3
Motorola Sensor Device Data
TEMPERATURE COMPENSATION
Figure 2 shows the typical output characteristics of the
MPXL10 series over temperature.
The X–ducer piezoresistive pressure sensor element is a
semiconductor device which gives an electrical output signal
proportional to the pressure applied to the device. This de-
vice uses a unique transverse voltage diffused semiconduc-
tor strain gauge which is sensitive to stresses produced in a
thin silicon diaphragm by the applied pressure.
Because this strain gauge is an integral part of the silicon
diaphragm, there are no temperature effects due to differ-
ences in the thermal expansion of the strain gauge and the
diaphragm, as are often encountered in bonded strain gauge
pressure sensors. However, the properties of the strain
gauge itself are temperature dependent, requiring that the
device be temperature compensated if it is to be used over
an extensive temperature range.
Temperature compensation and offset calibration can be
achieved rather simply with additional resistive components,
or by designing your system using the MPX2010D series
sensor.
LINEARITY
Linearity refers to how well a transducer’s output follows
the equation: Vout = Voff + sensitivity x P over the operating
pressure range (Figure 3). There are two basic methods for
calculating nonlinearity: (1) end point straight line fit or (2) a
least squares best line fit. While a least squares fit gives the
“best case” linearity error (lower numerical value), the cal-
culations 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. Output versus Pressure Differential
Figure 3. Linearity Specification Comparison
OFFSET
(VOFF)
70
O
60
50
40
30
20
10
0
0
MAX
POP
SPAN
(VFSS)
PRESSURE (kPA)
ACTUAL
THEORETICAL
LINEARITY
PRESSURE DIFFERENTIAL
O
80
70
60
50
40
30
20
10
0
0
0.3
2.0
0.6
4.0
0.9
6.0
1.2
8.0
10
1.5
PSI
kPa
SPAN
RANGE
(TYP)
OFFSET
(TYP)
VS = 3 Vdc
P1 > P2
–40
°
C
+25
°
C
+125
°
C
Figure 4 illustrates the Differential/Gauge Sensing Chip in
the basic Low Profile Package (Case 472B–01). A fluorosili-
cone gel isolates the die surface and wire bonds from the envi-
ronment, while allowing the pressure signal to be transmitted
to the sensor diaphragm.
The MPXL10 series pressure sensor operating characteris-
tics, 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 performance and long–
term reliability. Contact the factory for information regarding
media compatibility in your application.
Figure 4. Cross–Sectional Diagram
(Not to Scale)
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EPOXY CASE
FLUORO SILICONE
WIRE BONDS
LEAD FRAME
DIE
STAINLESS STEEL
METAL COVER