Pressure Thermometer Working principle,types, application, advantage & Limitations

1. Mechanical Measurement and Control System
PRESSURE THERMOMETER
Name –Deepak Kumar
ID-2015UME1075
Batch-M1

2. Objectives:
 Introduction
 Working Principle
 Construction &working
 Applications
 Advantages
 Limitations
 References

3. Introduction:
 A device used to measure temperature by measuring
pressure exerted by a given volume of gas or liquid.
 It is one of the most economical ,versatile and widely
used devices in industrial temperature measurement.

4. Working Principle:
 These thermometers work on the principle of thermal
expansion of the fluid with the change in temperature is to
be measured. Temperature change can be determined
using these thermometers, which rely on pressure
measurement

5. Construction:
A pressure thermometer comprises of
1. Bulb
2. Flexible capillary tube
3. Bourdon tube
4. Linkage and gearing mechanism
5. Pointer and scale arrangement

7. Bourdon Tube

8. Video:
How pressure gauge works!!

9. Classification:
Depending upon the type of Fluid Filled in the Bulb
1.Liquid pressure thermometer
2.Constant volume Gas thermometer
3.Liquid –Vapour thermometer

10. Liquid Pressure Thermometer:
Usually Mercury is used as liquid
Principle of working:
expansion of liquid due to an increase in the
pressure in a given volume
Range :-30°C to 550°C

11. Constant Volume Gas Thermometer:
 Inert Gas(usually Nitrogen )is used in place of
Mercury.
 Principle of working:
According to ideal gas law
PV = mRT
For constant volume
P α T
 Temperature Range: -130°C to +540°C.

12. Vapor Pressure Thermometer:
 Liquid and vapour of the same liquid(liquid –vapour
interface in the bulb)
 The liquid-vapour system does not have any error as it
follows Dalton’s laws of partial pressure which states that if
both liquid and vapour are present there is only one
saturation pressure corresponding to a given temperature.
 Range: - up to 100°C.

13. Applications:
 Industrial equipments, piping
 Boilers, compressors
 Automobile dash board
 Muscle microcalorimetry

14. Advantages:
 Fundamental Simplicity
 Direct reading or recording
 Less expensive
 Stable in Operation and have a Good Accuracy(+1 or-1 °C)
 More Sensitive &Responsive(Deliver a high-speed
response)
 Distance measurement
 Easy Maintenance

15. Limitations:
 Limited linearity and prone to errors.
 The bulb size may be too large to fit the available space.
 The maximum temperature is more limited than that in
some electrical measuring systems.
 Proper Calibration of bulb,Capillary tube and Bouden tube
is needed.
If bulb is raised by a hight h from the calibration elevation
,then the Bourden gauge experiences an increse in pressure
equal to
Error=(density).g.h

16. References:
 https://www.youtube.com/watch?v=BIef-w0MkY0&t=8s
 https://www.youtube.com/watch?v=f9MJAXhLSv0&t=174s
 http://youtube.com/watch?v=yALTyExeS8M
 https://www.ncbi.nlm.nih.gov/pubmed/22254362
 http://www.instrumentationtoday.com/filled-system-
temperature-measurement/2011/
 ENGINEEING METROLOGY & MEASUREMENT BY
RAGHAVENDRA &KRISHNAMURTHY
 INSTRUMENTATION MEASUREMENT &ANALYSIS BY
NAKRA &CHAUDHRY
 9