Temperature sensors and their main differences
Temperature sensors are one of the most common and widely used sensors. They are implemented in private houses as well as industrial buildings, business offices, hospitals, underground garages. Furthermore, they are also a very important part of for example automotive industry or the computer industry. Every car or laptop has a temperature sensor built in to measure the precise temperature and prevent overheating. The same is with building management systems. Temperature sensors control the room temperature by automatically control the A/C units, HVAC systems, heat pumps, etc…
1. Passive temperature sensors
What is a passive temperature sensor? It is a device that detects a physical quantity and converts it into another physical quantity. Does a passive sensor need the power to work properly? No, a passive sensor is a sensor that does not need the power to work.
There is a wide range of passive temperature sensors. Generally speaking, those sensors change resistor value, when the temperature changes. The most common and the most simple form of sensors are NTC or PTC. This stands for Negative Temperature Coefficient or Positive Temperature Coefficient. These components have two connections (like a resistor). In the case of an NTC, the value of the resistor will decrease if the temperature rises. The PTC will do the opposite.
In addition to that, passive sensors also have various other types of thermocouples available. The most common or popular are for example Pt100, Pt1000, Ni1000, NTC, LM235Z, DS18B20, and others. Most industrial sensors work with the help of a potentiometer that enables off-set calibration, calibration of one of 24 temperature ranges, and setting measurement accuracy at +/- 0.3K.
Technical datasheet for a passive outdoor temperature sensor ANDAUTF:
2. Active temperature sensors
Active temperature sensors always require an external power source to work properly and to control current and/or voltage to accomplish a purpose. Active sensors might transmit energy or drive a signal.
Active sensors also have an option to choose between two different output signals. First is the voltage output signal which represents the 0-10V and the second is the current output signal that is measured between 4-20mA. The main difference between them is the maximum operating distance. The 0-10V output signal is great on shorter distances and 4-20mA is better to use for longer distances. Both output signals are standardized output signals that are used in almost every smart building automation.
Advantages of active sensors are usually that they provide a selection of different measuring ranges, our sensors for example have an option to choose from 24 different measurement ranges. In addition to that, the sensors are very accurate because their accuracy is +/- 2K + max. of the final value. It is also possible to manually set the “offset” of sensors to +/-1 K using a potentiometer which means that it can be calibrated precisely. Some active sensors can be supplied with a low-energy LCD.
Active sensors are also more common in building management systems because they are really easy to install with an appropriate controller. Technicians, therefore, have an opportunity to read, collect and analyze the sensor’s data. According to the sensor’s readings, the appropriate action can be applied. Automatically or manually.
Technical datasheet for a active outdoor temperature sensor ANDAUTF/MU:
3. Modbus sensors
Modbus temperature sensors are very popular among all building automation projects. Why? Because they can be connected with only 1 wire separated into the slave sensor devices that are all connected to a master controller. That means that electrical wiring is much simpler as well as cost-effective. Modbus protocol has been used in building automation since the early 1980s.
The additional benefits of Modbus sensors are also, that they are mostly calibrated and tested by the company’s experts before shipping to the customer’s address. Why? Because the Modbus sensor needs some configuration (such as addressing, rate, reading registers, etc…) and therefore it has to be ready to plug into the existing controller. The configuration is usually done with two DIP switches that are integrated on the sensor’s PCB.
What kind of Modbus sensors exists? Well, you can get almost every temperature sensor also compatible with Modbus protocol. The protocol is so simple, reliable and widely used around the globe that sensor manufacturers, including us, can offer various temperature sensors for almost any project.
To sum up, temperature sensors are the most important sensors in building automation, smart devices, laptops, cars, etc. They control the temperature which is directly related to energy savings and people’s costs. With the help of technology, we can build really smart devices that would work for us.
Technical datasheet for a Modbus outdoor temperature sensor ANDAUTF/MD:
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