Do you know what a sensor is? What it’s for, or how it works? In this article, besides giving answers to these questions, we will talk about 12 different types of sensors . As we shall see, these vary according to the type of variable they measure or detect.

In addition, we will explain their general characteristics, what they are used for, how they work, and we will mention some examples of them.

What is a sensor?

Before explaining the different types of sensors that exist, let’s see what a sensor is. It’s probably a concept that rings a bell in physics, or even in chemistry. But what exactly is it?

A sensor is a device or an object that has the capacity to capture different stimuli from the outside, and to transform them through a transducer into electrical energy (electric impulse) . That is, it transforms (or translates) information or energy coming from the outside into an electric impulse (usually a digital impulse). This external information can be of any type (physical, chemical…).

These impulses are then analysed, processed and transformed in order to generate a specific response. We can find different types of sensors, as we will see below.

Types of sensors

Thus, we find different types of sensors, depending on the type of variable they must measure or detect. In this article we explain which are the 12 types of sensors we can find, how they work and some examples of them .

1. Temperature sensor

The temperature sensor provides us with information on the temperature of the outside (i.e. the medium), by means of electrical impulses. These sensors allow the room temperature to be monitored.

Temperature sensors are actually resistors, whose value increases with temperature, or decreases with it. In the first case, we call it PTC thermistor, and in the second case, NTC thermistor.

In turn, temperature sensors can be of different types: contact, non-contact, mechanical and electrical. An example of a temperature sensor is a thermometer (the classic mercury one) (in this case, it is a mechanical sensor).
This type of sensor is especially used in the industrial sector; its objective is to control the temperature of different machines, among others.

2. Light sensors

Other types of sensors are light sensors; in this case, are electronic devices that respond to the change in light intensity .

In other words, they allow the presence of light to be determined. Thus, this type of sensor detects visible light (i.e. light perceived by the eye), and also responds according to its intensity.

An example of a light sensor is the photoelectric cell, a device that transforms light energy into electrical energy, through an effect called the “photoelectric effect”. This device allows the generation of photovoltaic solar energy.

3. Distance sensors

Distance sensors are devices that allow you to measure distances; furthermore, depending on the type, can also be used as presence or motion sensors .

An example of a distance sensor is the infrared, based on a system of emission and reception of radiation. We also find, as an example of a distance sensor, the ultrasonic sensor, which sends pulses making the waves bounce off the surface.

4. Proximity sensors

The following types of sensors, the proximity ones, consist of transducers that detect the presence of objects (obstacles, people…) without the need for a contact. In some cases they can also be configured to measure distance.

5. Position sensors

Position sensors allow us to determine which location a certain object has . As a characteristic of them, we find that they generally have a particular electronic system, so that they can determine the location with the maximum precision.

6. Colour sensors

The colour sensors convert light into frequency, in order to be able to detect the colours of certain objects from their reflected radiation ; what they do is compare these radiations with the stored reference values.

These types of sensors emit three types of light: red, green and blue, and do so on the objects they intend to analyze. Finally, these devices generate an output signal (a response).

7. Moisture sensors

These types of sensors measure the relative humidity as well as the temperature of the environment. Specifically, they work by emitting a conditioned signal, thanks to a series of integrated circuits that they have.

The humidity sensors pick up signals from the environment to detect these parameters (humidity and temperature) . In addition, the margin of error they have is usually very small.

On the other hand, as an example, this type of sensor can be applied to detect the level of liquid in a tank; they are also used in garden irrigation systems, with the aim of determining when plants need watering and when they do not.

8. Speed sensors

Also known as “speedometers”, speed sensors can detect the speed of an object (usually a vehicle) .

An example of this is radar, which detects if a vehicle was travelling at a speed higher than the permitted one.

9. Sound sensors

The following types of sensors are sound sensors; they are in charge of capturing the sounds from the outside (environment) , through a microphone or a sonar system.

The sound waves received by these sensors propagate through the surrounding air and are then detected by the sensors.

They are normally used to receive stimuli from the outside in the form of commands (from people), remotely.

10. Contact sensors

Contact sensors are intended to detect the end of the travel of mechanical components (or in other words, their limit position) . An example of this is: doors that open automatically, that when they are already fully open, the motor that operates them “knows” that it must stop.

11. Optical sensors

In this case, these types of sensors can detect the presence of an object (or a person) that interrupts a beam of light reaching the sensor.

An example of these (and the main ones) are the so-called “photoresistors” (also called LDR) . LDRs are used especially in robotics, with the goal of regulating the motion of robots and stopping their movement when they are about to collide with some other object.

12. Magnetic sensors

The magnetic sensors work by detecting the magnetic fields that are caused by electric currents or magnets .

An example of these types of sensors is the reed switch, which consists of two metal plates inserted into a capsule; these plates are in the presence of a magnetic field, and are attracted to each other (i.e. they close the circuit).

Bibliographic references:

  • Brindley, K. (1988). Sensors and Transducers. Heinemann Newnes.

  • Norton, H.N. (1989). Handbook of Transducers. Prentice-Hall.

  • Pallás, R. (2003). Signal sensors and conditioners, Ed. Marcombo.