MPX10
Sensors
4 Freescale Semiconductor
Pressure
Temperature Compensation
Figure 2 shows the typical output characteristics of the
MPX10 series over temperature.
Because this strain gauge is an integral part of the silicon
diaphragm, there are no temperature effects due to
differences 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: V
out
= V
off
+ 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
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.
Freescale’s specified pressure sensor linearities are based
on the end point straight line method measured at the
midrange pressure.
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 series pressure sensor operating
characteristics 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.Refer to application note AN3728, for more
information regarding media compatibility.
Figure 2. Output vs. Pressure Differential
Figure 3. Linearity Specification Comparison Figure 4. Unibody Package — Cross-Sectional Diagram
(Not to Scale)
Pressure Differential
Output (mVdc)
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)
MPX10
V
S
= 3 V
DC
P1 > P2
-40°C
+25°C
+125°C
Linearity
Actual
Theoretical
Offset
(V
OFF
)
Max
P
OP
Output (mVdc)
Pressure (kPa)
70
60
50
40
30
20
10
0
0
Span
(V
FSS
)
Silicone
Die Coat Die
P1
P2
Wire Bond
Lead Frame
RTV Die
Bond
Epoxy
Case
Stainless Steel
Metal Cover
