What is Temperature Sensor? A temperature sensor is a device which is used for measuring the temperature of anything or any place. In temperature sensors, RTD (resistance temperature detector) elements are used for measuring a temperature which is made by wrapping a fine wire around a ceramic or glass. Normally, copper, nickel or platinum wire is for RTD elements. The thermocouple is also used in temperature sensors which are made from two different materials and generates a voltage when a temperature is changed. These voltages are directly proportional to temperature means when a temperature is increased then the voltage is also increased, similarly when a temperature is decreased then voltages is also decreased. Various types of temperature sensor are shown in figure 1
Figure 1 Various Types Temperature Sensor
Different Types of Temperature Sensor
Normally six types of temperature sensors are currently used in market,
Thermocouple: This is a most common type temperature sensor and is abbreviated by TC. This is very low-cost, self-powered and voltage generates temperature sensor means its voltages change are changed by changing temperature. It could be used for long distance and different type of thermocouple type sensor are available in the market for different distance. The thermocouple type temperature sensor is shown in figure 2.
Figure 2 Thermocouple Type Temperature Sensor
Resistance Temperature Detector (RTD): Resistance temperature detector sensor works on the principle of resistance change by changing temperature. Resistance is directly proportional to temperature and has a wide range of temperature measurements capabilities. These are more accurate temperature sensor and have ranged between -270 C0 to 850 C0
Figure 3 Resistance Temperature Detector (RTD)
Thermistors: This is the third type of temperature sensor which is less costly as compared to other types and is very easy to use. The working principle of a thermistor type temperature sensor is same as RTD type temperature sensor means resistance is changed by changing temperature. These are made with nickel or any ceramic type material. The thermistor type temperature sensor is shown in figure 3.
Figure 4 Thermistor Type Temperature Sensor
Thermometer: It is a device which is used to measure the temperature of any glass solids or liquids. In this type mercy or alcohol is used in a tube whose volume is changed by changing the temperature. Its volume is directly proportional to temperature. Thermometer type temperature sensor is shown is figure 5
Figure 5 Thermometer Type Temperature Sensor
IR Sensors: These are an electronic and non-contacting sensor which have a certain characteristic such that it can detector emits the IR radiations. Normally two types of IR sensors are currently used in a market first one is an infrared sensor and second one is a quantum infrared sensor. It detects the temperature by merit of radiations. the Its cost depends on its working capabilities means it accuracy level depends upon its cost in other works low cost has low accuracy level and high cost have high accuracy level. IR sensor is shown in figure 6
Figure 6 IR Type Temperature Sensor
ICs of Temperature Sensors
Semiconductor sensors are the sixth type of temperature sensor which are available in the market in the form of ICs and these are called temperature ICs sensors. These sensors are divided into different types such as current output sensors whose output current is changed by changing temperature, voltage output sensors whose output voltage is changed by changing temperature, silicon temperature sensors with resistance output whose output resistance is changed by changing temperature, digital output temperature sensors and diode temperature sensors etc. Currently, available temperature sensors provide high accuracy and high linearity over an operating temperature range almost 55 C0 to + 155 C0 Popular temperature sensor which is easily available in the market are AD 590, LM 35, TMP 102, LM 94023 and LMT 84. Semiconductor temperature sensor IC TMP 102 is shown in figure 7, which is digital temperature sensor have high accuracy in replacement of thermistor
Working Operation of LM 35 Temperature Sensor
The LM 35 temperature sensor is mounted as the same way as the other temperature sensors are mounted means in a PCB board or any other way and its temperature will be within the range of 0.01 C0 as compared to surface temperature. Let’s suppose, the ambient air temperature is same at surface temperature but when the air temperature is lower or higher the surface temperature than an actual temperature of LM 35 temperature sensor would die at an intermediate level between the air temperature and surface temperature. This temperature sensor has so many applications in the field of process control and environment and it is also in the test for communication and measurements purposes. It is directly calibrated in Celsius (Centigrade) and have a full operating range between -55 C0 to +150 C0. It has very low-cost due to water level trimming, very low self-heating, so much suitable for remote application and operates at 4 to 30 V. It has typical non-linearity level between +- 1/4 C0. The LM 35 temperature sensor is shown is figure 8
Figure 7 The LM 35 Temperature Sensor
Different Applications of Temperature Sensors
Temperature sensor are currently used in different applications here some of their applications are given below,
- These are used in electric motors for measuring the motor winding temperature, internal housing temperature, bearing temperature, brushes temperate and external body temperature.
- These are used in electric cables for measuring the cable internal temperature and in this application, these are used in the form of heat shrink tube or metal housing.
- These are used in mechanical engines for measuring the engine oil temperature and engine bearing temperature.
- These are used in the heating control systems such as in building where temperature controls for the switch on or off the heating or cooling system.
- These are used in HVAC (heating ventilation and air conditioning) system for controlling the temperature of shopping malls building, University building, hospital building and industrial and commercial buildings.
- These are frequently used in humidity and air control conditioning equipment.
- These sensors are frequently used in water incoming tubes for measuring the water internal temperature.
- These sensors have so many applications in renewable energy applications such as in solar heating pumps, biomass combustion applications, wind power applications, epithermal regulation applications, Geothermal drilling applications and in rail vehicles.
- These sensors are used in rubber and plastic industry.
- These sensors also have so many applications in biomedical industry.
Different Advantages of Temperature Sensors
- By using these sensors, the motor temperature could be controlled easily and motor could be on or off automatically and save the motor.
- By using these sensors, the electric cables could be saved from burning due to overheating.
- By using these sensors, the user could easily control the engine oil and bearing temperature.
- By using these sensors, the user can easily control the room temperature automatically by swathing on or off the cooling system.
- By using these sensors, the user can easily control the humidity and air conditioning of their buildings.
- By using these sensors, the user can easily check the water temperature and switch on or off the water heater and control the monthly bill.
- By using these sensors, the drilling operator could easily control the drilling temperature in geothermal applications