What temperature sensors exist with practical use cases

Have you ever wondered what temperature sensors exist? There are probably more temperature types of sensors that you may have heard of. We know passive, active, and other special types of sensors, such as Modbus sensors. What is the difference? Which sensor do I need? We will guide you through the basics of temperature sensors. With real practical use cases of indoor and outdoor implementation, we believe that we will be giving you enough information and ideas to choose the correct sensor by yourself.

Let’s see what we will cover in this blog post. We want you to understand the differences between the temperature sensor categories as well as using the right sensor type for indoor or outdoor implementation.

1. Temperature sensors categories
2. Practical indoor and outdoor use cases

1. Temperature sensors categories

As we already mentioned before we have to place temperature sensors into three main categories which are passive sensors, active sensors, and special sensors. We will start with the most basic sensors to help you understand the difference.

Passive sensors

Passive temperature sensors are the most popular. They are the first choice in almost any building management system. Usually, they are very cheap and are easy to install thanks to their polarity independence. They do not transmit the power or signals, control electricity directly, and also, they do not require external power supplies to measure the temperatures.

Selecting the proper temperature thermocouple depends on its application. The sensor can be used for measuring the temperature in liquids, gases, surfaces of solids, and molten masses. Therefore, the temperature range, accuracy, response time, and chemical properties define the decision of using the correct sensor element, calling thermocouple.

The most common and widely used thermocouples due to their high stability and repeatability are Platinum (Pt1000 / Pt100) and Nickel. Both of them have a positive temperature coefficient. This means that the resistance increases with increasing temperature.

Differences between the most common thermocouples:

Active sensors

Industrial and construction engineering often requires active temperature sensors, mainly due to long cable connections. Active sensors differ from conventional temperature sensors in that they convert the measured temperature into a digital signal and thus communicate with the control system.

Those sensors usually have implemented the most common thermocouple Pt1000 as their source to measure the temperature which is then converted into a standardized output signal 0-10V (voltage output) or 4-20mA (current output). The main difference between the voltage output signal and the current output signal is that the current output signal (4-20mA) can be used on much longer distances. If the distance is longer than 20m, we suggest you install the 4-20mA version of the sensor.

The main advantages of active sensors are that they provide a lot of easy customization, including selecting different measurement ranges. Their accuracy is often very precise. The industry-standard sensors have accuracy +/- 2K + max. of the final value. It is also possible to manually set the “offset” of sensors to +/- 1K using a potentiometer.

Other temperature sensors

What are the benefits of using the special temperature sensor if it is possible to solve every case with a passive or active sensor? Most of the time, special building management systems that run by one or more different protocols also support sending the measuring temperature data over their protocols. In those cases, the special temperature sensors are more than welcomed as they are easy to use, install, and implement into the existing ecosystem.

Nowadays, we know a lot of standard industry protocols, such as Modbus, KNX, BACnet, Wi-Fi, etc. While we could implement the passive or active sensors in the system, it is still better to use the proper sensors, because they can be connected directly to the input-output unit or controller itself. That means that the temperature readings will be projected to the system instantly and therefore be used to control the building automation.

We work with Modbus protocol mostly and therefore our technicians developed the Modbus sensors which can be connected to our controller U-DDC or any other 3^rd party Modbus systems as well.

2. Practical indoor and outdoor use cases

The practical use cases for measuring the temperature can be found everywhere we look around. We will give you some basic ideas on how to implement the temperature measurement into the room or outdoor. The sensors can be very widely used. They can be installed on the surface as well as into machines, devices, etc.

Most of the time the indoor temperature sensor ANDRTF3 or thermostat TRB is the perfect solution to measure the temperature of the room. If you need more hidden implementation, we suggest looking at cable temperature sensor ANDKBTF which also supports adjusting the cable length according to the needs.

Thermostats TRB and TRC are usually the most popular choices because the people can control the heating and cooling, but on the other hand, the thermostats can also have connected external temperature sensors which allow configuring the thermostats to perfection.

Most of the time the indoor temperature sensor ANDRTF3 or thermostat TRB is the perfect solution to measure the temperature of the room. If you need more hidden implementation, we suggest looking at cable temperature sensor ANDKBTF which also supports adjusting the cable length according to the needs.

The temperature outside can be easily measured also with weather stations ANDWST or Stevenson screen ANDWHT. The main advantage over the temperature sensor is to measure also the wind speed, rain, light, etc. With such various measured data, the system can control the whole building by knowing the exact weather conditions (blinds, lights, A/C units, etc.).

Usually, production plants have to be monitored very precisely. Therefore, we suggest using the combined sensor of humidity and temperature ANDARFT or ANDRFFT to not only measure the temperature, but also the humidity. Those sensors are available also in the Modbus version which is mostly the first choice.