3–17
Motorola Sensor Device Data
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TEMPERATURE COMPENSATION
Figure 2 shows the typical output characteristics of the
MPX10 and MPXV10GC series over temperature.
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.
Several approaches to external temperature compensa-
tion over both –40 to +125
°
C and 0 to +80
°
C ranges are
presented in Motorola Applications Note AN840.
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
Figure 4. Unibody Package — Cross–Sectional
Diagram (not to scale)
ééééééééééé
ééééééééééé
ééééééééééé
ééééééééééé
ééééééééééé
P2
SILICONE
DIE COAT
WIRE BOND
LEAD FRAME
DIE
STAINLESS STEEL
METAL COVER
EPOXY
CASE
RTV DIE
BOND
OFFSET
(VOFF)
MAX
70
O
60
50
40
30
20
10
0
0
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 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 MPX10 and MPXV10GC 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 per-
formance and long term reliability. Contact the factory for
information regarding media compatibility in your application.
F
Freescale Semiconductor, Inc.
n
.