03-06-2013, 04:37 PM
Development of a computer interface for a clamp-on ultrasonic flow meter
[attachment=54701]
Abstract
The section for volume, flow and temperature at SP Technical Research
Institute of Sweden performs measurements of volume, flow and temperature
in liquids.
Flow meters are best calibrated in its installation to take sources of error like
installation effects and the medium into account. If this can be done without
having to place measurement equipment inside the pipe it will mean several
practical benefits.
Since many years, clamp-on ultrasonic flow meters have been available on the
market. But even with today’s improvements they still have a measurement
uncertainty in the measurements that is five to ten times too big to make them
useful as references for calibration procedures.
This thesis focuses on analysis, using reversed engineering, of an existing
clamp-on ultrasonic flow meter.
Introduction
This thesis is performed at SP Technical Research Institute of Sweden.
The goal of the thesis ”Development of computer interface for a clamp-on
ultrasonic flow meter” is to develop a new and improved computer interface for
a clamp-on ultrasonic flow meter. The primary goal is to make the ultrasonic
flow meter easier to use and get the flow rate-information in real-time.
Background
The section for volume, flow and temperature at SP Technical Research
Institute of Sweden performs measurement of volume, flow and temperature in
liquids.
Flow meters are best calibrated in its situation to take sources of error, like
installation effects and the medium, into account. If this can be done without
placing measurement equipment inside the pipe, the process can proceed,
undisturbed, when calibrating the flow meter of interest. This is associated with
many practical benefits. Since many years – clamp-on flow meters have been
available on the market. They offer a solution to non-intrusive flow
measurements. But even with today’s improvements they still have a
measurement uncertainty that is five to ten times too big to make them useful
as references for calibration-procedures. There are, however, opportunities for
improvement by combining the measurement of flow rate with additional
information and improved data processing.
Clamp-on ultrasonic flow meter
The ultrasonic flow meter [1] measures the flow rate of liquids in a pipe
through the use of ultrasound using a technique called Transit Time Differential
Measurement [2]. The equipment (Figure 1.1) consist of a sensor device with
two ultrasonic transducers that are clamped on to the pipe, a meter-unit
containing electronics for digital signal processing (DSP) [3] of the signals
received from the sensor-unit, user interface consisting of display and simple
keyboard and a computer interface with application software.
Description of problem
SP wishes to improve accuracy and simplify the use of the ultrasonic flow
meter through the design of a new and improved computer interface. SP uses
Microsoft Excel to analyze the measurements of flow rate, pressure and
temperature. The user application for the ultrasonic flow meter creates a dumpfile
with values, which needs to be converted before it can be imported into
another program, such as Microsoft Excel. Then the flow rate of the liquid in
the pipe needs to be calculated from the acquired transit-times presented in the
dump-file. This is very time-consuming and makes real-time measurement of
the liquid’s flow rate difficult.
It is possible to access the flow meter, using the original computer interface
from Microsoft Excel through the use of a custom Visual Basic application and
the virtual COM-port used by the computer interface. However, it quickly
became obvious that the overhead associated with the RS232-protocol in
combination with the interpretative nature of VBA offered a solution to slow to
fulfill SP: s real-time requirements for data acquisition of the flow rates.
To solve this problem the development of new hardware is required to offer a
new computer interface that supports faster data acquisition of the transit times,
compared to what is possible using the RS232-interface, as well as support for
measurements using several sensors in parallel.
The first task is to, through the use of reversed engineering, study the design of
the flow meter and its computer interface. SP does not have access to sufficient
technical documentation for the ultrasonic flow meter. This makes reversed
engineering the method of choice for studying the unit.
Scope and Requirements
The new hardware for the improved computer interface needs to be small
enough and have low weight to be portable since SP often needs to perform
measurements “on the field” when visiting clients.
The project must not be too costly while at the same time be flexible enough to
offer further development such as connection of multiple flow meters and other
type of sensors. After a discussion with the supervisors at SP, an agreement for
a solution with support for four flow meter-interfaces with the option of
attaching external devices to the I2C-bus was reached
Environmental requirements
SP has high requirements on moisture and dust-durability as well as
electromagnetic compatibility (EMC) [4] because they work with sensitive
equipment that must not be exposed to interference caused by other equipment.
Electromagnetic compatibility means that the device must not be susceptible to
or transmit electromagnetic interference. These factors are important to
consider when designing the printed circuit boards for the flow meter-interface
and the selection of enclosure.
[attachment=54701]
Abstract
The section for volume, flow and temperature at SP Technical Research
Institute of Sweden performs measurements of volume, flow and temperature
in liquids.
Flow meters are best calibrated in its installation to take sources of error like
installation effects and the medium into account. If this can be done without
having to place measurement equipment inside the pipe it will mean several
practical benefits.
Since many years, clamp-on ultrasonic flow meters have been available on the
market. But even with today’s improvements they still have a measurement
uncertainty in the measurements that is five to ten times too big to make them
useful as references for calibration procedures.
This thesis focuses on analysis, using reversed engineering, of an existing
clamp-on ultrasonic flow meter.
Introduction
This thesis is performed at SP Technical Research Institute of Sweden.
The goal of the thesis ”Development of computer interface for a clamp-on
ultrasonic flow meter” is to develop a new and improved computer interface for
a clamp-on ultrasonic flow meter. The primary goal is to make the ultrasonic
flow meter easier to use and get the flow rate-information in real-time.
Background
The section for volume, flow and temperature at SP Technical Research
Institute of Sweden performs measurement of volume, flow and temperature in
liquids.
Flow meters are best calibrated in its situation to take sources of error, like
installation effects and the medium, into account. If this can be done without
placing measurement equipment inside the pipe, the process can proceed,
undisturbed, when calibrating the flow meter of interest. This is associated with
many practical benefits. Since many years – clamp-on flow meters have been
available on the market. They offer a solution to non-intrusive flow
measurements. But even with today’s improvements they still have a
measurement uncertainty that is five to ten times too big to make them useful
as references for calibration-procedures. There are, however, opportunities for
improvement by combining the measurement of flow rate with additional
information and improved data processing.
Clamp-on ultrasonic flow meter
The ultrasonic flow meter [1] measures the flow rate of liquids in a pipe
through the use of ultrasound using a technique called Transit Time Differential
Measurement [2]. The equipment (Figure 1.1) consist of a sensor device with
two ultrasonic transducers that are clamped on to the pipe, a meter-unit
containing electronics for digital signal processing (DSP) [3] of the signals
received from the sensor-unit, user interface consisting of display and simple
keyboard and a computer interface with application software.
Description of problem
SP wishes to improve accuracy and simplify the use of the ultrasonic flow
meter through the design of a new and improved computer interface. SP uses
Microsoft Excel to analyze the measurements of flow rate, pressure and
temperature. The user application for the ultrasonic flow meter creates a dumpfile
with values, which needs to be converted before it can be imported into
another program, such as Microsoft Excel. Then the flow rate of the liquid in
the pipe needs to be calculated from the acquired transit-times presented in the
dump-file. This is very time-consuming and makes real-time measurement of
the liquid’s flow rate difficult.
It is possible to access the flow meter, using the original computer interface
from Microsoft Excel through the use of a custom Visual Basic application and
the virtual COM-port used by the computer interface. However, it quickly
became obvious that the overhead associated with the RS232-protocol in
combination with the interpretative nature of VBA offered a solution to slow to
fulfill SP: s real-time requirements for data acquisition of the flow rates.
To solve this problem the development of new hardware is required to offer a
new computer interface that supports faster data acquisition of the transit times,
compared to what is possible using the RS232-interface, as well as support for
measurements using several sensors in parallel.
The first task is to, through the use of reversed engineering, study the design of
the flow meter and its computer interface. SP does not have access to sufficient
technical documentation for the ultrasonic flow meter. This makes reversed
engineering the method of choice for studying the unit.
Scope and Requirements
The new hardware for the improved computer interface needs to be small
enough and have low weight to be portable since SP often needs to perform
measurements “on the field” when visiting clients.
The project must not be too costly while at the same time be flexible enough to
offer further development such as connection of multiple flow meters and other
type of sensors. After a discussion with the supervisors at SP, an agreement for
a solution with support for four flow meter-interfaces with the option of
attaching external devices to the I2C-bus was reached
Environmental requirements
SP has high requirements on moisture and dust-durability as well as
electromagnetic compatibility (EMC) [4] because they work with sensitive
equipment that must not be exposed to interference caused by other equipment.
Electromagnetic compatibility means that the device must not be susceptible to
or transmit electromagnetic interference. These factors are important to
consider when designing the printed circuit boards for the flow meter-interface
and the selection of enclosure.