GB2107455A

GB2107455A - Apparatus for contactless measurement of temperature

Info

Publication number: GB2107455A
Application number: GB08222313A
Authority: GB
Inventors: Franz Engel; Siegfried Riedel; Norbert Kuntke
Original assignee: WEINERT E MESSGERAETEWERK
Current assignee: WEINERT E MESSGERAETEWERK
Priority date: 1981-08-04
Filing date: 1982-08-03
Publication date: 1983-04-27
Also published as: BG47902A1; RO85527B; CS248273B1; FR2511150B1; HU186549B; RO85527A; DD219068A3; DE3226145C2; CS570682A1; DE3226145A1; FR2511150A1; GB2107455B

Abstract

An apparatus for the contactless measurement of temperature comprising a blackened cavity formed by a metallic tube (2) which is enclosed within a pyrometer housing (1) with an air cushion (12) therebetween. The tube (2) is connected to the housing (1) by a means which serves to thermally isolate the cavity from the housing. This means can be, for example, a region (5) of thinner cross section or a region of thermal insulation material between the tube and the housing. A slot (6) extends into the tube and contains a reflecting chopper (7). One end of the tube (2) contains a detector (4). Disposed opposite the detector (4) is an infrared optical system such as a lens (3). A temperature sensor (8) is arranged in the cavity in good thermal contact therewith. <IMAGE>

Description

SPECIFICATION Apparatus for the contactless measurement of temperature The invention relates to an apparatus for the contactless measurement of temperature based on radiation pyrometry.

Pyrometers for portable and stationary use are known by which it is possible to obtain a usable measurement of temperature only after equilization of the housing temperature and the ambient temperature, that is to say, with stable temperature conditions in the measuring apparatus. (Lit.: publications by the firm Ahl bo, n, AGA, Wahl and Mawitherm).

Furthermore, portable and stationary variable radiation pyrometers are known which use bolometers, photoelectric reflectors and thermopiles as radiation receivers. In these kinds of pyrometers, it is necessary to compensate for the ambient temperature dependence of the sensitivity of the radiation receiver, whereby relatively long compensation operations also have to be accepted. (Lit.: publications by the firms Heimann, Williamson Corp).

Solutions are also known which use a thermostatically controlled reference radiator and/or a thermostatically controlled radiation receiver. This also involves a relatively long running-in time for the thermostat after the apparatus has been switched on until the desired temperature of the thermostat has been reached and stabilized. (Lit.: publications by the firms Heimann GmbH, Banes Eng./Corp. and NPO Thermopribor Lwow).

The pyrometers known hitherto and having pyroelectrical radiation receivers also require compensation for the change in the sensitivity of the radiation receiver in dependence upon the ambient temperature and still have an unjustifiably long running-in time. (Lit.: publication by the firm Land Pyrometers Ltd.).

An object of the present invention is to obviate the above-mentioned disadvantages of the known arrangements.

In accordance with the present invention, there is provided an apparatus for the contactless measurement of temperature comprising a pyrometer housing, an enclosed blackened cavity disposed within the pyrometer housing such that an air cushion is located between the pyrometer housing and the cavity means serving to provide thermal isolation of the cavity from the housing at a location of mechanical connection between the two, a slot disposed in the cavity for receiving a reflecting chopper, an optics holder which includes an infrared optical system and which is rigidly connected to the cavity so as to close an object end of the cavity, the end of the cavity opposite said object end being defined by a detector, and a temperature sensor disposed in good thermal contact with the cavity and in the direction of sight of the detector.

The useful effect of the present invention chiefly resides in the fact that the measurement of temperature is affected to only a small extent by varying ambient temperatures. This is particularly important in the case of portable pyrometers which are used in different locations. The use of the invention renders it possible for the apparatus to be ready for immediate use in the required manner after it has been switched on, without first having to wait for thermal equilization. Furthermore, the residual additional error during measurement is substantially less than that in comparable known arrangements.

Thus, an apparatus is provided for the contactless measurement, under varying ambient temperatures, of the temperatures of test objects having temperatures which, in particular, can be in the vicinity of the ambient temperatures, the apparatus being immediately ready for use, and the error caused by the ambient temperature being almost negligible.

The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 shows one embodiment of an apparatus in accordance with the invention; and Figure 2 shows an alternative possibility for obtaining high heat-transfer resistance.

With reference to Figure 1, an enclosed and blackened cavity 2, formed preferably by a tube, is provided within a pyrometer housing 1 so as to be separated from the later over substantially the whole of its area by an air cushion 12. The object side of the cavity 2 is closed by an infrared optical optical system, such as a lens 3 in a holder 10.

A detector 4 is located opposite to the lens 3. A groove 5 for reducing the cross section of the material is provided in the tube 2 directly beyond the point of connection between the pyrometer housing 1 and the tube 2. The tube 2 has an obliquely disposed slot 6 for receiving a reflector chopper 7. A temperature sensor 8 in good thermal contact with the tube is disposed in the direction of sight of the detector 4. The radiation from the optics holder 10 rigidly connected to the pyrometer housing 1 and to the tube 2 outside the housing 1 is prevented from impinging on the detector4 by diaphragms 9 located in the cavity 2.

Figure 2 shows an embodiment of the apparatus in accordance with the invention in which thermally insulating material 11 is used, whereby a high heat-transfer resistance relative to the housing 1 is also obtained.

The effect of a varying ambient temperature on the measurement result is reduced by the arrangement of the cavity 2 with its low heat-transfer resistance relative to the pyrometer housing 1. The chopper 5 moves in the slot 6 of the cavity 2 and, when the object radiation is masked, reflects the radiation of the cavity, detected by the temperature sensor 8, onto the detector 4. The radiation of the cavity serves as reference radiation. Variations are detected by means of the temperature sensor 8 and are compensated for by, for example, an electronic circuit.

Advantageously, a pyroelectrical lithium niobate detector is used whose radiant sensitivity has so low a dependence upon the ambient temperature that it can be ignored.

1. An apparatus for the contactless measure

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for the contactless measurement of temperature The invention relates to an apparatus for the contactless measurement of temperature based on radiation pyrometry. Pyrometers for portable and stationary use are known by which it is possible to obtain a usable measurement of temperature only after equilization of the housing temperature and the ambient temperature, that is to say, with stable temperature conditions in the measuring apparatus. (Lit.: publications by the firm Ahl bo, n, AGA, Wahl and Mawitherm). Furthermore, portable and stationary variable radiation pyrometers are known which use bolometers, photoelectric reflectors and thermopiles as radiation receivers. In these kinds of pyrometers, it is necessary to compensate for the ambient temperature dependence of the sensitivity of the radiation receiver, whereby relatively long compensation operations also have to be accepted. (Lit.: publications by the firms Heimann, Williamson Corp). Solutions are also known which use a thermostatically controlled reference radiator and/or a thermostatically controlled radiation receiver. This also involves a relatively long running-in time for the thermostat after the apparatus has been switched on until the desired temperature of the thermostat has been reached and stabilized. (Lit.: publications by the firms Heimann GmbH, Banes Eng./Corp. and NPO Thermopribor Lwow). The pyrometers known hitherto and having pyroelectrical radiation receivers also require compensation for the change in the sensitivity of the radiation receiver in dependence upon the ambient temperature and still have an unjustifiably long running-in time. (Lit.: publication by the firm Land Pyrometers Ltd.). An object of the present invention is to obviate the above-mentioned disadvantages of the known arrangements. In accordance with the present invention, there is provided an apparatus for the contactless measurement of temperature comprising a pyrometer housing, an enclosed blackened cavity disposed within the pyrometer housing such that an air cushion is located between the pyrometer housing and the cavity means serving to provide thermal isolation of the cavity from the housing at a location of mechanical connection between the two, a slot disposed in the cavity for receiving a reflecting chopper, an optics holder which includes an infrared optical system and which is rigidly connected to the cavity so as to close an object end of the cavity, the end of the cavity opposite said object end being defined by a detector, and a temperature sensor disposed in good thermal contact with the cavity and in the direction of sight of the detector. The useful effect of the present invention chiefly resides in the fact that the measurement of temperature is affected to only a small extent by varying ambient temperatures. This is particularly important in the case of portable pyrometers which are used in different locations. The use of the invention renders it possible for the apparatus to be ready for immediate use in the required manner after it has been switched on, without first having to wait for thermal equilization. Furthermore, the residual additional error during measurement is substantially less than that in comparable known arrangements. Thus, an apparatus is provided for the contactless measurement, under varying ambient temperatures, of the temperatures of test objects having temperatures which, in particular, can be in the vicinity of the ambient temperatures, the apparatus being immediately ready for use, and the error caused by the ambient temperature being almost negligible. The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 shows one embodiment of an apparatus in accordance with the invention; and Figure 2 shows an alternative possibility for obtaining high heat-transfer resistance. With reference to Figure 1, an enclosed and blackened cavity 2, formed preferably by a tube, is provided within a pyrometer housing 1 so as to be separated from the later over substantially the whole of its area by an air cushion 12. The object side of the cavity 2 is closed by an infrared optical optical system, such as a lens 3 in a holder 10. A detector 4 is located opposite to the lens 3. A groove 5 for reducing the cross section of the material is provided in the tube 2 directly beyond the point of connection between the pyrometer housing 1 and the tube 2. The tube 2 has an obliquely disposed slot 6 for receiving a reflector chopper 7. A temperature sensor 8 in good thermal contact with the tube is disposed in the direction of sight of the detector 4. The radiation from the optics holder 10 rigidly connected to the pyrometer housing 1 and to the tube 2 outside the housing 1 is prevented from impinging on the detector4 by diaphragms 9 located in the cavity 2. Figure 2 shows an embodiment of the apparatus in accordance with the invention in which thermally insulating material 11 is used, whereby a high heat-transfer resistance relative to the housing 1 is also obtained. The effect of a varying ambient temperature on the measurement result is reduced by the arrangement of the cavity 2 with its low heat-transfer resistance relative to the pyrometer housing 1. The chopper 5 moves in the slot 6 of the cavity 2 and, when the object radiation is masked, reflects the radiation of the cavity, detected by the temperature sensor 8, onto the detector 4. The radiation of the cavity serves as reference radiation. Variations are detected by means of the temperature sensor 8 and are compensated for by, for example, an electronic circuit. Advantageously, a pyroelectrical lithium niobate detector is used whose radiant sensitivity has so low a dependence upon the ambient temperature that it can be ignored. CLAIMS

1. An apparatus for the contactless measure ment of temperature comprising a pyrometer housing, an enclosed blackened cavity disposed within the pyrometer housing such that an air cushion is located between the pyrometer housing and the cavity, means serving to provide thermal isolation of the cavity from the housing at a location of mechanical connection between the two, a slot disposed in the cavity for receiving a reflecting chopper, an optics holder which includes an infrared optical system and which, is rigidly connected to the cavity so as to close an object end of the cavity, the end of the cavity opposite said object end being defined by a detector, and a temperature sensor disposed in good thermal contact with the cavity and in the direction of sight of the detector.

2. An apparatus as claimed in claim 1, wherein the cavity is defined by a tube connected to the housing and said thermal insulation means is provided by a portion of reduced cross section in the tube in the region where the tube is joined to the housing.

3. An apparatus as claimed in claim 2, wherein said portion of reduced diameter is formed by a groove in the wall of the tube.

4. An apparatus as claimed in claim 1, wherein the cavity is defined by a tube mounted in the housing and said thermal insulation means is provided by thermal insulation material disposed in the connection between the tube and the housing.

5. An apparatus as claimed in any of claims 2 to 4, wherein the tube is metallic.

6. An apparatus as claimed in any of claims 1 to 5, wherein the detector is of the pyroelectrical lithium niobate type.

7. An apparatus for the contactless measurement of temperature, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.