GAS METER AND REGULATOR COMBINATION

Abstract: A combination gas meter and regulator (10) is disclosed. The meter (18) is disposed in a high pressure region upstream of the regulator (14). The meter (18) includes an ultrasonic transmitter/receiver arrangement (20a, 20b) that transmits a relatively low frequency ultrasonic signal through a gas flow tube (22). Variations in the time of flight of the signal are used to determine the gas flow. The combination further includes a pressure sensor (24a, 24b) in the high pressure region, the output of the meter being a pressure compensated measurement of the gas flow.

Description: 1 GAS METER AND REGULATOR COMBINATION BACKGROUND OF INVENTION The invention relates to gas meter and regulator installations of the type used for measuring gas consumption by a commercial or residential premises. Typical gas meter and regulator installations, interposed between the high pressure gas supply and the gas piping of the premises, have a regulator valve which drops the high, variable gas pressure in the gas supply pipe to a lower, predetermined pressure supplied to the piping in the premises. The meter is located downstream of the regulator, measuring the gas volume as used by the premises. Such installations have gained widespread use but in order to offer reasonable accuracy they must be quite large. SUMMARY OF INVENTION The present invention aims to provide a new gas meter and regulator combination, which overcomes or ameliorates the above disadvantage. It is an aim of preferred forms of the invention to provide a meter and regulator combination adapted to give operational advantages to a gas meter of the type employing acoustic transducers. The present inventors have discovered that significant advantages are attained by employing an arrangement in which the metering means is located at the high pressure side of the regulator. Accordingly, the present invention provides a gas meter and regulator combination for measuring gas consumption by a premises, including a high pressure gas supply inlet, a regulator for reducing gas pressure to a predetermined lower pressure, the regulator defining a downstream limit of a high gas pressure region between the inlet and the regulator, a low pressure gas outlet downstream of the regulator, and metering means Substitute Sheet (Rule 26) RO/AU generating an output, wherein said metering means is located in said high pressure region, further including gas pressure measurement means measuring gas pressure in said high pressure region, said pressure measurement means generating an output, and calculating means receiving outputs from the metering and pressure measurement means and generating a pressure-compensated meter measurement. Preferably, the gas meter and regulator combination is contained within a single housing. Preferably also, the metering means includes a gas flow tube, means for transmitting and receiving an acoustic signal along said gas flow tube so as to determine the gas flow in the gas flow tube. Preferably the gas flow is determined from variations in the time of flight of the acoustic signals. BRIEF DESCRIPTION OF THE DRAWINGS Further preferred embodiments of the invention will be described with reference to the figure, which is a schematic view of a preferred arrangement. DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 shows a gas meter/regulator unit 10 having a gas inlet 12 for connection to a high, variable pressure gas supply, typically at 40-600 kPa, a filter 13 and an outlet 14 for connection to the gas plumbing of the premises for which the meter/regulator unit is installed. Within the unit 10, the gas flow path is divided into a high, variable pressure region between the inlet 12 and a regulator 14, and a low pressure region downstream of the regulator. The regulator acts to reduce the high gas supply pressure to a lower, substantially constant pressure at which the gas is supplied to the premises, typically in the range of 0.5-3.5 kPa. The regulator 14 may be mechanically operated, such as of conventional spring-biased diaphragm operated construction but of reduced size, or 3 electronically controlled by the processor/controller 16. Alternatively the regulator may be a combined electro-mechanical regulator. Located upstream of the regulator 14 in the high pressure region of the gas path is a metering apparatus 18, consisting of acoustic transducers 20a, 20b situated at upstream and downstream ends of gas flow tube 22. The transducers are controlled by the processor 16 to transmit and receive acoustic (e.g. ultrasonic) signals through measurement tube 22 to determine the gas flow velocity through tube 22 and send outputs to the processor 16. The gas flow velocity is calculated from the variation in the time taken for the signal to pass in each direction along the tube 22. Further details of an acoustic metering apparatus are described in Australian Patent No. 682498, the contents of which are incorporated herein by reference. Pressure sensors 24a, 24b disposed at each end of the gas flow tube 22 are used to determine the average pressure within the gas flow tube. Alternatively one pressure sensor may be employed at either end of the tube 22 and a correction algorithm used to compensate for the pressure drop within the tube 22 to determine the average pressure. One or both of the sensors 24a, 24b may also incorporate a sensor for measuring the gas temperature. The processor 16 receives the outputs from the transducers 20a, 20b, sensors 24a, 24b and, optionally, from any other sensors and from this information calculates the gas flow quantity passing through the unit and into the premises. A cumulative quantity reading is communicated to a display 26 on the unit. The processor 16 may also be provided with an external communications link 28 allowing remote reading and control of the meter/regulator unit. For example, if an electronically controlled regulator is used, the unit may have facility for the gas supply authority to send a signal causing the processor 16 to close the regulator valve 14, shutting off the gas supply to the premises. The advantages of the present invention include the ability to utilise a more advantageous construction of the acoustic metering apparatus than is practical in the prior art arrangement due to pressure drop limitations. With the metering tube in the illustrated embodiment of the present invention now in the high pressure region upstream of the regulator, the allowable pressure drop across the metering tube is no longer a significant limiting factor. Therefore the length of the measuring tube can be increased. This increases the time taken for the transducer signal to traverse the tube (i.e. the time of flight of the signal) and hence enables an increase in the overall accuracy of the meter. The prior art acoustic gas meters were required to use relatively high frequency transducers in order to gain the required accuracy. However because the accuracy depends upon the time of flight of the transducer signal, and in the present invention this can be increased as desired by lengthening the metering tube, lower frequency signals requiring less energy to produce can be utilised. Transducer signals of approximately 30-90 kHz, preferably 30-60 kHz and more preferably about 40 kHz, (compared with 100-200 kHz for typical prior art meters) can be used, which can significantly reduce the energy requirements of the meter. Preferably the signal frequency is selected so that the wavelength of the signal is greater than the internal diameter of the metering tube. This has the effect of increasing the strength of the signal by suppressing the higher order harmonics of the acoustic signal. Though not shown in the schematic diagram of Figure 1, in practice the metering tube can include several loops within the meter as a way of increasing the tube length while still allowing a compact meter unit. A further advantage is that because metering is effected before the regulator, the accuracy of the regulated gas pressure is less critical than in prior art arrangements, which relied on accurate regulated pressure (within about 1%) for accuracy of metering - far more accuracy than needed for proper functioning of gas appliances. This requirement for accurate pressure required the use of a large surface area diaphragm within the regulator and therefore the entire regulator unit was large. In contrast, the present invention allows a significantly smaller and cheaper regulator to be employed, as the regulator accuracy need only be within about 10%. The size reduction in the regulator and the suitability of the arrangement for acoustic metering due to the present invention increase the practicality of including both within one housing, to deter tampering. Size reductions of as much as 10 times compared to prior art meter and regulator installations can be achieved. It will be appreciated that while the meter and regulator combination is preferably embodied within a single housing, as illustrated, it will be possible to provide separate housings for the meter and regulator without departing from the scope of the present invention. While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims: CLAIMS 1. A gas meter and regulator combination for measuring gas consumption by a premises, including a high pressure gas supply inlet, a regulator for reducing gas pressure to a predetermined lower pressure, the regulator defining a downstream limit of a high gas pressure region between the inlet and the regulator, a low pressure gas outlet downstream of the regulator, and metering means generating an output, wherein said metering means is located in said high pressure region, further including gas pressure measurement means measuring gas pressure in said high pressure region, said pressure measurement means generating an output, and calculating means receiving outputs from the metering and pressure measurement means and generating a pressure-compensated meter measurement. 2. A gas meter and regulator according to claim 1 wherein said metering means includes a gas flow tube and means for transmitting and receiving an acoustic signal along said gas flow tube so as to determine the gas flow in said gas flow tube. 3. A gas meter and regulator according to claim 2 wherein the gas flow is determined from time of flight of said acoustic signal. 4. A gas meter and regulator according to claim 2 wherein the acoustic signal has a frequency of substantially 30-90 kHz. 5. A gas meter and regulator according to claim 4 wherein the acoustic signal has a frequency of about 40 kHz. 6. A gas meter and regulator according to claim 2 wherein the gas flow tube has an internal diameter of less than the wavelength of the acoustic signal. 7. A gas meter and regulator according to claim 2 wherein the gas flow tube is formed with one or more loops. 8. A gas meter and regulator according to claim 1 wherein the gas meter and regulator are contained within a single housing. 9. A gas meter and regulator according to claim 1 further including gas temperature measurement means wherein said calculating means receives an output from said gas temperature measurement means and wherein said meter measurement is compensated for temperature. 10. A gas meter and regulator according to claim 1 further including an external communication link for remote control and reading of said meter and regulator.

Inventors: GRAY JAMES ALASTAIR, SMITH ERNEST ROBERT YARWOOD, VRACHNOS ANDREAS, GRAY, JAMES, ALASTAIR, SMITH, ERNEST, ROBERT, YARWOOD, VRACHNOS, ANDREAS
Applicants: EMAIL LTD, GRAY JAMES ALASTAIR, SMITH ERNEST ROBERT YARWOOD, VRACHNOS ANDREAS, EMAIL LIMITED, GRAY, JAMES, ALASTAIR, SMITH, ERNEST, ROBERT, YARWOOD, VRACHNOS, ANDREAS
Application year: 1999
Main classification: G01F1
IPC codes: G01F1