GB2124760A - Temperature of elongate articles - Google Patents
Temperature of elongate articles Download PDFInfo
- Publication number
- GB2124760A GB2124760A GB08321179A GB8321179A GB2124760A GB 2124760 A GB2124760 A GB 2124760A GB 08321179 A GB08321179 A GB 08321179A GB 8321179 A GB8321179 A GB 8321179A GB 2124760 A GB2124760 A GB 2124760A
- Authority
- GB
- United Kingdom
- Prior art keywords
- article
- detector
- light source
- light
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K5/00—Measuring temperature based on the expansion or contraction of a material
- G01K5/48—Measuring temperature based on the expansion or contraction of a material the material being a solid
- G01K5/50—Measuring temperature based on the expansion or contraction of a material the material being a solid arranged for free expansion or contraction
- G01K5/52—Measuring temperature based on the expansion or contraction of a material the material being a solid arranged for free expansion or contraction with electrical conversion means for final indication
Abstract
For determining the temperature or change of temperature of an elongate article (25) such as a strip or wire, particularly a linearly moving article, measurement is made of the amount or change in amount of light incident on a first photodetector (27) from a collimated or uniform light beam (24) through which the article extends. A reference photodetector (33) receives light directly from the light source (20) and the output is fed back to the light source (20). The outputs of the two photodetectors (27,33) are compared in voltage comparator (29) and the resulting output indicated (37) and recorded (36). The technique permits measurement despite transverse movement or vibration of the article. <IMAGE>
Description
SPECIFICATION
Temperature measurement of elongate articles
This invention relates to the measurement of temperature or change of temperature of an elongate article such as for example a wire or strip and has particular application although not exclusively relating to the temperature measurement of such articles when moving in the axial direction.
The measurement of the temperature of a thin wire moving at high speed has long been a problem.
Such a wire vibrates in directions transverse to its axis. Techniques have been employed which involve determining the wire temperature from the total power input to a heating device heating the wire and the measurement of physical parameters of samples of the wire. Techniques from which the thermal radiation from the wire is monitored suffer from problems if the emissivity of the wire changes or if the distance of the wire from the radiant energy monitor should vary or if the temperature rise to the wire is small.
According to one aspect of the present invention, a method of determining the temperature or change of temperature of an elongate article comprises passing the article between a light source and a first photodetector giving an electrical output signal proportional to or related to the amount of light impinging on it, the light source and detector being so arranged that the amount of light falling on the detector is dependent on the width of the article in the direction transverse to its lengthwise direction, sensing the radiation from the light source with a second photodetector and using a difference signal from the two detectors as a measure of the temperature of said article.
The use of two detectors and a difference signal enables a very high sensitivity to be obtained; if the signals at the two detectors are equal or nearly equal, a small change in one signal give a proportionally much larger change in the difference signal.
In some cases, it may be preferred to utilise a
reference article, for comparison purposes, between the light source and second detector; this enables similar or matched conditions to be employed in the two optical paths.
Because of thermal expansion, the amount of light falling on the detector will decrease as the temperature of the article rises and the detector output can
be calibrated, for any given article, in terms of temperature. Such an arrangement may readily be made insensitive to the effect of transverse vibration
or movement of the article. In a simple arrangement, the light beam between the light source and first
detector may be collimated and made wider than the
dimension of the article being determined so that the
article will remain in the beam irrespective of
movement of the article in this direction and of
movement of the article in the direction from the
light source to the detector or vice versa.It will be
appreciated that the width of the beam will have to
be such as to allow for any possible amplitude of
movement of the article but this is readily achieved
in practice. Provided the collimated beam is of uniform flux density and provided the first detector has a planar detecting surface normal to the beam, vibratory movement of the article transverse to its length will not affect the amount by which the beam is obscured by the article. Diffraction of light around the edge of the article does not significantly affect the determination since the detector effectively sums all the light which is not obscured by the article. Provided the first detector has a linear response, the spatial variations of light intensity due to diffraction are immaterial.
An arrangement employing a collimated light beam in this way is thus particularly suitable for the measurement of temperature of a thin wire. In the manufacture of treatment of wire, often the wire is moved at high speed through for example treatment apparatus such as heat treatment apparatus. The technique described enables the temperature of such a moving wire to be determined without contact with the wire.
Although the use of a collimated light beam provides a convenient way of obtaining an output which is independent of vibration of other transverse movement of the article, other arrangements of light source and first detector may be employed. In one convenient arrangement, a linear light source (e.g. a fluorescent strip lamp) is employed having a sub stantiaily uniform light emission per unit length, with the light source arranged parallel to a planar photodetector constituting the aforesaid first detector, the article passing between the light source and planar photodetector with a direction of movement generally parallel to the surface of the planar photodetector and transverse to the length of the light source, the light source having a length and the planar photodetector having a dimension parallel to the light source which is greater than the width of the article between them and which is uniform and the light source and the planar photodetector each having, in a direction parallel to the length of the article, a uniform dimension.The light source may be relatively narrow compared with the dimensions of the first detector measured in the lengthwise direction of the article. It will be immediatelyappa- rent that, with such an arrangement, movement of the article either parallel to the length of the light source or in the direction from the light source to the first detector will not significantly affect the obscuration of the light on that detector. The amount of detected light will therefore depend on the width of the article measured parallel to the length of the light source and hence will depend on the temperature of the article. Such an arrangement is particularly convenient for measuring relatively wide articles such as metal strip.
It is preferred to provide means, e.g. guides or rollers, to steady the article as it passes through the light beam, to prevent movement in the direction
between the light source and first detector.
The two detectors may be two separate detectors or two parts of a split detector.
The light beam may be modulated, e.g. chopped, and the resultant detector signal at the modulation frequency may be utilised as a measure of the light obscuration at the detector. Such modulation of the light removes or substantially reduces the problem of photon radiation from the wire at high temperatures which radiation may cause an increase in the d.c. level of the signal at the detector and hence a lowering of the apparent temperature.
The size of the article, e.g. the diameter of the wire, when the article is at a known temperature, e.g.
before or after the wire leaves a heater, may be monitored. Knowing the velocity of movement of the article, any variation in size detected by the monitor may be utilized to correct for the datum size at the point of temperature measurement.
According to another aspect of the invention, apparatus for measurement of the temperature of an elongate article comprises a light source, first and second photodetectors, a light source, means for passing the article between the light source and the first detector, the light source and first detector being arranged so that the obscuration of the first detector by the article is proportional to a linear transverse dimension of the article, the second detector being arranged to receive radiation from the light source to provide a reference signal, and means sensing the difference of electrical output signals from the two detectors. The first detector is preferably a planar detector. As previously explained, collimated light may be employed for example by providing a beam collimator.Alternatively an elongate light source may be utilised having a lengthwise direction transverse to the axis of the article extending across the dimension to be measured and lying parallel to the plane of the detector, the light source being longer in its lengthwise direction and the width of the first detector in this direction being greater than the dimension of the article to be measured and the light source and the first detector furthermore each having substantially uniform dimensions in the direction of the axis of the article.
Although reference has been made more particu
larly to the measurement of the temperature of wire or strip it is more generally applicable to other components, e.g. glass fibres, rod, bar, tubing etc, enabling non-contact temperature measurement to
be made, even if the article is moving at high speed.
In the following description, reference will be
made to the accompanying drawings in which:
Figure 1 is a diagram for explaining the principles of the invention;
Figure2 is a diagram illustrating one embodiment of the invention for measuring the temperature of a wire;
Figure 3 illustrates a modification of the apparatus
of Figure 2; and
Figures 4 and 5are plan and elevation diagrams
illustrating an apparatus for measuring the temperature of a strip.
Referring to Figure 1,there is shown diagrammatically a wire 10 which typically may be moving at
high speed, for example out of heat treatment
apparatus, the movement being in the axial direction
of the wire. Such a wire in practice will vibrate with
components of vibration in two transverse directions
as shown by the arrows 11, 12. The present invention may be used for the measurement of the temperature of such a wire and for this purpose, in one form, employs a uniform parallel light beam indicated diagrammatically by the arrows 13 this light beam being normal to the axis of the wire and normal to the plane of a photosensitive detector 14.
The wire will produce a shadow shown at 15 across the detector 14. This shadow will move up and down across the detector as indicated by the arrows 16.
The beam of light is of uniform cross-sectional intensity. The detector is a photovoltaic detector of the kind utilised as a position sensor. Such a detector has a rectangular photosensitive region with electrodes along each of the four sides. For the present purpose, these electrodes are connected together to give a single voltage output representative of the total light flux incident on the data at the surface.
Such detectors have a substantially uniform sensitivity over the detecting surface and hence the voltage output is linearly related to the amount of light impinging on the detector screen irrespective of movement of the wire transverse to its axis and parallel to the plane of the detector. Movement of the wire normal to the plane of the detector will not affect the size of the shadow since the incident light is a parallel beam. Thus the detector can provide an output signal which is a function of the wire diameter and hence a function of temperature.
In practice, photodetectors of adequate sensitivity are readily obtainable and typically, for a 0.5 mm diameter aluminium wire it is possible to obtain an output sensitivity of approximately 0.32 mV/ C over a temperature range of 0 to 150 C.
Referring to Figure 2, an apparatus for measuring temperature in this way is shown in further detail. A light source 20 energised from a controllable power supply 21 with a main input 22 produces light passing through a lens system indicated diagrammatically at 23 to produce a parallel beam of light indicated at 24. This lens system 23 typically comprises a condenser lens and a collimator system comprising further lenses. Alternatively an optical integrator may be employed. A wire whose diameter is to be measured is shown at 25, the wire having its axis normal to the plane of paper. The shadow of the wire falls on a photovoltaic detector 27. It will be noted that the width of the beam (transverse to axis of the wire) is several times greater than the width of the wire, typically 5 to 10 times.The detector also
has a width (transverse to the axis of the wire) greater than the width of the wire. The detector is of
rectangular form to have a uniform dimension
parallel to the axis of the wire. This ensures that
movement of the wire in the vertical direction in
Figure 2 does not change the effective area of the detector obscured by the shadow. The light source in this arrangement produces a collimated beam which, in all directions transverse to the axis of the
beam, has dimensions larger than the area of the
detector so that, in the absence of the wire, the whole surface area of the detector is illuminated. The
electrical output of the detector 27 is passed to a
buffer amplifier 28 and thence to one input of a
differential amplifier 29. The second input of the
differential amplifier is a reference signal dependent
on the light emission from the light source 20. In this particular embodiment, the parallel light beam 24, before reaching the wire 25, is passed through a prism 30 acting as a partial reflector and so constituting a beam splitter. This provides a reference beam 31, which for convenience is turned through 90 by a further prism 32 before impinging on a photodetector 33 feeding an adjustable gain amplifier 34. This amplifier can be adjusted to provide the required balancing input to the differential amplifier 29 and also to provide feedback control 35 for the power supply 21.
The output from the differential amplifier 29 provides a signal for a recorder 36 and/or an indicator 37. It will be appreciated that the recorder and/or indicator can be calibrated to measure the actual diameter of the wire or the change from a reference value.
Referring to Figure 3, there is shown a modification of the apparatus of Figure 2. In Figure 3, the light source, indicated at 40, is modulated by a modulator 41. Conveniently the light output is chopped at a constant frequency to produce a series of pulse signals. The light is converted into a parallel beam 42 by a condenser lens 43 and collimating lens 43,44 before reaching a photosensitive detector 45. The shadow of the wire 46 to be measured falls on this detector. The electrical output from detector 45 is applied to two separate amplifiers 47,48 controlled by the switching signal for modulator 41 to produce respectively signals corresponding to the detector output during the light pulse and in the absence of the light pulse. The latter signal is representative of the d.c. level of output due to any high temperature photon radiation from the wire.This can be subtracted from the output during the light pulses by means of a difference amplifier 49 to provide a corrected signal representative of the obscuration of the detector.
In Figure 3, the feedback control for the light source is indicated diagrammatically by partial reflector 50 in the light beam providing a reference beam to a reference detector 51 feeding a feedback control 52 for the light source 40. The feedback control 52 provides a balancing signal for the output from amplifier 49, shown, for simplicity, as being applied to a further differential amplifier 53. The reference signal output in each of the abovedescribed embodiments is combined with the output from the detector detecting variations in width of the wire as a backing-off signal in order to increase the overall sensitivity of the system and to reduce the noise level on the output. It will be appreciated that any light intensity variation in the two halves of the split beam will be similar and this arrangement enables their effect to be eliminated or substantially eliminated.
For measuring the temperature of a relatively wide object, such as a metal strip, it is convenient to use an elongate light source, as shown in Figures 4 and
5, and to steady the article to limit any movement in the direction towards and away from the detector.
Referring to Figure 4, a metal strip 60 passes over guide rollers 61 and, between these rollers, passes
between a light source 62 and an aperture mask 63.
Steady rollers 64 steady the strip in this region to prevent movement towards and away from a detector 65. A lens system is shown diagrammatically at 66,67. The light source 62, as seen in Figure 5, is an elongate source such as a fluorescent strip lamp 62, which extends across the lengthwise direction of the strip 60. A flat planar photodetector 65 having its surface parallel to the axis of the lamp is positioned on the opposite side of the strip and is of uniform width measured parallel to the axis of the strip and is of sufficient area that, despite vibration of the strip, gives an output which is a function of the strip width.
By the use of the steady rollers 64, it is not necessary to have a collimated or parallel beam of light. The aperture mask 63 determines the one dimension of the area of the detector subject to light or shadow.
The other dimension of the shadow will depend on the temperature of the strip and hence the changes in shadow area will be related to changes of temperature. The electrical output of the detector 65 can thus operate an indicator or recorder calibrated in terms of temperature for a strip of known width.
The output from the detector 63 is amplified by amplifier 66 and fed to one input of a differential amplifier 67. The second input is provided by a reference photodetector 68 receiving light radiation from the source 62 and feeding an adjustable gain amplifier 69 which provides not only the second input for amplifier 67 but also a feedback control signal at 70 for controlling lamp 62. The output at 71 from differential amplifier 67 is fed to a recorder or indicator as in the previously-described embodiments.
In all the above-described embodiments, the output signal may be used for control purposes, e.g. to control some process parameter which determines the width of the wire or strip.
Claims (22)
1. A method of determining the temperature or change of temperature of an elongate article comprising positioning the article between a light source and a first photodetector giving an electrical output proportional to or related to the amount of light impinging on it, the light source and detector being so arranged that the amount of light falling on the detector is dependent on the width of the article in the direction transverse to its lengthwise direction, sensing the radiation from the light source with a second photodetector and using a difference signal from the two detectors as a measure of the temperature or change of temperature of said article.
2. A method as claimed in claim 1 wherein the light beam between the light source and the first detector is collimated and made wider than the dimension of the article being determined so that the article will remain in the beam irrespective of movement of the article in this direction and of movement of the article in the direction from the light source to the first detector or vice versa.
3. A method as claimed in claim 2 wherein the collimated beam is of uniform flux density and wherein the first detector has a planar detecting surface normal to the beam.
4. A method as claimed in any of the preceding claims wherein the response of the first detector is linearly related to incident flux.
5. A method as claimed in any of the preceding claims wherein the article is an elongate article moving in its lengthwise direction between the light source and said first detector.
6. A method as claimed in claim 5 wherein the article is wire.
7. A method as claimed in claim 6 wherein the article is a rod or tube or fibre.
8. A method as claimed in claim 1 wherein the light source is a linear light source having a substantially uniform light emission per unit length and wherein the first detector is a planar photodetector, with the light source arranged parallel to the surface of the photodetector and the article passing between the light source and planar photodetector with a direction of movement generally parallel to the surface of the planar photodetector and transverse to the length of the light source, the light source having a length and the planar photodetector having a dimension parallel to the light source which is greater than the width of the article between them and which is uniform and the light source and planar photodetector each having, in a direction parallel to the length of the article, a uniform dimension.
9. A method as claimed in claim 8 wherein the light source is relatively narrow compared with the dimensions of the planar photodetector measured in the lengthwise direction of the article.
10. A method as claimed in either claim 6 or claim 9 wherein the article is a metal strip.
11. A method as claimed in any of claims 8 to 10 wherein the article is steadied to restrict movement in the direction between the light source and the planar photodetector.
12. A method as claimed in any of the preceding claims wherein the light from the light source is modulated and wherein the resultant detector signal at the modulation frequency from the first detector is utilised as a measure of the light obscuration at that detector.
13. A method as claimed in any of the preceding claims wherein the size of the article when the article is at a known temperature is monitored and wherein any variation in size detected by the monitor is utilised to correct for the datum size at the point of temperature measurement.
14. A method as claimed in any of the preceding claims wherein a reference article is positioned between the light source and the second detector.
15. Apparatus for measurement of the temperature of an elongate article comprises a light source, a planar detector and means for passing the article between the light source and the detector, the light source detector being arranged so that the obscuration of the detector by the article is proportional to a linear transverse dimension of the article.
16. Apparatus as claimed in claim 12 and including a collimator to collimate the light beam.
17. Apparatus as claimed in claim 12 wherein an elongate light source is utilised having a lengthwise direction transverse to the axis of the article extending across the dimension to be measured and lying parallel to the plane of the detector, the light source being longer in its lengthwise direction and the width of the detector in this direction being greater than the dimension to be measured and the light source and detector furthermore each having substantially uniform dimensions in the direction of the axis of the article.
18. Apparatus as claimed in claim 17 wherein means are provided to steady the article in the light beam to restrict or prevent movement in the direction between the light source and detector.
19. Apparatus as claimed in any of claims 15 to 18 and including means for modulating the light beam and means for detecting the resultant modulation in the detector output.
20. Apparatus as claimed in any of claims 15 to 19 and including means for detecting obscuration of light by a reference article to produce a reference signal for combination with the output of said detector.
21. A method of determining the temperature of an elongate article substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 or Figures 4 and 5 of the accompanying drawings.
22. An apparatus for determining the temperature of an elongate article substantially as hereinbefore described with reference to Figures 1 and 2 or
Figure 3 or Figures 4 and 5 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08321179A GB2124760B (en) | 1982-08-05 | 1983-08-05 | Temperature of elongate articles |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8222627 | 1982-08-05 | ||
| GB08321179A GB2124760B (en) | 1982-08-05 | 1983-08-05 | Temperature of elongate articles |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8321179D0 GB8321179D0 (en) | 1983-09-07 |
| GB2124760A true GB2124760A (en) | 1984-02-22 |
| GB2124760B GB2124760B (en) | 1986-02-12 |
Family
ID=26283525
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08321179A Expired GB2124760B (en) | 1982-08-05 | 1983-08-05 | Temperature of elongate articles |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2124760B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2173590A (en) * | 1985-04-12 | 1986-10-15 | Esm Int Inc | Apparatus for and a method of measuring the amount of a viewing frame filled by a product |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB979480A (en) * | 1961-11-16 | 1965-01-06 | Zeiss Stiftung | Measurement of glass tubes |
| GB1003028A (en) * | 1961-06-12 | 1965-09-02 | Licentia Gmbh | Improvements in and relating to thermally responsive devices |
| GB1100125A (en) * | 1964-02-29 | 1968-01-24 | Reiners Walter | Thread supervision device |
| GB1132128A (en) * | 1965-07-24 | 1968-10-30 | Heberlein & Co Ag | Improvements in or relating to electro-optical thread clearers |
| GB1254958A (en) * | 1968-06-21 | 1971-11-24 | Philips Electronic Associated | Checking variations in the diameter of a fibre |
| GB1430947A (en) * | 1972-07-03 | 1976-04-07 | Aga Ab | Method and apparatus for contactless measuring a dimension of a movable object |
| GB1555874A (en) * | 1976-05-05 | 1979-11-14 | Zumbach Electronic Ag | Device for measuringa least one dimensiion of an opject and a method of operating said device |
| GB2021260A (en) * | 1978-03-09 | 1979-11-28 | British Steel Corp | Optical gauging of cross- sectional dimensions |
| GB1557441A (en) * | 1976-05-10 | 1979-12-12 | Dresser Ind | Optical position sensor |
-
1983
- 1983-08-05 GB GB08321179A patent/GB2124760B/en not_active Expired
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1003028A (en) * | 1961-06-12 | 1965-09-02 | Licentia Gmbh | Improvements in and relating to thermally responsive devices |
| GB979480A (en) * | 1961-11-16 | 1965-01-06 | Zeiss Stiftung | Measurement of glass tubes |
| GB1100125A (en) * | 1964-02-29 | 1968-01-24 | Reiners Walter | Thread supervision device |
| GB1132128A (en) * | 1965-07-24 | 1968-10-30 | Heberlein & Co Ag | Improvements in or relating to electro-optical thread clearers |
| GB1254958A (en) * | 1968-06-21 | 1971-11-24 | Philips Electronic Associated | Checking variations in the diameter of a fibre |
| GB1430947A (en) * | 1972-07-03 | 1976-04-07 | Aga Ab | Method and apparatus for contactless measuring a dimension of a movable object |
| GB1555874A (en) * | 1976-05-05 | 1979-11-14 | Zumbach Electronic Ag | Device for measuringa least one dimensiion of an opject and a method of operating said device |
| GB1557441A (en) * | 1976-05-10 | 1979-12-12 | Dresser Ind | Optical position sensor |
| GB2021260A (en) * | 1978-03-09 | 1979-11-28 | British Steel Corp | Optical gauging of cross- sectional dimensions |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2173590A (en) * | 1985-04-12 | 1986-10-15 | Esm Int Inc | Apparatus for and a method of measuring the amount of a viewing frame filled by a product |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2124760B (en) | 1986-02-12 |
| GB8321179D0 (en) | 1983-09-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920805 |