11-1 DIGITAL AND ANALOG QUANTITY
DIGITAL
Digital quantity has two possibilities: i.e. 0 or 1, LOW or HIGH, true or false, etc.
Digital signal has discrete form. Digital Signal: logic circuit, microprocessor, digital clock,
ANALOG
Most real-world information is analog. For instance, time, speed, weight, pressure, and position
measurements are all analog in nature. Analog quantity has a continuous range of values, i.e. 27.6mV,
27.72A, etc. Analog Signal: microphone, transducer, thermistor, photocell, etc.
Some circuits are purely analog or digital circuit. Some circuits are combination of digital and analog
circuit. The below is an example of how analog interface with digital.
Transducer
The physical variable is normally a non-electrical quantity. A Transducer is a device that converts the
physical variable to an electrical variable.
Example: thermistor, pressure sensor, photocells, etc.
Analog-to-digital Converter (ADC)
The ADC converts analog input to digital output.
Digital System (Computer)
It stores the digital value and processes it according to a program of instruction.
Digital-to-Analog Converter (ADC)
The ADC convert the digital output from the computer and converts it to a proportional analog value.
Actuator
It receives analog signal and control the physical variable. A actuator might be a electronic valve to
control the flow rate of water.
Questions:1. What is the function of a transducer?
2. What is the function of an ADC and DAC?
3. What is the function of an actuator?