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Analog Signal

An analog signal is a type of continuous signal in a form of wave that varies smoothly over time, representing data with infinited possible values. For example, sound waves, radio signals, and temperature changes are all using analog signal to represent its value or device/sensor data.

An analog signal uses some property of the medium to convery the signal’s information. Any information may be conveyed by an analog signal, often such a signal is measured change in physical phenomena, such as sound, light, temperature, position, or pressure. For example, in sound recording, changes in air pressure (ie. a sound) strikes the diaphragm of a microphone which causes related changes in a voltage or the current in some electric circuit. The voltage or the current is said to be an “analog” of the sound.

Analog signals are more prone to noise and distrotion and they are usually used in analog electronics. Analog signal can vary in a continuous manner, as opposed to a digital signal that only takes discrete values.

Reference to Analog Signal (Wikipedia) page for more details and information. The sigidwiki.com (Signal Identification Wiki) contains a visual representation of analoge signals on different signal samples.

Analog to Digital (ADC) Convesion

The conversion between the Analog<~>Digital Signals is a technique used to convert Analog to Digital (ADC - Analog-to-Digital Converter), and vice-versa, Digital to Analog (DAC - Digital-to-Analog Converter) signals.

The ADC uses so called resolution specification, indicating how accurately the ADC measures the analog input signal. Common ADCs are either 8-bit, 10-bit, and 12-bit. For example, if the reference voltage of ADC is 0V to 5V, then an 8-bit ADC will break it within 256 divisions, so it can measure it accurately up to 5V/256V = 19mV (approx.). In case of a 10-bit ADC, the break range for same voltage values would be within 5V/1024 = 4.8mV (approx.). Therefore, the 8-bit ADC wouldn’t be able to tell the difference between 1mV ~ 18mV. Other specifications of the ADCs include sampling rate (how fast the ADC can take the readings), among others specs provided by the ADC datasheet.

Reference to blog Using the ADC of PIC Microcontroller for more details on ADC usage in real-world circuits with PIC microcontrollers. Alternatively, reference to Using ADC of AVR Microcontroller.

Reference to Visualize ADC data on PC via USART for detailed tutorial on how to use ADCGraph2 software on WindowsNT via the USART Port.

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Digital Signal

Digital signals are more reliable for long-distance transmission and storage. The digital signal only takes discrete values (ie. LOW/HIGH data in a binary form), as opposed to Analog Signal which can vary in a continuous manner.