chap1 - Automation Engineering Services(ENG3618 Chapter 1...

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Automation & Engineering Services (ENG3618) Chapter 1 Page 1 Chapter 1 Signal Processing in Sensors Often the signals from transducers are not in the form we would like them to be. For example, they may be Too small Too noisy due to electromagnetic interference Having the wrong information because of faulty design Having a DC offset because of static errors Therefore, we need to process the signals from the output of the sensors. Signal processing is classified into two types: Analog signal processing Digital signal processing In the analog processing, we use very often Operational Amplifiers and analog filters. In the digital signal processing, microprocessor and digital machines are used. There should also be devices to convert an analog signal to digital form and vice versa. And to this end, we have the Analog-to-Digital (A/D) Converter and the Digital-to-Analog (D/A) Converter. Operational Amplifiers An operational amplifier (Op Amp) is an Integrated Circuit (IC) consisting of transistors, resistors and capacitors in a Dual In-line Package (DIP) e.g. National Semiconductor’s 741 and Texas Instrument’s TL071. They can act as amplifiers, integrators, summers, differentiators, comparators, analog-to-digital (A/D) and digital-to-analog (D/A) converters, active filters and, sample and hold amplifiers. It is an active device , i.e. its output voltage can exceed the input voltage without any voltage source within itself. They require a voltage source to perform though. Note that a passive device is always associated with a voltage drop along the circuit due to impedance. The schematic diagram of an Op Amp is shown in Figure1. - + V o V 1 V 2 Figure 1 Operational Amplifier Schematics
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Automation & Engineering Services (ENG3618) Chapter 1 Page 2 In an Op Amp, all voltages are referred to a common ground. At the inputs V 1 and V 2 , the input impedance of the Op Amp is infinite . This is equivalent to saying there is zero current flowing through the Op Amp from its input locations and therefore, the voltage level at both input locations is equal . Also, the output impedance of the Op Amp at the output location is zero . This is equivalent to saying that the voltage at the output location does not depend on the current from the Op Amp to the output point . The Op Amp is the basic building block for:
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chap1 - Automation Engineering Services(ENG3618 Chapter 1...

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