The flow meter is free from an external fluid flow noise. The detector
has measuring pipe 1 inlet 2 and outlet 3 both axially lined up
with base axis X. Pipe 1 is a straight one with opposite upstream
and downstream closed ends, provided in each of which ends is echo
sounder 4a, 4b capable of both transmitting and receiving the ultrasound.
Inlet 2 is connected with a side of the upstream end via bent 2a.
Outlet 3 is connected with another side of the downstream end via
another bent 3a, which another side is radially opposite to the
former side part in pipe 1 so that pipe 1 is tilted at a certain
angle from base axis X which is axially lined up with axes of both
inlet 2 and outlet 3; and, a center of base axis X coincides with
a center of a flow path of a measured fluid inside pipe 1. (See
A Karman vortex flow meter has detection passages located along
a fluid flow in a duct. Flow outlets of the detection passages are
disposed on an end face of a vortex generation element and flow
inlets are disposed upstream from the flow outlets. Heating coils
for detecting flow velocity change of a fluid caused by a negative
pressure of a Karman vortex are mounted in the detection passages.
A flow meter is used that lessens dust accumulation on heating coils,
etc., and reliably detects Karman vortexes.
A pump housing is provided with a conduit extending through the
housing between a pump inlet and pump outlet. A pump device is disposed
within the housing and in communication with the conduit to pump
fluid therethrough. A fluid flow meter also is disposed within the
housing and in communication with the conduit to monitor fluid flow
rate through the conduit. The fluid flow meter generates signals
related to the fluid flow rate which are fed back to a control device
operable to control the flow rate through the pump device. The flow
meter may include a pair of meshed modified elliptical gears. The
modified elliptical gears are based on a true elliptical shape,
with bulged portions added between the major and minor axes of the
elliptical shape. The modified elliptical gears have involute teeth
that are relatively thick adjacent the minor axis and relatively
thin adjacent the major axis.
A thermally-sensitive type flow meter measures a flow rate with
a high accuracy by eliminating a noise generated in a source voltage.
The flow meter includes a sensor chip comprising a substrate carrying
sensing elements. First and second resistors are provided on first
and second bridges formed over a depression formed on the substrate.
The first bridge is positioned on an upstream side and the second
bridge is positioned on a downstream side. The first and second
resistors generate a heat by the same voltage source. First and
second temperature measuring resistors are provided adjacent to
the first and second resistors, respectively, to measure a temperature
of the first and second resistors. Third and fourth temperature
measuring resistors are provided for measuring the temperature of
the fluid. A temperature control unit, including the first, second,
third and fourth temperature measuring resistors, controls a temperature
of each of the first and second resistors to be constant. A flow
rate of the fluid is determined based on a voltage difference between
a first voltage applied to the first resistor and a second voltage
applied to the second resistor.