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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 pres-
sure.
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 minimum, maximum and typical output
characteristics of the MPX2050 series at 25
°
C. The output is
directly proportional to the differential pressure and is essen-
tially 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 Diagram (not to scale)
O
kPa
PSI
40
35
30
25
20
15
10
5
0
–50
12.5
1.8
25
3.6
37.5
5.4
50
7.25
SPAN
RANGE
(TYP)
OFFSET
(TYP)
ééééééééééé
ééééééééééé
ééééééééééé
ééééééééééé
SILICONE
DIE COAT
WIRE BOND
LEAD FRAME
DIE
STAINLESS STEEL
METAL COVER
EPOXY
RTV DIE
BOND
P1
MAX
TYP
MIN
VS = 10 Vdc
TA = 25
°
C
MPX2050
P1 > P2
Figure 4 illustrates 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 MPX2050 series pressure sensor operating charac-
teristics and internal reliability and qualification tests are
based on use of dry air as the pressure media. Media other
than dry air may have adverse effects on sensor perfor-
mance and long term reliability. Contact the factory for in-
formation regarding media compatibility in your application.
F
Freescale Semiconductor, Inc.
n
.