Is it better to use thermocouple or RTD, and what is the difference between RTD and thermocouple

I think that choosing a thermocouple is not only accurate but also easy to use, and as you said, measurement accuracy is the key to the success or failure of your experiment. Let's take a look at the difference between the two. Thermocouple thermocouple is one of the most commonly used temperature sensing components in the industry, and the working principle of thermocouple is based on the Seeback effect, that is, two conductors of different compositions are connected at both ends to form a loop, and if the temperature of the two connecting ends is different, a thermal current is generated in the loop.

The advantages are: High measurement accuracy. Since the thermocouple is in direct contact with the object to be measured, it is not affected by the intermediate medium.

Wide measuring range. Commonly used thermocouples can be measured from -50 +1600, and some special thermocouples can measure as low as -269 (e.g. gold-iron-nickel-chromium) and up to +2800 (e.g. tungsten-rhenium). It is simple to construct and easy to use.

Thermocouples are usually made up of two different wires, and are not limited by size and start, and have a protective sleeve on the outside, which is very convenient to use. 1 The basic principle of thermocouple temperature measurement is to weld two conductors of different materials or semiconductors A and B together to form a closed loop, as shown in Figure 2-1-1. When there is a temperature difference between the two attachment points 1 and 2 of conductors A and B, an electromotive force is generated between them, thus forming a large amount of current in the loop, a phenomenon called thermoelectric effect.

Thermocouples work with this effect. When using the thermocouple compensation wire, it is necessary to pay attention to the matching of the models, the polarity can not be wrong, and the temperature of the connection between the compensation wire and the thermocouple cannot exceed 100.

RTDDs are the most commonly used temperature detectors in the low and medium temperature regions. Its main features are high measurement accuracy and stable performance. Among them, the measurement accuracy of platinum thermal resistance is the highest, and it is not only widely used in industrial temperature measurement, but also made into a standard reference instrument.

1. The principle of RTD temperature measurement and the temperature measurement of material RTD are based on the fact that the resistance value of the metal conductor increases with the increase of temperature. Thermal resistance is mostly made of pure metal materials, platinum and copper are currently the most widely used, and materials such as nickel, manganese and rhodium are now used to make thermal resistance.

What are RTDs and thermocouples, and what is the difference between them?

As long as you choose the right one, whether it is a thermocouple or a RTD, you can measure the temperature very well, you can refer to the book Measuring Instruments and Automation, which has a good explanation. Personally, I still recommend using thermocouples, which are very accurate in the corresponding temperature range, and there is a lot of research in this area.

Different sensors are suitable for different application conditions, and there is no absolute good or bad, otherwise the bad ones will be completely eliminated.

For example, thermocouples.

It is suitable for higher temperatures, but it is less sensitive than RTD.

Therefore, thermocouples are not used in applications where the temperature is not so high.

Agree with this netizen.

RTD has its advantages - it is a resistance signal, which is a passive signal. The advantages of the low temperature zone are obvious, 1Linearity and relatively high accuracy; The downside is that it is expensive.

In the industry, I feel like half and half.

There are more PT100 in pharmaceutical production, and the SIP of the process control temperature will not exceed 200;

There are many thermocouples in the petrochemical industry, and the temperature of many reactors is relatively high.

The differences between RTDs and thermocouples are as follows:

1. The materials are different.

Thermal resistance is a metallic material, a metallic material with a temperature-sensitive change, and thermal coupling is a bimetallic material, i.e., two different metals that produce a potential difference at the ends of two different wires due to the change in temperature.

2. The signal is different.

The thermal resistance itself is a resistance, and the change of temperature makes the resistance produce a positive or negative resistance change; Thermal coupling, on the other hand, produces a change in the induced voltage, which changes with the change of temperature.

3. The measurement range is different.

The temperature range detected by the two sensors is different, the thermal resistance generally detects the temperature range of 0-150 degrees, and the thermocouple can detect the temperature range of 0-1000 degrees, so the former is a low temperature detection and the latter is a high temperature detection.

4. The temperature measurement characteristics are different.

Thermocouples are composed of two different conductors, A and B, and form a circuit, when the measured temperature changes, a thermal electromotive force will be generated in the circuit, forming a thermal current, which is the so-called thermoelectric effect.

Resistance measures temperature based on the fact that the resistance value changes with the change of temperature, that is, the change in temperature is expressed by the change of resistance value. That is to say, RTD is a pure metal, such as commonly used platinum, copper, nickel, etc., and commonly used RTD is PT100, PT1000, etc.

5. The wiring method is different.

Thermocouples are two-wire, while RTDs can be two-wire, three-wire, or four-wire.

Let me tell you the difference between thermocouple and RTD:1A thermocouple is a temperature sensor that measures temperature, and is a temperature sensor like a RTD.

2.The nature of the signal, the thermal resistance itself is the resistance, and the change of temperature makes the resistance produce a positive or negative resistance change; Thermal coupling, on the other hand, produces a change in the induced voltage, which changes with the change of temperature. 3.

The temperature range detected by the two sensors is different, the thermal resistance generally detects the temperature range of 0-150 degrees, and the thermal coupling can detect the temperature range of 0-1000 degrees, so the former is a low temperature detection and the latter is a high temperature detection. 4.Thermal resistance is a metal material, a metal material with a temperature-sensitive change, and a thermal coupling is a bimetallic material, which is two different metals, due to the change in temperature, a potential difference is generated at both ends of two different metal wires.

Extended Content:1How thermocouples work:

2.Thermocouples are one of the most commonly used temperature sensing components in the industry. The advantages of thermocouples are numerous, which are:

High accuracy in temperature measurement. 3.Because the thermocouple is in direct contact with the object to be measured, it is not affected by the intermediate medium.

Temperature sensing is fast and accurate. Wide range of measuring temperatures.

Thermocouple swim and RTD are both elements that measure temperature, RTD is the element where the resistance changes with temperature, and thermocouple is the element where the thermoelectric potential (voltage) changes with temperature. Generally, thermal resistance is used at low temperatures, and thermal heat is used at high temperatures.

1.The application temperature range is different.

RTDs are generally used below 300 degrees, and thermocouples are generally used above 300 degrees.

2.The material is different.

Thermal resistance is generally made of pure metal resistance wire, and thermocouples are generally made of two alloys of different materials.

3.The wiring (compensation) method is different.

Thermocouples require special two-wire compensation wires to draw out signals, and RTDs are generally three copper wires.

4.The signals are different.

Resistance is the resistance value corresponds to the measured temperature, and thermocouple is a millivolt signal corresponding to the measured temperature. （

Thermocouples and RTDs are both contact temperature measurements in temperature measurement, although their functions are the same to measure the temperature of an object, but their principles and characteristics are different.

Thermocouple is the most widely used temperature device in temperature measurement, its main characteristics are wide measurement range, stable performance, simple structure, good dynamic response, and can transmit 4-20mA electrical signal remotely, which is convenient for automatic control and centralized control. The thermocouple's temperature measurement principle is based on the thermoelectric effect. When two different conductors or semiconductors are connected into a closed loop, when the temperature at the two contacts is different, a thermoelectric potential is generated in the loop, a phenomenon known as the thermoelectric effect, also known as the Seebeck effect.

The thermoelectric potential generated in a closed loop consists of two potentials: the thermoelectric potential and the contact potential.

Although RTD is widely used in industry, its application is limited to a certain extent due to its temperature measurement range, and the temperature measurement principle of RTD is based on the characteristics that the resistance value of a conductor or semiconductor changes with the change of temperature. It also has many advantages, it can also transmit electrical signals remotely, with high sensitivity, strong stability, interchangeability and accuracy, but it needs power excitation and cannot measure temperature changes instantaneously.