• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
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    • 专利摘要:
    14 ABSTRACT The invention regards a temperature monitoring circuit comprising a power source (3) for feeding acurrent to the circuit (1). The circuit (1) comprises a plurality of resistive thermal detectors (11', 11",11"'... 11“). The actual resistance of one of the resistive thermal detectors (11'), during the use of thecircuit (1), corre|ates to a predictable temperature influencing the resistive thermal detector (11'). Acentral data unit (15) associated with the circuit for determination of said actual resistance andtemperature. Each resistive thermal detector (11', 11", 11"'... 11“) is connected in series with a respective seriesresonance circuit SRC (13), the series connections are connected together in parallel to the powersource (3). The power source (3) is provided with a frequency generator means (5) for generating arange of varying frequencies of the current. Each series resonance circuit (13) is individually adaptedto give free passage for current to a certain frequency within said range of frequencies, whereinother frequencies hinder the current to pass. (Fig. 1)
    公开号:SE1250161A1
    申请号:SE1250161
    申请日:2012-02-22
    公开日:2013-08-23
    发明作者:Bengt Aakerblom
    申请人:Daprox Ab；
    IPC主号:
    专利说明:

    Temperature monitoring circuit The present invention regards a temperature monitoring circuit according to the preamble of claim 1.
    The invention relates to industries including devices such as refiners, moulding apparatuses, or otherindustries, such as food processing industry, using temperature measuring devices for determiningactual temperatures prevailing in the process.
    Prior art temperature monitoring circuits often consist of a set of temperature detectors, each ofwhich coupled to the central data unit for determining the actual temperature. This involves a bunchof cables coming from the circuit.
    Circuit or electrical circuit herein is defined as a number of electronic components being connectedto each other with electrical wires or leads. ln some circuits, the wire leads are provided in a bundle.Also a power unit can be regarded as a part of the circuit.
    There has been several attempts trying to provide an extremely simple circuit structure. For example,in the car industry, one way to measure the temperatures in a battery unit is shown in US 7 554 300.A set of temperature sensors is connected to a multiplexer via connection nodes. The resistancechange of each sensor is converted into voltage change, which being converted into a digital signal.However, still the circuit shown in US 7 554 300 involves a large amount of lead wires coming fromthe circuit.
    An object of the present invention is to provide a temperature monitoring circuit which is easy tomount and handle, having the less amount of wire leads as possible. The temperature measuringdevice encompassing the resistive thermal detectors should have a small amount of cables exitingfrom the device, at the same time as different temperatures at different positions in/at the deviceare possible to measure.
    Another object is to provide a not bulky temperature monitoring circuit.
    Another object is to provide a temperature monitoring circuit which can be put in use for a "plug-instick” for contactless electrical communication and mounting in a refiner disc.
    Another object is to provide a temperature monitoring circuit which is rigid and robust and which haslong life endurance.
    SUMMARY OF THE INVENTION This has been solved by the circuit defined in the introduction comprising the features claimed in thecharacterizing part of claim 1. ln such way the number of lead wires coming from the circuit is reduced. This is made by earmarkingthe individual resistive thermal detector (RTD) by arranging each one in series with a specific seriesresonance circuit (SRC) having a certain frequency at which the current is given passage. The locationof the individual RTD is predetermined and can be stored in the central data unit. By sweeping the frequency of the current in the circuit, the specific temperatures in the different positions can bedetermined.
    By injecting various frequencies of the current it is thus possible to achieve individual signatures ofeach resistive thermal detector (RTD). The rate of changing the direction of the AC (alternatingcurrent) defines the frequency. The frequency is suitably provided by a signal generator associatedwith the AC power source (transformer driver). The current is preferably transformed via atransformer for transforming the current from a high voltage (e.g. 230V) to a low voltage (e.g. 14V).The purpose of the transformer is thus to transform the voltage and thereby the current from theprimary side to the secondary side. The transformer comprises a primary and a secondary coil. Thetransformer may comprise ferromagnetic core material or may comprise inductors linkedmagnetically through the air. The coils can be wound onto one single square iron core having thecoils wound around the opposite sides. The primary coil could also be wound around a circular ironcore with the secondary coil wound onto the primary coil, etc. When the AC voltage is applied to theprimary coil, it creates a magnetic flux in the core, which induces an AC voltage in the secondary coilin-phase with the source AC voltage.
    Preferably, a signal generator, being connected to the power source, is adapted to generate afrequency sweep from 10 kHz to 200 kHz to the circuit. The signal generator thus generates electricaloutput waveforms over a preferable range of frequencies (5-250 kHz). The power source(transformer driver) supplies the transformer with an AC driving voltage, wherein the driving voltageinvolves the frequency being controlled by a frequency sweep controller when the transformer isenergized, so as to execute the frequency sweep. The frequency of the driving voltage is preferablyswept from a predetermined upper frequency 300 kHz to a predetermined lower frequency 0,5 kHzby means of a sweep generator connected to the power source.
    Furthermore, the signal generator preferably includes a function of automatically and repetitivelysweeping the frequency of the output waveforms by means of a voltage controlled oscillatorbetween two defined limits.
    Thus, by injecting various frequencies of the current is it possible to achieve individual signatures ofeach resistive thermal detector (RTD). Said individual signature is made by earmarking each RTD bycoupling an earmarked RTD to a specific series resonance circuit (the abbreviation of which usedherein is SRC) having a different resonance frequency than the others due to its certain RLC(resistance of e.g. lead wire, inductance, capacitance). The series resonance circuit SRC comprises alead wire, inductor, capacitor connected in series. The higher the frequency of the current, thehigher resistance (reactance) of the inductor. The higher the frequency of the current, the lessresistance (reactance) of the capacitor prevails. The earmarked RTD is connected in series with thecertain SRC (which is adapted to give passage of current for a specific frequency) and is used torespond selectively to signals of the specific frequency. Thus, at each resonance frequency, the seriesimpedance is as low as possible wherein the current will be as high as possible (U=|*R).
    Thus, by sweeping frequency of the current over a specific frequency range (for example 10-200 kHz)covering the different individually set resonance frequencies of the various SRCs (in this example; afirst SRC is set to 10 kHz, a second set to 20 kHz, a third set to 30 kHz, etc., and up to 200 kHz for thelast SRC.
    As the capacitor and the inductor of the individual SRC are connected in series, the current has topass the both components. lt is sufficient if any one of them provides a high reactance for creating ahigh total reactance of the actual SRC. The resonance frequency is defined as the frequency at whichthe reactance of the capacitor and the inductor is equal. When the both components (capacitor andinductor) thus are equal in reactance (the capacitance of the capacitor is equal to the inductance ofthe inductor), the current will have free passage through the series resonance circuit. The currenthaving a low frequency is hindered to pass the certain RTD, since the capacitor provides highreactance. A current having a high frequency is hindered to pass the RTD due to the high reactanceof the inductor. For example, a certain RTD is connected in series to a series resonance circuit set to50 kHz by providing the capacitor and inductor to have the same reactance thus giving free passagethrough this specific RTD. The other RTDs of the temperature monitoring circuit are closed since theyindividually are adapted for other resonance frequencies.
    As the frequency of the current changes due to the sweep and the next SRC will give free passage forthe current, since this SRC is set to 60 kHz. This specific 60 kHz SRC also comprises a capacitor and aninductor of the same reactance for providing free passage of the current, however the size of theboth components is smaller than that of the 50 kHz SRC. The smallest size of the components, in thisexample, is that of the capacitor and inductor of the 200 kHz adapted SRC.
    Preferably, the power source is an AC voltage power unit provided for generating an AC current overa transformer comprising a secondary winding being included in the temperature monitoring circuit. ln such way it is possible to design a temperature monitoring apparatus which can be used as oneunit for different applications, such as a temperature stick adapted for installation in a grinding, as avacuum bag per se embedded with the temperature monitoring circuit, as a temperature measuringdevice used in food processing, etc.
    Suitably, the central data unit is associated with a micro processor unit. The word ”associated” canmean ”connected by wires" or "wire-less connection”. ln such way the resistance of activated RTD is measured and transferred to the central data unit forexecuting the presentation of the actual temperature value.
    Alternatively, the temperature monitoring circuit is arranged removable from a primary winding,which in its turn is connected to the AC power source.
    Suitably, this is achieved by designing the transformer as a transformer coupling, wherein thesecondary winding (belonging to the temperature monitoring circuit) during the use of thetemperature monitoring circuit, is positioned peripherally the primary winding. ln such way is achieved a temperature monitoring circuit, which is not bulky and which is easy tohandle. lt will also be possible to mount the temperature monitoring circuit to an object, which object lateron will be used in production line or in laboratory, by easy connection of the object to an AC voltagepower source via a plain "plug-in" connection not having any electrical contact surfaces or tangledcables or lead wires.
    Preferably, the primary winding is installed in a probe, which is detachable from a grinding segment.
    Suitably, the frequency generator means is arranged for generating a range of varying frequencies ofabout 10-200 kHz.
    Preferably, the frequency is adapted within a frequency range in such way that the frequency upperlimit is not so high that cross-talk from one circuit to another will occur. Cross-talk is usually causedby undesired capacitive, inductive coupling between the circuits. To high frequency also hinders thecurrent through an inductor if the AC voltage has a far too high frequency, due to high reactance.
    Suitably, the frequency interval between two different into specific frequency adapted seriesresonance circuits is about 10 kHz. ln such way is achieved that an envelope curve can be calculated with high degree of accuracy, as thenumber of measure points over a spatial extent can be as many as twenty if the range of varyingfrequencies is about 10-200 kHz. ln such way is achieved that it also will be possible to mount the temperature monitoring circuit toan object, which object later on will be used in production line or in laboratory, by easy connection ofthe object to an AC voltage power source via a plain "plug-in" connection not having any electricalcontact surfaces or tangled cables.
    Suitably, the resistive thermal detector is a PT 100 element. ln such way a resistive thermal detector RTD is used as a resistance thermometer for each individualset series resonance circuit, which detector can be used in temperatures up to about 600 °Cdepending upon the design of the detector. The resistance is defined as 100 Q at 0 °C and 138,5 Q at100 °C. Such relative spectrum provides a sensibility of 0,4 Q per centigrade. ln such way a vaststability and therefore a presentation of several predictable properties can be achieved, which isdesirable for accuracy.
    Alternatively, the resistive thermal detector is a varistor. The varistor being an digital element havinga diode-like nonlinear current- voltage attribute. Such varistor may be shifted from gegahertz to afew megahertz frequency region.
    Thereby a temperature monitoring circuit is achieved, which is robust and can be used in higherfrequency ranges.
    Preferably, a thermistor can be used. The thermistor has an exponential change with temperaturewhich may be used for calculating the resistance for a specific temperature.
    Suitably, the temperature monitoring circuit is designed to be mounted in a refiner disk segment formeasurement of the temperature of a pulp being refined. ln such way is it possible to arrange the temperature monitoring circuit with a plurality of RTD's,wherein the temperature monitoring circuit will provide different temperature values in differentsections of the refiner disk segment essentially in the radial extension of the disk.
    Resistance thermometer or the so called resistive thermal detector (RTD) is a sensor used to measuretemperature by means of correlating the present resistance of the RTD-element with a predictable (made known in advance) temperature. The RTD may comprise a metal thin film, a coil, a fine wirewound about a glass or ceramic core. The wire could be pure metal, such as platinum, cupper, etc.,having a specific resistance at various temperatures, which resistance beforehand has beendocumented. When the temperature changes, also the material's electrical resistance changes. Thischange in resistance is thus predictable and correlates to the change in temperature and is used todetermine the present temperature. The RTD material and resistance at various temperatures hasbeen documented. The design of the circuit comprising the RTD-element is optional, the resistancecould be determined by measuring the voltage drop (keeping the current at a constant predetermined level) or by measuring the current and prevailing voltage at the RTD-element position.
    Like the thermistor, RTDs are passive resistive devices and by passing a constant current through thetemperature sensor it is possible to obtain an output voltage that increases linearly withtemperature. A typical RTD has a base resistance of about 100Q at 0 °C, increasing to about 140 Q at100 °C with an operating temperature range of between -200 to +600 °C.
    The material has a predictable change in resistance as the temperature changes; it is this predictablechange that is used to determine temperature.
    The specific SRC application (for earmarking a certain RTD-element) involves a different resonancefrequency than other SRC due to its beforehand provided resistance (of e.g. lead wire, inductance,capacitance) R-L-C. The series circuit of the R-L-C forms an oscillator for current induced in the circuitand will resonate with a specific pre-determined frequency. The determination of the value of theresonance frequency is set by the capacitance of the capacitor and the inductance of the inductor.The SRC is known in the art and can be used for several applications where resonance frequenciesare adaptable to a specific purpose. The adaption of a specific inductance of the inductor and aspecific capacitance of the capacitor for a specific R-L-C circuit will provide that the circuit only givefree passage to a certain frequency and thereby otherwise for other frequencies hinders the currentto flow pass. There are many applications for such R-L-C-series circuit and they can be used in manydifferent types of oscillator circuits. They can be set to select a narrow range of frequencies fromambient radio waves for the tuning of e.g. radio receivers, wherein they are used as a band-passfilter. The series resonance generated in the R-L-C circuit implies a specific frequency determined bythe values of resistance, inductance, capacitance, and has minimum impedance and zero phase. Theresonance occurs when the inductive and capacitive reactances are equal in magnitude. When they |II are apart 180 degrees in phase they "cance each other. The SRCs (serial resonance circuits) areused to respond to a given frequency of the current, while discriminating against signals of differentfrequencies. lf the response of the circuit is more narrowly peaked around the chosen frequency, the circuit is adapted to have higher "selectivity".
    Several methods and means for measure of the prevailing resistance of the circuit due to a certainRTD activation at a specific current frequency exist. For example, the current can be held constantand the voltage is measured or the current can be measured while knowing the injected voltage oreven the resistance per se can be measured by a micro chip circuit having associated and inconnection with the central data unit.
    BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described by way of examples with references to theaccompanying schematic drawings, of which: Fig. 1 illustrates a temperature monitoring circuit according to a first embodiment; Figs. 2a-2c illustrate magnitude p|ots for the respective resistive therma| detector (RTD) beingautomatically activated by the sweeping of frequency and converting the resistance of each activatedRTD into a temperature graph due to the predetermined positions of the RTDs in the circuit; Fig. 3a illustrates the cross-section of a temperature stick comprising the circuit with RTD and SRC; Fig. 3b illustrates in cross-section a portion of a refiner disc comprising a temperature monitoringcircuit provided with an energy generating probe; Fig. 4a illustrates in a front view a refiner disc of a refiner;Fig. 4b shows the refiner in a side view;Figs. 5a and 5b show a refiner disc segment comprising a temperature measure probe; Figs. 6a and 6b show a cross-section of a portion of the energy generating probe for simpleconnection with the central data unit; Figs. 7a and 7b show a temperature measure device in a perspective view and in cross-section; Fig. 8 shows a temperature measure device comprising a temperature monitoring circuit according toa further embodiment; Fig. 9a shows the RTD and the SRC connected in series for determination of a specific position of theRTD; Fig. 9b shows a graph illustrating the voltage drop at a specific frequency when a certain RTD isactivated; Figs. 10a and 10b show two different embodiments of the temperature monitoring circuit; and Fig. 11 shows a further embodiment of a temperature monitoring circuit mounted in a vacuum bagfor detecting cure temperatures in different positions of the bag.
    DETAILED DESCRIPTION OF PREFFERED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to theaccompanying drawings, wherein for the sake of clarity and understanding of the invention somedetails of no importance are deleted from the drawings. Some reference numbers correspond todetails having the same functionality, but being comprised in different embodiments.
    Fig. 1 illustrates a temperature monitoring circuit 1 (herein called circuit) according to a firstembodiment. The circuit 1 comprises a power source 3 for feeding an AC current to the circuit 1. Thepower source 3 is provided with a frequency generator means 5 for generating a range of varying frequencies of the current. The frequency generator means 5 is in this embodiment arranged forgenerating a range of varying frequencies of about 5-90 kHz. The power source 3 is an AC voltagepower unit provided for generating the AC current over a transformer 7 comprising a primarywinding 27 and a secondary winding 9, the secondary winding 9 being included in the circuit 1.
    The circuit 1 comprises a p|ura|ity of resistive thermal detectors (RTDs) 11', 11", 11"'... 11V'”.
    Each RTD 11 is connected in series with a respective series resonance circuit (SRC) 13', 13", 13"'...13V'”. The series connections are connected together in parallel to the secondary winding 9. The SRC13' permits passage of current at 10 kHz (the other SRCs close passage of the current at 10 kHz). TheSRC 13" permits passage of current at 20 kHz (the other SRCs close passage of the current at 20 kHz).The SRC 13"' permits passage of current at 30 kHz (the other SRCs close passage of the current at 30kHz). And so on, until last SRC V”' at 80 kHz is activated, thereafter the 70 kHz SRC is activated etc.
    A micro processor unit 8 measures the resistance of the circuit 1 by means of voltage drop indicatorunit (not shown) provided on the primary winding 27 side for measuring the actual current passingthe circuit 1 during the generation of varying frequencies. This means that no further cables must bearranged to the circuit 1 for measure of the ampere current.
    Each SRC 13 is individually adapted to give free passage to a certain frequency within said range offrequencies, wherein other frequencies hinder the current to pass. ln such way an earmarking ofeach RTD 11 is provided. The actual resistance of one of the RTD's 11, during the use of the circuit 1,correlates to a predictable temperature influencing the activated RTD 11. The actual resistance isthus detected by said micro processor unit 8.
    The earmarked RTD 11 being in such way connected in series with the certain SRC 13 (which isadapted to give passage of current for a specific frequency) and is used to respond selectively tosignals of a specific frequency.
    A central data unit 15 associated with the micro processor unit 8 of the circuit 1 for determination ofthe actual resistance and temperature. ln this embodiment the voltage drop is measured and theactual resistance determined. As the resistance is given, the temperature can be extracted due toknown resistance/temperature properties of the RTDs 11. The RTD 11 is in this embodiment a PT 100element, comprising a coil of platinum. The PT 100 element has a specific resistance at varioustemperatures, which resistance beforehand has been documented. ln case the temperature to bemeasured changes, the RTD's 11 electrical resistance will change. This change in resistance is thuspredictable and correlates to the change in temperature and is used to determine the presenttemperature. The PT 100 element has a base resistance of about 100 Q at 0 °C, increasing to about140 Q at 100 °C with an operating temperature range of between -200 to +600 °C.
    Fig. 2a is a graph schematically illustrating magnitude plots R1, R2...R8 generated by a respectiveresistive thermal detector (RTD) 11 of a p|ura|ity of RTDs, the positions of which are spread out overan area to be measured regarding temperature variations. The earmarking of the respective RTD 11makes use of said series resonance circuits SRC 13. Each plot indicates that a certain RTD 11 gives asignal, for example a voltage drop VD in the circuit 1. The actual voltage drop prevails momentarydue to the actual resistance present for the indicated (by frequency sweeping) RTD 11.
    The resistance generated by the RTD 11 is dependent on the actual temperature. The selection ofeach RTD 11 is made automatically by activation of a certain RTD by sweeping the frequency of thecurrent in the circuit.
    Fig. 2b illustrates an envelope (dotted line) of a diagram showing the resistance values R for the (insequence due to sweeping frequency) activated RTDs 11 positioned over a length r to be measured.The resistance of each separately activated RTD 11 is converted into a temperature graph. Thepositions of the RTDs 11 in the circuit 1 are spatially predetermined and the temperature values thusbeing detected in a physical manner. ln Fig. 2c is shown a temperature graph illustrating the monitoring of the temperature peak movingfrom r1 to r2. lt is a way to find the relations between actual temperatures in the object to bemeasured and predetermined. As the current is measured on the primary winding side 27 in Fig. 1,the exact current does not have to be determined, but it is the relations between the peaks. Thecircuit has no extra cables connected to a measuring device as prior art.
    Fig. 3a schematically illustrates in cross-section a portion of a refiner disc 17 comprising atemperature monitoring circuit 1 according to a second embodiment. The circuit 1 is provided withcurrent from the power source (not shown), which also can be regarded as a component of thecircuit 1. The RTDs 11 are situated near the relief of a grinding surface 19 of the refiner disc 17, butwith sufficient distance to the grinding surface 19 so that eventual wearing out of the grindingsurface 19 would not affect the circuit 1. The RTDs 11 and SRCs 13 are arranged in a temperaturestick 21 which is mounted in the refiner disc 17. Only two current lead wires 23 are connectedbetween the circuit 1 (comprising the RTDs) and the secondary winding 9, all forming the circuit 1.
    Fig. 3b schematically illustrates the cross-section of a temperature stick 21 comprising the major partof the circuit 1 including the different RTDs 11 and SRCs 13. An energy generating probe 25connected to a power source (not shown) comprising a primary winding 27 is mounted to thetemperature stick for transforming high voltage into low voltage to the circuit 1 via the secondarywinding 9. Power lead wires 29 connect the power source with the primary winding 27. Thesecondary winding 9 of the achieved transformer is connected to the RTDs 11 via only two lead wires23. A frequency generator means (not shown) generates a sweeping frequency range between 0,1kHz and 200 kHz of the current provided to the circuit. The position P of the unique RTD 11 isregistered and stored in the memory of the central data unit in relation to a reference point RPdefining a distance D between the each unique (earmarked by the SRC 13 permitting current to passfor a certain frequency) RTD's 11 spatial position and the reference point RP. This position in space isbeforehand registered and correlates to the frequency permitting the current to flow through theRTD 11 by adapting the SRC 13 for this frequency. The other SRC are adapted for permitting currentto flow through at other frequencies, each SRC being unique for determining the distance to thereference point RP. The actuated RTD 11 will give a certain resistance depending upon the actualtemperature, wherein the resistance is measured on the primary winding 27 side comprised withinthe energy generating probe 25.
    Fig. 4a schematically illustrates, in a front view, the refiner disc 17 in Fig. 3a. Material to be grinded isfed from a central opening 31 of the disc 17 and will be propelled in radial direction towards theperiphery of the disc 17. The circuit 1 is designed to be mounted in a refiner disk segment 33 formeasurement of the temperature of the pulp (material) 20 being grinded.
    Fig. 4b schematically shows the refiner disc 17 in a side view. The temperature stick 21 beingmounted in a segment 33 of the disc 17. The disc 17 has no superfluous cables exiting from the disc17 which in prior art techniques are used for measuring the actual temperature. Service personal caneasily mount the energy generating probe 25 into the disc 17 in contact with the temperature stick21 so that the primary winding 27 of the probe 25 transforms current to the secondary winding 9properly, without having any superfluous lead wires coming from temperature sensors at differentpositions. The actual ampere current being detected on the primary winding 27 side.
    Fig. 5a schematically shows a refiner disc segment 33 comprising the temperature stick 21 closer indetail. Fig. 5b shows the disc segment 33 in cross-section. The temperature stick 21 is mounted in thesegment 33 from behind before the segment 33 is mounted onto a refiner stator fundament 35. Fig.5b schematically shows the refiner stator fundament 35 in a side view.
    Figs. 6a and 6b show a cross-section of a portion of the circuit 1 for simple connection with thecentral data unit and energy supply (not shown) via an energy probe 25'.
    Figs. 7a and 7b show a temperature measure device 37 in a perspective view and in cross-section. lnFig. 7a is schematically illustrated the temperature stick 21 and the energy generating probe 25. Thecross-section in Fig. 7b shows the positioning of the RTDs R1-R8 (reference signs 11'- llvm) physicallyand spatially for determining the temperature variation in a radial direction of the refiner disc 17shown in Fig. 4a. Also, the inserted energy generating probe 25 is shown. A transformer 38 is formedby primary 27 and secondary 9 windings, when probe 25 is mounted in the stick 21.
    Fig. 8 shows a temperature measure device 37 comprising a temperature monitoring circuit 1according to a further embodiment. The power source 3 is situated centrally in the circuit 1 and thecircuit 1 comprises two lines with RTDs 11 and SRC 13s. A frequency generator 5 is coupled to thepower source 3. The different resistance values are measured by detector 39.
    Fig. 9a shows more in detail an embodiment of the RTD 11 and the SRC 13 connected in series (vialead wires having resistance RL) for determination of a certain position of the RTD 11 in thetemperature device 37 and circuit 1. The SRC 13 is provided to create passage for current for acertain frequency. This certain frequency is registered in the central data unit 15 for each RTD 11 asan unique ID. As the sweeping of frequency generates a large range of frequencies, the number ofRTDs 11 can be large. The position of each RTD 11 (having the unique ID) in the temperature device isalso registered in the central data unit 15 so that when the voltage drop is registered in the circuit 1at a certain frequency (the current ampere is constant), the central data unit 15 will know which oneof the RTDs that is active and where it is placed in the temperature device 37. The smallest frequencyinterval between two different (could be physically adjacent each other) frequency- adapted RTDs(only two RTDs 11 are shown in Fig. 9a), in this embodiment, is about 10 kHz. At 50 kHz the RTD 11 isactivated. |.e. current is permitted to pass through the RTD 11 due to the adaption of the SRC 13 to50 kHz. The adaption of a specific inductance L of the inductor and a specific capacitance C of thecapacitor for this first R-L-C circuit will provide that the circuit only give free passage to 50 kHz andfor other frequencies hinders the current to flow pass. The distance D1 from reference point RP isknown as the 50 kHz property of the SRC 13 is known. Sweeping the frequency, following at 60 kHzthe RTD 11' is activated and the RTD 11 is closed. |.e. current is permitted to pass through the RTD 11'due to the fact that the adaption of the SRC 13' is set to 60 kHz. The adaption of inductance L1 of theinductor and capacitance C1 of the capacitor for this second R-L-C circuit will provide that the circuit only give free passage for current to 60 kHz, thus passage through this earmarked RTD 11'. As theother RTDs are set in series with their respective SRCs (each SRC adapted to diverted seriesresonance frequencies of i.e. 40 kHz, 50 kHz, 70kHz, 80 kHz etc.), those RTDs are closed. The distanceD2 is predetermined as the SRC 13' property is known. The central data unit registers thatmomentary 60 kHz is injected and therefore the RTD 11' at distance D2 is activated and measuredresistance during this very short moment is converted into a temperature value. The ampere currentis measured on the primary winding 27 side of the transformer 7.
    Fig. 9b shows a graph illustrating the voltage drop VD at a specific frequency at which a certain RTD isactivated due to the permitted current passage provided by the SRC (series resonance circuit) 13coupled in series with the RTD 11.
    Fig. 10a schematically shows a circuit 1 comprising an ampere meter 39 coupled to the primarywinding side 27 for determining the resistance in the circuit 1. The ampere meter 39 is coupled to thecentral data unit 15 via a lead wire 41 for determining the actual resistance (and thereby thetemperature in a specific position of the temperature device 37) of the activated RTD 11.
    Fig. 10b schematically shows an embodiment of the temperature monitoring circuit 1 where signalsregarding the resistance of an activated RTD 11 are transmitted to a laptop 43 by measuring the ampere current at the primary winding 27 side of the transformer 7 by means of an ampere meter 8”.
    A signal regarding the frequency sweep (10-200 kHz) of the current for determining the positions ofthe activated RTD 11 is also transmitted to the laptop 43. The laptop's 43 screen shows atemperature graph 45. The resistance for a specific frequency is measured and since this frequencydetermines which RTD 11 being activated, the position of active RTD 11 can be determined. As theresistance is measured also the temperature at that position can be calculated. The resistance ispredictable and correlates to the temperature. For example, a PT 100 element has a base resistanceof about 100 Q at 0 °C, increasing to about 140 Q at 100 °C. For instance, if the resistance for thisspecific frequency is 127,075 Q, the temperature will be 70 °C. The frequency generator meanssweeps 5 the frequency and closes the used RTD 11 and opens another RTD. This RTD gives aresistance in the circuit of 130, 897 Q and the temperature will be indicated as 80 °C for this position.The central data unit 15 is programmed with data regarding the position of each unique RTD 11 inthe circuit 1. Each unique RTD is opened at different frequencies due to different combinations ofassembly of the SRCs 13.
    Fig. 11 shows a further embodiment of a temperature monitoring circuit 1 mounted in a vacuum bag47 for detecting cure temperatures in different positions of the bag 47. Each earmarked (by currentfrequency sweep and series coupling of RTD 11 and SRC 13 for determining the position of theactivated RTD) RTD 11 is adapted to provide signals to the central data unit 15. A terminal 49 iscoupled to the central data unit 15 for generating a display of the cure temperature. The powersupply 3' and the central data unit 15 can be plugged in edge contacts 51 of the bag 47. Amperemeter 8' detects the actual ampere current.
    The present invention is of course not in any way restricted to the preferred embodiments describedabove, but many possibilities to modifications, or combinations of the described embodiments,thereof should be apparent to a person with ordinary skill in the art without departing from the basicidea of the invention as defined in the appended claims. Other means for measuring the resistance ofthe circuit are possible. For example, a micro chip resistance detector could be provided in the RTD 11 per se. The signal generator may generate electrical output waveforms over a preferable range offrequencies, such as 0,1 kHZ-1000 kHz, or other ranges. The resistive thermal detectors could be ofdifferent types or other than mentioned PT 100-element, varistors, thermistors.
    权利要求:
    Claims (7)
    [1] 1. A temperature monitoring circuit comprising -a power source (3) for feeding a current to the circuit (1); -the circuit (1) comprises a plurality of resistive thermal detectors (11', 11", 11"'... 11“),wherein the actual resistance of one of the resistive thermal detectors (11'), during the useof the circuit (1), corre|ates to a predictable temperature influencing the resistive thermaldetector (11'); -a central data unit (15) associated with the circuit for determination of said actual resistanceand temperature, characterized by that -each resistive thermal detector (11', 11", 11"'... 11“) is connected in series with a respectiveseries resonance circuit SRC (13), the series connections are connected together in parallel tothe power source (3); -the power source (3) is provided with a frequency generator means (5) for generating arange of varying frequencies of the current; -each series resonance circuit (13) is individually adapted to give free passage for current to acertain frequency within said range of frequencies, wherein other frequencies hinder thecurrent to pass.
    [2] 2. The temperature monitoring circuit according to claim 1, wherein the power source (3) is anAC voltage power unit provided for generating an AC current over a transformer (7, 38)comprising a secondary winding (9) being included in the temperature monitoring circuit (1).
    [3] 3. The temperature monitoring circuit according to claim 1 or 2, wherein the central data unit(15) is associated with a micro processor unit (8, 8', 8").
    [4] 4. The temperature monitoring circuit according to any of claims 1 to 3, wherein the frequencygenerator means (5) is arranged for generating a range of varying frequencies of about 10-200 kHz.
    [5] 5. The temperature monitoring circuit according to any of the preceding claims, wherein thefrequency interval between two different into frequency adapted series resonance circuitsSRCs (13) is about 10 kHz.
    [6] 6. The temperature monitoring circuit according to any of the preceding claims, wherein theresistive thermal detector (11) is a PT 100 element. 13
    [7] 7. The temperature monitoring circuit according to any of the preceding claims, wherein thetemperature monitoring circuit (1) is designed to be mounted in a refiner disk segment (33)for measurement of the temperature of a pu|p being refined.
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    同族专利:
    公开号 | 公开日
    SE536384C2|2013-10-01|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
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    优先权:
    申请号 | 申请日 | 专利标题
    SE1250161A|SE536384C2|2012-02-22|2012-02-22|Temperature monitoring Switching Circuit|SE1250161A| SE536384C2|2012-02-22|2012-02-22|Temperature monitoring Switching Circuit|
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