Measuring and testing – Volume or rate of flow – By measuring electrical or magnetic properties
Reexamination Certificate
1997-12-04
2001-01-16
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Volume or rate of flow
By measuring electrical or magnetic properties
C073S861120
Reexamination Certificate
active
06173616
ABSTRACT:
BACKGROUND TO THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic flow-rate measurement system which is configured using electromagnetic flowmeters capable of measuring the flow of a conductive fluid.
2. Description of the Related Art
One of the pieces of measurement apparatus used for measuring the flow of conductive fluids is the electromagnetic flowmeter, the high degree of accuracy and durability of which has led to its wide adoption for use in industry.
FIG. 1
shows an example of the configuration of an electromagnetic flowmeter for industrial use.
The electromagnetic flowmeter shown in this drawing comprises a detector
1
and a converter
2
. The detector
1
has a pair of electrodes
4
a
,
4
b
on the internal wall of the measurement pipe
3
through which the conductive fluid which is to be measured is passed, and a flow-rate measurement coil
5
located on the exterior of the measurement pipe
3
impresses a magnetic field on the fluid in a direction which intersects at right-angles the line along which the electrodes
4
a
,
4
b
face each other. The converter
2
converts the electromotive force which is generated between the electrodes
4
a
,
4
b
into voltage signals in an amplifier
6
, and outputs them from an output circuit
8
via a sampling circuit
7
. A switch
10
serves to switch between constant-current sources
9
a
,
9
b
, thus allowing an alternating current to flow to the flow-rate measurement coil for the purpose of excitation. The switching of the switch
10
is controlled by a exciting signal which is generated by a timing circuit
11
in synchronisation with a sampling signal from the sampling circuit
7
.
FIG. 2
illustrates the timing of the above-mentioned electromagnetic flowmeter.
Control of the switch
10
by means of the exciting signal illustrated in this drawing allows the alternating current to flow to the exciting coil
5
, and the electromotive force generated between the electrodes
4
in accordance with the flow-rate of the fluid which is to be measured is amplified by the amplifier
6
. The output of this amplifier
6
is sampled when stable, and a flow-rate signal is transmitted from the output circuit
8
.
Another example of a device which measures the flow-rate of a fluid in the same way as an electromagnetic flowmeter is the water meter which measures the amount of water consumed for household use. Recent demand for the rationalisation of meter-reading and a reduction in the number of meters which are difficult to read has led to the popularisation of centralised and mass meter-reading, where meters are read from a distance by electrical or magnetic means.
If the industrial electromagnetic flowmeter could be adapted to use with the household water meter, it would be possible to implement a high-precision remote centralised meter-reading system. However, in practice there are a number of factors which have prevented the adaption of the electromagnetic flowmeter to use with household water meters. Some of the reasons which may be adduced are as follows. There has been a problem in that the faintness of the electromotive force (flow-rate signal) generated between the electrodes
4
a
,
4
b
has necessitated a complicated configuration of circuits (sampling circuit
7
, output circuit
8
etc.) in order to process the signal in the converter
2
. Another problem has been the high cost involved in providing the electrical energy to generate an alternating magnetic field by means of the flow-rate measurement coil
5
, and the cost of the exciting circuit comprising the constant-current sources
9
a
,
9
b
and the switch
10
. Yet another problem has been the increased cost of power consumption running to several watts as compared with other types of mechanical water meter. Finally, it has been necessary to renew wiring and other equipment because the detector
1
normally requires an external power source.
Recent developments in electronics technology have succeeded in facilitating signal processing on a cheaper and smaller scale, but the continued need for an exciting circuit and wiring to supply the required electric power mean that problems of size and expense still remain.
Thus, any attempts hitherto to construct a remote centralised meter-reading system or other flow-rate measurement system by adapting electromagnetic flowmeters to use with household water meters have been fraught with problems size and expense resulting from the need to provide the exciting circuit and wiring to supply the required electric power.
SUMMARY OF THE INVENTION
It is an object of the present invention, which has been devised in view of the circumstances outlined above, to provide a flow-rate measurement system which permits the implementation of a cheap, accurate and durable remote centralised meter-reading system for water meters by configuring it in such a manner that wiring installed for the purpose of remote meter-reading can be used to supply the required power sources for exciting and circuitry.
It is possible to achieve the object of the present invention with the aid of an electromagnetic flow-rate measurement system configured as is described below.
It is an electromagnetic flow-rate measurement system, wherein detection units located in a plurality of positions in order to measure a fluid are each connected by way of a common bus-line to a meter board, flow-rate values detected by each of the detection units being collected to the meter board.
The detection units are provided with a measurement pipe through which the fluid which is to be measured flows, electrodes attached to the interior wall of this measurement pipe in a latitudinal direction, an exciting coil which is connected to the common bus-line and imparts a magnetic field in a direction which intersects at right-angles the axial direction of the measurement pipe, an amplifier which serves to amplify the electromotive force generated between the electrodes, a sampling circuit which samples the output of this amplifier, a signal-processing circuit which takes flow-rate signals or cumulative flow-rate signals from the output of this sampling circuit, and a communications circuit which is connected to between the two ends of the exciting coil and serves both to transmit the flow-rate signals or cumulative flow-rate signals to the meter board in synchronization with an alternating waveform voltage of the common bus-line, and to receive signals from the meter board in synchronisation with the alternating waveform voltage.
The meter board is provided with an alternating waveform voltage-generating sources which are connected to the common bus-line and generates alternating waveform voltage, and a communications circuit which is connected to the common bus-line and serves both to transmit signals to the detection units in synchronisation with the alternating waveform voltage, and to receive signals from the detection units in synchronisation with the said alternating waveform voltage.
REFERENCES:
patent: 4373400 (1983-02-01), Sekiguchi
patent: 4408497 (1983-10-01), Suzuki
patent: 4409846 (1983-10-01), Ueno
patent: 4969363 (1990-11-01), Mochizuki
patent: 5388465 (1995-02-01), Okaniwa et al.
patent: 5487310 (1996-01-01), Higuchi
patent: 5677496 (1997-10-01), Mochizuki
patent: 0262658 (1988-04-01), None
Fuller Benjamin R.
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Jagdish
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