Analog vs. Digital Input: Data Transmission Signals for Different Devices

Analog and digital signals transmit information via electric signals. So you can define a signal as an electric or electromagnetic current that sends data from one system to another. But analog and digital inputs differ, and you cannot use them on all devices. We will compare analog vs. digital input signals to determine the best one for different applications. Take a look!

What Are Analog Signal Inputs?

Analog signal inputs are continuous waveforms applied to PLCs (Programmable Logic Controller) and vary depending on the field conditions. The most typical ones range from 0-10V DC or 0-20mA.

A programmable logic controller

An example of an analog signal input is the one from a water pipe pressure monitor. A pressure transmitter with a 0-10 bar range can give a signal ranging from 0-10V and send it to an app or display to show the pressure level.

What Are Digital Signal Inputs?

Digital circuits use a binary scheme to provide digital input signals. These binary inputs (0 or 1) are two voltage levels that can vary from 5-230V, depending on the programmable logic controller.

An analog signal vs. digital signal

Switches and push buttons also provide digital signals, and these discrete signals indicate the ON/OFF status of any device. For instance, with a 24V DC module, a 0V DC voltage input will be the OFF state (binary 0), while 24V DC is the ON state (binary 1).

Analog vs. Digital Input: Differences Between Analog and Digital Signal Inputs

A fader potentiometer for professional video and audio control systems

Analog vs. Digital Processing

Analog and digital signal processing occurs in the following two ways.

How They Handle Time

• Analog signal processing occurs continuously. So the output changes when the input changes, and the only delay is due to the time it takes for electrons to move through the circuit.

An analog signal vs. digital signal

• Digital processing occurs discreetly, meaning there is some delay when inputs change until the systems register the change. The sampling frequency determines the delay duration, which a clock signal controls.

How They Affect Resolution

• Analog processing theoretically features infinite resolution because the signal does not get rounded. But this unlimited resolution is not achievable in practice.
• A digital signal processor can only handle binary signals (on/off or 0/1). The process involves rounding the values to reduce them to binary numbers.

An infographic shows how an analog audio signal is digitized for storage in a hard drive. The process involves rounding the values on the graph to the nearest discrete binary number. 

So, if you want to detect if a door is open or closed using an on/off switch, here's a comparison of the effect on time.

With Analog Processing

Once the door opens, the circuit responds to the change immediately and turns on a bulb immediately. On closing the door, the bulb goes off instantly.

With Digital Processing

Assuming the sampling frequency is 0.1Hz, the system will read the switch's state every 10 seconds, then set the light bulb. So you can open and close the door as many times as possible in those 10 seconds, and the bulb will not change its state.

If you use a potentiometer, here's how the analog and digital inputs will perform.

With Analog Processing

The door opens gradually, and the potentiometer will categorize the opening to a percentage that matches the voltage output. So the bulb's brightness will vary depending on how far you open the door.

A potentiometer

With Digital Processing

You can map the analog output signal from the potentiometer into different zones. For instance, you will have four values (0, 1, 2, and 3) if using a two-bit number.

So the value for the fully open door will be 3, while that of a fully closed door will be 0 . 1 and 2 will represent the door when 1/3 and 2/3 open, respectively. These four levels will adjust the bulb's brightness in four stages.

Analog vs. Digital Sensors

Consider an example involving building a water tank level control using an analog or digital sensor. The analog sensor input will show you the water level in real-time. On the other hand, a digital sensor will only indicate if the tank is full or not.

With a Digital Sensor

A digital sensor connected to a float will detect whether the water pushes the switch to change its state from 0 to 1 and vice versa. You can set 0 to mean not full and 1 to mean full.

A float switch for sensing the water level in a tank

With an Analog Sensor

Instead of using a switch, an analog sensor will be in the form of a slider potentiometer. Since the float rises gradually as the water level goes up, it will lift the potentiometer. And the potentiometer will produce variations in voltage between 0 and 100% when connected to a voltage source. You can map this variable analog voltage to show the precise water level using a microcontroller to display it on a screen.

A water level monitoring system (with an ultrasonic sensor, not a potentiometer)

Analog vs. Digital Input: Why Digital Input Is Better For Advanced Technology

While analog input signals are ideal for tank water level and water pipe pressure-monitoring systems, digital inputs are better for modern technology, such as robotics.

Why?

Advanced technology requires computers to program the systems, and computers use digital processing. Additionally, there are the following benefits.

• Digital data experiences low or zero noise during transmission
• The cost of digital data processing is lower than analog signal processing
• Digital processing has a wide range of applications

Wrap Up

In conclusion, analog and digital inputs have unique applications brought about by their signal waveform differences. But the digital type is more applicable in modern computing applications due to the benefits explained above. We hope this article has been insightful. Contact us for further information if you have any questions or think we left something out.