Temperature-limiting optical fiber temperature probe

Abstract

The use of an optical sensor with an output that mimics the output of a thermocouple or thermistor instead provides more accurate feedback to the control system in a noisy electrical environment without requiring additional changes or modifications to the control system.SOLUTION: An optical temperature sensing system including an optical fiber sensor as a primary temperature sensor for reading the temperature of a measurement target or a measurement environment is disclosed. The temperature probe is coupled to a transducer that generates a temperature output using solid state electronic components without the use of software. A temperature sensing system is also disclosed that includes a temperature sensor for reading a temperature of a measurement target and a dual transducer module having a first transducer providing a primary temperature sensor signal and a second transducer generating a secondary temperature sensor signal from a signal provided by the first transducer. Also described is an optical temperature sensor with a conversion module that produces an output that mimics the output of a thermistor or thermocouple.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] cross reference This application claims priority to U.S. Provisional Application No. 62 / 705,323, filed June 22, 2020. The contents of U.S. Provisional Application No. 62 / 705,323 are incorporated herein by reference. Technical Field The following describes a fiber optic temperature probe for temperature limiting applications. [Background technology]

[0002] background Thermocouples and thermistors are common types of temperature sensors used in temperature limiting applications. Many control systems have been designed to accept the output of a thermocouple or thermistor as feedback to regulate and limit temperature. Because both thermocouples and thermistors are electrical, and the wires act as antennas when exposed to radio frequency (RF) fields, the signals they output are often noisy and inaccurate, and in high RF fields (such as in some semiconductor processes that use plasma), large induced voltages can pose a safety risk to workers.

[0003] In systems that use active heater temperature control, redundant temperature sensors may be required to ensure safety specifications are met for "over-temperature" conditions. For example, Semi-S2 requirements may require compliant systems to ensure that there are no failure modes that would result in the inability to detect an unsafe condition without redundancy. Various other standards, such as IEC 60730-1 and UL 60730-1 (the successor to UL 873), may also require similar or other types of redundancy. Over-temperature specifications generally require that there be no single-point failure modes; that is, if a device is out of tolerance but does not report a temperature, it is considered OK. Under-temperature failure modes, while undesirable, are also generally acceptable. Summary of the Invention

[0004] overview Applications requiring active heating and RF exposure through plasma generation, such as plasma deposition processes, can benefit from fiber optic technology to ensure accurate temperature measurements for closed-loop control. Fiber optic technology can be used in conjunction with a secondary sensor to provide measurements of over-temperature conditions.

[0005] Traditionally, when two temperature channels are needed for redundant temperature sensing, these channels are provided using thermocouples or thermistors, with one used as a backup for the other. Fiber optic sensors are used for control functions but are not used as temperature-limited sensors because they require safety-rated software or safety-rated solid-state electronics to comply with applicable safety standards. This is likely due to the disadvantage that optical sensors are not susceptible to the same inaccuracies and noise when placed in an electric field, compared to thermocouples and thermistors.

[0006] Using optical sensors with outputs that mimic those of thermocouples or thermistors instead can provide more accurate feedback to control systems in noisy electrical environments without requiring additional modifications or adaptations to the control system. Also, by using only solid-state devices and safety-compliant software, temperature control equipment can be designed to meet established safety standards. Furthermore, since programmable devices typically increase the cost of obtaining device certification, using an analog design makes it easier to meet such standards.

[0007] In one aspect, a temperature sensing system is provided that includes a phosphor-based fiber optic sensor as a primary temperature sensor for reading the temperature of an object to be measured, and a secondary redundant temperature sensor connected to an over-temperature protection circuit.

[0008] In another aspect, a temperature sensing system is provided that includes a temperature sensor for reading a temperature of an object to be measured, a dual transducer module including a first transducer for providing a primary temperature sensor signal, and a second transducer for generating a secondary temperature sensor signal from the signal provided by the first transducer.

[0009] In yet another aspect, an optical temperature sensor is provided having a conversion module that produces an output that mimics the output of a thermistor or thermocouple.

[0010] In yet another aspect, an optical temperature sensor system for detecting temperature in an environment is disclosed. The optical temperature sensor system includes a temperature probe having a fiber optic temperature sensor and a converter that generates a temperature output using solid-state electronic components without the use of software. In an exemplary embodiment, the fiber optic temperature sensor generates a signal in response to sensing the temperature of the environment. The signal varies according to a decay rate responsive to temperature. The converter includes a signal processing system including semiconductor electronics configured to convert the signal into an intermediate signal representative of the decay rate by comparing one or more signal characteristics to one or more expected signal characteristics, and to convert the intermediate signal into a temperature output by comparing the intermediate signal to an expected decay rate associated with a reference temperature.

[0011] In an exemplary embodiment, the temperature output is in the form of the output of a thermocouple or a thermistor.

[0012] In an exemplary embodiment, the fiber optic sensor is a phosphor-based or GaAs-based fiber optic sensor.

[0013] In an exemplary embodiment, the signal processing system includes a logarithmic amplifier configured to convert the signal to an intermediate signal having a rate of change inversely proportional to the decay rate. In an exemplary embodiment, the signal processing system includes one or more comparators configured to generate one or more pulses in response to the intermediate signal crossing one or more thresholds, and the temperature output is generated based on the decay rate observed between the one or more pulses. In an exemplary embodiment, the signal processing system has a separate non-volatile memory that converts the intermediate signal to a temperature output based on a pre-programmed conversion.

[0014] In an exemplary embodiment, the system further includes a secondary temperature sensor configured to generate an additional signal in response to sensing the temperature of the environment, the additional signal being provided to the temperature limit protection circuit as a redundant temperature reading.

[0015] In yet another aspect, an optical temperature sensor system for detecting temperature in an environment is disclosed, the system including a temperature probe having a fiber optic temperature sensor and a transducer that generates separate first and second temperature outputs based on a signal from the fiber optic temperature sensor by two or more parallel readout electronics.

[0016] In an example embodiment, the two or more parallel readout electronics are solid state electronics with no software.

[0017] In an exemplary embodiment, the first temperature output or the second temperature output indicates an over-temperature condition.

[0018] In an exemplary embodiment, the first temperature output or the second temperature output indicates a fault condition.

[0019] In an exemplary embodiment, at least one of the two or more readout electronics includes programmable hardware.

[0020] In an exemplary embodiment, the first temperature output or the second temperature output is in the form of a thermocouple or thermistor output. In an exemplary embodiment, the first temperature output or the second temperature output is a voltage value of a K-type thermocouple.

[0021] In an exemplary embodiment, the temperature probe includes a single probe with a single thermally conductive tip for measuring the surface temperature of an object in the environment.

[0022] In an exemplary embodiment, a temperature probe is housed within the sheath to measure the temperature inside the liquid or gas.

[0023] In yet another aspect, a system for sensing the temperature of an object is disclosed. The system includes a fiber optic temperature sensor that generates a signal in response to temperature sensing, the signal varying according to a temperature-responsive attenuation rate, and a redundant temperature sensor configured to generate a redundant signal in response to the temperature sensing. The system further includes a signal processing system configured to convert the signal into an intermediate signal representative of the attenuation rate by comparing one or more signal characteristics to one or more expected signal characteristics, and to convert the intermediate signal into a temperature output by comparing the intermediate signal to the expected attenuation rate. The signal processing system outputs the redundant signal and / or the temperature output to a temperature limiting protection circuit.

[0024] In an exemplary embodiment, the signal processing system is constructed from one or more solid state components.

[0025] In an exemplary embodiment, the fiber optic temperature sensor and the redundant temperature sensor are in a single probe.

[0026] In an exemplary embodiment, the fiber optic temperature sensor and the redundant temperature sensor are housed within a single thermally conductive tip of a single probe for measuring the surface temperature of an object.

[0027] In an exemplary embodiment, a fiber optic temperature sensor and a redundant temperature sensor are housed within a single sheath to measure the temperature within a liquid or gas.

[0028] In an exemplary embodiment, the temperature output is a voltage value of a K-type thermocouple.

[0029] In an exemplary embodiment, the fiber optic temperature sensor is a phosphor-based or GaAs-based fiber optic sensor.

[0030] In an exemplary embodiment, the redundant temperature sensors are phosphor-based or GaAs-based fiber optic sensors.

[0031] In an exemplary embodiment, the redundant temperature sensors are thermocouples or thermistors, and the signal processing system consists of a programmable memory used to convert the signal into a temperature output.

[0032] In an exemplary embodiment, the programmable memory includes one or more parameters and / or calibration values ​​associated with one or more of the object and redundant temperature sensors.

[0033] In yet another aspect, a heating system is disclosed that includes a heating element coupled to a heating element controller, a temperature probe having a fiber optic temperature sensor, and a transducer. The transducer generates a first temperature output based on a signal from the temperature probe using solid-state electronics without software, generates a second temperature output based on processing the signal in one or more memories, and outputs the first and second temperature outputs to the heating element controller. The heating element controller adjusts operation of the heating element based on the received first and second temperature outputs.

[0034] In an exemplary embodiment, the heating element is a radio frequency heater powered by a radio frequency power source and the first temperature output is a UL Listed or IEC 61508 standard programmable readout interpretable by the heating element controller. [Brief explanation of the drawings]

[0035] BRIEF DESCRIPTION OF THE DRAWINGS Embodiments will now be described with reference to the accompanying drawings, to which reference will now be made.

[0036] [Figure 1] FIG. 1 is a schematic block diagram of a temperature sensing environment and a temperature controller for controlling a heating system in such an environment.

[0037] [Figure 2] FIG. 2 is a schematic block diagram of a functional safety system for a fiber optic temperature sensor and a temperature controller.

[0038] [Figure 3a] FIG. 3a is a block diagram illustrating a dual independent temperature probe configuration.

[0039] [Figure 3b] FIG. 3b is a block diagram illustrating a combined dual temperature probe configuration.

[0040] [Figure 3c] FIG. 3c is a block diagram illustrating a single probe, single optical fiber, dual conversion module configuration.

[0041] [Figure 4a] FIG. 4a is a schematic block diagram showing further details of the arrangement shown in FIG. 3b.

[0042] [Figure 4b] FIG. 4b is a schematic block diagram showing further details of the arrangement shown in FIG. 3a.

[0043] [Figure 5] FIG. 5 is a schematic block diagram showing further details of the arrangement shown in FIG. 3c.

[0044] [Figure 6] FIG. 6 is a schematic block diagram illustrating a single probe multi-channel configuration.

[0045] [Figure 7] FIG. 7 is a cross-sectional view of a combined sensor probe having primary and secondary temperature channels.

[0046] [Figure 8] FIG. 8 is an enlarged cross-sectional view of a sensing tip for a dual temperature sensor probe.

[0047] [Figure 9] FIG. 9 is a cross-sectional view of a dual temperature sensor probe.

[0048] [Figure 10] FIG. 10 is a schematic diagram for performing safe temperature analog conversion from an optical signal.

[0049] [Figure 11a-b] 11a and 11b are an example block diagram for safe temperature conversion using a fiber optic temperature sensor input.

[0050] [Figure 12] FIG. 12 is a chart showing signals of interest in a simulation of the block diagram of FIGS. 11a and 11b. DETAILED DESCRIPTION OF THE INVENTION

[0051] Detailed Description Turning now to the figures, FIG. 1 illustrates an example of a sensing environment 10 in which a heating system 16 provides heat to an object whose temperature is desired to be measured, such as a semiconductor showerhead, pedestal, or electrostatic chuck (ESC). One or more temperature sensors 12, 14 are used to measure the temperature of the object during an application requiring active heating, such as a plasma deposition process, that is exposed to RF radiation. The temperature sensors 12, 14 are coupled to a temperature controller 18, which is used to control the heating system 16 coupled to or disposed within the sensing environment 10. One of the temperature sensors 12, 14 is used for a safety-critical function or application. For example, the temperature sensors 12, 14 may be used by a temperature limiting function 20 of the temperature controller 18.

[0052] 2 illustrates a first safety temperature sensor 12 defining a functional safety system for sensing temperature within environment 10. Safety temperature sensor 12 includes a sensing element 22 (e.g., a phosphor-based or gallium arsenide (GaAs)-based element) positioned to measure the temperature within environment 10 and a safety interface 24 configured to couple to a controller interface 26 of temperature controller 18. Controller 18 also includes a heater interface 28 that couples to a corresponding heater interface 30 of heating system 16. Heating system 16 also includes, in this example, an RF heater 32 positioned to act as a heat source within environment 10.

[0053] Multiple temperature sensors 12, 14 can be used in applications within environment 10 to provide redundancy or to serve as primary and secondary temperature sensing roles. In the examples provided herein, first temperature sensor 12 refers to the aforementioned “safety” sensor configured to provide reliability as its primary purpose, and second temperature sensor 14 refers to another temperature sensor whose primary purpose is not necessarily reliability (e.g., accuracy) and therefore can be used for other, non-safety-critical functionality. As described herein, first temperature sensor 12 can include an optical sensor with an output that mimics that of a thermocouple or thermistor to provide more accurate feedback to a control system in noisy electrical environment 10 (by using an optical sensor) without requiring additional modifications to the control system. Second temperature sensor 14 can also include an optical sensor and have software available for calibration and temperature calculations.

[0054] 3a, 3b, and 3c illustrate exemplary configurations for obtaining first and second temperature signals, at least one of which provides input to a safety-critical function, such as for temperature limits within environment 10. In FIG. 3a, first temperature sensor 12 is provided using a temperature probe separate from second temperature sensor 14. That is, first and second temperature sensors 12, 14 may themselves be packaged as separate, independent probes that are coupled to temperature controller 18 (not shown in FIG. 3a). In FIG. 3b, first and second temperature sensors 12, 14 are packaged together into a combined temperature probe 40. In FIG. 3c (shown in more detail in FIG. 5), first temperature sensor 12 is provided using a single probe 42, and a first temperature conversion module 43 provides data obtained from probe 42 to a second temperature conversion module 44 that includes hardware and / or software configured to provide a second temperature signal, thus operating as second temperature sensor 14.

[0055] Turning now to FIG. 4a, the combined temperature probe 40 is shown in further detail. The combined probe 40 may include a housing or other physical structure that holds, contains, or otherwise aligns the first and second temperature sensors 12, 14 to independently measure the temperature of a target surface, area, or volume. In this exemplary configuration, the first temperature sensor 12 includes a sensing probe 48 and a safety transducer 50 that is used to generate a signal for a safety-critical function, such as the temperature limiting function 20. The sensing probe 48 includes a sensing element 22 and a probe optical interface 52 that is in optical communication with a transducer optical interface 54 of the safety transducer 50. The safety transducer 50 includes a light source 56 that generates light that is sent to the sensing element 22, which generates a return signal that varies with temperature and is detected by a detection element 58. The sensing element 58 generates an analog readout 60 that is used by a safety computing element 62 to generate a safety signal (i.e., a logic signal or other desired analog or digital output), for example, one that mimics the output of a thermistor or thermocouple, and the safety signal can be transmitted via the safety interface 24 to the interface 26 of the temperature controller 18.

[0056] As described below, the safety computing element 62 is used to overcome the electrical noise issues present in some safety-rated thermocouple- and thermistor-based temperature limiting devices and provide electrical hazard mitigation by employing a fiber optic temperature sensor 12 with electronics capable of generating a signal similar to a thermocouple or thermistor, such that fiber optic sensing can be substituted. The safety computing element 62 can be configured to use only solid-state electronics or can use safety-rated software that complies with regulations and specifications related to temperature limiting applications.

[0057] The second temperature sensor 14 shown in FIG. 4a includes a sensing probe 48 and an exemplary converter 70, which may utilize any suitable and available technology, not necessarily meeting safety-critical specifications. For example, the exemplary converter 70 may employ software and calibration algorithms to prioritize temperature accuracy over compliance with safety certifications. The sensing probe 48 includes a sensing element 22 and a probe optical interface 52 in optical communication with a transducer optical interface 54, similar to the arrangement relative to the first temperature sensor 12. The exemplary converter 70 also includes a light source 56, a detection element 58, and an analog readout 60. The exemplary converter 70 may utilize stored parameters and / or calibration values ​​66 and employ a software computation element 64 to generate a temperature signal for a digital interface 68. The digital interface 68 may be used to connect the second temperature sensor 14 to a control or monitoring function.

[0058] Figure 4b is identical to the configuration shown in Figure 4a, except that the temperature sensors 12, 14 are provided by separate probes 48 rather than by a combined probe 40 or by a structure that physically couples the probes 48. The choice between the configurations shown in Figures 4a and 4b can be made according to regulatory or application-specific requirements or packaging restrictions.

[0059] 5 illustrates a single-probe combination sensor 42. In this "hybrid" configuration, a single probe 48 having a sensing element 22 and an optical interface 52 interfaces with a safety transducer 50 in the same manner as shown in FIGS. 4a and 4b. However, in this configuration, an analog readout 60 is not only provided to a safety computation element 62, but also to a software computation element 64 of an exemplary transducer 70' modified to utilize the analog readout 60 in this manner. Here, the software computation element 64 receives the output of the analog readout 60 and parameter / calibration values ​​66 also used by the safety transducer 50, and generates a software-based digital temperature signal that can be provided to a digital interface 68.

[0060] FIG. 6 shows yet another configuration in which a single fiber optic probe 48 is used to perform temperature sensing using a coupling transducer 71. In this exemplary configuration, the probe optical interface 52 optically communicates with the transducer optical interface 54 via an optional extension cable 72. The extension cable 72 includes a pair of optical interfaces 74, 76. The extension cable 72 can optionally be used to provide a longer extension of the probe 48 relative to the housing 73 of the coupling transducer 71. The coupling transducer 71 includes the light source 56, the sensing element 58, the safety interface 24, and the digital interface 68. A control module 80 is also used to provide feedback to the light source 56, which excites the phosphor sensing element. The control module 80 can be used to control the transimpedance gain of the detection light (LED) current level, or other optical parameters of the excitation and detection functions. The output of sensing element 58 is fed to both calibration module 66 for generating a digital temperature signal for digital interface 68 and safety interface 24, allowing combination transducer 71 to be used with, in this example, a UL Listed or IEC 61508 programmable readout and relay 90 for controlling an RF power source 92 for RF heater 32. Also shown in Figure 6 are optional interfaces 82, 86, including digital interface 68, analog interface 84, and EtherCAT interface 88, by way of example.

[0061] 7-9, exemplary configurations for a combined temperature probe are shown. In FIG. 7, a dual sensing chip 100 includes a sensing element 102 for the second temperature sensor 14 and can incorporate any other suitable sensing element for the first temperature sensor 12, used for redundancy and / or temperature limiting functionality. It can be understood that the first and second temperature sensors 12, 14 can be interchanged in other embodiments, such as using a phosphor sensing element 102 for the first temperature sensor 12. The dual sensing chip 100 is coupled to the end of a probe shaft 104 extending from a probe mount 106. In exemplary embodiments, the dual sensing chip 100 can include a first conventional temperature sensor 12 (e.g., including a thermistor and / or thermocouple) and a second optical temperature sensor 14, where the thermistor and / or thermocouple of the first conventional sensing element 102 can be used for over-temperature detection by sensing voltage without modification to account for the second optical temperature sensor 14.

[0062] Figure 8 illustrates a dual-fiber sensing chip 110 having a single sensing element 112 that can be used with a pair of optical fibers mounted in parallel channels 116 arranged to provide separation 114 between the fibers. As also seen in Figure 8, the sensing chip 110 can also provide a gap G between the sensing element 112 and the ends of the fibers disposed in the channels 116.

[0063] FIG. 9 shows an example of a composite optical fiber probe 111 incorporating a dual sensing tip 110. In this example, the sensing tip 110 is supported at the tip of a leading shaft 112. The leading shaft 112 is connected to a fiber rod 118 via a rod holder 114 and a modular tube 116, such as a stainless steel tube (SST). A relatively high temperature region is permitted in front of the fiber rod 118, and T aAbove the line identified as , relatively low temperatures, e.g., below 200°C, are acceptable. The probe 111 includes a rear shaft 128 that extends through a mount nut 126, a washer 122, and a clip 120 and is attached to the fiber rod 118. A spring 124 may be interposed between the washer 122 and the mount nut 126 to provide some resilience to the probe 111. The rear shaft 128 may also be threadably received in a housing or device coupled to the probe 111 for connecting the probe 111 to a fiber optic cable adapter 132 that houses a pair of optical fibers 134, 136. In this example, the interface between the rear shaft 128 and the holder 130 is adapted to withstand a relatively low temperature T b can withstand.

[0064] Turning now to FIGS. 10-12, further details regarding the safety computation element 62 will be described. FIG. 10 provides a high-level schematic diagram to explain the operation of the safety transducer 50. Here, excitation optics and electronics, e.g., light source 56, generate an excitation signal, such as a pulsed LED or laser. This signal interacts with the phosphor sensing element 22, generating a decay signature, e.g., a pulsed exponential response, in return. Readout electronics 150 within the transducer 50 includes an analog conversion module 152 that uses the decay signature to convert the time decay to temperature. Module 152 may also convert the temperature to a safety signal. As described below, this can be done using a logarithmic amplifier, with the output based on whether the signal is within a specific temperature range. The output of analog conversion module 152 is a logic signal, e.g., HIGH = safe operation, LOW = safety fault. Optionally, as shown in FIG. 10, the analog temperature signal can be converted to a logic signal for use in triggering heating termination, if desired. This can be done either within module 150, as shown, or externally.

[0065] 11a and 11b illustrate an exemplary embodiment for the analog conversion module 152 or the secure computing module 62. This implementation for the analog conversion module 152 does not utilize software or firmware and therefore may not require the additional authentication(s) required for temperature-limited applications using programmable devices. Furthermore, this example allows the use of a fiber optic sensing probe 48 while mimicking the analog or digital voltage values ​​expected from a K-type thermocouple. In this manner, a sensing configuration less susceptible to RF interference can be used with existing ubiquitous control devices that expect to receive temperature signals from thermocouples or thermistors. In another embodiment, the examples shown in FIGS. 11a and 11b can omit the comparator for other applications, for example, when a differential amplifier is used to perform a single analog linear calibration. In yet another embodiment, the examples shown in FIGS. 11a and 11b can omit the logarithmic amplifier, inverter, and differential amplifier for lower accuracy requirements.

[0066] It has been found that most current solutions for fiber optic temperature sensing involve some sort of programmable controller (e.g., MCU, FPGA, SoC), which can bring cost savings and provide flexibility to implement various algorithms.

[0067] The solution shown in Figures 11a and 11b does not involve programmable devices or require the implementation of specific algorithms. Instead, the solution employs discrete, i.e., analog or digital, solid-state components, or components that operate as solid-state components. For ease of reference, components described with respect to the embodiment discussed in Figures 11a and 11b shall be understood to be solid-state components unless otherwise indicated, even though they are not labeled as such (e.g., splitter 161 is a solid-state splitter).

[0068] 11a and 11b, splitter 161 is shown in the upper left corner. The signal returning from probe 48 through splitter 161 (shown as "out") is detected by photodetector 162, which outputs a current. The current produced by photodetector 162 is converted to a voltage in some manner (e.g., using a transimpedance amplifier 163 as shown in FIG. 11a, which is typically made using an op-amp, a capacitor, and a resistor, although other architectures for this conversion can be used).

[0069] The output from the transimpedance amplifier 163 is an exponentially decaying voltage and includes the various signals of interest generated by the simulator as shown in Figure 12. The output from the transimpedance amplifier 163 is trace Vout0 200. It can be appreciated that the same module can also employ some amplification circuitry to provide more gain.

[0070] The decay time can be calculated using the difference between the maximum amplitude and the amplitude at a fixed point during the decay period, but this calculation is difficult and sometimes prone to error because the signal can be quite noisy and the maximum amplitude, based on experience and experimental observation, is not exactly constant for each and every cycle. Therefore, a solution to alleviate this situation is to rely not on measuring pure voltage levels but on measuring the slope (rate of change) of a linear decaying signal, generated, for example, using a logarithmic amplifier (such as any logarithmic amplifier 164).

[0071] The theory behind using a logarithmic amplifier is as follows.

[0072] For the transistor in the negative reaction loop, one is as follows:

[0073] Ic=Is(e^(Vbe / Vt)-1)~Is×e^(vbe / vt), therefore

[0074] Vbe=vtln(Ic / Is) Ic=Vin / R1, so

[0075] Vout1=-vt×ln(Vout0 / IsR1)

[0076] If Vin=Axe^(-t / 'T)

[0077] Vout1=-vtln(Ae^-(t / 'T) / IsR1)=-vt(ln(Ae^-(t / 'T)-ln(IsR1))=

[0078] =-vt(lnA+(-(t / 'T))-ln(IsR1))=

[0079] =(vt / 'T)×t-vtln(A / IsR1)

[0080] Therefore, the slope (rate of change) of the logarithmic amplifier output is (vT / 'T), and is therefore inversely proportional to the decay time.

[0081] Also, although there is an offset represented by the second term in the above equation, the signal can be further processed to calculate only the rate of change, and the offset does not need to be included in the calculation.

[0082] You may notice that the measured slope also depends on VT, a temperature-dependent offset that occurs in the diode. There are considerations specific to logarithmic amplifier circuits to mitigate it. Alternatively, you may be in a position to not care about these considerations, as their effect may be so small that it does not affect temperature accuracy beyond the capabilities of common electrical-based temperature sensing solutions such as RTDs and thermocouples.

[0083] This signal is further inverted (because it is negative) and amplified by inverter 165. The output of the inverter is the Vout3 signal 204 in FIG.

[0084] To increase the resolution of the temperature measurement, a fixed voltage can be further subtracted and the resulting signal can be further amplified by a differential amplifier 166, which has as its output the VouT5 signal 206, which is a signal that can be further used to determine the temperature.

[0085] Therefore, the next comparator start block compares the Vout5 voltage 206 with a fixed voltage and can generate a rising edge signal (Vout7 208) when the Vout5 voltage 206 is less than the fixed threshold voltage (Vout6) 202. This transition is converted into a positive pulse (Vout8 212) by the next RC differentiator, which is the output of the comparator start block 167. The pulse start pulse can be used to reset the discrete counter 169 (for example, a clock frequency of about 1 MHz is sufficient) so that it starts counting time from this moment for slope (and therefore time decay) calculation. Another comparator end module, the comparator end block 168, compares the Vout5 voltage 206 with another lower fixed voltage and can generate a rising edge signal (Vout4 214) when the Vout5 voltage 206 is less than the fixed threshold voltage. This transition is converted into a positive pulse (Vout6) 202 by the next RC differentiator, which is the output of the comparator end block 168.

[0086] The end-of-pulse pulse can be used to latch into digital latch 170 the calculated time that has elapsed since the pulse start instant, the value of which corresponds to the slope of Vout5 206 and is therefore proportional to the decay time which is representative of the temperature detected by probe 48.

[0087] Referring again to FIG. 11a, the value latched in latch 170 can be used as an address to a separate non-volatile memory 171, for example a one-time programmable memory chip (represented by the module downstream of latch 170).

[0088] The memory chip 171 contains data such as digital values ​​corresponding to the voltages exhibited by a K-type thermocouple at various temperatures (eg, one voltage reading per degree C is sufficient).

[0089] In this way, any dependency between temperature and a measurement of interest can be programmed into the memory chip 171 once during manufacturing. In this way, the memory acts like a fixed, solid-state digital circuit. This is one of many solutions for performing calibration.

[0090] If the output value needs to be an analog voltage, a digital-to-analog converter (e.g., DAC 172) can be added. Based on the above-described embodiments, temperature information (digital or analog) can be continuously available and updated in real time without the need for running firmware or software.

[0091] It will be appreciated that the components used in the configurations shown in Figures 11a and 11b are typically inexpensive, yet do not require firmware or software, providing a solution that is relatively easy to UL safety (temperature limit) certified, and a simple, inexpensive ASIC implementation may also be provided.

[0092] It will be appreciated that the components described in connection with FIGS. 11a and 11b are solid-state components in that they do not require any firmware or software to be simultaneously executed in order to operate. For example, according to exemplary embodiments, a solid-state component may limit its input positive or negative charge when generating an output. Solid-state components may be crystalline, polycrystalline, amorphous elements, etc. Solid-state components may include one or more semiconductors, conductors, insulators, etc., and may include components with moving parts, such as exemplary latch implementations. Some solid-state components may output signals that can be amplified or otherwise manipulated (e.g., via an operational amplifier) ​​depending on requirements.

[0093] Those skilled in the art will understand that the embodiments described herein may be practiced without these specific details or specific solid-state components. Modifications of the solid-state components are contemplated, such as modifying the type or characteristics of the solid-state components (e.g., changing the output threshold in an amplifier) ​​to manipulate the signal. Similarly, consequential modifications to the methods and procedures associated with the solid-state parts (e.g., further modifying the signal to provide additional gain), establishing different thresholds, or employing other noise filtration techniques to arrive at temperature measurements are also contemplated.

[0094] In other applications, the same principles can be used to provide temperature sensing solutions that are more easily certified for safety (e.g., since process temperature limits are often required), because it is very difficult and resource-intensive to certify equipment safety (especially by UL) if the functionality relies on firmware and / or software. In such other applications, the same type of circuitry can be used, but the functionality can be significantly simpler, because no memory devices need to be employed and no latches are required.

[0095] For a higher than threshold temperature condition, the output of the counter may be less than a predetermined threshold value representing the temperature threshold (a condition that can be read by employing only simple logic gate combinations) and is converted to the aforementioned logic gate combination going from zero to one. That logic level becomes the output of the process temperature limit detector, again, implementable without firmware, software, or memory devices.

[0096] For simplicity and clarity of illustration, reference numerals may be repeated among the figures where considered appropriate to indicate corresponding or analogous elements. Furthermore, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those skilled in the art that the embodiments described herein may be practiced without these specific details. In other embodiments, well-known methods, procedures, and components have not been described in detail so as not to obscure the embodiments described herein. Furthermore, this description should not be considered as limiting the scope of the embodiments described herein.

[0097] It will be understood that the examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For example, components and modules can be added, removed, modified, or arranged in different connections without departing from these principles.

[0098] It will also be understood that any module or component illustrated herein that executes instructions may include or be otherwise accessible to a computer-readable medium, such as a storage medium, computer storage medium, or data storage device (removable and / or non-removable), e.g., magnetic disks, optical disks, or tape. Computer storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and that is accessible by an application, a module, or both. Any such computer storage medium may be part of, or accessible to, or connectable to, the sensors 12, 14, the controller 18, the heating system 16, any component thereof, or components associated therewith, etc. Any applications or modules described herein may be implemented using computer-readable / executable instructions that may be stored or otherwise maintained by such computer-readable media.

[0099] The steps or operations in the flowcharts and diagrams described herein are merely examples. There may be many variations on these steps or operations without departing from the principles described above. For example, steps may be performed in a different order, or steps may be added, deleted, or modified.

[0100] While the above principles have been described with reference to specific embodiments, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims.

Claims

1. 1. An optical temperature sensor system for detecting a temperature of an environment, comprising: a temperature probe having an optical fiber temperature sensor; a transducer that generates a temperature output using solid state electronics and without software; An optical temperature sensor system comprising:

2. The fiber optic temperature sensor generates a signal in response to sensing a temperature of the environment, the signal varying with an attenuation rate responsive to the temperature. The converter comprises: converting the signal into an intermediate signal representative of the attenuation rate by comparing one or more signal characteristics with one or more expected signal characteristics; 10. The system of claim 1, comprising a signal processing system including solid-state electronics configured to convert the intermediate signal into a temperature output by comparing the intermediate signal to an expected decay rate associated with a reference temperature.

3. 3. The system of claim 1 or 2, wherein the temperature output is in the form of an output from a thermocouple or a thermistor.

4. 4. The system of claim 1, wherein the fiber optic sensor is a phosphor-based or GaAs-based fiber optic sensor.

5. 5. The system of claim 1, wherein the signal processing system comprises a logarithmic amplifier configured to convert the signal into the intermediate signal having a rate of change that is inversely proportional to the attenuation rate.

6. the signal processing system includes one or more comparators configured to generate one or more pulses in response to the intermediate signal crossing one or more thresholds; The system of claim 5 , wherein the temperature output is generated based on an observed decay rate during the one or more pulses.

7. 6. The system of claim 5, wherein the signal processing system includes a separate non-volatile memory that converts the intermediate signal to the temperature output based on a pre-programmed conversion.

8. 8. The system of claim 1, further comprising a secondary temperature sensor configured to generate a further signal in response to sensing a temperature of the environment, the further signal being provided to the temperature limiting protection circuit as a redundant temperature measurement.

9. 1. An optical temperature sensor system for detecting a temperature of an environment, comprising: a temperature probe having a fiber optic temperature sensor; and a transducer for generating separate first and second temperature outputs based on signals from the fiber optic temperature sensor by two or more parallel readout electronics.

10. 10. The system of claim 9, wherein the two or more parallel readout electronics are solid-state electronics with no software.

11. 11. The system of claim 9 or 10, wherein the first temperature output or the second temperature output indicates an over-temperature condition.

12. 11. The system of claim 9 or 10, wherein the first temperature output or the second temperature output indicates a fault condition.

13. 13. The system of claim 9, wherein at least one of the two or more readout electronics comprises programmable hardware.

14. 15. The system of claim 9, 10, or 14, wherein the first temperature output or the second temperature output is in the form of a thermocouple or thermistor output.

15. 15. The system of claim 14, wherein the first temperature output or the second temperature output is a voltage value of a K-type thermocouple.

16. 16. The system of claim 9, wherein the temperature probe comprises a single probe with a single thermally conductive tip for measuring the surface temperature of an object in the environment.

17. 16. A system according to any one of claims 9 to 15, wherein the temperature probe is housed within a sheath for measuring the temperature within a liquid or gas.

18. 1. A system for sensing the temperature of an object, comprising: a fiber optic temperature sensor that generates a signal in response to sensing temperature, the signal varying according to an attenuation rate responsive to temperature; redundant temperature sensors configured to generate redundant signals in response to sensing temperatures; converting said signal into an intermediate signal representative of the rate of decay by comparing one or more signal characteristics with one or more expected signal characteristics; and converting the intermediate signal into a temperature output based on comparing the intermediate signal to an expected decay rate; and a signal processing system configured to output the redundant signal and / or the temperature output to a temperature limiting protection circuit.

19. 20. The system of claim 18, wherein the signal processing system is constructed from one or more solid state components.

20. 20. The system of claim 18 or 19, wherein the fiber optic temperature sensor and the redundant temperature sensor are in one probe.

21. 21. The system of claim 20, wherein the fiber optic temperature sensor and the redundant temperature sensor are contained in a single thermally conductive tip of the single probe to measure a surface temperature of the object.

22. 21. The system of claim 20, wherein the fiber optic temperature sensor and the redundant temperature sensor are housed within a single sheath and measure temperature within a liquid or gas.

23. 23. The system of any of claims 18 to 22, wherein the temperature output is a K-type thermocouple voltage.

24. 24. The system of any of claims 18 to 23, wherein the fiber optic temperature sensor is a phosphor-based or GaAs-based fiber optic sensor.

25. 25. The system of any one of claims 18 to 24, wherein the redundant temperature sensors are phosphor-based or GaAs-based fiber optic sensors.

26. 25. The system of any of claims 18 to 24, wherein the redundant temperature sensors are thermocouples or thermistors, and the signal processing system includes a programmable memory used to convert the signals to the temperature output.

27. 27. A system according to any of claims 18 to 26, wherein the programmable memory contains one or more parameters and / or calibration values ​​associated with one or more of the objects and the redundant temperature sensors.

28. a heating element coupled to a heating element controller; a temperature probe having a fiber optic temperature sensor; generating a first temperature output based on a signal from the temperature probe using solid state electronics without software; generating a second temperature output based on processing the signal in one or more memories; a converter that outputs the first temperature output and the second temperature output to the heating element controller; The heating element controller adjusts operation of the heating element based on the received first temperature output and the received second temperature output.

29. 30. The system of claim 28, wherein the heating element is a radio frequency heater powered by a radio frequency power source, and the first temperature output is a UL Listed or IEC 61508 programmable readout readable by the heating element controller.

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