8 Data Acquisition and Process Control

Chapter 8 Data Acquisition and Process Control

Physics Lecture Notes – Phys 395 Electronics Book
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Summary of Contents

Physics Lecture Notes – Phys 395 Electronics Book

  • Chapter 8Data Acquisition and Process ControlThe purpose of most electronic systems is to measure or control some physical quantity.The system will need to acquire data from the environment, process this data and record it.Acting as a control system it will also have to interact with the environment.The flow of information in a typical data acquisition system (DAQ) can be described asfollows.1. The input transducers measure some property of the environment.2. The output from the transducers is conditioned (amplified, filtered, etc.).3. The conditioned analog signal is digitized using an analog-to-digital converter (ADC).4. The digital information is acquired, processed and recorded by the computer.5. The computer may then modify the environment by outputting control signals.6. The digital control signals are converted to analog signals using a digital-to-analogconverter (DAC).7. The analog signals are conditioned (eg. amplified and filtered) appropriately for anoutput transducer.8. The output transducer interacts with the environment.8.1TransducersElectrical systems are only able to respond to voltage and current signals in the electricaldomain: amplitude, frequency, phase and time constant. An input transducer is necessaryto convert a signal from its domain of origin (non-electrical) into the electrical domain.A transducer may generate an electrical signal by varying one of the following: voltage,current, resistance, capacitance, self-inductance, mutual-inductance, VPN , VZ, hfe or gm Themost fundamental transducers respond to temperature, electromagnetic radiation intensity,force, displacement or chemical concentration. If coupled to the time domain these devicescan be used to measure any physical or chemical quantity. Examples of input transducers157