This document discusses different types of bimetallic thermometers used for temperature measurement in industrial environments. It describes how bimetallic thermometers work using two metals with different coefficients of thermal expansion joined together. When temperature changes, the differential expansion causes the bimetallic strip to twist, rotating a pointer to indicate the temperature reading on a calibrated scale. Common configurations include a spiral strip or coil design to translate thermal expansion into rotational movement. While simple and inexpensive, bimetallic thermometers have limitations such as accuracy below 400°C and potential for permanent deformation over time.

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 the 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

7. 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

8. 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 porti
on of the thermometer sensitive to temperature changes.

10. 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.

11. 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.

12. PRESSURE THERMOMETER

13. INTRODUCTION
• A vapour pressure thermometer is a thermometer that uses a
pressure gauge to measure the vapour pressure of a liquid.

14. PRINCIPLE
• The 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.

15. APPLICATIONS
• Industrial equipment,
• piping,
• boilers,
• pipeline,
• heating, cooling, ventilation ... these
thermometers are often mounted on pipes online.

16. LIQUID PRESSURE
THERMOMETER

18. TEMPERATURE
MEASUREMENT SCALES

19. 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.

20. The Celsius Scale
The 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.

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

22. 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