Module 2.pdf
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This document discusses temperature measurement and different types of thermometers. It describes the dynamic characteristics of liquid-in-glass thermometers, including how they respond to step changes in temperature over time. The document presents equations to model the heat transfer and response of the thermometer based on factors like the thermal capacitance of the glass. It also briefly mentions other types of thermometers like mineral insulated thermocouples and different varieties of thermocouples for industrial temperature measurement applications.
Module 2.pdf
- 1. Temperature measurement Dr Sourav Poddar National Institute of Technology Warangal, TS, India
- 2. Industrial thermocouples Perfluoroalkoxy alkanes (PFA), Polytetrafluoroethylene (PTFE)
- 38. Dynamic characteristic of liquid-in-glass thermometer (thermal capacitance of glass wall is not included) The heat energy balance for mercury in the bulb: = period time system the of out heat of flow period time system the in heat of flow period time system a within heat of on accumulati _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Thermal capacitance of the glass walls is neglected. (1) (2) (3) (4) (5) (6) (7) (8)
- 39. (9)
- 40. (10)
- 42. (16)
- 43. Figure A - shows a dynamic response of this thermometer to a step change in temperature. Dynamic Response of a Liquid-in-Glass Thermometer to a Step Change in Temperature 0 2 4 6 8 10 0 50 100 150 200 250 300 350 400 Time, s Temperature (in deviation form), C
- 44. Figure A. Dynamic response of liquid-in-glass thermometer to a step change in temperature. From equation (12) we can get: Using a block diagram in Figure B we can get the following expression for a transfer function: Figure B. Block diagram of a thermometer. ) 1 ( 1 ) ( ) ( ) ( ' ) ( ' ) ( ' ' + = = = s s T s T s f s y s G fl m (17) (18) (19)
- 45. Dynamic characteristic of liquid-in-glass thermometer (thermal capacitance of glass wall is included) (1) (2) (3) (4) (5)
- 46. Figure C. Liquid-in-glass thermometer.
- 47. (6) (7) (8) (9)
- 49. Substitute (9) into (15) and after manipulations we get: (16) (17) Equation (17) is a second-order differential equation.
- 50. (18) (19)
- 52. (24) (25)
- 53. Let: A = 10oC and 龍 = 85,s . Then we can plot a transient response of this thermometer to a step change in the input variable (see Figure D). Figure D. Transient response of liquid-in-glass thermometer. Transient response of Liquid-in-Glass Therm om eter 0 2 4 6 8 10 0 100 200 300 400 500 600 T ime , s T e mpe rature (in de v iation form), C
- 114. THANK YOU