Abstrict Flow meter electronics are described for providing a flow rate
of a material flowing through a flow meter sensor of a Coriolis
flow meter. The flow meter electronics comprise a processing system
and a single output port. The processing system receives pick-off
signals from the flow meter sensor and processes the pick-off signals
to determine the flow rate. The processing system receives an instruction
for a frequency output signal or a digital communication protocol
signal. If the instruction is for a frequency output signal, then
the processing system processes the flow rate to generate a frequency
output signal and transmits the frequency output signal over the
single output port. If the instruction is for a digital communication
protocol signal, then the processing system processes the flow rate
to generate a digital communication protocol signal and transmits
the digital communication protocol signal over the single output
port.
Claims What is claimed is:
1. Flow meter electronics for providing a flow rate of a material
flowing through a flow meter sensor of a Coriolis flow meter, said
flow meter electronics comprising: a single output port; and a processing
system coupled to said single output port and configured to: receive
pick-off signals from said flow meter sensor, process said pick-off
signals to determine said flow rate of said material, receive an
instruction for a frequency output signal or a digital communication
protocol signal, if said instruction is for said frequency output
signal, then said processing system is configured to process said
flow rate to generate said frequency output signal having a frequency
proportional to said flow rate, and transmit said frequency output
signal over said single output port, and if said instruction is
for said digital communication protocol signal, then said processing
system is configured to process said flow rate to generate said
digital communication protocol signal that represents said flow
rate, and transmit said digital communication protocol signal over
said single output port.
2. The flow meter electronics of claim 1 wherein said processing
system is further configured to: determine a direction of flow of
said material; if said direction of flow is in a first direction,
then generate said frequency output signal to have a duty cycle
below 0.5; and if said direction of flow is in a second direction,
then generate said frequency output signal to have a duty cycle
above 0.5.
3. The flow meter electronics of claim 1 wherein said processing
system is further configured to: determine if a fault has occurred;
and generate said frequency output signal to have a predetermined
frequency responsive to determining said fault.
4. The flow meter electronics of claim 1 wherein said processing
system is further configured to: receive said instruction over said
single output port from a user after a power cycle, wherein said
single output port acts as an input/output port for a time period
after said power cycle.
5. The flow meter electronics of claim 1 wherein said flow rate
comprises a mass flow rate.
6. The flow meter electronics of claim 1 wherein said flow rate
comprises a volumetric flow rate.
7. The flow meter electronics of claim 1 wherein said flow rate
comprises a net volumetric flow rate.
8. A method of operating flow meter electronics for providing a
flow rate of a material flowing through a flow meter sensor of a
Coriolis flow meter, said method comprising the steps of: receiving
pick-off signals from said flow meter sensor; processing said pick-off
signals to determine said flow rate of said material; receiving
an instruction for a frequency output signal or a digital communication
protocol signal; if said instruction is for said frequency output
signal, then processing said flow rate to generate said frequency
output signal having a frequency proportional to said flow rate
and transmitting said frequency output signal over a single output
port; and if said instruction is for said digital communication
protocol signal, then processing said flow rate to generate said
digital communication protocol signal that represents said flow
rate and transmitting said digital communication protocol signal
over said single output port.
9. The method of claim 8 further comprising: determining a direction
of flow of said material; if said direction of flow is in a first
direction, then generating said frequency output signal to have
a duty cycle below 0.5; and if said direction of flow is in a second
direction, then generating said frequency output signal to have
a duty cycle above 0.5.
10. The method of claim 8 further comprising: determining if a
fault has occurred; and generating said frequency output signal
to have a predetermined frequency responsive to determining said
fault.
11. The method of claim 8 wherein receiving an instruction for
said frequency output signal or a digital communication protocol
signal comprises: receiving said instruction over said single output
port from a user after a power cycle, wherein said single output
port acts as an input/output port for a time period after said power
cycle.
12. The method of claim 8 wherein said flow rate comprises a mass
flow rate.
13. The method of claim 8 wherein said flow rate comprises a volumetric
flow rate.
14. The method of claim 8 wherein said flow rate comprises a net
volumetric flow rate.
15. A software product for providing a flow rate of a material
flowing through a flow meter sensor of a Coriolis flow meter, said
software product comprising: flow meter software configured when
executed by a processing system to direct the processing system
to receive pick-off signals from said flow meter sensor, process
said pick-off signals to determine said flow rate of said material,
receive an instruction for a frequency output signal or a digital
communication protocol signal, process said flow rate to generate
said frequency output signal having a frequency proportional to
said flow rate and transmit said frequency output signal over a
single output port if said instruction is for said frequency output
signal, and process said flow rate to generate said digital communication
protocol signal that represents said flow rate and transmit said
digital communication protocol signal over said single output port
if said instruction is for said digital communication protocol signal;
and a storage media configured to store said flow meter software.
16. The software product of claim 15 wherein said flow meter software
is further configured to direct said processing system to: determine
a direction of flow of said material; if said direction of flow
is in a first direction, then generate said frequency output signal
to have a duty cycle below 0.5; and if said direction of flow is
in a second direction, then generate said frequency output signal
to have a duty cycle above 0.5.
17. The software product of claim 15 wherein said flow meter software
is further configured to direct said processing system to: determine
if a fault has occurred; and generate said frequency output signal
to have a predetermined frequency responsive to determining said
fault.
18. The software product of claim 15 wherein said flow meter software
is further configured to direct said processing system to: receive
said instruction over said single output port from a user after
a power cycle, wherein said single output port acts as an input/output
port for a time period after said power cycle.
19. The software product of claim 15 wherein said flow rate comprises
a mass flow rate.
20. The software product of claim 15 wherein said flow rate comprises
a volumetric flow rate.
21. The software product of claim 15 wherein said flow rate comprises
a net volumetric flow rate.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to the field of flow meters, and in particular,
to flow meter electronics capable of outputting either a frequency
output signal or a digital communication protocol signal over a
single output port.
2. Statement of the Problem
Coriolis mass flow meters measure mass flow and other information
with respect to materials flowing through a pipeline as disclosed
in U.S. Pat. No. 4491025 issued to J. E. Smith, et al., of Jan.
1 1985 and U.S. Pat. No. Re. 31450 to J. E. Smith of Feb. 11
1982. These flow meters typically comprise a flow meter electronics
portion and a flow meter sensor portion. Flow meter sensors have
one or more flow tubes of a straight or curved configuration. Each
flow tube configuration has a set of natural vibration modes, which
may be of a simple bending, torsional, radial, or coupled type.
Each flow tube is driven to oscillate at resonance in one of these
natural vibration modes. The natural vibration modes of the vibrating,
material filled systems are defined in part by the combined mass
of the flow tubes and the material within the flow tubes. When there
is no material flowing through a Coriolis flow meter sensor, all
points along the flow tubes oscillate with a substantially identical
phase. As material flows through the flow tubes, Coriolis accelerations
cause points along the flow tubes to have a different phase. The
phase on the inlet side of the flow meter sensor lags the driver,
while the phase on the outlet side of the flow meter sensor leads
the driver.
Coriolis flow meter sensors typically include two pick-offs for
producing sinusoidal signals representative of the motion of the
flow tubes at different points along the flow tubes. A phase difference
of the sinusoidal signals received from the pick-offs is calculated
by the flow meter electronics. The phase difference between the
pick-off signals is proportional to the mass flow rate of the material
flowing through the flow meter sensor. An example of a Coriolis
flow meter is described below in FIG. 1.
The flow meter electronics receive the pick-off signals from the
pick-offs. The flow meter electronics process the pick-off signals
to compute a mass flow rate, a density, or another property of the
material passing through the flow meter sensor. The flow meter electronics
typically have multiple output ports or multiple communication channels
for outputting the mass flow rate, the density, or other information.
For instance, typical flow meter electronics have a milliamp output,
a discreet voltage output, a digital communications protocol output,
and a frequency output. Each output has its own physical port. The
flow meter electronics with multiple output ports provide a great
deal of versatility to users, which can be useful for certain applications.
Unfortunately, flow meter electronics with multiple output ports
can be expensive and may have more functionality than is needed
for simple applications.
To help solve this problem, less complex and cheaper flow meter
electronics have been developed. The less complex flow meter electronics
still receive the pick-off signals from the pick-offs, and process
the pick-off signals to compute a mass flow rate, a density, or
another property of the material passing through the flow meter
sensor. The less complex flow meter electronics differ by having
a single output port. The less complex flow meter electronics only
generate a digital communication protocol signal that represents
the mass flow rate, the density, or the other properties. Unfortunately,
some users have legacy systems that are configured to receive a
frequency or pulse signal and do not understand a digital communication
protocol signal.
Traditionally, the flow meter industry mainly involves mechanical
flow meters, such as positive displacement meters, oval gear, or
turbine flow meters. These mechanical flow meters generate a pulse
signal when the chamber, gear, or blade passes through a magnetic
field, or from a magnetic rotating component on a shaft. Legacy
systems receive the pulse signal and provide a read out of the flow
rate, adjust a valve based on the flow rate, or perform another
function. Newer electronic flow meters have also been configured
to generate a pulse signal proportional to a flow rate to interface
with these legacy systems. Unfortunately, no flow meter electronics
have been developed that will interface with legacy systems and
current flow systems, but are cost effective for less complex applications.
SUMMARY OF THE SOLUTION
The invention helps solve the above problems with flow meter electronics
that can be programmed to either output a frequency output signal
or a digital communication protocol signal over a single output
port. The invention advantageously provides flow meter electronics
that are cheaper and better suited for less complex applications.
The flow meter electronics are also capable of interfacing with
legacy systems with the frequency output signal or interfacing with
more modem systems with the digital communication protocol signal.
One embodiment of the invention includes flow meter electronics
for providing a flow rate of a material flowing through a flow meter
sensor of a Coriolis flow meter. The flow meter electronics comprise
a processing system and a single output port. The processing system
receives pick-off signals from the flow meter sensor and processes
the pick-off signals to determine the flow rate of the material.
The processing system receives an instruction for a frequency output
signal or a digital communication protocol signal. If the instruction
is for a frequency output signal, then the processing system processes
the flow rate to generate a frequency output signal having a frequency
proportional to the flow rate, and transmits the frequency output
signal over the single output port. If the instruction is for a
digital communication protocol signal, then the processing system
processes the flow rate to generate a digital communication protocol
signal that represents the flow rate, and transmits the digital
communication protocol signal over the single output port.
In another embodiment, the processing system determines a direction
of flow of the material. If the direction of flow is in a forward
direction, then the processing system generates the frequency output
signal to have a duty cycle below 0.5. If the direction of flow
is in a reverse direction, then the processing system generates
the frequency output signal to have a duty cycle above 0.5.
In another embodiment of the invention, the processing system determines
if a fault has occurred. The processing system generates the frequency
output signal having a predetermined frequency responsive to determining
the fault.
The invention also includes other embodiments described below.
The following depict aspects of the invention. One aspect is flow
meter electronics for providing a flow rate of a material flowing
through a flow meter sensor of a Coriolis flow meter, said flow
meter electronics comprising: a single output port; and a processing
system coupled to said single output port and configured to: receive
pick-off signals from said flow meter sensor, process said pick-off
signals to determine said flow rate of said material, receive an
instruction for a frequency output signal or a digital communication
protocol signal, if said instruction is for said frequency output
signal, then said processing system is further configured to process
said flow rate to generate said frequency output signal having a
frequency proportional to said flow rate, and transmit said frequency
output signal over said single output port, and if said instruction
is for said digital communication protocol signal, then said processing
system is further configured to process said flow rate to generate
said digital communication protocol signal that represents said
flow rate, and transmit said digital communication protocol signal
over said single output port.
Preferably, the processing system is further configured to: determine
a direction of flow of said material; if said direction of flow
is in a first direction, then generate said frequency output signal
to have a duty cycle below 0.5; and if said direction of flow is
in a second direction, then generate said frequency output signal
to have a duty cycle above 0.5.
Preferably, the processing system is further configured to: determine
if a fault has occurred; and generate said frequency output signal
having a predetermined frequency responsive to determining said
fault.
Preferably, the processing system is further configured to receive
said instruction over said single output port from a user.
Preferably, the flow rate comprises a mass flow rate.
Alternatively, the flow rate comprises a volumetric flow rate.
Alternatively, the flow rate comprises a net volumetric flow rate.
Another aspect is a method of operating flow meter electronics
for providing a flow rate of a material flowing through a flow meter
sensor of a Coriolis flow meter, said method comprising the steps
of: receiving pick-off signals from said flow meter sensor; processing
said pick-off signals to determine said flow rate of said material;
receiving an instruction for a frequency output signal or a digital
communication protocol signal; if said instruction is for a frequency
output signal, then processing said flow rate to generate said frequency
output signal having a frequency proportional to said flow rate
and transmitting said frequency output signal over a single output
port; and if said instruction is for said digital communication
protocol signal, then processing said flow rate to generate said
digital communication protocol signal that represents said flow
rate and transmitting said digital communication protocol signal
over said single output port.
Preferably, the method further comprises: determining a direction
of flow of said material; if said direction of flow is in a first
direction, then generating said frequency output signal to have
a duty cycle below 0.5; and if said direction of flow is in a second
direction, then generating said frequency output signal to have
a duty cycle above 0.5.
Preferably, the method further comprises: determining if a fault
has occurred; and generating said frequency output signal having
a predetermined frequency responsive to determining said fault.
Preferably, the method further comprises receiving said instruction
over said single output port from a user.
Preferably, the flow rate comprises a mass flow rate.
Alternatively, the flow rate comprises a volumetric flow rate.
Alternatively, the flow rate comprises a net volumetric flow rate.
Another aspect is a software product for providing a flow rate
of a material flowing through a flow meter sensor of a Coriolis
flow meter, said software product comprising: flow meter software
configured when executed by a processing system to direct the processing
system to receive pick-off signals from said flow meter sensor,
process said pick-off signals to determine said flow rate of said
material, receive an instruction for a frequency output signal or
a digital communication protocol signal, process said flow rate
to generate said frequency output signal having a frequency proportional
to said flow rate and transmit said frequency output signal over
a single output port if said instruction is for said frequency output
signal, and process said flow rate to generate said digital communication
protocol signal that represents said flow rate and transmit said
digital communication protocol signal over said single output port
if said instruction is for said digital communication protocol signal;
and a storage media configured to store said flow meter software.
Preferably, the flow meter software is further configured to direct
said processing system to: determine a direction of flow of said
material; if said direction of flow is in a first direction, then
generate said frequency output signal to have a duty cycle below
0.5; and if said direction of flow is in a second direction, then
generate said frequency output signal to have a duty cycle above
0.5.
Preferably, the flow meter software is further configured to direct
said processing system to: determine if a fault has occurred; and
generate said frequency output signal having a predetermined frequency
responsive to determining said fault.
Preferably, the flow meter software is further configured to direct
said processing system to receive said instruction over said single
output port from a user.
Preferably, the flow rate comprises a mass flow rate.
Alternatively, the flow rate comprises a volumetric flow rate.
Alternatively, the flow rate comprises a net volumetric flow rate.
DESCRIPTION OF THE DRAWINGS
The same reference number represents the same element on all drawings.
FIG. 1 illustrates a Coriolis flow meter in the prior art.
FIG. 2 illustrates flow meter electronics having multiple output
ports in the prior art.
FIG. 3 illustrates flow meter electronics for a Coriolis flow meter
in an example of the invention.
FIG. 4 illustrates an example of a Coriolis flow meter connected
to a user system in an example of the invention.
FIG. 5 illustrates frequency output signals in an example of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1-5 and the following description depict specific examples
of flow meter electronics to teach those skilled in the art how
to make and use the best mode of the invention. For the purpose
of teaching inventive principles, some conventional aspects of the
flow meter electronics have been simplified or omitted. Those skilled
in the art will appreciate variations from these examples that fall
within the scope of the invention. Those skilled in the art will
appreciate that the features described below can be combined in
various ways to form multiple variations of the invention. As a
result, the invention is not limited to the specific examples described
below, but only by the claims and their equivalents.
Prior Art Coriolis Flow Meter--FIGS. 1-2
FIG. 1 illustrates a Coriolis flow meter 5 in the prior art. Coriolis
flow meter 5 comprises a Coriolis flow meter sensor 10 and Coriolis
flow meter electronics 20. Flow meter electronics 20 is connected
to flow meter sensor 10 via path 100 to provide for mass flow rate,
density, volume flow rate, totalized mass flow information, and
other information over path 26. Path 26 represents multiple output
ports carrying information on multiple channels of communications
as is depicted in FIG. 2. A variety of commercially available Coriolis
flow meters providing these measurements may be purchased from Micro
Motion of Boulder, Colo.
Flow meter sensor 10 includes a pair of flanges 101 and 101', manifold
102 and flow tubes 103A and 103B. Connected to flow tubes 103A
and 103B are driver 104 and pick-off sensors 105 and 105', and temperature
sensor 107. Brace bars 106 and 106' serve to define the axis W and
W' about which each flow tube 103A and 103B oscillates.
When flow meter sensor 10 is inserted into a pipeline system (not
shown in FIG. 1) which carries a material that is being measured,
the material enters flow meter sensor 10 through flange 101 passes
through manifold 102 where the material is directed to enter flow
tubes 103A and 103B, flows through flow tubes 103A and 103B and
back into manifold 102 from where it exits flow meter sensor 10
through flange 101'.
Flow tubes 103A and 103B are selected and appropriately mounted
to the manifold 102 to have substantially the same mass distribution,
moments of inertia, and elastic modules about bending axes W-W and
W'-W', respectively. The flow tubes 103A-103B extend outwardly from
manifold 102 in an essentially parallel fashion.
Flow tubes 103A-103B are driven by driver 104 in opposite directions
about their respective bending axes W and W' at what is termed the
first out of phase bending mode of the flow meter. Driver 104 may
comprise any one of many well known arrangements, such as a magnet
mounted to flow tube 103A and an opposing coil mounted to flow tube
103B and through which an alternating current is passed for vibrating
both flow tubes. A suitable drive signal is applied by flow meter
electronics 20 via lead 110 to driver 104. Pick-off sensors 105
and 105' are affixed to at least one of flow tubes 103A and 103B
on opposing ends of the flow tube to measure oscillation of the
flow tubes. As flow tubes 103A-103B vibrate, pick-off sensors 105-105'
generate a first pick-off signal and a second pick-off signal. The
first and second pick-off signals are applied to leads 111 and 111'.
Temperature sensor 107 is affixed to at least one of flow tubes
103A and 103B. Temperature sensor 107 measures the temperature of
the flow tube in order to modify equations for the temperature of
the system. Path 112 carries temperature signals from temperature
sensor 107 to flow meter electronics 20.
Flow meter electronics 20 receive the first and second pick-off
signals appearing on leads 111 and 111', respectively. Flow meter
electronics 20 process the first and second pick-off signals to
compute the mass flow rate, the density, or other property of the
material passing through flow meter sensor 10. This computed information
is applied by meter electronics 20 over path 26 to a utilization
means (not shown in FIG. 1).
FIG. 2 illustrates flow meter electronics 20 having multiple output
ports 201-204 in the prior art. In FIG. 2 flow meter sensor 10
is depicted in block diagram form for the sake of simplicity. Flow
meter electronics 20 comprises processing system 208 and output
ports 201-204. Output ports 201-204 make up path 26 in FIG. 1. Processing
system 208 outputs different types of signals over output ports
201-204. Processing system 208 outputs a milliamp signal over output
port 201. Processing system 208 outputs a discreet voltage signal
over output port 202. Processing system 208 outputs a digital communication
protocol signal over output port 203. Processing system 208 outputs
a frequency signal or pulse signal over output port 204. Unfortunately,
flow meter electronics 20 with multiple output ports 201-204 can
be expensive and may have more functionality than is needed for
simple applications.
There also exists other prior art flow meter electronics that are
simpler and lower-cost than flow meter electronics 20. The flow
meter electronics have only one output port, such as output port
203 that outputs a digital communication protocol signal. One problem
with these types of flow meter electronics is that they can only
output a digital communication protocol signal and some legacy systems
do not understand a digital communication protocol signal.
Flow Meter Electronics--FIG. 3
FIG. 3 illustrates flow meter electronics 302 for a Coriolis flow
meter 300 in an example of the invention. Coriolis flow meter 300
is illustrated in block diagram form for simplicity. Flow meter
electronics 302 is coupled to flow meter sensor 10 over path 100.
Flow meter electronics 302 is comprised of processing system 304
coupled to a single output port 306. Single output port 306 provides
a single channel of communications out of flow meter electronics
302. Flow meter electronics 302 may have one or more power connections
(not shown) in addition to single output port 306.
Flow meter sensor 10 operates as described in FIG. 1 to transmit
pick-off signals to flow meter electronics 302 over path 100 as
a material flows through flow meter sensor 10. Flow meter sensor
10 could also transmit other signals, such as a temperature signal,
to flow meter electronics 302. Processing system 304 receives the
pick-off signals from flow meter sensor 10. Processing system 304
processes the pick-off signals to determine a flow rate of the material
flowing through flow meter sensor 10.
Processing system 304 also receives an instruction 318 for a frequency
output signal or a digital communication protocol signal. The frequency
output signal comprises any signal that represents a single property
of a material flowing through a flow meter sensor, such as a square
wave signal or a sinusoidal signal. The frequency of the frequency
output signal represents a property of a material flowing through
a flow meter sensor. For instance, a frequency output signal may
represent a mass flow rate, wherein the frequency of the frequency
output signal is proportional to the mass flow rate. A digital communication
protocol signal comprises any signal, that represents multiple properties
of a material flowing through a flow meter sensor, that can be read
by conventional digital processing circuitry. For instance, a digital
communication protocol signal may represent a mass flow rate, a
density, and other properties. Instruction 318 could be transmitted
to flow meter electronics 302 by a user who is programming flow
meter electronics 302.
If instruction 318 is for a frequency output signal, then processing
system 304 processes the flow rate to generate a frequency output
signal 322. Frequency output signal 322 has a frequency proportional
to the flow rate of the material. Processing system 304 transmits
frequency output signal 322 over single output port 306.
If instruction 318 is for a digital communication protocol signal,
then processing system 304 processes the flow rate to generate a
digital communication protocol signal 324. Digital communication
protocol signal 324 represents the flow rate of the material. Processing
system 304 transmits digital communication protocol signal 324 over
single output port 306. Signal 326 represents either frequency output
signal 322 or digital communication protocol signal 324 depending
on which signal that processing system 304 transmitted over single
output port 306. Based on this disclosure, those skilled in the
art will appreciate how to modify existing flow meter electronics
to make flow meter electronics 302.
Flow meter electronics 302 is advantageously less expensive to
build and simpler to operate than flow meter electronics having
multiple output ports. At the same time, flow meter electronics
302 provides flexibility to a user by allowing the user to program
flow meter electronics 302 to output either a frequency output signal
322 or a digital communication protocol signal 324.
In one embodiment of the invention, processing system 304 determines
a direction of flow of the material. If the direction of flow is
in a forward direction, then processing system 304 generates frequency
output signal 322 to have a duty cycle below 0.5. If the direction
of flow is in a reverse direction, then processing system 304 generates
frequency output signal 322 to have a duty cycle above 0.5.
In another embodiment, processing system 304 determines if a fault
has occurred. The fault may have occurred in flow meter sensor 10
flow meter electronics 302 or in the pipeline (not shown) connected
to flow meter sensor 10. Processing system 304 generates frequency
output signal 322 having a predetermined frequency responsive to
determining the fault.
In another embodiment of the invention, the above-described flow
meter electronics 302 may be comprised of instructions that are
stored on storage media. The instructions can be retrieved and executed
by a processor. Some examples of instructions are software, program
code, and firmware. Some examples of storage media are memory devices,
tape, disks, integrated circuits, and servers. The instructions
are operational when executed by the processor to direct the processor
to operate in accord with the invention. The term "processor"
refers to a single processing device or a group of inter-operational
processing devices. Some examples of processors are computers, integrated
circuits, and logic circuitry. Those skilled in the art are familiar
with instructions, processors, and storage media.
Example of Flow Meter Electronics--FIGS. 4-5
FIG. 4 illustrates an example of a Coriolis flow meter 400 connected
to a user system 406 in an example of the invention. Flow meter
electronics 404 is coupled to flow meter sensor 402 over path 420.
Flow meter electronics 404 is coupled to user system 406 over path
422. Flow meter electronics 404 is comprised of processing system
414 coupled to a single output port 416.
Flow meter electronics 404 is configured to output a frequency
output signal or a digital communication protocol signal. A user
430 can program flow meter electronics 404 to output the frequency
output signal or the digital communication protocol signal with
user system 406. User system 406 could be a computer, a display,
or any other system or apparatus that interfaces user 430 with flow
meter electronics 404.
On power up, single output port 416 acts as an input/output port
for a time period, such as 5 seconds. Single output port 416 also
acts as an input/output port for a time period after a power cycle.
During this time period, processing system 414 waits for digital
signals received over single output port 416. User 430 can program
flow meter electronics 404 to operate in frequency mode or digital
mode, select other operating options, or transmit operating parameters
or other information to flow meter electronics 404 by transmitting
instructions to flow meter electronics 404. Frequency mode means
that flow meter electronics 404 outputs a frequency output signal.
Digital mode means that flow meter electronics 404 outputs a digital
communication protocol signal.
Following the time period after power up, processing system 414
operates in either frequency mode or digital mode. The operating
mode can be a default programmed into processing system 414 or be
programmed by user 430.
In frequency mode, processing system 414 receives the pick-off
signals from flow meter sensor 402 and processes the pick-off signals
to determine a flow rate of the material flowing through flow meter
sensor 402. The flow rate may represent a mass flow rate, a volumetric
flow rate, or a net volumetric flow rate. Processing system 414
generates frequency output signal 424 based on the flow rate of
the material. Frequency output signal 424 has a frequency proportional
to the flow rate of the material. Frequency output signal 424 may
be scalable to 10000 Hz.
Processing system 414 also determines a direction of flow of the
material flowing through flow meter sensor 402. Processing system
414 generates frequency output signal 424 based on the direction
of flow of the material. If the direction of flow is in a forward
direction, then frequency output signal 424 has a duty cycle below
0.5. If the direction of flow is in a reverse direction, then frequency
output signal 424 has a duty cycle above 0.5. Examples of frequency
output signal 424 are depicted in FIG. 5. Processing system 414
transmits frequency output signal 424 to single output port 416.
Processing system 414 also determines if a fault has occurred.
If a fault has occurred, processing system 414 generates frequency
output signal 424 to have a fixed, high frequency. Processing system
414 operates in frequency mode until a power cycle occurs.
In digital mode, processing system 414 receives the pick-off signals
from flow meter sensor 402 and processes the pick-off signals to
determine the flow rate of the material flowing through flow meter
sensor 402. Processing system 414 generates digital communication
protocol signal 426 based on the flow rate of the material. Digital
communication protocol signal 426 represents the flow rate of the
material. Processing system 414 operates in digital mode until a
power cycle occurs.
In digital mode, processing system 414 can also determine a direction
of flow of the material flowing through flow meter sensor 402 and
determine if a fault has occurred. Processing system 414 outputs
digital communication protocol signal 426 representing the direction
of flow of the material or fault information. |