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WO2011070319A1 - Temperature measuring apparatus - Google Patents

Temperature measuring apparatus

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Publication number
WO2011070319A1
WO2011070319A1 PCT/GB2010/002242 GB2010002242W WO2011070319A1 WO 2011070319 A1 WO2011070319 A1 WO 2011070319A1 GB 2010002242 W GB2010002242 W GB 2010002242W WO 2011070319 A1 WO2011070319 A1 WO 2011070319A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
temperature
sensor
shutter
object
optical
Prior art date
Application number
PCT/GB2010/002242
Other languages
French (fr)
Inventor
Timothy Kenneth Barry
Original Assignee
Calex Electronics Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00Radiation pyrometry
    • G01J5/02Details
    • G01J5/06Arrangements for eliminating effects of disturbing radiation
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00Radiation pyrometry
    • G01J5/10Radiation pyrometry using electric radiation detectors
    • G01J5/12Radiation pyrometry using electric radiation detectors using thermoelectric elements, e.g. thermocouples
    • G01J5/14Electrical features
    • G01J5/16Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00Radiation pyrometry
    • G01J5/02Details
    • G01J5/06Arrangements for eliminating effects of disturbing radiation
    • G01J2005/067Compensating for environment parameters
    • G01J2005/068Ambient temperature sensor; Housing temperature sensor
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00Radiation pyrometry
    • G01J5/02Details
    • G01J5/08Optical features
    • G01J5/0803Optical elements not provided otherwise, e.g. optical manifolds, gratings, holograms, cubic beamsplitters, prisms, particular coatings
    • G01J5/0834Optical elements not provided otherwise, e.g. optical manifolds, gratings, holograms, cubic beamsplitters, prisms, particular coatings using shutters or modulators
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42Wire connectors; Manufacturing methods related thereto
    • H01L2224/47Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805Shape
    • H01L2224/4809Loop shape
    • H01L2224/48091Arched

Abstract

Apparatus for measuring the temperature of an object comprises an optical tube, a first temperature sensor located at a closed end of the optical tube, a lens located at an open end of the optical tube and arranged to focus radiation from the object onto the first temperature sensor, a shutter located at the open end of the optical tube, the shutter having an open position allowing radiation from the object to reach the first temperature sensor and a closed position preventing radiation from the object reaching the first temperature sensor, a second temperature sensor located on the shutter, a third temperature sensor for measuring the substrate temperature of the first temperature sensor, a control device arranged to open and close the shutter, and a processing device connected to the first temperature sensor, the second temperature sensor, the third temperature sensor and the control device. The processing device is arranged to take first measurements from the first, second and third temperature sensors when the shutter is in its closed position, calculate an offset value from these measurements, open the shutter, take a second measurement from the first temperature sensor, and calculate the temperature of the object from the second measurement, the substrate temperature and the offset value.

Description

TEMPERATURE

MEASURING APPARATUS

This invention relates to apparatus for measuring the temperature of an object.

United States of America Patent 7,276,697 discloses an infrared apparatus for detecting the temperature of an object. In this Patent, an infrared temperature sensor measures infrared energy radiated by an object. This energy is focussed by a lens, which is mounted in an optical tube, onto a thermopile detector contained in a TO transistor case. The output voltage of the thermopile along with that of a contact temperature sensor mounted on the thermopile substrate, are measured by a measurement circuit and an algorithm based on Planck's Blackbody Radiation Law is used to calculate the temperature of the object from these measurements.

However, in such apparatus, thermal gradients develop across the thermopile detector substrate and TO transistor case. These gradients take two forms. Firstly, heat transferred from the electronic circuit to the thermopile case, either through the air-space or conducted along the legs of the thermopile, can cause the base of the TO case and thermopile substrate to heat. This causes a thermal gradient between the front and rear of the thermopile case which results in a net flow of energy between the case and the thermopile. This results in an error in the thermopile output voltage. Secondly, localised heat sources in the vicinity of the measurement instrument, such as heaters on a machine, can cause the thermometer case to be heated. Again, this manifests as a net flow of heat between case and thermopile which results in an error in the thermopile output voltage.

Prior art thermometers have sought to overcome this problem by either increasing the thermal mass of the thermopile housing to slow down the transient effects and reduce the size of the steady state thermal gradients, or take measures to reduce the flow of heat between electronics and sensor, for example by using long thin conductors. These solutions are only effective if no optical components at a different temperature to the thermopile substrate are present between the thermopile detector and the object to be measured since energy is also introduced by these items.

In an instrument with precision optics, an optical tube of considerable length compared to that of the thermopile housing is used to mount a lens at a focal distance from the thermopile. This optical tube suffers the same issues described above but to a larger extent. Since the optical tube has a high emissivity, it emits a high percentage of energy relative to its temperature. This causes a relatively large error voltage when a temperature difference exists between the tube and cold junction reference sensor. Due to its size, a significant thermal gradient can manifest itself.

When the entire optical assembly including lens, optical tube, thermopile housing and thermopile cold junction reference are all at the same temperature, the calculated temperature accurately correlates with the actual object temperature. However, if any part of the optical assembly is at a different temperature to the thermopile cold junctions, the measurement will not be accurate. This is due to net flow of energy between the optical assembly and the thermopile leading to an offset in the thermopile output voltage.

When measuring low temperatures it is usually necessary to use lens materials which will transmit wavelengths between 8pm and 14pm. These materials typically have a transmissivity of less than 0.8 so the lens absorbs energy, which changes the lens temperature. The lens will then emit infrared radiation according to its own temperature. Since this temperature is likely to be different to that of the thermopile cold junction, there will be a flow of energy causing a further offset on the thermopile output voltage. It is therefore an object of the invention to improve upon the known art.

According to a first aspect of the present invention, there is provided apparatus for measuring the temperature of an object comprising an optical tube, a first temperature sensor located at a closed end of the optical tube, a lens located at an open end of the optical tube and arranged to focus radiation from the object onto the first temperature sensor, a shutter located at the open end of the optical tube, the shutter having an open position allowing radiation from the object to reach the first temperature sensor and a closed position preventing radiation from the object reaching the first temperature sensor, a second temperature sensor located on the shutter, a third temperature sensor for measuring the substrate temperature of the first temperature sensor, a control device arranged to open and close the shutter, and a processing device connected to the first temperature sensor, the second temperature sensor, the third temperature sensor and the control device, the processing device arranged to take first measurements from the first temperature sensor, the second temperature sensor and the third temperature sensor when the shutter is in its closed position, calculate an offset value from the first measurements, open the shutter, take a second measurement from the first temperature sensor, and calculate the temperature of the object from the second measurement, the substrate temperature and the offset value.

According to a second aspect of the present invention, there is provided a method of operating apparatus for measuring the temperature of an object, the apparatus comprising an optical tube, a first temperature sensor located at a closed end of the optical tube, a lens located at an open end of the optical tube and arranged to focus radiation from the object onto the first temperature sensor, a shutter located at the open end of the optical tube, the shutter having an open position allowing radiation from the object to reach the first temperature sensor and a closed position preventing radiation from the object reaching the first temperature sensor, a second temperature sensor located on the shutter, a third temperature sensor for measuring the substrate temperature of the first temperature sensor, a control device arranged to open and close the shutter, and a processing device connected to the first temperature sensor, the second temperature sensor, the third temperature sensor and the control device, wherein the method comprises the steps of taking first measurements from the first temperature sensor, the second temperature sensor and the third temperature sensor when the shutter is in its closed position, calculating an offset value from the first measurements, opening the shutter, taking a second measurement from the first temperature sensor, and calculating the temperature of the object from the second measurement, the substrate temperature and the offset value.

Owing to the invention, it is possible to provide temperature apparatus that will provide compensation for errors caused by transient or steady state thermal gradients, in particular to the use of thermopile sensors in non-contact infrared (IR) thermometry. The apparatus is able to remove errors due to thermal gradients across the optical assembly of a thermometer. Preferably, the device comprises an infrared sensing device mounted in an optical tube with a lens to focus infrared energy onto the sensing device and a movable shutter blade having a high emissivity positioned immediately in front of the lens. The optical assembly is designed so that with the shutter in its open position infrared energy from the object to be measured and infrared energy from all optical components having a different temperature to the sensing device, is measured by the sensing device. With the shutter closed, infrared energy from the shutter and infrared energy from all optical components having a different temperature from the sensing device, is measured by the sensing device. A contact temperature sensor advantageously mounted in the centre of the shutter blade provides the shutter temperature, which enables a calibration algorithm to calculate and remove the offset voltage caused by infrared energy from all optical components having a different temperature to the sensing device.

Ideally, it is a feature of this apparatus that all surfaces within the sensor which are visible to the thermopile when the shutter is in its open position are also visible to the thermopile when the shutter is in its closed position. This ensures that all thermal gradients are compensated for. The shutter being positioned in front of the lens is of further advantage when the instrument is moved from a cold to hot environment as it protects the lens from condensation of water vapour, which itself has low transmissivity and will block infrared energy from the target. It is a feature of this apparatus that the shutter temperature detector be mounted on the measured surface of the shutter, therefore giving a true indication of the shutter temperature.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a diagrammatic perspective view of a conventional thermopile,

Figure 2 is a graph showing a typical curve of radiance on an object plotted against temperature of the object,

Figure 3 is a perspective view of the conventional thermopile,

Figure 4 is a schematic cross-sectional view of a preferred embodiment of the apparatus,

Figure 5 is a schematic cross-sectional view of a further embodiment of the apparatus,

Figure 6 is a schematic end view of a shutter of the apparatus in two configurations,

Figures 7 and 8 are schematic cross-sectional views of further embodiments of the apparatus, and

Figure 9 is a flowchart of a method of operating the apparatus.

Figure 1 shows the construction of a thermopile detector. The absorber 4 is supported on a thin membrane 5 on which thermocouples of two different metals or semiconductors A and B are also supported. Infrared energy from the object 6 is focussed by a lens 7 onto the absorber, which causes the absorber to rise in temperature. The difference in temperature between cold junctions 2 and hot junctions 3 produces a voltage proportional to the temperature difference.

Figure 1 shows conductors of the thermocouples made from dissimilar materials A and B deposited on a silicon substrate 1 with the cold junctions 2 located at the periphery, and the hot junctions 3 organised as a miniature array at the centre. This array or absorber 4 is thermally insulated from the cold junctions 2 by etching the substrate to produce an extremely thin self- supporting membrane 5. As its purpose is to detect the infrared (IR) radiation produced by an object 6 at a temperature To, the absorber 4 is blackened to increase its absorption of incident radiation and to maximise its resulting temperature rise as the radiation is transformed into heat. The cold junctions 2 are mounted on the substrate 1 and therefore they are ideally at or near ambient temperature TAMB-

Detecting IR energy over a wide band is not recommended in IR thermometry applications as unwanted energy absorption occurs in the atmosphere at certain wavelengths. To overcome this problem, an optical band pass filter (not shown) is usually placed in front of the absorber 4. Generally this filter is designed to pass IR radiation only for wavelengths in the range 8 to 14 μηη where the atmospheric absorption is minimal. Figure 2 shows the relationship between radiance and temperature as defined by Planck's Blackbody Radiation Law. This Figure shows that the radiance l_o is a severe non-linear function of the object temperature T0. The radiance Lo is the radiance of the object 6 and is the radiant power emitted in a specified direction per unit projected area of surface, per unit solid angle, which is expressed in watts per steradian per square metre (W sr"1 m"2). An appropriate optical system 7 is employed to collect the radiation from the object 6 and focus it on the absorber 4.

Figure 3 shows a thermopile detector housed in a hermetically sealed TO transistor case 8, 9, with optical filter window 10 transmitting IR radiation focussed by the lens. Thin wires 11 connect the thermopile terminals to leads 12. A cold junction reference sensor 13 indicates the temperature of the thermopile substrate. This Figure shows the typical construction of a thermopile. The substrate 1 supporting the thermally isolated absorber 4 is mounted with good thermal contact on a standard TO-transistor baseplate 8. A transistor cap 9 having a window 10 is hermetically mounted on the baseplate 8, thus sealing the sensor chip 1 inside. Usually the window 10 is fitted with material having the appropriate optical characteristics to satisfy the IR band pass filter requirements. Bonding wires 11 between the substrate 1 and baseplate leads 12 allow the generated thermopile emf to be brought out to the processing electronics (not shown).

A thermopile can only be used to measure the temperature of an object relative to the absorber temperature TA. For absolute temperature measurements, knowledge of TA is required. Unfortunately, as the absorber 4 is thermally isolated from the substrate 1 it is not possible to measure TA directly. However, as the substrate temperature Tcj tracks TA to within a few tenths of a degree, a separate substrate temperature measuring sensor can be used to estimate TA. The sensor can be external to the thermopile case (as shown in Figure 7); however, the preferred solution, as illustrated in Figure 3, is to use a thermopile with an integral sensor such as a thermistor or resistance temperature device (RTD) 13. Mounting the sensor 13 in good thermal contact with the baseplate 8 and close to the substrate 1 will ensure a close approximation of TCj and hence TA.

Figure 4 shows a cross section of the preferred embodiment of the invention. IR energy 15 is focussed by a lens 7 onto thermopile 100. The optical tube 16 houses the lens 7 and the thermopile 100 which along with cold junction temperature sensor 13 is connected to a PCB 23 by thin wires 22. A shutter blade 17 is moveable by shaft 18 and solenoid 19 so that in its closed position it occupies the entirety of the optical path of the IR energy 15. Note that no part of the overall assembly that appears between the object to be measured and the shutter blade 17 is visible to the thermopile 100 in either the open or closed position of the shutter 17. This ensures that all thermal offset energy caused by thermal gradients is common to both shutter positions. Alternative arrangements to the operation of the shutter 17 are possible. For example, the apparatus may include a shutter 17 which is operable by a linear actuator such that the shutter 17 opens away from the lens 7, like a door. By adding a rubber seal to the perimeter of the optical tube 16, the shutter 17 would form a dust-tight seal when in its closed position.

The optical tube 16 has a first temperature sensor 100 (in the preferred embodiment this is a thermopile) located at a closed end of the optical tube 16. The opposite end of the optical tube 16 is open to radiation and a lens 7 located at this open end of the optical tube 16 is arranged to focus the radiation 15 from the object onto the first temperature sensor 100. The shutter 17 is also located at the open end of the optical tube 16, the shutter 17 having an open position allowing radiation 15 from the object to reach the first temperature sensor 100 and a closed position preventing radiation 15 from the object reaching the first temperature sensor 100. The shutter is open and closed using the solenoid 19 (a control device) which rotates the shaft 18. A second temperature sensor is located on the shutter 17. The circuitry 23 acts as a processing device 23 controlling the operation of the apparatus and is connected to the first temperature sensor 100, the second temperature sensor 26, the third temperature sensor 13 and the control device 19.

In standby mode the shutter 17 is in the closed position. On request for a temperature measurement, the thermopile voltage (VTP(Ciosed))> the cold junction temperature sensor voltage (VCj) and the shutter temperature sensor voltage (Vs) are sampled by the measurement circuit. Shutter temperature Ts and cold junction temperature TCJ are calculated from Vs and VCJ respectively. The offset voltage caused by thermal gradients VoffSet is calculated using equation 1 below.

VTP(clG38d) - · _ I (7C;)) + VOffMt

Equation 1 where TP(Ciosed) is the thermopile voltage with the shutter in the closed position, es is the emissivity of the shutter, ko is a constant defining the throughput of the optical system, G is a calibration gain factor, Ts is the temperature of the shutter blade, TCj is the temperature of the thermopile substrate, L(Ts) is the radiance of a blackbody with temperature Ts, L(Tcj) is the radiance of a blackbody with temperature TCj and ν0¾βί is the offset voltage caused by thermal gradients across the optical assembly.

The shutter blade 17 is then moved to the open position. The thermopile voltage and the cold junction temperature sensor voltage (VCj) are sampled by the measurement circuit. Equation 2 is used to calculate object temperature To using the offset voltage calculated in equation 1 to remove the error voltage.

VTP(optm) - · {L O) - L(TCj)) + Vaffsat Equation 2 where VTP(open) is the thermopile voltage with the shutter in the open position, ε0 is the emissivity of the object, To is the object temperature and L(To) is the radiance of a blackbody with temperature T0.

A further embodiment of the apparatus is shown in Figure 5, with the addition of heaters 24 connected to the PCB 23 by wires 25. These heaters 24 can be used to regulate the temperature of the optical assembly and electronics to permit operation in low ambient temperatures. The heating elements 24 further reduce the possibility of frost or water vapour obscuring the lens 7. This also allows for operation in low ambient temperatures by maintaining the electronic components within their specified operating temperature range. Since the calibration technique will remove the errors due to the large and varying thermal gradients produced by this heating, the temperature measurement will remain accurate. The heaters 24 can either be permanently on, or controlled to switch on when the temperature falls below a set limit.

Figure 6 shows how the shutter blade 17 appears in its closed and open positions. Note that the shutter blade 17 does not intrude on the optical path 15 when in its open position. The temperature of the shutter blade 17 is measured by temperature sensing device 26 bonded to the centre of the shutter 7 and connected to the PCB 23 by wires 27.

Figure 7 is a view similar to Figure 4 of the improved apparatus. Two different positions for the cold junction reference sensor 13 are shown in this Figure. These are marked 13a and 13b and are each possible alternative locations for the cold junction reference sensor 13. The purpose of the reference sensor is to provide a measure of the temperature of the thermopile 100. In the preferred embodiment, shown in Figure 4, the cold junction reference sensor 13 is mounted directly on the thermopile 100, as this gives a more accurate reading, but Figure 7 shows alternative locations that are sufficiently close to the thermopile 100 to provide a working temperature measurement of the thermopile 100.

Figure 8 illustrates a yet further embodiment of the apparatus in which a fourth temperature sensor 28 connected to the PCB 23 by wires 29 is used to measure the ambient temperature surrounding the object being measured. In this embodiment of the apparatus, for use when the temperature surrounding the object being measured differs from the temperature of the instrument, a reflected energy term L(TR) is incorporated into Equation 2 whereby:

VrP(open} = ~ ^o l(To) + (1 - + L(TC}) )

Equation 3

This allows for greater measurement accuracy when the cold junction temperature is different from the ambient temperature surrounding the object being measured. For example, if the object being measured is in a furnace being viewed through a portal, the energy reflected by the object will be from the furnace walls, which will have a temperature of TR.

A flowchart of the operation of the apparatus is shown in Figure 9. Step S1 comprises taking first measurements ( Tp(C|0Sed), Ts, TCJ) from the first temperature sensor 100 (the thermopile), the second temperature sensor 26 located on the shutter 17 and the third temperature sensor 13, when the shutter 17 is in its closed position. The next step, step S2 comprises calculating an offset value (V0ffset) from the first measurements. This is followed by opening the shutter 17, step S3 and taking a second measurement ( TP(open)) from the first temperature sensor 100 at step S4. The final step in the method is step S5, which comprises calculating the temperature of the object from the second measurement, the temperature of the substrate (measure by the sensor 13) and the offset value.

The apparatus can be used for outdoor temperature measurement.

When measuring temperatures outdoors, an IR temperature sensor is exposed to extremes in temperature as well as fast changes in temperature. Most IR temperature sensors are not able to operate below 0°C due to the fact that water vapour can condense on the lens, or in extreme conditions ice can form. To overcome this problem it is necessary to heat the optical assembly. However, this causes large errors in temperature due to the transient thermal gradients when the heaters are switched on/off, and the steady state thermal gradients when the heat is maintained. The technique described above can be used to compensate for the errors due to thermal gradients. In addition, the fact that the shutter 17 remains closed between measurements protects the lens 7 from dust, condensation and ice.

A second application is food temperature measurement. In a supermarket environment, for example, there are large differences in temperature between different areas. A freezer department may have an ambient temperature of close to 0°C, whereas a bakery may have an ambient temperature of higher than 25°C. If a non-contact IR temperature sensor is to be used in both of these sections within a short time interval, errors will occur due to the optical assembly rapidly changing temperature when being taken from one area to the other. This can be compensated for using the method described above. In addition, the shutter 17 protects the lens 7 from the build up of water vapour when the instrument is taken from cold to warm.

Claims

1. Apparatus for measuring the temperature (T0) of an object (6) comprising:
o an optical tube (16),
o a first temperature sensor (100) located at a closed end of the optical tube (16),
o a lens (7) located at an open end of the optical tube (16) and arranged to focus radiation (15) from the object (6) onto the first temperature sensor (100),
o a shutter (17) located at the open end of the optical tube (16), the shutter (17) having an open position allowing radiation (15) from the object (6) to reach the first temperature sensor (100) and a closed position preventing radiation (15) from the object (6) reaching the first temperature sensor (100),
o a second temperature sensor (26) located on the shutter (17), o a third temperature sensor (13) for measuring the substrate temperature (TCj) of the first temperature sensor (100), o a control device (19) arranged to open and close the shutter (17), and
o a processing device (23) connected to the first temperature sensor (100), the second temperature sensor (26), the third temperature sensor (13) and the control device (19), the processing device (23) arranged to
■ take first measurements (VTP(Ciosed), Ts, Tcj) from the first temperature sensor (100), the second temperature sensor (26) and the third temperature sensor (13) when the shutter (17) is in its closed position,
calculate an offset value (V0ffSet) from the first measurements (VTp(Ciosed), Ts, TCj),
■ open the shutter (17), take a second measurement (VT (0pen)) from the first temperature sensor (100), and
calculate the temperature (To) of the object (6) from the second measurement (VTP(0pen)), the substrate temperature (Tcj) and the offset value (V0ffSet)-
2. Apparatus according to claim 1 , wherein the second temperature sensor (26) is located within the area on the shutter (17) which is visible to the first temperature sensor (100).
3. Apparatus according to claim 1 or 2, and further comprising a fourth temperature sensor (28) for measuring the ambient temperature (TR) surrounding the object (6) being measured and wherein the calculation of the temperature (T0) of the object (6) uses the ambient temperature (TR) in conjunction with the second measurement (νΤρ(0ρβη)), the substrate temperature (TCJ) and the offset value (V0ffSet)-
4. Apparatus according to claim 1 , 2 or 3, wherein the second temperature sensor (26) is located substantially centrally on the shutter ( 7).
5. Apparatus according to any preceding claim, wherein the shutter (17) is located externally of the lens (7).
6. Apparatus according to any preceding claim, and further comprising heating elements (24) arranged to heat all or part of the optical assembly and electronics (16).
7. Apparatus according to claim 6, wherein the processing device (23) is connected to the heating elements (24) and is arranged to switch on the heating elements (24) when a detected temperature falls below a preset threshold.
8. Apparatus according to any preceding claim, wherein the shutter (17) has a relatively high emissivity.
9. Apparatus according to any preceding claim, wherein the shutter (17) can form a dust tight seal with the optical tube (16).
10. A method of operating apparatus for measuring the temperature (To) of an object (6), the apparatus comprising:
o an optical tube (16),
o a first temperature sensor (100) located at a closed end of the optical tube (16),
o a lens (7) located at an open end of the optical tube (16) and arranged to focus radiation (15) from the object (6) onto the first temperature sensor (100),
o a shutter (17) located at the open end of the optical tube (16), the shutter (17) having an open position allowing radiation (15) from the object (6) to reach the first temperature sensor (100) and a closed position preventing radiation (15) from the object (6) reaching the first temperature sensor (100),
o a second temperature sensor (26) located on the shutter (17), o a third temperature sensor (13) for measuring the substrate temperature (TCJ) of the first temperature sensor (100), o a control device (19) arranged to open and close the shutter (17), and
o a processing device (23) connected to the first temperature sensor (100), the second temperature sensor (26), the third temperature sensor (13) and the control device (19), wherein the method comprises the steps of:
taking first measurements (VTp(ciosed), Ts, TCj) from the first temperature sensor (100), the second temperature sensor (26) and the third temperature sensor (13) when the shutter (17) is in its closed position, calculating an offset value (V0ffset) from the first measurements (VTP(Ciosed), Ts, TCJ),
opening the shutter (17),
taking a second measurement (V-rP(open)) from the first temperature sensor (100), and
calculating the temperature (To) of the object (6) from the second measurement the substrate temperature (TCJ) and the offset value (V0ffSet)-
11. A method according to claim 10, and further comprising measuring the ambient temperature (TR) surrounding the object (6) and wherein the step of calculating the temperature (To) of the object (6) uses the ambient temperature measurement (TR) in conjunction with the second measurement (VTp(0pen)), the substrate temperature (TCJ) and the offset value
(Voffset)-
12. A method according to claim 10 or 11 , and further comprising heating all or part of the optical assembly and electronics (16) with heating elements (24).
13. A method according to claim 12, and further comprising switching on the heating elements (24) when a detected temperature falls below a preset threshold.
PCT/GB2010/002242 2009-12-08 2010-12-08 Temperature measuring apparatus WO2011070319A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0837600A2 (en) * 1996-10-15 1998-04-22 Nippon Avionics Co., Ltd. Infrared sensor device with temperature correction function
US7276697B2 (en) 2002-02-01 2007-10-02 Calex Electronics Limited Infrared apparatus
US20080210872A1 (en) * 2003-08-11 2008-09-04 Opgal Ltd. Radiometry Using an Uncooled Microbolometer Detector

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7304297B1 (en) * 2004-07-01 2007-12-04 Raytek Corporation Thermal imager utilizing improved radiometric calibration technique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0837600A2 (en) * 1996-10-15 1998-04-22 Nippon Avionics Co., Ltd. Infrared sensor device with temperature correction function
US7276697B2 (en) 2002-02-01 2007-10-02 Calex Electronics Limited Infrared apparatus
US20080210872A1 (en) * 2003-08-11 2008-09-04 Opgal Ltd. Radiometry Using an Uncooled Microbolometer Detector

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GB2476040A (en) 2011-06-15 application
GB0921456D0 (en) 2010-01-20 grant

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