Bimetallic Strip thermometer Its needs, working and principle and applications

1. Bimetallic Strip Thermometer
Presented by : Sudhanshu Sharma
2015UME1089
M1

2. Contents:-
• Introduction
• Construction
• Working & Principle
• Types of Bimetallic Strip
• Applications
• Advantages & Disadvantages
• Radius of Curvature of BS

3. Temperature Measurement (Introduction)
• Temperature measurement in today’s industrial environment has a
wide variety of needs and applications.
• It is a very critical and widely measured variable for most industries.
• The industry has developed a large number of sensors and devices to
handle this demand.

4. Introduction(cont…)
• The industrial names given to such temperature sensors are
Temperature Indicators (TI) or Temperature Gauges (TG).
• In industries, there is always a need to measure and monitor
temperature of a particular spot, field or locality.
• Widely used sensor for this purpose is a Bimetallic Thermometer

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

6. Principle
Two basic principles of operation is to be followed in case of a
bimetallic sensor.
• A metal tends to undergo a volumetric dimensional change
(expansion/contraction), according to the change in temperature.
• Different metals have different co-efficient of thermal expansion. The
rate of volumetric change depends on this co-efficient.

7. Metals used in Bimetallic Strips:-
• HIGH EXPANSION
 Yellow Brass
 Nickle - Iron alloy with Chromium and Manganese.
• LOW EXPANSION
 Invar (Alloy of Nickle and Iron)
 Iron

8. Mechanical properties of commonly used thermal
materials:-

9. Types of BST
Cantilever type
Spiral type
Helix type

10. Applications

11. Advantages
1. They are simple, robust and inexpensive.
2. Their accuracy is between +or- 2% to 5% of the scale.
3. they are fully mechanical devices no need of power source.
4. These thermometers work best at higher temperatures.

12. Disadvantages
1. They are not recommended for temperature above 4000
C.
2. When regularly used, the bimetallic may permanently deform, which
in turn will introduce errors.
3. Their sensitivity and accuracy is less at low temperatures.

13. Radius of Curvature of BS

15. References
• mech.at.ua/HolmanICS.pdf
• www.mechnol.com/bi-metallic-mechanical-thermometer-and-
applications.html
• www.ooshutup.com/bimetallic-strip-thermometers-working-principle-
and-features.html
• www.electrical4u.com/bimetallic-strip-thermometer
• automationwiki.com/index.php?title=Bimetallic_Thermometers
• www.idconline.com/technical_references/pdfs/.../Bimetallic_Thermomete
r.pdf
• instrumentationandcontrollers.blogspot.com/2010/09/bimetallic-
thermometer.html

16. Thank You