In automation applications, we often encounter many applications of analog signals such as 4-20mA signals or 0-10V signals. These are considered the two most common types of analog signals today. It can be said that all equipment in the factory from temperature sensor, water pressure sensor, water level sensor… we all see the presence of analog signals. So what is an analog signal? What is an analog signal? And how is analog signal different from digital signal?

What is an analog signal

? What is a digital signal?

Let’s find out in the following article!

First, let’s go over some concepts:

What is signal?

For a simple example, when you open the light switch in your house, the light comes on. It is a form of light signal.

Watching: What is Analog

Or simply when you hear a certain noise such as a motorbike, singing; …. It is also an audio signal.

In a nutshell, a signal is something exposed to us for the purpose of providing information. We can feel it and we can also touch it.


What is an analog signal? What is a digital signal?2 Analog signal processing:

What is an analog signal? What is a digital signal?

Wow, what do we need to learn about analog signals?

For example we need to process analog signal s7-1200 or process analog signal in s7-300. In addition to mastering the knowledge of PLC programming; It is also important to understand the nature of analog signals in these devices to be processed. This helps us to process faster and save a lot of time.

To better understand, we will go into understanding each of the following concepts:

What is a digital signal?

Also known as digital signal. This signal works on binary system; ie the values ​​are represented by digits as 0 and 1. In which the number 1 represents the ON form and the number 0 represents the OFF form.

We often see the type of electrical switch in our house. When we turn on the switch, the light comes on and when we turn off the switch, the light goes out.

Then then; The digital signal is represented by a 1 when we turn the switch on and a 0 when we turn it off.

For better understanding, see the description below:

Graph of digital signal

According to the figure above, we can see that the digital signal has 2 states, on and off, corresponding to the value 0 and 1. Another feature is that the digital signal is a discrete signal, not in series with each other. time.

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In fact, digital signals do not exist in nature. The very word “digital” also shows that a digital signal is a type of signal created by humans using technology. That’s why digital signals can be manipulated by humans.

For example an audio signal one can adjust the loudness/smallness of the sound or with a light signal one can increase/decrease its brightness.

What is an analog signal?

Unlike digital signals, analog signals are a type of sequential and analog signals. That is, after 1 period of time, the signal will be repeated and only differ in intensity.

To learn what an analog signal is, let’s look at the representation of an analog signal as follows:

Graph of analog signal

As shown above; we can see that the graph of the analog signal is a sinusoidal graph; cos or any up and down curve.

What is an analog signal?

You may not know, “analog” means … similar.

So you already know what an analog signal is, right? Analog signal is another name for analog signal.

Simple is that.

An analog signal is an analog signal. However, similar does not mean that it will repeat exactly the same after 1 period of time. It will be the same in nature of the signal and the strength of the latter may be stronger or weaker than the former.

Difference between analog and digital signals

?The fundamental difference between analog and digital signals lies in the nature of the signal.

A digital signal is a signal with only two high and low levels corresponding to the on/off value and it does not repeat after a period of time. As for the analog signal, it will repeat the nature in a certain period of time.

Another difference is that digital signals can be stored and processed on computers because computers also use binary to store data. As for the analog signal, if we want to store and process it on a computer, we have to split the signal into many values ​​of 0s and 1s to save.

Commonly used analog signal types:

In everyday life as well as in the automation industry, we can see analog signals in applications:

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For electrical equipment, automatic equipment, the analog signal is usually 0-20mA, 4-20mA or 0-10V.

In the telecommunications industry, analog signals are usually electromagnetic waveforms.

In everyday life, analog signals can be sounds that we hear; light that we can see.

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Processing analog signals:

It can be said that analog signals are almost the default signal for industry processing automation. Especially for 4-20mA or 0-10V signal. To be able to process analog signals, we will have the following methods.

Analog to digital converter:

For example, in the factory, there is a device that is a pressure sensor with an analog signal of 4-20mA to measure the pressure on the pipeline.

The problem is that when the pressure on the pipeline exceeds the allowable threshold, it will alarm with a light/horn or turn off the pump to reduce pressure.

Then, we will do the job is to convert the 4-20mA analog signal into an on/off alarm signal with a light/horn.

Analog to digital converter

There are many different ways to transfer. However, the simplest and easiest way is to use Seneca’s Z109REG2-1 analog output relay converter.

This converter has the effect of converting 4-20mA analog signal from the pressure sensor to a reliable signal for control.

Converter analog signal to relay Z109REG2-1

Digital to analog converter:

Digital signals in the factory can be signals from Encorder, flow meter. To measure the flow rate or to count the number of revolutions of the motor; We have to send this signal to the PLC to program the controller.

However, the problem is if the PLC can only read standard analog signals or cannot read high-frequency pulse signals.

Digital to analog converter

So then, what should we do?

First we need to determine what kind of digital signal we need to convert?

If the signal is a pulse, in this case, we just need to use Seneca’s Z111 pulse signal converter to convert the pulse signal to 4-20mA.

Z111 . pulse signal converter

Analog Amplifier:

Also known as analog rectifier. We already know that, when the 4-20mA signal is transmitted in the factory, it is certainly impossible to just round the number of 4mA or 20mA but it will have a little error. For example 3.96mA or 19.96mA.

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For example, we need to process analog signals in mitsubishi plc for example. If we take this signal correctly, programming will result in a not very nice signal.

Analog signal amplifier application

So we can use Seneca’s K109S signal amplifier to reflow it … a little more beautiful. When using this kit, the input signal will be tuned to make it more accurate.

K109S . analog signal amplifier

Analog noise suppressor:

The analog signal in the factory is very susceptible to interference when transmitted through high-power inverters or motors.

It can be noticed that the analog signal noise is when we send the signal to the PLC; signal will flicker or change value continuously; value cannot be read.

Finding the cause of the signal interference will take a lot of time and effort.

However, there is a much simpler way, which is to use the Seneca Z109REG2-1 anti-interference kit.

This kit is capable of isolating signals up to 3750 Vac at the power supply/input/output which will ensure the signal is safely protected.

Analogue Isolator Z109REG2-1

Analog splitter:

Splitting the analog signal is especially useful when we need two analog outputs. 1 signal is displayed locally and 1 signal is transmitted to the programmable PLC.

For example, we have a sensor that measures the water level in a 10m high tank, for example. We want to display the current number of meters of water in the tank using the water level indicator. At the same time, I want to give one more signal to the PLC for programming. For example, when the water exceeds 9m, the pump will be turned off to avoid overflow, and when the water drops to 1m, the water will open the pump.

Z170REG-1 . analog splitter

So at this point, we need 2 output analog signals from 1 input analog signal.

The Z170REG-1 splitter is designed precisely to do this for you.

When using this set; We will have 2 analog signals 4-20mA or 0-10V from 1 analog input signal.

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Z170REG-1 . analog splitter

Above are my shares about what analog information is, what digital information is; as well as analog signal processing. Hope the article can provide you with useful information.