Development of a Pyrometer That Measures the True Temperature Field of the Two-Dimensional Array

applied sciences

Article Development of a Pyrometer That Measures the True Temperature Field of the Two-Dimensional Array

Bojun Sun 1 , Xiaogang Sun 1,*, Meisheng Luan 2, Jingmin Dai 1 and Shuanglong Cui 1

1 School of Instrumentation Science and Engineering, Harbin Institute of Technology, No.92, Xidazhi Street, Harbin 150001, China; [email protected] (B.S.); [email protected] (J.D.); [email protected] (S.C.) 2 Library of HIT, Harbin Institute of Technology, No.92, Xidazhi Street, Harbin 150001, China; [email protected] * Correspondence: [email protected]; Tel.: +86-13074589432

Received: 28 March 2020; Accepted: 17 April 2020; Published: 22 April 2020

Abstract: This paper develops a two-dimensional array pyrometer, which can measure the true temperature field of the two-dimensional array. The pyrometer consists of an optical part, a circuit part and a software part. In the optical part, the radiation energy of the two-dimensional array target is obtained by scanning with the rotating mirror. Then, the radiation signal is converted and amplified by the circuit part. The software component realizes the functions of the pyrometer calibration, signal acquisition and data processing. The data processing adopts the secondary measurement method to calculate the true temperature and uses the multi-threaded method to improve the operational efficiency. Experiments show that the uncertainty of the two-dimensional pyrometer array can reach 1.43%. Compared with the single-threaded method, the true temperature operation time of the two-dimensional pyrometer array is improved by 77%, which verifies that the software operational efficiency is greatly improved.

Keywords: two-dimensional array pyrometer; true temperature measurement; radiation energy; secondary measurement method

1. Introduction Radiation thermometry [1–3] frequently uses a multi-wavelength pyrometer (MWP) [4–6] to overcome the restrictions from the unknown emissivity of traditional one-color pyrometers and the constant emissivity vs. wavelength for two-color ratio pyrometers [7,8]. A multi-wavelength pyrometer can obtain the true temperature of the target without emissivity information by using the principle of multi-wavelength radiation thermometry [9]. Gardner et al. developed a six-wavelength pyrometer with filter arrays for metal melting applications [10]. Hiernaut et al. developed a six-color pyrometer with a fiber-optic bundle [11]. Radousky and Mitchel developed an ultraviolet pyrometer to measure shock temperatures with a semi-transparent and semi-reflective mirror in 1989 [12]. Levendis et al. developed a three-color ratio pyrometer that employed one visible and two near-infrared wavelengths to measure the surface temperatures of burning carbonaceous particles [13]. Ng and Fralick explored a multi-wavelength pyrometer with a spectrometer to measure the true temperatures of transparent substances and combustion gases [14]. In 2017, Mei et al. developed a long-distance multi-wavelength pyrometer [15], which placed the core of the instrument 100 m from the probe. The current multi-wavelength radiation pyrometers [16,17] are all designed for single point or multi-point targets. This paper develops a multi-wavelength radiation pyrometer that can be used to measure the true temperature field of the two-dimensional array. It consists of an optical part, a circuit part and a software part. In the optical part, the data of the two-dimensional array are achieved by combining the longitudinal scanning by the rotating mirror with the transverse

Appl. Sci. 2020, 10, 2888; doi:10.3390/app10082888 www.mdpi.com/journal/applsci Appl.Appl. Sci.Sci. 20202020,, 1010,, 2888x FOR PEER REVIEW 22 ofof 1514 by combining the longitudinal scanning by the rotating mirror with the transverse multi-target points’ multi-target points’ method. In this way, the hardware space resources are saved, and the operation method. In this way, the hardware space resources are saved, and the operation process of data process of data acquisition is simplified at the same time, illustrating that the hardware resources acquisition is simplified at the same time, illustrating that the hardware resources and the and the measurement speed are both considered. The circuit part includes an I/V conversion circuit, measurement speed are both considered. The circuit part includes an I/V conversion circuit, a V/V a V/V amplification circuit and a data acquisition card. The I/V conversion circuit uses AD820 to amplification circuit and a data acquisition card. The I/V conversion circuit uses AD820 to convert convert the signal into a voltage signal. The V/V amplification circuit uses OP07 to amplify the the signal into a voltage signal. The V/V amplification circuit uses OP07 to amplify the voltage signal. voltage signal. Finally, the pyrometer uses the USB5630 data acquisition card to obtain the voltage Finally, the pyrometer uses the USB5630 data acquisition card to obtain the voltage signal, so as to signal, so as to realize the information interaction between hardware circuit and upper computer. The realize the information interaction between hardware circuit and upper computer. The software part software part is compiled by using Visual Studio as the development environment and using C# as the is compiled by using Visual Studio as the development environment and using C# as the language, language, mainly including the functions of pyrometer calibration, data acquisition and data processing. mainly including the functions of pyrometer calibration, data acquisition and data processing. Data Data processing adopts a secondary measurement method to calculate true temperatures [18] and uses processing adopts a secondary measurement method to calculate true temperatures [18] and uses a a multi-threaded method to improve the operation efficiency. multi-threaded method to improve the operation efficiency. After the development of the pyrometer, this work carries out the uncertainty analysis and the After the development of the pyrometer, this work carries out the uncertainty analysis and the two-dimensional array true temperature measurement experiment, and finally obtains the uncertainty two-dimensional array true temperature measurement experiment, and finally obtains the of the two-dimensional array pyrometer. uncertainty of the two-dimensional array pyrometer. 2. Principles of Measurement 2. Principles of Measurement According to reference [18], a flow chart of the secondary measurement method is shown in According to reference [18], a flow chart of the secondary measurement method is shown in Figure1. Figure 1.

FigureFigure 1.1. AA ﬂowflow chartchart ofof thethe secondarysecondary measurementmeasurement method.method.

TheThe principlesprinciples ofof measurementmeasurement areare asas followsfollows [18[18]:]: IfIf thethe multi-wavelength multi-wavelength pyrometer pyrometer has hasn spectral n spectral channels, channels, the output the output signal Vsignali of the i thof channel the ith ischannel deﬁned is as defined in Equation as in Equation (1): (1):    1  = ·( ,) · 1  ( = 1,2, … , ) = ( )   ( = ) (1) Vi Aλi ε λi, T  c  i 1, 2, ... , n (1) · · 2 −1 λ 5 e λiT 1  i − where is a temperature-independent calibration constant, which is related to the wavelength, and is also related to the spectral responsiveness of the detector, the transmittance of the optical Appl. Sci. 2020, 10, 2888 3 of 15

where Aλi is a temperature-independent calibration constant, which is related to the wavelength, and is also related to the spectral responsiveness of the detector, the transmittance of the optical element, the geometric size at that wavelength and the ﬁrst radiation constant; λi is the eﬀective wavelength of the ith channel; ε(λi, T) is the target spectral emissivity at temperature T; and c2 is the second radiation constant, which is 14,388 µm K. · Equation (1) can be rewritten into the form shown in Equation (2):

c2 5 λ T V = A ε(λ , T) λ − e− i (i = 1, 2, ... , n) (2) i λi · i · i ·

The output signal V0i of the ith channel of blackbody is as follows:

c2 5 λ T V 0 = A λ − e− i 0 [ε(λ , T) is 1.0 here, so it is omitted.] (3) i λi · i · i The ratio of Equations (2) and (3) is described by:

c2 c2 Vi λ T λ T = ε(λi , T) e− i e i 0 (4) Vi0 · · where Vi is called the radiation energy equivalent of ith channel. V0i Note Vi,1 as the output signal of the ith channel at the first temperature. Note Vi,2 as the output 0 signal of the ith channel at the second temperature. Note T1 as the estimated value of the first 0 temperature. Then, the estimated emissivity εi,1 of the ith channel at the first temperature can be described as in Equation (5), according to Equation (4):

c2 c2 0 Vi,1 λ T0 = i 1 − λiT0 εi,1 e e (5) Vi0 · ·

The emissivity at the second temperature T2 is as follows:

h 0i ε = ε0 1 + k T T (6) i i,1 2 − 1 where ε ε0 ε, ε0 + ε , T T0 M, T0 + M , k ( η, η), ε >0, η >0, M >0. i0,1 ∈ i,1 − i,1 2 ∈ 1 − 1 ∈ − Note Ti,2 as the calculated temperature of the ith channel at the second temperature. According to Equation (4): 1 Ti,2 = (7) 1 λi εi Vi + ln · 0 T0 c2 Vi,2 Rewrite Equation (6) as follows:

h 0i ε = ε0 1 + k T T (8) i i,1 i,2 − 1 Combine Equations (7) and (8):

1 = Ti,2 0 (9) ε0 [1+k(Ti,2 T )] Vi 1 + λi ln i,1 − 1 · 0 T0 c2 Vi,2

For the same reason, the calculated temperature of the ith channel at the ﬁrst temperature is as follows: 1 = Ti,1 0 (10) ε Vi 1 + λi ln i,1· 0 T0 c2 Vi,1 Appl. Sci. 2020, 10, 2888 4 of 15

Equations (9) and (10) are Ti,l(l = 1, 2)-related equations, which can be solved by an iterative method. The criterion of the optimal solutions is to minimize the variance of Ti,1 and Ti,2:

2 n  n 2 X X 1 X  min F = T T  (11)  i,l − n i,l l=1 i=1 i=1

Appl. Sci.Based 2020 on, 10 formulas, x FOR PEER mentioned REVIEW above, the optimal solution of the true temperatures can be obtained.4 of 14 Appl. Sci. 2020, 10, x FOR PEER REVIEW 4 of 14

3. Design of Pyrometer 3. Design of Pyrometer The block diagram and physical figurefigure of the two-dimensional array pyrometer are shown in The block diagram and physical figure of the two-dimensional array pyrometer are shown in Figures2 2 and and3 3respectively. respectively. The The pyrometer pyrometer is is mainly mainly composed composed of of an an optical optical part, part, a a circuit circuit part part and and Figures 2 and 3 respectively. The pyrometer is mainly composed of an optical part, a circuit part and a software part.part. The radiation energy of the target will be transmitted to the rotating mirror of the a software part. The radiation energy of the target will be transmitted to the rotating mirror of the optical part first.first. The optical part uses ten side-by-sideside-by-side optical fibersfibers to transmit the radiated signal optical part first. The optical part uses ten side-by-side optical fibers to transmit the radiated signal of the target. The The circuit circuit part part receives the signals from the optical part for signal conversion and of the target. The circuit part receives the signals from the optical part for signal conversion and amplification,amplification, and then uses a USB5630USB5630 data acquisitionacquisition card toto collectcollect data.data. At last, the USB5630 amplification, and then uses a USB5630 data acquisition card to collect data. At last, the USB5630 transmits the data to the PCPC forfor storage,storage, processingprocessing and display.display. The pyrometer has a temperaturetemperature transmits the data to the PC for storage, processing and display. The pyrometer hasµ a temperature measurement range of 1100–3000 K, a measurement spectrum range of 0.525–0.980 μm, and a single measurement range of 1100–3000 K, a measurement spectrum range of 0.525–0.980 μm, and a single channel acquisition rate of 100 kHz. channel acquisition rate of 100 kHz.

Figure 2. A block diagram of the two-dimensional array pyrometer. Figure 2. A block diagram of the two-dimensional array pyrometer. Figure 2. A block diagram of the two-dimensional array pyrometer.

Figure 3. A physical figure ﬁgure of the two-dimensional array pyrometer: ( a) front and (b) back. Figure 3. A physical figure of the two-dimensional array pyrometer: (a) front and (b) back.

3.1. Design of the Optical Part 3.1. Design of the Optical Part In the optical part, hardware resources will be saved but the measurement speed will be In the optical part, hardware resources will be saved but the measurement speed will be seriously reduced if the single point scanning scheme is adopted, whereas the measurement speed seriously reduced if the single point scanning scheme is adopted, whereas the measurement speed will be increased but the hardware resources requirements will be too large if the multi-point staring will be increased but the hardware resources requirements will be too large if the multi-point staring scheme is adopted. Therefore, the data acquisition function of the two-dimensional array pyrometer scheme is adopted. Therefore, the data acquisition function of the two-dimensional array pyrometer is realized by the cooperation of the longitudinal scanning by the rotating mirror and the transverse is realized by the cooperation of the longitudinal scanning by the rotating mirror and the transverse multi-target points’ method. The target information of the two-dimensional array is composed of ten multi-target points’ method. The target information of the two-dimensional array is composed of ten one-dimensional transverse target points side by side (black spots in Figure 2) and a rotating mirror one-dimensional transverse target points side by side (black spots in Figure 2) and a rotating mirror Appl. Sci. 2020, 10, 2888 5 of 15

3.1. Design of the Optical Part In the optical part, hardware resources will be saved but the measurement speed will be seriously reduced if the single point scanning scheme is adopted, whereas the measurement speed will be increased but the hardware resources requirements will be too large if the multi-point staring scheme is adopted. Therefore, the data acquisition function of the two-dimensional array pyrometer is realizedAppl.Appl. Sci. Sci. 2020 by 2020, the10, ,10 x cooperation, FORx FOR PEER PEER REVIEW REVIEW of the longitudinal scanning by the rotating mirror and the transverse5 of5 of14 14 multi-target points’ method. The target information of the two-dimensional array is composed of tenchangingchanging one-dimensional the the longitudinal longitudinal transverse position, position, target so so as points as to to optimize optimize side by the side the measurement (blackmeasurement spots speed in speed Figure and and2 )use anduse of aof hardware rotating hardware mirrorresources.resources. changing the longitudinal position, so as to optimize the measurement speed and use of hardware resources. 3.1.1.3.1.1. Subsection Subsection 3.1.1. Subsection TheThe radiation radiation energy energy of of the the target target is isfirst first tr ansmittedtransmitted to to the the rotating rotating mirror. mirror. A Astructural structural schematicschematicThe radiation diagram diagram energy of of the the ofrotating rotating the target mirror mirror is ﬁrst is is transmittedshown shown in in Figure toFigure the 4, rotating 4,and and the mirror.the physical physical A structural figure figure is is schematicshown shown in in diagramFigureFigure 5. 5.of the rotating mirror is shown in Figure4, and the physical ﬁgure is shown in Figure5.

FigureFigure 4. 4.AA Astructural structural structural schematic schematic diagram diagram of ofthe the rotating rotating mirror. mirror.

FigureFigure 5. 5.A Aphysical physical figure figure diagram diagram of ofthe the rotating rotating mirror. mirror. Figure 5. A physical ﬁgure diagram of the rotating mirror.

TheThe motor motor drives drives the the double-sided double-sided mirror mirror to to rotatero rotatetate clockwise clockwise through through the the conveyor conveyor belt belt and and realizesrealizes the the longitudinal longitudinal scanning scanning functionfunction function ofof of the the target target throughthro throughugh the the mirror mirror rotation. rotation. The The motor motor model model is is WS2845-24-250-1, WS2845-24-250-1, and and the the speed speed is is 25,000 25,000 rr/min./ min.r/min. The The eyepiece eyepiece above above the the rotating rotating mirror mirror is is used used for for focusingfocusing and and accurate accurate observation. observation.

3.1.2.3.1.2. Optical Optical Fiber Fiber and and Filter Filter TheThe radiation radiation energy energy of of the the target target enters enters the the ligh light receivingt receiving area area of of the the optical optical fiber fiber probe probe after after passingpassing through through the the rotating rotating mirror, mirror, objective objective and and raster. raster. The The light light receiving receiving area area is isdivided divided for for 10 10 targets,targets, and and there there are are 10 10 channels channels of of optical optical fiber fiber bundles bundles connected connected behind behind the the optical optical fiber fiber probe probe to to transmittransmit the the radiation radiation energy energy under under different different ta targets.rgets. Respectively, Respectively, 6-bunch 6-bunch optical optical fibers fibers are are connectedconnected to to each each channel channel to to divide divide the the radiation radiation energy energy of of each each channel channel into into six six channels, channels, and and the the sixsix channels channels of of radiation radiation energy energy are are respectively respectively equipped equipped with with filters filters of of different different effective effective wavelengthswavelengths to to obtain obtain energy energy information information at at the the specific specific wavelengths. wavelengths. A Aschematic schematic diagram diagram of of the the opticaloptical fiber fiber transmission transmission struct structureure with with 10-channels-int 10-channels-into-60-channelso-60-channels is isshown shown in in Figure Figure 6. 6.The The effectiveeffective wavelengths wavelengths of of each each channel channel are are shown shown in in Table Table 1. 1. Appl. Sci. 2020, 10, 2888 6 of 15

3.1.2. Optical Fiber and Filter The radiation energy of the target enters the light receiving area of the optical fiber probe after passing through the rotating mirror, objective and raster. The light receiving area is divided for 10 targets, and there are 10 channels of optical fiber bundles connected behind the optical fiber probe to transmit the radiation energy under different targets. Respectively, 6-bunch optical fibers are connected to each channel to divide the radiation energy of each channel into six channels, and the six channels of radiation energy are respectively equipped with filters of different effective wavelengths to obtain energy information at the specific wavelengths. A schematic diagram of the optical fiber transmission structureAppl. Sci. 2020 with, 10 10-channels-into-60-channels, x FOR PEER REVIEW is shown in Figure6. The e ffective wavelengths of each6 of 14 channelAppl. Sci. 2020 are, shown 10, x FOR in PEER Table REVIEW1. 6 of 14

FigureFigure 6. 6.A A schematicschematic diagramdiagram ofof thethe opticaloptical fiberfiber transmission transmission structure. structure. Figure 6. A schematic diagram of the optical fiber transmission structure. TableTable 1. 1.The The e effectiveffective wavelength wavelength of of each each channel. channel. Table 1. The effective wavelength of each channel. Channel Channel 1 Channel1 Channel 2 2 Channel Channel 3 3Channel Channel 4 4 Channel Channel 5 5 Channel Channel 6 6 WavelengthWavelength/ /µmμm 0.525 Channel0.525 1 0.635 Channel 0.635 2 0.700 Channel 0.700 3 0.808 Channel 0.808 4 Channel 0.903 0.903 5 Channel 0.980 0.980 6 Wavelength/μm 0.525 0.635 0.700 0.808 0.903 0.980 3.2.3.2. DesignDesign ofof CircuitCircuit PartPart 3.2. Design of Circuit Part TheThe functionfunction ofof thethe circuitcircuit partpart isis toto convert convert thethe radiation radiation energyenergy acquiredacquired byby thethe opticaloptical partpart The function of the circuit part is to convert the radiation energy acquired by the optical part intointo a a voltage voltage signal. signal. AfterAfter passingpassing throughthrough thethe opticaloptical fiberfiber andand filter,filter, the the energy energy signal signal enters enters the the into a voltage signal. After passing through the optical fiber and filter, the energy signal enters the photoelectricphotoelectric detector, detector, and and then then uses uses the Ithe/V conversionI/V conversion circuit circuit and V /andV amplification V/V amplification circuit to circuit amplify to photoelectric detector, and then uses the I/V conversion circuit and V/V amplification circuit to theamplify signal. the Finally, signal. theFinally, pyrometer the pyrometer uses the uses high-speed the high-speed data acquisition data acquisition system system to collect to collect the data. the amplify the signal. Finally, the pyrometer uses the high-speed data acquisition system to collect the Thedata. design The design of circuit of circuit part is part shown is shown in Figure in 7Figure. 7. data. The design of circuit part is shown in Figure 7.

Figure 7. The design of the circuit part.

3.2.1. Photoelectric Detector ArrayFigure 7. The design of the circuit part. Figure 7. The design of the circuit part. 3.2.1.The Photoelectric photoelectric Detector detector Array adopts a silicon photoelectric detector array. Each channel of the3.2.1. 60 Photoelectric channel optical Detector ﬁber Array is connected with one silicon photodiode behind, i.e., a total of 60 siliconThe photoelectricphotoelectric detectorsdetector adopts are used. a silicon The model photoe oflectric silicon detector photoelectric array. detectorEach channel is S1336-5BK, of the 60 The photoelectric detector adopts a silicon photoelectric detector array. Each channel of the 60 withchannel a spectral opticalresponse fiber is range connected of 0.320–1.100 with oneµm. silicon The photosensitivityphotodiode behind, vs. wavelength i.e., a total dependence of 60 silicon of channel optical fiber is connected with one silicon photodiode behind, i.e., a total of 60 silicon S1336-5BKphotoelectric is shown detectors in Figure are used.8[19]. The model of silicon photoelectric detector is S1336-5BK, with a photoelectricspectral response detectors range are of used.0.320–1.100 The model μm. ofThe silic photosensitivityon photoelectric vs. detector wavelength is S1336-5BK, dependence with ofa spectralS1336-5BK response is shown range in Figure of 0.320–1.100 8 [19]. μm. The photosensitivity vs. wavelength dependence of S1336-5BK is shown in Figure 8 [19]. Appl.Appl. Sci.Sci. 20202020,, 1010,, 2888x FOR PEER REVIEW 77 ofof 1514 Appl. Sci. 2020, 10, x FOR PEER REVIEW 7 of 14

Figure 8. The photosensitivity vs. wavelength dependence of S1336-5BK. FigureFigure 8.8. TheThe photosensitivityphotosensitivity vs.vs. wavelengthwavelength dependencedependence ofof S1336-5BK.S1336-5BK. 3.2.2. I/V Conversion Circuit and V/V Amplification Circuit 3.2.2.3.2.2. II/V/V ConversionConversion CircuitCircuit andand VV/V/V AmplificationAmplification CircuitCircuit A structure diagram of the I/V conversion circuit and V/V amplification circuit is shown in A structure diagram of the I/V conversion circuit and V/V amplification circuit is shown in Figure9. FigureA 9.structure The selection diagram range of theof the I/V feedback conversion resi stancecircuit R2and of V/V the I/Vamplification conversion circuit circuit isis shown1–10 M inΩ The selection range of the feedback resistance R2 of the I/V conversion circuit is 1–10 MΩ and the Figureand the 9. selection The selection range rangeof the offeedback the feedback capacitance resistance Cf is R2 1–10 of thepf. TheI/V conversionselected operational circuit is 1–10amplifier MΩ selection range of the feedback capacitance Cf is 1–10 pf. The selected operational amplifier model modeland the of selection the I/V conversion range of the circuit feedback is AD820. capacitance The 10 Cf times is 1–10 V/V pf. amplification The selected circuit operational is built amplifier after the of the I/V conversion circuit is AD820. The 10 times V/V amplification circuit is built after the I/V modelI/V conversion of the I/V circuit, conversion and the circuit selected is AD820. operationa The 10l amplifier times V/V model amplification of the V/V circuit amplification is built after circuit the conversion circuit, and the selected operational amplifier model of the V/V amplification circuit is OP07. isI/V OP07. conversion circuit, and the selected operational amplifier model of the V/V amplification circuit is OP07.

FigureFigure 9.9. A structure diagram of the II/V/V conversionconversion circuitcircuit andand VV/V/V amplificationamplification circuit.circuit. Figure 9. A structure diagram of the I/V conversion circuit and V/V amplification circuit. 3.2.3. High-Speed Data Acquisition System 3.2.3. High-Speed Data Acquisition System 3.2.3.The High-Speed two-dimensional Data Acquisition array pyrometer System needs to collect the two-dimensional array temperature The two-dimensional array pyrometer needs to collect the two-dimensional array temperature field information, including ten targets, and each target contains six channels. Each channel needs to field Theinformation, two-dimensional including array ten targets, pyrometer and needseach ta torget collect contains the two-dimensional six channels. Each array channel temperature needs to collect two-stage voltage data (I/V conversion circuit and V/V amplification circuit) at the same time, collectfield information, two-stage voltage including data ten (I/V targets, conversion and each circuit target and contains V/V amplification six channels circuit). Each atchannel the same needs time, to so it needs to meet the demand of collecting 120 channels of signals at the same time. The maximum socollect it needs two-stage to meet voltage the demand data (I/V of collectingconversion 120 circuit channels and V/Vof signals amplification at the same circuit) time. at Thethe samemaximum time, speed of a single channel needs to reach 100 kHz during the acquisition process. speedso it needs of a singleto meet channel the demand needs ofto collectingreach 100 kHz120 channels during the of signalsacquisition at the process. same time. The maximum In this work, two USB5630 data acquisition cards are used to constitute the high-speed data speedIn of this a single work, channel two USB5630 needs to data reach acquisition 100 kHz during cards arethe acquisitionused to constitute process. the high-speed data acquisition system. A single USB5630 data acquisition card has 64 available channels, and we use acquisitionIn this system.work, two A single USB5630 USB5630 data dataacquisition acquisit cardion scard are hasused 64 to available constitute channels, the high-speed and we usedata a a 64 single-ended analog inputs method here. The maximum acquisition voltage range can be 10 V, 64acquisition single-ended system. analog A single inputs USB5630 method data here. acquisit The maximumion card hasacquisition 64 available voltage channels, range canand bewe ±±10 use V, a 5 V, 2.5 V, 0~10 V and 0~5 V (we use 10 V here), and the single channel acquisition rate can reach ±±564 V,single-ended ±±2.5 V, 0~10 analog V and inputs 0~5 V (wemethod use ±10±here. V Thehere), maximum and the single acquisition channel voltage acquisition range ratecan canbe ±10 reach V, 500±5 V, kHz. ±2.5 The V, 0~10 sampling V and is 0~5 multiplexed V (we use here. ±10 V The here), ADC and resolution the single is channel 16 bits, and acquisition the voltage rate resolution can reach 500 kHz.1 The sampling is multiplexed here. The ADC resolution is 16 bits, and the voltage resolution can be 20 V 0.3 mV here. USB or Ethernet can be chosen to transmit the acquisition data to can500 kHz.be 216 The1 ∗∗ sampling 20 V ≈ ≈ 0.3 is multiplexedmV here. USB here. or Ethernet The ADC can resolution be chosen is to16 transmitbits, and thethe acquisitionvoltage resolution data to achieve the− function of data acquisition, storage and processing. In this work, Ethernet transmission is can be ∗ 20 V ≈ 0.3 mV here. USB or Ethernet can be chosen to transmit the acquisition data to adopted,achieve the and function the maximum of data transmissionacquisition, storage speed is an 100d processing. Mbps. In this work, Ethernet transmission achieveis adopted, the andfunction the maximum of data acquisition, transmission storage speed an isd 100processing. Mbps. In this work, Ethernet transmission The physical figure of the USB5630 data acquisition card is shown in Figure 10. is adopted,The physical and the figure maximum of the transmissionUSB5630 data speed acquisition is 100 Mbps.card is shown in Figure 10. The physical figure of the USB5630 data acquisition card is shown in Figure 10. Appl. Sci. 2020, 10, 2888 8 of 15 Appl.Appl. Sci. Sci. 2020 2020, ,10 10, ,x x FOR FOR PEER PEER REVIEW REVIEW 88 of of 14 14

FigureFigureFigure 10. 10.10. A A physical physical figure figurefigure of ofof the thethe USB5630 USB5630USB5630 data datadata acquisition acquisitionacquisition card, card, ( (aa))) outside outside and and ( (bb)) inside. inside. 3.3. Design of the Software Part 3.3.3.3. Design Design of of the the Software Software Part Part The software part uses Visual Studio 2015 as the platform and C# as the programming language TheThe software software part part uses uses Visual Visual Studio Studio 2015 2015 as as the the platform platform and and C# C# as as the the programming programming language language for software development. All experiments in this paper use the same computer environment: Intel (R) forfor softwaresoftware development.development. AllAll experimentsexperiments inin thisthis paperpaper useuse thethe samesame computercomputer environment:environment: IntelIntel Core (TM) i7-7700Hp @ 2.80 GHz. (R)(R) Core Core (TM) (TM) i7-7700Hp i7-7700Hp @ @ 2.80 2.80 GHz GHz The main purpose of the software system is to obtain the voltage data received by the data TheThe mainmain purposepurpose ofof thethe softwaresoftware systemsystem isis toto obtainobtain thethe voltagevoltage datadata receivedreceived byby thethe datadata acquisition card and process the data to get the true temperatures of the target at different times. acquisitionacquisition card card and and process process the the data data to to get get the the true true temperatures temperatures of of the the target target at at different different times. times. The The The software part mainly consists of pyrometer calibration, data acquisition and data processing. softwaresoftware partpart mainlymainly consistsconsists ofof pyrometerpyrometer calibration,calibration, datadata acquisitionacquisition andand datadata processing.processing. TheThe The flow chart of software part is shown in Figure 11. flowflow chart chart of of software software part part is is shown shown in in Figure Figure 11. 11.

FigureFigure 11. 11. A AA flow ﬂowflow chart chartchart of ofof the thethe software softwaresoftware part. part.

TheThe software software part part mainly mainly includes includes three three functions:functions: (1)(1) PyrometerPyrometer Calibration: Calibration: In In the the process process of of calibration, calibration, the the ACCESS ACCESS database databasedatabase is isis called calledcalled to toto realize realizerealize the thethe storagestorage of ofof calibration calibration temperaturetemperature data. data.data. The TheThe process procprocessess of ofof calling callingcalling ACCESS ACCESSACCESS basics basicsbasics operations operationsoperations such suchsuch as ascreation,as creation,creation, design, design,design, connection, connection,connection, real-time real-timereal-time change, changechange disconnection,, , disconnection,disconnection, database databasedatabase closing closingclosing and so andand on occurs. soso onon occurs.Theoccurs. real-time TheThe real-timereal-time change of changechange database ofof includes databasedatabase insert, includesincludes update, insert,insert, delete, update,update, query delete,delete, and other queryquery operations. andand otherother (2) operations.Dataoperations. Acquisition: When the high-speed data acquisition system collects data, it needs to transfer (2)(2) DatatheData voltageAcquisition: Acquisition: data When inWhen the the butheff high-speed high-speeder area into data data the acquisition txtacquisition file for system storage,system collects collects so as to data, data, prevent it it needs needs it from to to transfer transfer being theoverwrittenthe voltagevoltage data bydata the ininnext thethe data.bufferbuffer The areaarea implementation intointo thethe txttxt fifile processle forfor storage,storage, includes soso creation, asas toto preventprevent saving, itit modification, fromfrom beingbeing overwrittendeletion,overwritten exit by andby thethe other nextnext operations data.data. The ofThe the implemenimplemen txt file. tationtation processprocess includesincludes creation,creation, saving,saving, (3) modification,Datamodification, Processing: deletion, deletion, In the exit exit process and and ofotherother data operations operations processing, of of thethe the energytxt txt file. file. equivalent information is obtained (3)(3) DatafromData Processing: Processing: the calculated In In the the voltage process process data of of and data data collected processing, processing, voltage the the energy data,energy and equivalent equivalent then the information trueinformation temperature is is obtained obtained of the fromtwo-dimensionalfrom the the calculated calculated array voltage voltage target data data is and calculatedand collected collected by voltage thevoltage secondary data, data, and and measurement then then the the true true method. temperature temperature of of the the two-dimensionaltwo-dimensional array array target target is is calculated calculated by by the the secondary secondary measurement measurement method. method.

4.4. Calibration Calibration Appl. Sci. 2020, 10, 2888 9 of 15

Appl.4. Calibration Sci. 2020, 10, x FOR PEER REVIEW 9 of 14 The calibration procedure is as follows: The calibration procedure is as follows: (1) Close the lens cover of the pyrometer; (1) Close the lens cover of the pyrometer; (2) Take 500 samples of the output voltage data, take the average value, and get the zero voltage; (2) Take 500 samples of the output voltage data, take the average value, and get the zero voltage; (3) Open the lens cover and aim the pyrometer at the window of the high temperature blackbody (3) Open the lens cover and aim the pyrometer at the window of the high temperature blackbody furnace, in which the temperature of the high temperature blackbody is measured with furnace, in which the temperature of the high temperature blackbody is measured with a a standard pyrometer; standard pyrometer; (4) When the temperature is constant, record the output voltage value and subtract the zero voltage; (4) When the temperature is constant, record the output voltage value and subtract the zero voltage; (5) RecordRecord the the data data of of the output voltage (after th thee subtraction of the zero voltage) and measured temperaturetemperature in in ACCESS. ACCESS. The scene of field calibration is shown in Figure 12. When calling the calibration voltage data, The scene of field calibration is shown in Figure 12. When calling the calibration voltage data, the second stage data are called first. When the second stage data exceed 9900 mv, they are considered the second stage data are called first. When the second stage data exceed 9900 mv, they are considered as saturation data, and then the first stage data are called. Through the process mentioned above, as saturation data, and then the first stage data are called. Through the process mentioned above, the the pyrometer can obtain a curve of voltage vs. temperature and store the fit parameters. pyrometer can obtain a curve of voltage vs. temperature and store the fit parameters.

Figure 12. Field calibration.

5. Uncertainty Uncertainty The uncertainty of the two-dimensional array pyro pyrometermeter is is obtained by by three part synthesis: uncertainty of circuit ue,, uncertaintyuncertainty of calibration uc,, andand uncertaintyuncertainty ofof true temperature construction uuε. The combined uncertainty of the two-dimensional array pyrometer uu is uu = p The combined uncertainty of the two-dimensional array pyrometer Total is Total 2 + 2 + 2 ue +uuc +uuε . . 5.1. Uncertainty of the Circuit 5.1. Uncertainty of the Circuit The uncertaintyuncertainty ofof the the circuit circuit mainly mainly comes comes from from the temperaturethe temperature drift drift and theand noise the ofnoise the siliconof the photoelectricsilicon photoelectric detector, detector, the noise ofthe the noise I/V conversion of the I/V circuit conversion and the noisecircuit of theand V /theV ampliﬁcation noise of the circuit. V/V amplification5.1.1. Uncertainty circuit. of the Silicon Photoelectric Detector

5.1.1.The Uncertainty equation of for the calculating Silicon Photoelectric the drift of Detector the silicon photoelectric detector S1336-5BK is uetw = K ∆T[17]; where ∆T = 2 K and K = 0.05%, uetw is 0.10%. T· The equation for calculating± theT drift of the silicon± photoelectric detector S1336-5BK is u = The noise of the silicon photoelectric detector mainly derives from shot noise and thermal K ·∆T [17]; where ∆T = ±2 K and K = 0.05%, u is ±0.10%. noise [18,20]. The noise of the silicon photoelectric detector mainly derives from shot noise and thermal noise Shot noise is generated by the PN junction random current of the silicon photoelectric detector and [18,20]. p 19 is evaluated according to Ietzs = 2qIs∆f (where q is the electric charge 1.6 10− C, diode working Shot noise is generated by the PN7 junction random current of the silicon∗ photoelectric detector bandwidth ∆f = 1 MHz, and Is = 10− A). and is evaluated according to I = 2qI ∆f (where q is the electric charge 1.6 ∗ 10 C, diode Thermal noise is generated by the free electron thermal motion of the silicon photoelectric detector working bandwidth ∆f = 1 MHz,q and I =10A). 4KT∆f 9 and is calculated by Ietzr = (where K is the Boltzmann constant and Rsh = 10 is the bypass Thermal noise is generatedRsh by the free electron thermal motion of the silicon photoelectric resistance). ∆ detector and is calculated by I = (where K is the Boltzmann constant and R =10 is the bypass resistance). Appl. Sci. 2020, 10, 2888 10 of 15

2 2 √Ietzr +Ietzr Therefore, the uncertainty of the noise is uetz = 0.17%. Is ≈p 2 2 The uncertainty of the silicon photoelectric detector is uet = uetw + uetz 0.20%. ≈ 5.1.2. Uncertainty of the I/V Conversion Circuit and V/V Amplification Circuit The uncertainty of the I/V conversion circuit is based on AD820, and its temperature drift is h + i calculated by u = ∆eos Rf1 Rsh + ∆Ib ∆T [15] (where ∆eos = 2µV/K is the voltage drift when the ea1 ∆T Rf1Rsh ∆T Is ∆T ∆Ib temperature change is 1 K, the current drift is ∆T = 2pA/K, and the feedback resistance of the first 8 9 stage amplifier is R = 10 MΩ. When Is = 10 A and R = 10 Ω, u 0.04%. f1 − sh ea1 ≈ The uncertainty of the V/V amplification circuit is based on OP07, and its temperature drift is h i ∆eos Rf2+R2 ∆Ib ∆T calculated by uea2 = + R2 [15] (where the input resistance of the second stage ∆T Rf2 ∆T Vs is R2 = 50 KΩ, the input voltage is Vs = 5 mV, and the feedback resistance is Rf2 = 500 KΩ. When ∆eos = 1.3µV/K and neglecting ∆Ib , u 0.057%. ∆T ∆T ea2 ≈ According to the data from ART company’s technician, the uncertainty of USB5630 is u = 0.1%. p AD 2 2 2 2 In conclusion, the total uncertainty of the circuit is ue = uet + u + u + u 0.23%. ea1 ea2 AD ≈ 5.2. Uncertainty of the Calibration The emissivity of the high temperature blackbody furnace in the calibration experiment is 0.990. The temperature deviation is less than 2 K. [18] The standard pyrometer and cavity blackbody furnace are used in the calibration process, and the quantization error is not higher than 0.3%. [21] According to the calibration results, the uncertainty of the calibration is uc = 1.00%.

5.3. Uncertainty of the True Temperature Construction In this work, the method used in the construction of true temperature is the secondary measurement method. According to reference [15], the uncertainty of the true temperature construction is uε = 1.00%.

5.4. Combined Uncertainty All the uncertainty causes analyzed above are added in quadrature, leading to the combined p 2 2 2 uncertainty of the two-dimensional array pyrometer being u = ue + uc + uε 1.43%. Total ≈ 6. Actual Measurement Experiment The two-dimensional array pyrometer designed in this work is used to carry out the actual measurement experiment on a high-temperature furnace. The temperature of the high-temperature furnace is adjusted to 1273 K. The scene of the actual measurement experiment is shown in Figure 13. The data of the two-dimensional array target (high-temperature furnace) are composed of the data of a total of 100 target points with ten longitudinal axes (target1–target10) at ten time points. The ten time points (time1–time10) are 49.46, 49.49, 49.53, 49.58, 49.61, 49.65, 49.68, 49.71, 49.75 and 49.81 s after the start of the measurement. The energy equivalent measured by the pyrometer is shown in Figure 14. The true temperature is calculated by the software part, and the true temperature measurement results of the two-dimensional array target are shown in Table2. The true temperature operation time of the two-dimensional array pyrometer is shown in Table3. Appl. Sci. 2020, 10, 2888 11 of 15

Appl. Sci. 2020, 10, x FOR PEER REVIEW 11 of 14 Appl. Sci. 2020, 10, x FOR PEER REVIEW 11 of 14

Figure 13. The actual measurement experiment. FigureFigure 13. 13. TheThe actual actual measurement measurement experiment. experiment.

Figure 14. Cont . Appl. Sci. 2020, 10, 2888 12 of 15 Appl. Sci. 2020, 10, x FOR PEER REVIEW 12 of 14

FigureFigure 14. The14. The energy energy equivalent equivalent of the of high-temperaturethe high-temperature furnace furnace (a–j ),(a respectively,for–j), respectively, target1–target10. for target1– target10.

Table 2. Table 2.The The truetrue temperature measurement measurement results. results.

True True Temperature Temperature of of Each Each Target/K Target /K Target Target Target Target Target Target Target Target Target Target Target Target Target Target Target Target Target Target Target Target 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 no no no no no no no no no no Time1 novalue novalue novalue valueno valueno valueno valueno valueno value no value no Time1 no no no no no no no Time2 value value value value 1136.6value 1174.1value 1150.1value value value value novalue novalue novalue valueno valueno value no value no Time2 no no no 1136.6 1174.1 1150.1 no no Time3 value value value value1185.3 1264.9 1264.1 1231.1 1186.8value value value novalue novalue novalue value no value no Time3 no no no 1185.3 1264.9 1264.1 1231.1 1186.8 no no Time4 value value value 1197.5 1256.6 1267.7 1272.8 1180.4 value value novalue novalue novalue value no value no Time4 no no 1197.5 1256.6 1267.7 1272.8 1180.4 no Time5 value value value1151.6 1248.7 1285.4 1271.1 1281.8 1243.5 1155.6value value value value value no no no no no no Time5Time6 1151.61167.6 1248.71189.8 1281.2 1285.4 1281.1 1271.1 1273.2 1281.8 1212.0 1243.5 1162.2 1155.6 valuevalue valuevalue valuevalue no no nono no no no no Time6Time7 1167.6 1189.81172.7 1271.8 1281.2 1277.7 1281.1 1265.3 1273.2 1190.2 1212.0 1162.2 valuevalue valuevalue value value valuevalue no no nono nono no no no no no no Time7Time8 1172.71157.2 1271.8 1188.3 1277.7 1166.9 1265.3 1190.2 valuevalue valuevalue valuevalue value value valuevalue valuevalue no no nono nono nono no no no no no no no no no Time8Time9 1157.2 1188.3 1166.9 valuevalue valuevalue valuevalue valuevalue value value value valuevalue valuevalue valuevalue no no nono nono nono nono nono no no no no no no no no Time9Time10 valuevalue valuevalue valuevalue valuevalue value valuevalue valuevalue valuevalue valuevalue valuevalue no no no no no no no no no no Time10 value value valueTable 3. Thevalue true temperaturevalue operationvalue time.value value value value

Operation Time/ms Target Target Target Target Target Target Target Target Target Target

1 2 3 4 5 6 7 8 9 10 no no no no no no no no no no Time1 value value value value value value value value value value Appl. Sci. 2020, 10, 2888 13 of 15

Table 3. The true temperature operation time.

Operation Time/ms Target Target Target Target Target Target Target Target Target Target 1 2 3 4 5 6 7 8 9 10 no no no no no no no no no no Time1 value value value value value value value value value value no no no no no no no Time2 210.07 263.776 227.124 value value value value value value value no no no no no Time3 159.530 224.23 220.786 212.759 192.015 value value value value value no no no no no Time4 148.854 213.155 258.888 205.867 183.006 value value value value value no no no Time5 263.700 148.750 227.274 291.130 173.583 181.484 138.459 value value value no no no Time6 304.769 234.414 219.112 287.03 197.443 152.904 85.938 value value value no no no no no Time7 241.907 216.698 255.736 146.963 158.437 value value value value value no no no no no no no Time8 205.244 213.274 138.696 value value value value value value value no no no no no no no no no no Time9 value value value value value value value value value value no no no no no no no no no no Time10 value value value value value value value value value value

Table2 shows that the uncertainty of the two-dimensional array pyrometer can reach 1.43%. In this paper, the software data processing part adopts multi-threaded parallel processing. The 100 true temperature operation processes are carried out at the same time. Therefore, the maximum value of the operation time in Table3 is the total time required for the true temperature operation process of the two-dimensional array pyrometer, which is 304.769 ms, while the total true temperature operation time of the 100 target points with the single-threaded method is 1330.220 ms. The time used by the multi-threaded method is 77% less than that used by the single-threaded method. Additionally, the two-dimensional array pyrometer can directly scan and measure the true temperature of the two-dimensional array target without complicated positioning operations, which greatly simpliﬁes the operation and improves the practicability of the two-dimensional array pyrometer.

7. Conclusions The uncertainty of the two-dimensional array pyrometer designed in this paper is 1.43%. The pyrometer uses a combination of multi-target and mirror rotation scanning to achieve fast acquisition of the two-dimensional array target data. During data acquisition, the pyrometer does not need to be moved. Compared with general single-target and multi-target pyrometers, the operation process is greatly simpliﬁed. At the same time, the two-dimensional array pyrometer uses multi-threaded parallel processing, and the true temperature operation time is reduced by 77% compared with that for single-threaded, which improves the software operation eﬃciency.

Author Contributions: Conceptualization and writing—original draft preparation, B.S.; methodology, B.S.; software, B.S.; validation, X.S. and J.D.; visualization, M.L. and S.C.; funding acquisition, X.S. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by National Natural Science Foundation of China (NSFC), grant number 61875046. Conﬂicts of Interest: The authors declare no conﬂict of interest. Appl. Sci. 2020, 10, 2888 14 of 15

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