BI_7B

Question 1

What is the principle operation of a liquid filled thermometer?

Answer 1

Thermal expansion of the liquid which rises against a graduated scale ref: p.109

Question 2

What is the operating principle of the bimetal-type thermometer?

Answer 2

Two strips of metal with widely different thermal expansion coefficients are bonded together - a room temperature change will cause the element to curve into an arc. Ref: p. 112

Question 3

Give four advantages of filled-system thermometers:

Answer 3

‘1. simple and inexpensive to manufacture 2. trouble free and accurate 3. good for remote reading or recording 4. sufficient force to act as a controller ref: p 110

Question 4

A source of error in a filled system is:
a. changes in ambient temperature
b. change in barometric pressure c. bulb elevation d. all of the above

Answer 4

‘d. all of the above ref: p.111

Question 5

Why is compensation usually necessary in a filled system?

Answer 5

Because difference in ambient temperature around the capillary tube and Bourdon case would otherwise cause inaccuracies. Ref: p.110-111

Question 6

What is a thermistor?

Answer 6

Thermo resistive oxides such as copper, iron, magnesium, nickel and tin that have a temperature-resistive characteristic for measuring temperatures. Ref: p.114

Question 7

What is the difference between an optical pyrometer and a radiation pyrometer?

Answer 7

‘-The optical determines temperature from intensity of a particular color emitted (red) -The radiation type measures a portion of the energy emitted. Ref: p.115-116

Question 8

On a temperature relief valve, what is the chief advantage of a sensitive bulb element with expansion bellows over a fusible plug type?

Answer 8

-The bulb and bellows type will reclose upon return to safe temperature -the fusible plug will remain open until replaced once it has operated. Ref: p.122