In the digital control system, an analog signal is an input, whereas the output of the digital controller is converted into a digital one with the help of a sample and hold circuit. Digital computers are used as system controllers in the digital control system. There is a huge importance of data acquisition and data distribution in the digital control system.
Data Acquisition in Digital Control System
In data acquisition, the physical variable is the input to the digital control system. Here, the input physical variable is converted into an electrical signal for further processing. The physical variables like velocity, temperature, and pressure are converted into an electrical signal (may be voltage or current signal) with the help of a transducer.There is the presence of an amplifier in the transducer which performs various operations.
The various operations carried out by the amplifier are signal buffering and conversion of the current signal. The current signal is converted to the voltage signal with the help of the amplifier. Also, it amplifies the voltage output of the transducer. Hence, the amplifier in the transducer plays an important role in all types of operations performed in the digital controller.
There is also the presence of noise in the output. This type of electronic noise is filtered or reduced by the low pass filter. The output of the low pass filter is the same as that of the digital controller i.e. an analog signal. There is also the presence of an analog multiplexer.
The main function of an analog multiplexer is to carry out the required operation by taking the output of the low pass filter. In other words, the output signal i.e. an analog signal is fed into the analog multiplexer. Later, the output of this analog multiplexer is transmitted to the sample and hold circuit.
The output of this sample & hold circuit is sent to the analog-to-digital converter where the analog signal is converted into the digital signal. Finally the output of the analog-to-digital converter i.e. the digital form signal is fed into the digital controller or digital computer.
Hence, the various elements used in the data acquisition process are the transducer, amplifier, low pass filter, analog multiplexer, sample & hold circuit, analog-to-digital converter, etc.
Data Distribution in Digital Control System
The opposite or reverse form of the data acquisition process is known as data distribution. The various elements required for the data distribution process are registers, a demultiplexer, a digital-to-analog converter, a hold circuit, etc.The main function of the demultiplexer is to extract the output signal of the digital controller into the original channels in the digital control plant.
The main function of the digital-to-analog converter is to convert the digital binary form signal into the required analog signal.
The converted analog signal is fed into the hold circuit for further processing. And, the output of the hold circuit is transmitted to the analog actuator.
The main operation performed by the analog actuator is to directly control the plant.