British Gas Plc

Lattice Intellectual Property Limited

Bg Intellectual Property Ltd.

Barry Leonard Price

Robert Richard Thurston

David Byrne

Francis Alan Humphrey

Paul Stephen Hammond

Graham Richard Roberts

Alan Brightwell

Keith J Adams

Gregory E Jones

Harry Gray

Andrew Jonathan Cole

David Richard Wightman

Paul Steven Hammond

Stuart M Pegler

Christopher J Thornhill

Paul Weall

A method and apparatus for measuring the relative density of a gas. The apparatus includes a chamber to which a gas in question, for example natural gas, is supplied through an inlet and leaves through an outlet. The speed of sound SoS at ambient temperature is measured using any suitable method such as electronic control and a calculating device and an ultra-sound emitter and an ultra-sound receiver. The ambient temperature T is observed by a temperature sensor, and a thermal conductivity sensor measures the thermal conductivity of the gas at two different temperatures above the ambient temperature. One value ThC of the thermal conductivity is measured at 70&deg; C. above ambient and the other value ThC of the thermal conductivity is measured at 50&deg; C. above ambient. The control calculates the relative density RD of the gas according to the formula RD&equals;g&middot;ThC &plus;h&middot;ThC &plus;i&middot;SoS&plus;j&middot;T &plus;k&middot;.T &plus;l where (g, h, i, j, k and l) are constants.

Method and apparatus for measuring the relative density of a gas

A method and apparatus for synthesizing an approximation to a sine wave comprising generating a number of pulse width modulated signals, each having a predetermine duty cycle and being the same frequency as each other, from a clock signal. The generated pulse width modulated signals are then combined to produce an approximation to a sine wave having the same frequency as the pulse width modulated signals. The clock signal is provided by an oscillator arranged to produce clock signals over a continuous range of frequencies so that approximations to a sine wave can be produced over a continuous range of frequencies.

Synthesizing a sine wave

An energy meter which measures a volume of gas supplied, which measures a calorific value of the gas supplied, and which calculates an energy value corresponding to the measured volume of gas supplied and the calorific value. The structure to measure the volume of the gas supplied and to calculate the energy value may be provided in a single unit. The structure to measure the calorific value of the gas supplied preferably includes a structure to measure the speed of sound in the gas and further preferably measures a first thermal conductivity of the gas at a first temperature and measures a second thermal conductivity of the gas at a second temperature which differs from the first temperature, and is arranged to produce the calorific value of the gas corresponding to the measured speed of sound in the first and second thermal conductivities.

Measuring energy consumption

A method and apparatus for determining the speed of sound in a gas. An acoustic transmitter is arranged to apply an acoustic signal to the interior of a resonator and an acoustic receiver is arranged to detect the amplitude of the acoustic signal in the interior of the resonator. A control means determines the speed of sound of gas within the resonator from the frequency of a detected non-radial resonant mode.

Measuring the speed of sound of a gas

Method and apparatus for measuring the calorific value of a gas

Determininig a frequency at which a resonator resonates comprising: driving an acoustic transmitter for applying an acoustic signal to the interior of a resonator by scanning through a first range of frequencies in substantially equidistant steps of a first size; detecting a signal from an acoustic receiver arranged to detect the amplitude of an acoustic signal within the resonator produced by driving the acoustic transmitter over the first range of frequencies; determining a frequency at which a maximum occurs in the detected signal for the first range of frequencies; driving the acoustic transmitter by scanning through a second range of frequencies containing the determined frequency from the first range of frequencies, the second range being smaller than the first range, and scanning through the second range of frequencies in substantially equidistant steps of a second size which is smaller than the steps of the first size; detecting a signal from the acoustic receiver produced by driving the acoustic transmitter over the second range of frequencies and determining a frequency at which a maximum occurs in the detected signal for the second range of frequencies.

Method and apparatus for determining a frequency at which a resonator resonates

A meter to measure the volumetric flow rate of a liquid, for example water, is formed with a pipe forming a liquid flow path containing a low power electrical heater. A first temperature sensor measures the temperature T of the liquid adjacent to an upstream end of the heater and a second temperature sensor measures the temperature T.sub.2 of the liquid adjacent to a downstream end of the heater. The heater adds heat power of a value P to the liquid. A control arrangement comprising a computer means calculates the flow rate Q using the expression ##EQU1## where ST.sub.1 and DT.sub.1 are respectively the specific heat capacity of the liquid and the density of the liquid at the temperature T.sub.1 measured by the first sensor.

Liquid metering

Apparatus and method for measuring heat power consumed in or extracted

Measuring probe

A monitor system for safety critical situations such as burner control receives at inputs 17-21 control information from a programmable logic control and reference information at inputs 12-16 from plant interlocks. This information passes via opto-isolators 40 and buffers 41 to the address bus of an EPROM so as to access information stored therein which normally mirrors the PLC information so as to control relays RL1-5 via drivers 45 to conform to the PLC instructions. The EPROM also contains reset and clock information for use by a counter 48 which allows different areas within the EPROM to be accessed. The reset information is also available to a parity check circuit 49 via oscillator 46 for dynamically testing the monitor for integrity of operation. Failure of the PLC or monitor components will cause access to shutdown addresses of the EPROM and operation of the appropriate relays including lockout relay RL6.

Monitor system

A burner control system includes an input interface 10 for receiving burner status inputs. These are passed to address bus 14 and used to access addresses within EPROM 18. Data at the accessed addresses are output on bus 20 to control the burner via output interface 23 with related relays. Oscillator 16 and counter 17 sequence the selected address areas of the EPROM via bus 15 and a start up sequence, for example, can thus be effected. Incorrect status of the inputs from input block 10, flame detector 12 or the internal system checks in blocks 28 or 29 to bus 14 will cause the EPROM to be addressed at locations which contain data in a form that will cause shutdown or lockout via relay 25. Parity check block 22 also actuates lockout if errors are detected. System status can be provided by display 19.

Control system improvements in or relating to burner

A testing circuit for a control system has a two-state input circuit connected across a plurality of switching devices. The input circuit assumes one state when any one of the contacts is closed and the other state when they are all open. An indicator device shows whether the contacts are functioning correctly.

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Quorn, United Kingdom

Barry Leonard Price