Temperature transducer is used to measure the temperature of the physical substances. Generally, transducer is nothing but converts the any kind of energy which means physical quantity into electrical energy. Here temperature transducer means, the transducer is used to converts thermal energy of the substances in to electrical energy. It is an electrical device used for automatic measuring of temperature. The ultimate aim of the temperature transducer is measuring the heat of the body in readable format.
The Main Function of Temperature Transducer:
- Thermal energy is always used as input of the transducer.
- Temperature transducer converts thermal energy into electrical energy
- It measures the temperature of the physical substances
Temperature transducer are consisting of sensing element, metal enclose, and external output terminal. In this, sensing element which is used as temperature transducer and it must have the properties of changing the characteristics with the variation of temperature. Mostly, 90 % of the industry we use resister temperature transducer in high pressure boiler, Also the cost is depending upon the temperature to be measure. Genrally, Sensing element have direct contact with the measurand. So that, It is enclosed by metal encloser that why sensing element are not visible for outside. However, they are categorized into two types…they are
- Contact sensor Device: Direct contact with the substances, and the heat transfer occurs to the sensing element in the form of conduction. These type of preferable for high temperature measurement, typically 50 to 2500 + deg. They are high cost. Example: PT100 used for measuring motor body temperature and thermocouple.
- Non-contact sensor device: It does not have direct contact with the substances. There is a metal enclose is used to protect the sensing element. They use convection phenomenon for the transfer of heat. The convection is the process in which the heat is transfer by the movement of the substance. They are Lesser cost.. Example: Panel Space Heaters. Some types of Non-contact sensor are…
Thermistor – The thermistor is a type of resistor whose resistance varies with the temperature. It works like potentiometer. A small amount of current passes through the thermistor and this current causes the voltage drop across the resistance. The voltage drop is measured by the digital measuring devices.
The resistance thermometer is categorized into two types.
- Negative Temperature Coefficient – Used for sensing the temperature.
- Position Temperature Coefficient – Used for controlling the current.
Resistance Thermometer – As you know, resistance thermometer are mostly used in hospital to check the body temperature of the patent. Here, the sensing element will be connected in front of the thermometer. The resistance of the sensor varies with the temperature. And this property of the metal is used for measuring the temperature. The resistance thermometer uses the platinum as the sensing element and hence measures the surrounding temperature.
Thermocouples – A Thermocouple is a sensor used to measure temperature. It converts the thermal energy into the electrical energy at the point of the contact. Thermocouples consist of two different material and their wire legs made are welded together at one end, creating a junction. This junction is where the temperature is measured. When the junction experiences a change in temperature, a voltage is created. The voltage is directly proportional to the changing in the temperature and The voltage can then be calculated/measured using thermocouple reference tables to calculate the temperature. Thermo couple measurement table.
Integrated Circuit Temperature Transducer – IC Temperature transducer used to sense the temperature on electronics device, mostly inside of the component’s. The best example is FS300 IGBT, NTC thermal transducer is placed inside of IGBT. All the temperature measurement will be taken from the IGBT terminal. The integrated temperature transducer has a linear characteristic. They are preferable for measuring low temperature typically 0-200deg, Due to their less operating range
Generall Function of sensing element in Temperature Transducer:
Changing in the temperature, which simultaneously changes the resistance of the sensing element. For given input voltage, the output voltage also varied according to the temperature of the substances. It just works like automatic potentiometer. It is called resistance temperature transducer (RTT). One of the best example is PT100.
Properties of Sensing element:
- Ability to catch small change in the temperature
- High resistivity
- Good thermal conductivity
The Metal encloser which surrounds the sensing element. It is mainly used to protect sensing element from direct contact with the high temperature body.