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49.

Protective coating by a suitable cover are applied over strain gauge in order to protect it against:

A.	temperature rise	B.	dust and dirt
C.	moisture	D.	ageing

50.

The resistance of strain gauge grid used in pressure transducers is of the order of :

A.	0.1 to 1 ohm	B.	1 to 10 ohm
C.	10 to 100 ohm	D.	100 to 2000 ohm

51.

During temperature changing conditions, quite appreciable difference, occurs be tween the -true-temperature and the measured temperature because of the time required for the transfer of heat through thermometer pockets (thermowells) to thermometer sensing element. This time lag is of the order of :

A.	0.1 to 1 sec	B.	1 to 2.5 sec
C.	2.5 to 10 or 20 sec	D.	25 to 100 sec

52.

Pick up false statement:

A.	copper-constantan thermocouple is a stable couple resistant to both oxidis�ing and reducing atmosphere, but needs protection from acidic vapours	B.	Iron-constantan thermocouple suffers from oxidation attack on iron wire, if exposed
C.	iron-constantant couple can be made stable by using enamelled iron	D.	Both wires of chromel-alumel ther-mocouples are prone to damage by sulphurous gases

53.

Automatic cold junction compensation in thermocouple is provided by :

A.	connecting thermocouple wires, in op-position	B.	a nickel wire resistance in series with a manganin resistance
C.	maintaining cold junction temperature constant by a cooling unit	D.	using a photovoltaic cell

54.

The material used for resistance temperature sensor is :

A.	copper	B.	nickel
C.	platinum	D.	any one of above

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