What Is Bimetallic thermometer

What Is Bimetallic thermometer

1. Bimetallic thermometer

2. INTROduction Temperature measurement in today’s industrial environment has a variety of needs and applications Industries has developed a number of sensors and devices to handle The industrial names given to such temperature sensor are TI and TG Widely used sensor is Bimetallic thermometer

3. Principle A metal tends to undergo a volumetric dimensional change , according to the change in temperature Different metals have different co-efficient of thermal expansion . The rate of volumetric change depends on th e co-efficient

4. Construction The temperature is measured by means of a bimetal system inside the temperature sensor Bimetal is made of two metal strips , each metal having a different thermal expansion coefficient The Strips are permanently joined together by means of welding or riveting

5. Bimetallic Spiral thermometer Strip Bimetallic Thermometer Here the bimetallic strip used is in spiral shaped. When temperature rises,due to bimetallic property, the spring twists more. Due to this mechanical deformation of the spring, a pointer attached to the dial moves and indicates the temperature, as the dial of this bimetallic strip thermometer is calibrated in temperature scale

6. Bimetallic coil (Helix) There are many versions of the bimetallic thermometer. Another type, which is quite common, consists of a bimetallic coil (helix) encased in a tube with an indicator and scale at the top In this type the twisting action of the coil  causes the  long shaft to rotate the pointer. The thermal element at the bottom of the shaft is the only  portion of the thermometer sensitive to temperature changes.

7. Advantages They are simple, robust and inexpensive. Their accuracy is between +or- 2% to 5% of the scale. They are fully mechanical devices no need of power source.

8. Disadvantages They are not recommended for temperature above 400°C. When regularly used, the bimetallic may permanently deform, which in turn will introduce errors. Their sensitivity and accuracy is less at low temperatures .

9. Pressure thermometer

10. introduction A vapour   pressure thermometer  is a  thermometer  that uses a pressure  gauge to measure the vapour   pressure  of a liquid.

11. Principle T he vapor pressure of a liquid is the pressure under which a liquid is in equilibrium with its vapor phase. the vapor pressure is a function of the temperature of the liquid in question. At a temperature corresponding pressure. At the temperature increase is an increase in the transition from liquid to gas, a state of equilibrium is created between liquid and vapor, as well as the pressure has increased. These thermometers are very sensitive but the scale is not linear.

12. Applications Industrial equipment, piping, boilers, pipeline, heating, cooling, ventilation ... these thermometers are often mounted on pipes online. 

13. Liquid pressure thermometer

14. Temperature measurement scales

15. The Fahrenheit Scale The  Fahrenheit  temperature scale is based on 32 °F for the freezing point of water and 212 °F for the boiling point of water, with the interval between the two being divided into 180 parts.

16. The Celsius Scale T he Celsius temperature scale is based on 0 °C for the freezing point and 100 °C for the boiling point of water, with the interval between the two being divided into 100 parts.

17. CONVERSION for converting a Celsius temperature to Fahrenheit is: F=95C+32. To convert Fahrenheit to Celsius, use the formula C=59(F–32).

18. KELVIN SCALE The  kelvin  is  defined  as the fraction  1 ⁄ 273.16  of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F). In other words, it is  defined  such that the triple point of water is exactly 273.16 K K=C+ 273