Temperature sensors are the main elements in many control systems. Thermal resistance PT100 is one of the types of devices that can be used. There are also devices Pt-500, Pt-100, 10K. Specifically, this type is made on the basis of platinum, but you can find both copper and nickel. In our article, we will consider the features of temperature measuring sensors.
Key Features
Pt100 platinum thermal resistance is a fairly common element, since it has a very good quality-price ratio. It can be used as a separate instrument for measuring. But it is possible to integrate into the sleeve of another device in order to record temperature change data. The main thing in this case is to correctly take into account the diameter of the sleeve so that there is no big difference in diameters. In this case, it will be possible to provide the best condition in order to analyze the temperature of the media.
Typically, such sensors are used to control the temperature in ventilation systems, thermal power plants, as well as other industries.
Principle of operation
It is based on elements of platinum, in which the resistance at 0 degrees is 100 Ohms. It is worth noting that platinum has a positive coefficient. And this means that the resistance increases with increasing temperature. For some devices in one case, three thermocouples can be enclosed at once. But most often in industry they use the thermal resistance Pt100 "Aries" with one element. Aries is a domestic company engaged in the production and sale of equipment for automation and data measurement.
Depending on the type of measuring circuit, a specific connection method is used - two-, three-, and four-wire. From where and for what the device is used, you can choose the most acceptable characteristic. Thermal Resistance Pt-100 can be used to measure the temperature of gases or liquids. However, it can also be used to control the temperature of products in the food industry.
These devices may be compatible with devices that have the same input impedance. The maximum temperature that the sensor allows to measure is about 350 degrees. But at the peak it can withstand jumps up to 400 degrees. But these are average values, they depend on the manufacturer. For some sensors, the working range is -40 .. + 90, for others it’s already -50 .. + 250. But there are models that work in the range of -100 .. + 600.
When can’t installation be done?
Installation of devices in such conditions is not allowed:
- If the vibration level is too high.
- High probability of damage to the case.
- Aggressive chemical environment.
- Explosive atmospheres.
- In close proximity to electrical noise sources.
Instrument Specifications
Technical features of the sensor (thermal relay is taken as an example):
- The case is made of stainless steel.
- Mass - 600 gr.
- Dimensions 62x66x67 cm. The size of the sensor itself is not taken into account.
- It can measure temperatures in the range of -50 .. + 100 degrees.
- The maximum value of the error is 2%.
- The maximum power consumption is 2 watts.
- Humidity of the environment in which the work takes place is 80% at a temperature of 35 degrees.
- Pressure - 0.01..1.6 MPa.
When carrying out installation work, it is extremely important to comply with safety requirements. At enterprises, the installation of these devices is carried out by persons who have undergone appropriate training. They must also be trained in the use of equipment. Installation, dismantling and inspection is possible only if the power is disconnected from the device.
Why do sensors break?
In total, there are three reasons for the failure of an element:
- Violated operating rules.
- Failure of one or more relay elements.
- Weak sensor hardware.
To avoid premature failure, it is necessary to carefully study the instructions before installation and maintenance.
How does the sensor work?
The principle of operation is not very complicated. As we said, the base is a platinum element, at which at 0 degrees the resistance is 100 Ohms. If we are talking about a sensor, for example, Pt1000, then it, accordingly, the resistance will already be 1000 Ohms (1 kOhm). Platinum devices have a positive coefficient, therefore, with increasing temperature, the resistance also increases.
In the figure you can see the connection of the thermal resistance Pt100. We mentioned that there are several connection options - with two, three, or four wires. Which one to choose is up to you. But it should be noted that the four-wire device will have the best accuracy. But if you do not need high accuracy, then it is wiser to use two-wire sensors.
There are also two accuracy classes - A and B. The latter is divided into two subclasses - B1 / 3DIN and B1 / 10DIN. They cannot be used independently over the entire temperature range.
To summarize
Very often, Pt-100 sensors are used in the power industry to maintain a given temperature in a measured medium. They are also often used for an automatic heating control system. This allows you to automate production and reduce system management costs.
Often, sensors are installed in underwater and underground pipelines. The product has a very high quality, which guarantees a long service life. If the installation is carried out correctly, of course. The thermal resistance characteristics of the Pt100 are quite good, which allows the device to be used in any areas.
The range of operating temperatures is large enough that allows you to use the device in almost any industry. Also, the sensor can monitor the state of the air. Therefore, it can be used in storage and industrial premises, which have certain requirements for the environment and climate. Disposal must be carried out in accordance with the regulations that apply to the recycling of electrical waste.