Heat meters

Claim 2

A heat meter comprising electromagnetic induction means arranged to provide a measurement representative of rate of flow of fluid, said induction means comprising magnetic pole pieces arranged to be disposed on opposite sides of a conduit carrying said fluid so as to form an interpole gap therebetween, a pair of electrodes arranged to be disposed on opposite sides of said conduit so as to form an interelectrode gap therebetween, said interpole gap extending substantially perpendicular to said interelectrode gap, and means for generating a magnetic field between said pole pieces, said magnetic field generating means comprising an operation amplifier, field coil means magnetically connected with said pole pieces, and means for supplying as a feedback signal to said operational amplifier a signal that is proportional to current flow in said field coil means; means for obtaining a measurement representative of difference in temperature of the fluid between two spaced locations; and means for applying as an input signal to one of said measurement means a signal that is representative of the output signal of the other measurement means, whereby an output signal obtained from said one measurement means is representative of the amount of heat exchanged with the fluid between said two spaced locations.

Claim 3

A heat meter according to claim 1, wherein said signal applying means is arranged to apply as said input signal to said temperature difference measurement means an output signal of said flow rate measurement means.

Claim 4

A heat meter according to claim 1, wherein said magnetic field generating means is arranged to energise said pole pieces intermittently.

Claim 5

A heat meter according to any of claims 3, comprising means defining said inter-pole gap and said inter-electrode gap as gaps of substantially rectangular cross-section.

Claim 6

A heat meter according to claim 1, wherein said temperature difference measurement means comprises temperature-sensitive resistive means.

Claim 7

A heat meter according to claim 5, wherein said temperature-sensitive resistance means comprises two platinum film sensors arranged in a Wheatstone bridge circuit.

Claim 8

A heat meter comprising a conduit for conducting flow of fluid; means for obtaining a measurement representative of rate of flow of said fluid through the conduit, said flow rate measurement means comprising means for generating a substantially unidirectional magnetic field across said conduit, and a pair of planar electrodes mounted in the conduit to extend parallel to said magnetic field; means for obtaining a measurement representative of difference in temperature of the fluid between two spaced locations, said temperature measurement means comprising temperature-sensitive resistance means that is arranged to form part of a Wheatstone bridge circuit; means arranged to supply current to the temperature-sensitive resistance means in proportion to the voltage induced between said electrodes; display means; and means arranged to supply a signal representative of the output of said bridge circuit to said display means, thereby to display the thermal power exchanged with the fluid between said spaced locations, said magnetic field generating means having pole pieces on opposite sides of said conduit and being arranged to energize said pole pieces with pulses of magnetic flux, each pulse having a portion corresponding to constant field current, the heat meter comprising means arranged to sample said output signal during said constant pulse portion and to hold said sample until said pole pieces are next pulsed.

Claim 9

A heat meter comprising a conduit for conducting flow of fluid; means for obtaining a measurement representative of rate of flow of said fluid through the conduit, said flow rate measurement means comprising means for generating a substantially unidirectional magnetic field across said conduit, and a pair of planar electrodes mounted in the conduit to extend parallel to said magnetic field; means for obtaining a measurement representative of difference in temperature of the fluid between two spaced locations, said temperature measurement means comprising temperature-sensitive resistance means that is arranged to form part of a Wheatstone bridge circuit; means arranged to supply current to the temperature-sensitive resistance means in proportion to the voltage induced between said electrodes; display means; and means arranged to supply a signal representative of the output of said bridge circuit to said display means, thereby to display the thermal power exchanged with the fluid between said spaced locations, said magnetic field generating means having pole pieces on opposite sides of said conduit and being arranged to energize said pole pieces with pulses of magnetic flux, each pulse having a portion corresponding to constant field current, the heat meter comprising means arranged to sample said output signal during said constant pulse portion and to hold said sample until said pole pieces are next pulsed.

Claim 10

A heat meter comprising conduit means of circular cross section having a measurement section of rectanuglar cross section arranged to convey fluid, means arranged to obtain a measurement representative of rate of flow of fluid in said conduit means, means arranged to obtain a measurement representative of difference in temperature of the fluid between two spaced locations within said conduit means, and means arranged to apply as an input signal to said temperature difference measurement means a signal that is representative of the output signal of said flow rate measurement means, whereby an output signal obtained from said temperature difference measurement means is representative of the amount of heat exchanged with the fluid between said two spaced locations, said temperature measurement means comprising temperature-sensitive resistance means, said flow rate measurement means comprising means for generating a substantially unidirectional magnetic field across said rectangular section of said conduit, a pair of planar electrodes mounted in said rectangular section of the conduit to extend parallel to said magnetic field and to a wall of said rectangular section, means to supply current through the temperature-sensitive resistance means that is proportional to the voltage induced between said electrodes.

Claim 11

A heat meter comprising conduit means of circular cross section having a measurement section of rectanuglar cross section arranged to convey fluid, means arranged to obtain a measurement representative of rate of flow of fluid in said conduit means, means arranged to obtain a measurement representative of difference in temperature of the fluid between two spaced locations within said conduit means, and means arranged to apply as an input signal to said temperature difference measurement means a signal that is representative of the output signal of said flow rate measurement means, whereby an output signal obtained from said temperature difference measurement means is representative of the amount of heat exchanged with the fluid between said two spaced locations, said temperature measurement means comprising temperature-sensitive resistance means, said flow rate measurement means comprising means for generating a substantially unidirectional magnetic field across said rectangular section of said conduit, a pair of planar electrodes mounted in said rectangular section of the conduit to extend parallel to said magnetic field and to a wall of said rectangular section, means to supply current through the temperature-sensitive resistance means that is proportional to the voltage induced between said electrodes.

Claim 12

A heat meter according to claim 8, comprising means arranged to energise the magnetic field intermittently.

Claim 13

A heat meter according to claim 8, wherein said temperature-sensitive resistance means is arranged to form part of a Wheatstone Bridge circuit, and wherein a signal representative of the output of said bridge circuit is supplied to display means, thereby to display the thermal power exchanged with the fluid between said spaced locations.

Claim 14

A heat meter according to claim 8, wherein said temperature-sensitive resistance means comprises two platinum film sensors arranged in a Wheatstone bridge circuit.