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A cross correlation fluid flow meter including a body having first
and second sensor devices positioned such that in use they are spaced
apart a known distance in the direction of fluid flow, each sensor
device having a signal transmitter and a signal receiver. According
to one embodiment of the flow meter, the signal transmitter of the
first sensor device is operable to transmit signals at a first frequency
and the signal receiver of the first sensor device is arranged to
receive signals at the first frequency. The signal transmitter of
the second sensor device is operable to transmit a second signal
at a second frequency and the signal receiver of the second device
is operable to receive signals at the second frequency, the first
and second frequencies being different from one another. The first
sensor is non-responsive to the second frequency and the second
sensor is non-responsive to the first frequency. Cross correlation
of the received signals provides an indication of the fluid flow
rate.
A fluid flow monitoring system comprised of a permanent magnet
mounted on a bendable spring blade that provide an output from a
Hall effect transducer as the permanent magnet is deflected toward
or away from the transducer. The permanent magnet can be mounted
to directly approach the Hall effect transducer or can also be mounted
to approach the transducer by a sideways bypass direction. Both
the direct motion and sideways bypass direction allows the use of
a variety of sizes and shapes of magnets that allow the magnetic
field intensity to be modified in any way desired. Various magnet
shapes such as cylinders, rectangles, pyramids, triangles or compound
magnets from these shapes may be used. The output signal of the
transducer is processed through a smoothing filter and circuits
that produce a linear output or a stepped digital output. The system
preferably uses a resistance/capacitance filter to provide a different
time constant for an increasing flow or a decreasing flow. The output
can be used as a flow switching circuit or as a flow meter, or as
a flow quantity totalizer.
An apparatus, such as, a heat flow meter instrument, for measuring
thermal properties of a specimen includes a first thermoelectric
device and a second thermoelectric device, each device being thermally
coupled to a hot plate and a cold plate, and a heat flow transducer,
thermally connectable to a specimen and constructed to measure heat
flowing through the specimen. The heat flow transducer and the specimen
are positionable in thermal contact between the hot plate of the
first thermoelectric device and the cold plate of the second thermoelectric
device. The apparatus also includes an electric power supply connected
to provide controlled amounts of electric power to the first and
second thermoelectric devices to maintain the plates at selected
temperatures, and a processor connected to receive from the heat
flow transducer a signal corresponding to the measured heat. The
processor is programmed to calculate a thermal property of the specimen
based on the temperatures and the measured heat. The apparatus includes
a closed loop heat exchange system, thermally connecting the cold
plate of the first thermoelectric device and the hot plate of the
second thermoelectric device, constructed and arranged to transfer
heat between the plates. The closed loop heat exchange system may
include a fluid pump and a first set of conduits thermally connected
to the cold plate of the first thermoelectric device and a second
set of conduits thermally connected to the hot plate of the second
thermoelectric device. The conduits convey a heat exchange fluid
in a closed loop arrangement.
A photo detecting flow sensing bending beam fluid flow switch and
flow meter system having blocking targets that selectively block
the optical path from an emission source to a photodetector. The
device provides a system which is very sensitive to fluid flow in
a pipe, container or duct by providing a shaped flexible flow sensitive
bending beam having a blocking target which is bent so that the
portion of the blocking target is displaced between the emission
source and a photodetector. The shaped blocking target is configured
to either interrupt or permit the transmission of emission from
the emitter to the photodetector. The presence or absence of the
source represents the presence or absence of a fluid flow rate above
or below a selected value thus, performing a fluid flow switch function.
By modifying the blocking target to provide a reflective control
from an emission to a photo detector or an absorption of the emission
by a target varying in opacity, the relative light output is continuously
modulated to produce a voltage output directly proportional to the
rate of fluid flow past the target on a flow sensitive bending beam.
In an optional embodiment, flow sensitivity is improved by adding
vortex shedding enhancements to the flow sensitive bending beam.
This combination of functional elements can provide an analog fluid
flow meter transducer for flow metering, totalizing in a flow monitoring
system having single or multiple flow switching set points.
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