7 Different Types Of Sensors To Measure Temperature

To go by the literal meaning, a temperature sensor is a device to sense the temperature of the environment it is placed in. It measures the degree of hotness and coldness of air, liquid or mass. Because of this functionality, a temperature sensor is an extremely useful device that is now being used everywhere. The range of its utility varies from simple household items such as thermometers, electronics like refrigerators, microwaves and water heaters to measuring temperature in huge and hazardous nuclear power plants, thermal power plants and in monitoring geotechnical activities.

The most basic fundamental behind the mechanism of every temperature sensor is the fact that they sense a change in the energy level of the matter which takes place due to the change in the physical characteristics of that matter.
Due to the versatility of their usage, wifi temperature sensors, are classified into 7 basic types.

Let us read further and learn more about these devices.

• Thermocouples: Thermocouples are devices that depend on changes in voltage to indicate temperature change. With the rising temperature, the output voltage of a thermocouple rises. The thermocouple is located inside a metal or ceramic container to protect it from the outer environment. The metal-covered thermocouples come in many types of outer coatings like Teflon. It is best to use in acids and strong caustic solutions.
• Resistive Temperature Measuring Devices: Resistive Temperature Diode a.k.a RTDs are another example of contact type temperature sensors. Unlike thermocouples, they use the resistance of the object to detect changes in temperature. Its work is based on the fact that when the temperature increases, the resistance offered by the matter is also high. They are more linear.

Thermistors are also resistive temperature measuring devices but work a little differently. They are highly nonlinear and semiconductor devices whose resistance decreases with rising temperature. RTDs are wifi temperature sensors.

• Infrared Sensors: These are non-contact temperature sensors. They sense the heat being emitted by the source object. For example, if a typical infrared temperature sensor is held in front of a mobile phone, the sensor would detect the heat radiations emanating from it and would give a temperature reading.
• Bimetallic Devices: Metals exhibit the property of expanding upon receiving external heat. Bimetallic sensors are based on the same principle. Two metals are joined together and are connected mechanically to the pointer. Upon being heated, one side of the metal strip expands more than the other and shows the temperature measurement at the pointer.

The merits of the bimetallic device are that they are portable and do not need any power supply just like wireless temperature sensors. However, they come with one disadvantage which weighs more than its merits. Bimetallic devices are not capable of giving accurate readings of temperature like electrical devices and also it’s not easy to record the temperature readings.

• Thermometers: These are the most basic type of temperature measurement devices. Their working principle is based on the expansion properties of the liquid. They are of two types. One is a mercury thermometer where the liquid that expands is mercury. One disadvantage of mercury type thermometers is mercury itself as it is hazardous to the environment.

Another type is the organic type which is safer to the environment and can be transported easily unlike mercury. There are alcohol thermometers that are specifically used in extremely colder regions. These thermometers are filled with ethanol. This is so because the freezing point of alcohol is -118 degrees Celcius and that of mercury is -38 degrees.

• Change-of-State Sensors: Unlike wifi temperature sensors, these sensors sense the change in the state of the matter under observation due to any fluctuation in temperature. This can be understood by a simple example of change from ice to water and from water to steam. Labels, pellets, crayons and lacquer are some types of change of state sensors available in the market.

Let’s understand this with the help of Labels, one of the above-mentioned sensors. Labels are used in steam traps. When these steam traps need adjustments, they become hot. The white dot on the label turns black thus indicating a rise in temperature. The dot remains black even when the temperature is down to normal.

Change-of-State Sensors have some limitations too. Their response time is very slow. Also, if there are sudden and quick temperature fluctuations, then they will not be able to provide precise readings.

• Silicone Diode: Silicone diode sensors are specially designed devices to measure temperature ranges below the freezing point of water. It is also called the cryogenic temperature range.

Final Note

The selection of temperature sensors depends on the field in which they will be used. For example, environments that are dangerous like nuclear and thermal power plants use non-contact or wireless temperature sensors. And industries like geotechnical monitoring use contact temperature sensors.