MPXM12GS datasheet(5/20 Pages) FREESCALE

5 / 20 page

MPX12

Sensors

Freescale Semiconductor

Pressure

Temperature Compensation

Figure 2 shows the typical output characteristics of the

MPX12 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.

Several approaches to external temperature

compensation over both –40 to +125

°C and 0 to +80°C

ranges are presented in 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

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 2. Output vs. Pressure Differential

Figure 3. Linearity Specification Comparison

Pressure Differential

0.3

2.0

0.6

4.0

0.9

6.0

1.2

8.0

1.5

PSI

kPa

Span

Range

(Typ)

Offset

(Typ)

VS = 3 VDC

P1 > P2

-40

°C

+25

°C

+125

°C

Linearity

Actual

Theoretical

Offset

(VOFF)

Max

POP

Pressure (kPa)

Span

(VFSS)

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