculations) and the
calculations are more straightforward for the user.
Motorola’s specified pressure sensor linearities are based on
the end point straight line method measured at the midrange
pressure.
Figure 2. Linearity Specification Comparison
LEAST
SQUARE
DEVIATION
R
PRESSURE (% FULLSCALE)
0
50
100
END POINT
STRAIGHT LINE FIT
EXAGGERATED
PERFORMANCE
CURVE
LEAST SQUARES FIT
STRAIGHT LINE
DEVIATION
OFFSET
ON–CHIP TEMPERATURE COMPENSATION and CALIBRATION
Figure 3 shows the output characteristics of the
MPX2102/MPXV2102G series at 25
°
C. The output is
directly proportional to the differential pressure and is
essentially a straight line.
The effects of temperature on Full Scale Span and Offset
are very small and are shown under Operating Characteris-
tics.
Figure 3. Output versus Pressure Differential
Figure 4. Cross–Sectional Diagrams (Not to Scale)
O
kPa
PSI
40
35
30
25
20
15
10
5
0
–50
25
3.62
50
7.25
75
10.87
100
14.5
SPAN
RANGE
(TYP)
OFFSET
(TYP)
TYP
MIN
VS = 10 Vdc
TA = 25
°
C
P1 > P2
MAX
ééééééééééé
ééééééééééé
ééééééééééé
ééééééééééé
ééééééééééé
P2
SILICONE GEL
DIE COAT
WIRE BOND
LEAD FRAME
DIFFERENTIAL/GAUGE
DIE
SMETAL COVER
EPOXY
CASE
DIE
BOND
ééééééééééé
ééééééééééé
ééééééééééé
SILICONE GEL
DIE COAT
WIRE BOND
LEAD FRAME
ABSOLUTE
DIE
SMETAL COVER
EPOXY
CASE
DIE
BOND
P2
Figure 4 illustrates the absolute sensing configuration
(right) and the differential or gauge configuration in the basic
chip carrier (Case 344). A silicone gel isolates the die
surface and wire bonds from the environment, while allowing
the pressure signal to be transmitted to the silicon
diaphragm.
The MPX2102/MPXV2102G series pressure sensor oper-
ating characteristics and internal reliability and qualification
tests are based on use of dry air as the pressure media. Me-
dia other than dry air may have adverse effects on sensor
performance and long term reliability. Contact the factory for
information regarding media compatibility in your application.
F
Freescale Semiconductor, Inc.
n
.