How to choose the temperature sensor?

In order to choose the temperature sensor that is most suitable for your needs, you should ask yourself the following questions:

Should I choose contact sensors or infrared sensors? The contact sensor can have different forms, a sensor suitable for measuring the surface temperature, or a sensor used to measure the internal temperature of the material. In any case, the quality of contact between the sensor and the object to be tested is very important.
Infrared sensors can only measure the temperature they target. Even if they do not need contact, you must pay attention to the atmosphere between the sensor and its goals, which will affect the measurement.

What technology should you use for contact sensors? There are several different options: thermocouple, resistance sensor, etc. It cannot be said that one technology is better than the other technology. Each technology has its advantages and disadvantages:

If you want to measure temperature changes, the response time of the sensor may also be important because the response time of the thermocouple is faster than the RTD.

When selecting the sensor itself, the temperature range you need to measure is obviously important, as well as its technology. The thermocouple and RTD are classified according to the material of its sensitive elements and have different measurement range.

Why choose the thermocouple temperature sensor?

The Armocouple sensor is based on the Syberg effect. It is welded together by two different metal wires at one end, called thermal welding. The voltage is measured by connecting the two remaining ends called the two remaining ends called reference welds, when the temperature of the thermal weld is different from the temperature of the reference weld.

There are several types of thermocouples corresponding to different metal pairs. Each metal pair has different measurement range:

 
The use of a type of thermocouple depends to a large extent on the temperature range it must work, and also depends on the type of the environment:

● E: Recommended environment for continuous oxidation or inertia.
● J: Suitable for vacuum, reducing or inert atmosphere.
● K: Recommended environment for continuous oxidation or neutral.
● N: The application of life problems that can be used for K -type components.
● T: It can be used for oxidation, restoration or inert atmosphere and vacuum. It is not corroded in a humid environment.
● R & S: Recommended for high temperature. Non -metallic protection tube and ceramic insulation must be protected. The R type is used in industry, and the S type is used in the laboratory.
● B: Same as R & S, but can measure higher temperatures.

Benefit:
● Tolerance and stability at high temperature
● There are many choices in diameter and size
● During the heat weld measurement
● Very short response time
● Affordable

Shortcoming:
● The accuracy is lower than other technologies
● Require expensive wiring, cold end compensation
● Weak electric signal

Features:
● Large temperature range
● Short response time
● K -type hot electric puppet
● T -type hot electric puppet

Why choose a resistor temperature sensor?

A resistor temperature sensor is usually called thermal resistance, which is a kind of contact sensor. It uses the resistance of metal (platinum, copper, nickel, or tungsten) with changes in temperature. This type of sensor uses a variety of metals to provide different measurement range:

● Platinum: -200 ° C to 600 ° C
● Copper: -190 ° C to 150 ° C
● Nickel: -60 ° C to 180 ° C
● tungsten: -100 ° C to 1,400 ° C
The most common metal of the resistor temperature sensor is platinum because it provides an interesting measurement range. This is called platinum resistor temperature sensor. The most famous is PT100 (100 ohm at 0 ° C) and PT1000 (the resistance is 1,000 ohm at 0 ° C). Compared with the PT100, the PT1000 has higher accuracy and greater container to long wire length.

Compared with the thermocouple, the resistance sensor provides better accuracy and more linear response. They are more stable in measurement and have a wide temperature range. However, they have longer response time and lower sensitivity.

Features:
● Accurate
● High response time
● Weak sensitivity
● Large measurement range
● Platinum 100
● Platinum 1000

Why choose the thermistor temperature sensor?

The thermistor temperature sensor is another type of resistance sensor that changes with the changes in the temperature of the metal oxide with the temperature of the metal oxide. There are two types of thermistor sensors: NTC (negative temperature coefficient ) usually have regular negative resistance changes, while PTC (positive temperature coefficient ) is narrow Sudden positive resistance changes are displayed within the temperature range.

Thermistor resistance has fast response time and is low in price, but they are very fragile and the measurement range is much narrower than other sensors.

Features:

● High sensitivity
● Good accuracy
● Affordable
● Limited temperature range
● NTC
● Positive temperature coefficient

Why choose infrared temperature sensors?

The surface temperature of the surface of the infrared temperature sensor measured in the infrared range. The main advantage of this type of sensor is that it can work remotely without any physical contact with the target surface.

The response time of these sensors is very fast. Unlike contact sensors, they do not need to establish heat balance (the same temperature). Therefore, these sensors can measure mobile objects, such as objects on the production line, objects that are difficult to enter the interior of the furnace.

On the other hand, they can only measure the surface temperature of the target, and the measurement will be affected by the target surface conditions (dust, rust, etc.), the cleanliness (dust) and the environment of the sensor lens. The light path between sensors and targets (dust, humidity, burning gas, etc.).

Features:
● Non -contact formula
● Remote
● Surface measurement
● Very fast response time
● Mobile objects