GB2034052A

GB2034052A - Fluid flow Transducer

Info

Publication number: GB2034052A
Application number: GB7936853A
Authority: GB
Original assignee: HPE SUPPLIES Ltd
Current assignee: HPE SUPPLIES Ltd
Priority date: 1978-10-25
Filing date: 1979-10-24
Publication date: 1980-05-29

Abstract

A transducer for measuring and monitoring fluid flow in a fluid circuit comprises a strain gauge sensor having an element located in the fluid circuit to monitor the fluid flow through the circuit, the element being such that impingement of the fluid flow produces a stress which results in changes of the electrical resistance of the element, said sensor being connected to one arm of a Wheatstone bridge in an electronic circuit. An unbalanced output signal from the bridge circuit provides a signal proportional to the fluid flow rate or flow rate changes and may be used to actuate a fluid flow metering device. An annulus may be used for flow constriction.

Description

SPECIFICATION Transducer Units for Measuring and Monitoring Fluid Flow This invention relates to transducer units for measuring and monitoring fluid flow.

More specifically the invention provides for transducer units for measuring and monitoring fluid flow rates in a fluid circuit particularly but not exclusively fluid circuits of a central heating or hot water supply system.

Transducers according to the invention provide a means for measuring fluid flow rates through pipes in a fluid circuit either in actual values for the purpose of measuring or displaying the flow rates, or as a means for determining changes in flow rate over a fixed range for the purposes of control or monitoring such changes.

Transducer units according to the invention have a particular application to monitor flow rate changes for use in determining calorific value of the fluid passing through the fluid circuit as the input to a heat meter.

According to the invention a transducer unit for measuring and monitoring fluid flow through pipes in a fluid circuit comprises a strain gauge sensor locatable in a pipe length of a fluid circuit and connected to one arm of an electronic bridge circuit, the resultant unbalance bridge voltage being fed to an output circuit to provide a signal which represents the fluid flow rate through the fluid circuit.

The strain gauge sensor may be in the form of a thin wire strain gauge element locatable diametrically of the pipe length so that the flow of fluid through the pipe length impinges on the element, the element being so constructed that impingement of the fluid flow produces a change in the electrical resistance of the element.

The strain gauge sensor may be in the form of a flexible carrier located within the pipe length and extending radially inwardly from a wall of the pipe length and connected to a sensor element externally of the pipe length.

The strain gauge sensor may be in the form of an annulus locatable in the pipe length to form a reduced diameter and a pressure element locatable on the downstream side of the annulus which responds to changes in pressure which changes are related to fluid flow rate through the pipe length.

Preferred embodiments of the invention are illustrated by way of example in the accompanying drawings in which: Fig. 1 is a diagrammatic illustration of a transducer unit according to the invention located in a pipe length; Fig. 2 is a diagrammatic illustration of a modified version of the transducer of Fig. 1; Fig. 3 is a diagrammatic illustration of a further embodiment of the transducer of the invention; and Fig. 4 is a schematic diagram of an electronic circuit for transducers according to the invention.

Referrring to Fig. 1 of the drawings a transducer unit for measuring and monitoring fluid flow through a pipe length in a fluid circuit comprises a strain gauge element 1 consisting of a thin wire strain gauge locatable in a pipe length 2 of a fluid circuit through which fluid flows. The element 1 extends diagonally across the pipe length 2 so that the flow of fluid through the pipe length impinges on the element. The element 1 is so constructed that changes in stress applied to the element produces changes in the electrical resistance of the element.

Sensor leads 3 connected to each end of the element 1 pass through or are connected to fluid tight connectors 4 on the walls of the pipe length 2. The sensor leads 3 are connected to one arm of a Wheatstone bridge 5 in an electronic circuit indicated generally at 6. Fig. 2 shows a modified side entry transducer unit in which a strain gauge sensor element 8 located externally of the pipe length and attached to a flexible carrier 9 located in the fluid flow within the pipe length 2. The flexible carrier 9 extends radially inwardly from a wall of the pipe length 2 and the ends of the sensor element are connected by leads 3 to an arm of the Wheatstone bridge 5 in the electronic circuit 6. Fluid flow through the pipe length produces a deflection of the carrier 9 and hence a strain on the sensor element 8 resulting in a change in the electrical resistance of the sensor element.

Fig. 3 shows a further embodiment in which a transducer unit comprises an annulus 11 of reduced diameter locatable in a pipe length 2 and a pressure pad 12, locatable downstream of and adjacent to the annulus 11, is provided with a strain gauge element which reacts to pressure on the pad to produce an electrical change in the strain gauge element. The strain gauge element is connected by leads 3 to an arm of the Wheatstone bridge 5 in the electronic circuit 6.

The electronic circuit 6 is schematically shown in Fig. 4 in which the resistance 14 represents the electrical resistance of one of the transducer of Figs. 1 to 3 which is connected to an arm of a Wheatstone bridge circuit 5. An unbalanced signal from the bridge circuit is fed through an amplifier stage 16 to an output circuit 17, the output of which is arranged to provide a signal proportional to the fluid flow rate or flow rate changes through the pipe length 2. The output from the output circuit 1 7 may be used to actuate a metering device to measure or monitor fluid flow or fluid flow changes through the pipe length 2 or to actuate a digital or other display device to register the fluid flow or fluid flow changes in the pipe length.

The pipe length 2 may be constituted by a section of pipe in a fluid flow system or the pipe length may be connectable to a pipe in a fluid flow system.

Claims

1. A transducer unit for measuring and monitoring fluid flow through pipes in a fluid circuit comprising a strain gauge sensor locatable

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Transducer Units for Measuring and Monitoring Fluid Flow This invention relates to transducer units for measuring and monitoring fluid flow. More specifically the invention provides for transducer units for measuring and monitoring fluid flow rates in a fluid circuit particularly but not exclusively fluid circuits of a central heating or hot water supply system. Transducers according to the invention provide a means for measuring fluid flow rates through pipes in a fluid circuit either in actual values for the purpose of measuring or displaying the flow rates, or as a means for determining changes in flow rate over a fixed range for the purposes of control or monitoring such changes. Transducer units according to the invention have a particular application to monitor flow rate changes for use in determining calorific value of the fluid passing through the fluid circuit as the input to a heat meter. According to the invention a transducer unit for measuring and monitoring fluid flow through pipes in a fluid circuit comprises a strain gauge sensor locatable in a pipe length of a fluid circuit and connected to one arm of an electronic bridge circuit, the resultant unbalance bridge voltage being fed to an output circuit to provide a signal which represents the fluid flow rate through the fluid circuit. The strain gauge sensor may be in the form of a thin wire strain gauge element locatable diametrically of the pipe length so that the flow of fluid through the pipe length impinges on the element, the element being so constructed that impingement of the fluid flow produces a change in the electrical resistance of the element. The strain gauge sensor may be in the form of a flexible carrier located within the pipe length and extending radially inwardly from a wall of the pipe length and connected to a sensor element externally of the pipe length. The strain gauge sensor may be in the form of an annulus locatable in the pipe length to form a reduced diameter and a pressure element locatable on the downstream side of the annulus which responds to changes in pressure which changes are related to fluid flow rate through the pipe length. Preferred embodiments of the invention are illustrated by way of example in the accompanying drawings in which: Fig. 1 is a diagrammatic illustration of a transducer unit according to the invention located in a pipe length; Fig. 2 is a diagrammatic illustration of a modified version of the transducer of Fig. 1; Fig. 3 is a diagrammatic illustration of a further embodiment of the transducer of the invention; and Fig. 4 is a schematic diagram of an electronic circuit for transducers according to the invention. Referrring to Fig. 1 of the drawings a transducer unit for measuring and monitoring fluid flow through a pipe length in a fluid circuit comprises a strain gauge element 1 consisting of a thin wire strain gauge locatable in a pipe length 2 of a fluid circuit through which fluid flows. The element 1 extends diagonally across the pipe length 2 so that the flow of fluid through the pipe length impinges on the element. The element 1 is so constructed that changes in stress applied to the element produces changes in the electrical resistance of the element. Sensor leads 3 connected to each end of the element 1 pass through or are connected to fluid tight connectors 4 on the walls of the pipe length 2. The sensor leads 3 are connected to one arm of a Wheatstone bridge 5 in an electronic circuit indicated generally at 6. Fig. 2 shows a modified side entry transducer unit in which a strain gauge sensor element 8 located externally of the pipe length and attached to a flexible carrier 9 located in the fluid flow within the pipe length 2. The flexible carrier 9 extends radially inwardly from a wall of the pipe length 2 and the ends of the sensor element are connected by leads 3 to an arm of the Wheatstone bridge 5 in the electronic circuit 6. Fluid flow through the pipe length produces a deflection of the carrier 9 and hence a strain on the sensor element 8 resulting in a change in the electrical resistance of the sensor element. Fig. 3 shows a further embodiment in which a transducer unit comprises an annulus 11 of reduced diameter locatable in a pipe length 2 and a pressure pad 12, locatable downstream of and adjacent to the annulus 11, is provided with a strain gauge element which reacts to pressure on the pad to produce an electrical change in the strain gauge element. The strain gauge element is connected by leads 3 to an arm of the Wheatstone bridge 5 in the electronic circuit 6. The electronic circuit 6 is schematically shown in Fig. 4 in which the resistance 14 represents the electrical resistance of one of the transducer of Figs. 1 to 3 which is connected to an arm of a Wheatstone bridge circuit 5. An unbalanced signal from the bridge circuit is fed through an amplifier stage 16 to an output circuit 17, the output of which is arranged to provide a signal proportional to the fluid flow rate or flow rate changes through the pipe length 2. The output from the output circuit 1 7 may be used to actuate a metering device to measure or monitor fluid flow or fluid flow changes through the pipe length 2 or to actuate a digital or other display device to register the fluid flow or fluid flow changes in the pipe length. The pipe length 2 may be constituted by a section of pipe in a fluid flow system or the pipe length may be connectable to a pipe in a fluid flow system. Claims

1. A transducer unit for measuring and monitoring fluid flow through pipes in a fluid circuit comprising a strain gauge sensor locatable in a pipe length of a fluid circuit and connected to one arm of an electronic bridge circuit, the resultant unbalance bridge voltage being fed to an output circuit to provide a signal which represents the fluid flow rate through the fluid circuit.

2. A transducer unit as claimed in claim 1 in which the strain gauge sensor comprises a thin wire strain gauge element locatable diametrically of the pipe length so that the flow of fluid through the pipe length impinges on the element, the element being so constructed that impingement of the fluid flow produces a change in the electrical resistance of the element.

3. A transducer unit as claimed in claim 1 in which the strain gauge sensor comprises a sensor element locatable on the side of the pipe length and a flexible carrier extending radially inwardly from a wall of the pipe length and connected to the sensor element, the sensor element being connected to one arm of a Wheatstone bridge.

4. A transducer unit as claimed in claim 1 in which the strain gauge sensor comprises an annulus of reduced diameter locatable in the pipe length and a pressure pad locatable within the pipe length downstream of and adjacent to the annulus, said pressure pad being provided with a strain gauge element which reacts to pressure on the pad to produce an electrical change in the strain gauge element.

5. A transducer unit as claimed in any of the preceding claims in which the electronic bridge circuit includes a Wheatstone bridge one arm of which is formed by the electrical resistance of the transducer to provide an unbalanced signal which is fed to an amplifier in an output circuit.

6. A transducer unit for measuring and monitoring fluid flow through a fluid circuit substantially as hereinbefore described with reference to the accompanying drawings.