Page 64 - Understanding Automotive Electronics

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THE SYSTEMS APPROACH TO CONTROL AND INSTRUMENTATION 2

measuring rapidly changing input quantities. Figure 2.16 illustrates such
dynamic errors for an analog sensor measuring an input that abruptly changes
between two values (this type of input is said to have a square wave waveform).
Figure 2.16a depicts a square wave input to the sensor. Figure 2.16b illustrates
the response that the sensor will have if its bandwidth is too small. Note that
the output doesn’t respond to the instantaneous input changes. Rather, its
output changes gradually, slowly approaching the correct value.
Signal processing can be An ideal sensor has a linear transfer characteristic (or transfer function), as
used to compensate for shown in Figure 2.17a. Thus, some signal processing is required to linearize the
systematic errors of sen- output signal so that it will appear as if the sensor has a straight line (linear)
sors. transfer characteristic, as shown in the dashed curve of Figure 2.17b.

Figure 2.16
Sensor Error Caused by Limited Dynamic Response of Sensor

UNDERSTANDING AUTOMOTIVE ELECTRONICS 51