GB2199954A

GB2199954A - Thermocouple array

Info

Publication number: GB2199954A
Application number: GB08728308A
Authority: GB
Inventors: Farouk Amin Assaf; Leslie Robertson; Dr David John Watmough
Original assignee: University of Aberdeen
Current assignee: University of Aberdeen
Priority date: 1986-12-04
Filing date: 1987-12-03
Publication date: 1988-07-20
Anticipated expiration: 2007-12-03
Also published as: GB8629016D0; GB8728308D0; GB2199954B

Abstract

A thermocouple arrangement comprises a base wire 1 and a plurality of junctions 3 spaced along said wire, each of said junctions being connected to a monitoring means which provides a visual indication of the temperature at each junction 3, e.g. on LED bar graph display for each junction. The base wire 1 may be placed in a PTFE tube. A heating coil 2 may be disposed along the length of the base wire 1 to assist in detection of liquid flow; flow transverse to the wire; indicated directly by the temperature measurements and for flow parallel to the wire a bubble is introduced and affects the output of the adjacent couple(s) (transit time measurement). The array of couples may also be used to indicate the output of an ultrasonic transducer, e.g. as used in hyperthermia treatment. Temperature gradients may also be assessed by the arrangement, including an assessment of time of death of a corpse. <IMAGE>

Description

MULTI POINT SENSOR The present invention relates to a multi point sensor and particularly a multi point sensor for sensing ultrasound energy output, liquid velocity or the presence or absence of bubbles in a liquid.

Thermocouples have long been available for the monitoring of temperature values. The concept however of using thermocouple arrays to measure real time ultrasound intensity profiles and hence ultrasound output from an ultrasound transducer is not comprehended in the art. Further the measurement of liquid velocity profiles in a conduit utilizing the same arrays are not known.

Referring therefore to a first aspect of the present invention there is provided a thermocouple device comprising a base wire and a plurality of junctions spaced at predetermined locations along said wire, each of said junctions being connected to a monitoring means, whereby said monitoring means provides a visual indication of the temperature at each junction. Such a thermocouple device may additionally be provided with a heating coil disposed along the length of the base wire so that the whole device may be raised to a predetermined temperature in situ.

In a preferred form of the invention the junctions having been welded rather than soldered are encapsulated with a non-toxic energy absorbing resin, such as an epoxy resin.

The monitoring means may comprise a signal amplifier, a linearizer and an electronic temperature compensator. The monitoring means preferably is provided with a light emitting diode (LED) bar graph linked to a suitable driver whereby either the LED operates in dot mode whereby a single diode is actuated in response to a given value of input signal, or the display may be operated in bar mode wherein a plurality of diodes are actuated dependent upon the strength of the input signal.

In a second aspect of the invention there is provided an ultrasound monitoring apparatus comprising a device as just described and further comprising means for securing an ultrasound transducer on an axis, means for securing a linear thermocouple array perpendicular to said axis and spaced by a predetermined distance from said transducer, said monitoring means being adapted to display the energy absorbed at each junction as a visual indication of transducer output at a predetermined distance from the axis.

In a preferred form of the invention the linear thermocouple array and the transducer are adapted to be surrounded by a suitable ultrasonic sound transmitting liquid such as water.

The invention also comprehends a method for the estimation of liquid flow in a conduit which method comprises disposing an assembly of the base wire and the heating coil as just described in a conduit, raising the temperature of the heating wire to a given value in a still liquid, and recording the observed change in visual indication on liquid flow. The base wire may be axially disposed in the conduit. In this circumstance liquid flow can be deduced by the introduction of a bubble into the liquid upstream of a thermocouple device; the time interval between linear expressions of a disturbance at successive thermocouple junctions being a measure of the time taken for the passage of a bubble over the junction.

In an alternative embodiment, the base wire is disposed perpendicular to the conduit, said base wire being provided with a heating coil to heat the thermocouple device to a predetermined temperature in a liquid contained within the conduit. The fall in temperature occurring as a function of liquid flow rate is then measured to give an indication of liquid velocity.

The thermocouples of the invention comprise therefore a base wire with a plurality of spaced junctions thereupon. If heating wire is applied thereto such an arrangement will also become an efficient bubble detector since the presence of a bubble at a junction prevents cooling by a liquid stream and hence the temperature at junction will rise. This may be observed on a bar chart or on any visual indication means.

The aspects of the present invention will now be described by way of illustration only, with reference to the accompanying drawings: Figure 1 shows a plan diagrammatic view of a ther-mocouple device according to the present invention with a heater wire in situ; Figure 2 shows a side view of a thermocouple with a junction wire, but excluding the heater wire; Figure 3 shows a diagrammatic plan view of a signal monitor; Figure 4 is a side elevation of a bar graph display for use in the present invention; Figure 5 shows a diagrammatic side elevation of an ultrasound monitoring device according to the invention; and Figure 6 shows a graph of a signal output of a device according to the present invention in bubble detection mode.

With reference to Figures 1 and 2, a base thermocouple wire 1 is provided at equally spaced intervals throughout its length with a plurality of junctions 3 which may be welded or soldered to a plurality of copper wires 4 constituting the means whereby the output signals are transferred to the monitoring means. The thermocouple wire may be a constantan wire, and the array may be positioned in a small bore biocompatible tube having, for example, a bore of lmm and being formed, for example, of polytetrafluoroethylene with a wall thickness of, for example 0.1 to 0.3mm. However, in many conduits where the liquid is not corrosive upon the thermocouple, the thermocouple may be utilized without a covering.

Each junction wire 4 is connected to its own amplifier 6 which in turn is connected to an LED display 7. The thermocouple amplifier 6 is temperature compensated by a compensator 5 acted upon by a compensator circuit input 8.

Each junction is individually connected to an arrangement shown in Figure 3. As the signal generated at the junction rises, the value of the input signal received by the thermocouple amplifier 6 also rises thereby actuating the LED display to show a higher value. Thus, with reference to Figure 4 an LED display- 9 shows a series of bar graphs 10, each bar being connected to a single junction point. It will be observed that the centre bar has 4 LEDs actuated whereas bars 1 and 7 only have one. This means that the major portion of a signal is to be found axially, or centrally, of an elongate thermocouple device.

With reference to Figure 6, the arrangement of Figures 1 and 2 can be utilized in a bubble detection mode.

As previously explained, the presence of a bubble at a thermocouple junction causes the temperature to rise locally by a marked degree. This is shown in Figure 6 where a temperature rise indicative by the presence of a bubble is shown on a temperature chart. It will be appreciated that the introduction of a single bubble into a liquid stream will also enable the bubble's velocity to be measured, and hence liquid flow velocity.

Turning now to the embodiment of Figure 5, there is provided a liquid tight enclosure 11 which may optionally contain water 12. Although the term "water" is used hereinafter, it will be appreciated that any ultrasound transmitting fluid can be used.

Thus, the enclosure 11 may be utilized without liquid (i.e. in air-based mode) if desired. By control of water bath temperature the device may be made to measure intensity in a quantitative fashion.

The enclosure 11 supports a transducer 13 under test; the transducer being aligned along an axis 14 by means of a clamping rig 18 which locates the transducer accurately on the axis 14, being secured by a nut 19.

Accurately spaced apart from the transducer 13 on the clamping rig 18 is a supporting annul us 15 disposed coaxially of the axis 14. The annulus 15 is secured by a nut 19. A base thermocouple wire 1 is disposed diametrially across the supporting anulus 15. In use the wire 1 is connected via junction wires 4 to LEDs 7 as shown in Figure 4. Actuation of the ultrasound transducer 13 causes an ultrasound flux to strike the thermocouple junctions 3 and increase their temperature. For reasons of symettry an odd number of junctions 3 is to be preferred. This causes the LED display 9 to show bar charts dependent upon the signal strength exerted by the transducer 13.

Malignant neoplasms are often treated by hyperthermia induced by ultrasound. In order to accurately position ultrasound, transducers must be operating in their correct modes and outputting a hyperthermia inducing radiation. Use of the arrangement of Figure 5 allows rapid checking of a single or an array of transducers to ensure their compliance with a predetermined treatment pattern.

The device as hereinbefore set forth may also be used to measure temperature gradients in materials such as bread, dough and other soft solids and liquids. In this case, of course, no heater is strictly necessary.

Similarly, of course, the device may be utilized to measure skin temperature in medical situations and by application of the heater may be utilized to assess blood flow in an artery or vein.

The device may also utilized to determine "time of death" of corpses by insertion of the array placed in a sheath into the body. For times of death up to a few hours earlier the gradient of temperature will be given and this provides an estimate of how long the body had been cooling.

Claims

CLAIMS:

1. A thermocouple device comprising a base wire and plurality of junctions spaced along said wire, each said junction being connected to monitoring means, whereby said monitoring means provides a visual indication of the temperature at each junction.

2. A thermocouple device according to claim 1 characterised by a heating coil disposed along the length of the base wire.

3. A thermocouple device according to claim 1 or claim 2 characterised in that the junctions are encapsulated with a non-toxic energy absorbing resin.

4. A thermocouple device according to any preceding claim characterised in that the monitoring means comprises a signal amplifier, a linearizer and an electronic temperature compensator.

5. A thermocouple device according to claim 5 including an LED bar graph.

6. An ultrasound monitoring apparatus comprising a device as claimed in claim 1 and further comprising means for securing an ultrasound transducer on an axis, means for securing a linear thermocouple array perpendicular to said axis, and spaced by a predetermined distance from said transducer, said monitoring means being adapted to display energy absorbed at each junction as a visual indication of transducer output at a distance from the axis.

7. An apparatus according to claim 6 characterised in that the transducer and the linear thermocoupler array are adapted to be surrounded by a liquid.

8. A method for the estimation of liquid flow in a conduit which method comprises disposing the base wire and heating coil of claim 2 in a conduit, raising the temperature of the heating wire to a given value in still liquid, and recording the observed change in visual indication on liquid flow.

9. A method according to claim 8 comprising disposing said base wire axially in the conduit, introducing a bubble into the liquid upstream of said thermocouple device, and measuring the time interval between the linear expressions of a disturbance at successive junctions, said disturbance being indicative of a passage of a bubble over a said junction.

10. A method according to claim 8 which comprises disposing the base wire perpendicular to the conduit, and measuring the fall in temperature due to an increase in liquid flow rate.

11. A method according to any of claims 8 to 10 which comprises utilizing a disturbance in the visual indication as indicative of bubble presence.

12. A method for monitoring ultrasound which comprises utilizing an apparatus according to claim 6.

13. A device substantially as hereinbefore set forth.

14. An ultrasound monitoring apparatus substantially as hereinbefore set forth.

15. A method for the estimation of liquid flow according to any of claims 8 to 10 and substantially as hereinbefore set forth.

16. A method for bubble detection in a closed conduit substantially as hereinbefore set forth.