Abstract: A method and apparatus for measuring the flow rate of a single phase fluid, particularly a gas, through a conduit. A pulse of tracer fluid is discharged or injected into a first fluid flowing through a conduit, the concentration of the tracer fluid is measured as a function of time at a downstream from where it is injected, and the flow rate of the first fluid is determined based on the concentration measurements. The concentration of tracer fluid is preferably sampled substantially continuously from when the tracer gas first passes the measuring point until substantially all of the tracer fluid has passed the measuring point and the sampled concentrations integrated. The concentration of tracer fluid is preferably determined by measuring the thermal conductivity of the mixture of the first fluid and tracer fluid which is dependent upon the concentration of the tracer fluid.

Abstract: 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 Ta 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 ThCH of the thermal conductivity is measured at 70° C. above ambient and the other value ThCL of the thermal conductivity is measured at 50° C. above ambient. The control calculates the relative density RD of the gas according to the formula RD=g·ThCH+h·ThCL+i·SoS+j·Ta+k·.Ta2+l where (g, h, i, j, k and l) are constants.

Abstract: 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.

Abstract: A method and apparatus for measuring the relative density of a gas, for example natural gas. The gas is supplied through an inlet to a chamber and is output through an outlet. Using a control and an ultra-sonic transducer emitter and an ultra-sonic transducer receiver, the speed of sound in the gas corrected to standard conditions is calculated. Then, the control operates to measure the relative density RD of the gas using the formula RD=a×SoSsc+b, where SoSsc is the speed of sound in the gas corrected to standard conditions, and a and b are constants.

Abstract: A method and apparatus for measuring the calorific value 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 temperatures Ta, 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 ThCH, of the thermal conductivity is measured at 70° C. above ambient and the other value ThCL of the thermal conductivity is measured at 50° C. above ambient. The control calculates the calorific value CV of the gas according to the formula: CV=a·ThCH+b·ThCL+C·SoS+d·Ta+e·Ta2 +f, where a, b, c, d, e and f are constants.

Abstract: An energy meter for measuring parameters of fuel gas. The meter has a gas inlet and outlet and a central tube along which the gas flows from inlet to outlet. Ultra-sound transducers and a control form a system whereby the speed of ultra-sound signals traveling through the gas between the transducers is measured and used in the control to calculate the volume of gas which is passed through the meter. The ultra-sound signals pass through apertures in the walls of chambers containing the transducers. Another ultra-sound transducer in the chamber which is connected to the control acts as an emitter and receiver of ultra-sound signals reflected by reflectors. These signals travel through the fuel gas in the chamber and their attenuation is observed and measured by the control when they are received by the transducer. The measured attenuation is used to derive the calorific value and/or Wobbe index of the gas.