
3–192
Motorola Sensor Device Data
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A second technique that still uses a single pressure
measurement as the input was investigated. In this method,
the sensitivity coefficients are calculated using a piece–wise
linearization technique where the total span variation is
divided into four windows of 10 mV (i.e., 30–39.99, 40–49.99,
etc.) and coefficients calculated for each window. The errors
that arise out of using this method are shown in Figures 10
through 13. This method results in a large majority of the
devices having errors <0.5%, while only one of the devices
was >1%. The sensitivity coefficients that are substituted into
equation [2] for the different techniques are given in Table 1.
It is important to note that for either technique the only
measurement that is required by the user in order to clearly
determine the sensitivity coefficients is the determination of
the full scale span of the particular pressure transducer.
Figure 10. Linearity Error of Piece–Wise Linear Fit at 1/4 FS
48
42
36
30
24
18
12
6.0
0.0
–2.0
37.69
33.92
30.15
26.38
22.62
18.85
15.08
11.31
7.54
3.77
–1.6 –1.4 –1.2 –1.0 –0.8 –0.6 –0.4 –0.2 0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4 1.6
1.8
2.0
NO. OF UNITS
LINEARITY ERROR (% FS)
General Fit
P = 1/4 FS
Average Error = 0.18
Standard Deviation = 0.159
%
–1.8
Table 1. Comparison of Linearization Methods
SPAN WINDOW
B0
B1
B2
GENERAL FIT
0.1045 + 2.95E – 3X
0.2055 + 1.598E – 3X + 1.723E – 4X2
1.293E – 13X5.681
PIECE–WISE LINEAR FIT
30–39.99
0.08209 – 2.246E – 3X
0.02433 = 1.430E – 2X
–1.961E – 4 + 8.816E – 6X
40–49.99
0.1803 – 4.67E – 3X
–0.119 + 1.655E – 2X
–1.572E – 3 + 4.247E – 5X
50–59.99
0.1055 – 3.051E – 3X
–0.355 + 2.126E – 2X
–5.0813 – 3 + 1.116E – 4X
60–69.99
–0.288 + 3.473E – 3X
–0.361 + 2.145E – 2X
–5.928E – 3 + 1.259E – 4X
X = Full Scale Span
F
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n
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