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The Data Acquisition System
As a user of MATLAB and the Data Acquisition Toolbox, you are interested in measuring and analyzing physical phenomena. The purpose of any data acquisition system is to provide you with the tools and resources necessary to do so.
You can think of a data acquisition system as a collection of software and hardware that connects you to the physical world. A typical data acquisition system consists of these components:
- Data acquisition hardware
- At the heart of any data acquisition system lies the data acquisition hardware. The main function of this hardware is to convert analog signals to digital signals, and to convert digital signals to analog signals.
- Sensors and actuators (transducers)
- Sensors and actuators can both be transducers. A transducer is a device that converts input energy of one form into output energy of another form. For example, a microphone is a sensor that converts sound energy (in the form of pressure) into electrical energy, while a loudspeaker is an actuator that converts electrical energy into sound energy.
- Signal conditioning hardware
- Sensor signals are often incompatible with data acquisition hardware. To overcome this incompatibility, the signal must be conditioned. For example, you might need to condition an input signal by amplifying it or by removing unwanted frequency components. Output signals might need conditioning as well. However, only input signal conditioning is discussed in this chapter.
- The computer provides a processor, a system clock, a bus to transfer data, and memory and disk space to store data.
- Data acquisition software allows you to exchange information between the computer and the hardware. For example, typical software allows you to configure the sampling rate of your board, and acquire a predefined amount of data.
The data acquisition components, and their relationship to each other, are shown below.
The figure depicts the two important features of a data acquisition system:
- Signals are input to a sensor, conditioned, converted into bits that a computer can read, and analyzed to extract meaningful information.
- For example, sound level data is acquired from a microphone, amplified, digitized by a sound card, and stored in MATLAB for subsequent analysis of frequency content.
- Data from a computer is converted into an analog signal and output to an actuator.
- For example, a vector of data in MATLAB is converted to an analog signal by a sound card and output to a loudspeaker.
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