These are generally
provided on the engine as optional accessories. This seems to be only due to
economic reasons, because the installation of the temperature gauge on the
dashboard helps the driver to avert serious consequences, as he has before him
the temperature indication all the time.
Supposing the thermostat gets stuck up
and does not open, the water circulation will stop and the engine temperature
will go very high. However, if the temperature gauge is provided, the driver
can stop the engine at once and remedy the situation, before the engine is
overheated and some damage has already occurred.
Bourdon
tube type
This
has a bourdon tube inside, which is connected by a capillary tube to the element,
containing some volatile liquid at a suitable temperature and which is inserted
in the cooling water circuit at an appropriate point, generally on the engine
side of the thermostat.
As the temperature of cooling water increases, the
liquid in the element evaporates and exerts its pressure in the capillary,
which is further transmitted to the Bourdon tube. Due to this pressure, the
Bourdon tube tries to straighten out and thus moves a pointer attached to it,
to show higher temperature on the scale.
Electrically
operated tube
This
contains an element made of such a material that its electrical resistance
decreases with the increase in temperature. The element is connected to the coils
inside the dash unit while depicting the entire electrical circuit. The gauge element
is inserted into the cooling water at some appropriate place.
As the cooling
water temperature increases, the resistance of the element decreases, which causes
more current to flow in the coil, thus increasing the e.m.f. built up there.
The pull of the coil on the armature carrying indicator pointer, therefore,
increases and the pointer moves to show the higher temperature.
Tags
technology