How to create digital levels from analogue inputs

This post answers the question “How to create digital levels from analogue inputs?”. The process of creating digital levels from analog Inputs is called an Analog to Digital Converter (ADC). Through Analog to Digital Converter, analog inputs are changed into an order of binary numbers that are known as encoded bits. From which digital levels are created by the transmitter.

There are two methods to create digital levels from analog inputs. That is sampling and resolution. ADC first samples the signal and then determines the resolution of the signal quantifying it.

And ultimately, it sets binary values and sends them to the system to read the digital levels. In this post, we will take a brief conception of these two methods to create digital levels from analog Inputs.

Sampling

This process is also known as sampling frequency that inspects the value of the voltage of an analog inputs signal at regular time intervals. The time between samples known as the sample period ( $T_{s}$ ) and the number of samples taken per second is known as the “sample frequency” ( $f_{s}$ )

Basically, sampling takes snap-shot values of the analog input signal so that you can understand how many samples or data points it can take within a second. The more samples or data points the ADC can take the higher frequencies can be handled.

The equation of the sample rate is: $f_{s} = \frac{1}{T_{s}}$ .

Here, $f_{s}$ is a sample rate/frequency, $T_{s}$ is a period of the sample or the time it takes before sampling again.

The sampling rate must be greater than the Nyquist rate otherwise it will create a problem known as aliasing.

$f_{N} = 2 f_{m a x}$

Here, $f_{m a x}$ is the highest frequency component of the analog signal.

The main thing is that the sampling frequency $f_{s}$ must be greater than $f_{N}$ . That means, $f_{S} > f_{N}$ .

For instance, if the input signals of the digital system have a max frequency of 100 kHz, then the sampling rate must be greater than 200 kHz. this will allow for the successful creation of digital levels from analog inputs.

Resolution of ADC

The resolution of the ADC is determined by its bit length. As much you increase the bit length, the levels will increase making the signal more nearly represent the original analog signal. The bit resolution is very important if you want an accurate voltage level for your system. But the bit resolution depends on both the bit size and the voltage reference. Here is given the equation to clearly understand.

Step size = $\frac{V_{r e f}}{N}$

Here, step size means the resolution of each level in terms of voltage, and $V_{r e f}$ means the range of voltages.

N

is the total level size of ADC where

N = 2^{n}

and

n

is considered the bit size.