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In a thermal type air flow meter, a temperature-dependent resistor
for sensing the flow rate of air is placed in the flow of air to
be measured, and another resistor for detecting a current flowing
through the above resistor is connected in series therewith. The
current is controlled so that the temperature-dependent resistor
is kept at a predetermined temperature which is higher than surrounding
temperature by, for example, 150.degree. C. The resistance of the
temperature-dependent resistor varies in accordance with the flow
rate of air. However, since the current is controlled so that the
temperature-dependent resistor is maintained at the predetermined
temperature, the current varies with the flow rate of air. Accordingly,
the speed of air can be obtained by measuring the current. In such
an air flow meter, when a key switch of an engine is turned on to
put a power supply to work, a short circuit is formed between both
ends of the current detecting resistor to cause a large current
to flow through the temperature-dependent resistor. Accordingly,
the flow rate of air can be measured immediately after the power
supply has been turned on.
This disclosure relates to a flow meter having an improved flow
restrictor for creating laminar flow in the flow meter. The improved
flow restrictor is an adjustable bypass or flow restrictor which
comprises a stack of alternate slotted discs and non-slotted, smaller
diameter, washers with a diameter of 80% of the slotted discs, to
form a plurality of micro-channels 0.09 mm square and 3 mm long
which is a length to area ratio sufficient to assure laminar fluid
flow through the flow meter.
A mass air flow meter for an internal combustion engine is described
in which the mass air flow into the engine is determined by the
measured throttle angular position, the sensed pressure above the
throttle and a stored schedule of values dependent upon the ratio
of the pressure below the throttle to the pressure above the throttle.
A fluid flow meter having a paddle wheel rotatably mounted in a
cylindrical cavity and an inlet conduit and an outlet conduit tangentially
aligned with the periphery of the cavity for directing a fluid to
flow through it. The paddle wheel's axis of rotation is displaced
from the cavity's centerline, in the direction of the inlet conduit
and substantially perpendicular to the flow of fluid entering the
cavity, such that the flow meter operates effectively over an extended
range of Reynolds numbers, spanning both turbulent and laminar flows.
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