Sensor, transmitter and related methods

Abstract

Embodiments of the present disclosure relate to sensors, emitters, and related methods. Examples refer to emitters, sensors, detectors, emitting methods, sensing methods, and non-transitory storage units storing instructions that, when executed on a computer, perform an emitting method or a sensing method. An emitter for emitting radiation of a particular wavelength can include a Joule-heated emission electrical conductor configured to emit radiation of the particular wavelength at an emission temperature, a controller configured to, in operation, control a variable voltage affected by the Joule-heated emission electrical conductor and modulated according to a duty cycle, the duty cycle being variable between a high average power duty cycle during a hot period such that the Joule-heated emission electrical conductor is affected by a high average power to reach and maintain the emission temperature, and a low average power duty cycle during a cold period alternating with the hot period such that the Joule-heated emission electrical conductor is affected by a low average power to reach a temperature less than the emission temperature.

Description

Technical Field

[0001] The following examples refer to transmitters, sensors, and detectors, such as those used for fluid sensing. The examples also relate to transmission methods and / or sensing methods that perform the transmission or sensing methods, as well as non-transitory storage units that store instructions that, when executed on a computer, perform the transmission or sensing methods.

[0002] One example involves a transmitter used to emit radiation, such as a visible light transmitter, an infrared (IR) transmitter, or a mid-infrared (MIR) transmitter.

[0003] One example involves fluid sensors, such as gas sensors. Fluid sensors can include transmitters and detectors. Detectors can be photoacoustic sensors (PAS), optical sensors, infrared (IR) sensors, and more specifically, MIR sensors.

[0004] One example relates to emission and sensing methods, for instance, for measuring the concentration of a fluid (e.g., a gas). Background Technology

[0005] Fluid sensors (e.g., gas sensors) can be used to detect the amount of a target fluid in a target environment. Fluid sensors can be, for example, microelectromechanical systems (MEMS) devices and can imply the use of microcontrollers.

[0006] Fluid sensors may include transmitters for emitting radiation of a specific wavelength onto a target environment. The target environment is typically filled with a target fluid, the amount (or concentration) of which will be measured. The radiation should have a specific wavelength associated with the target fluid to excite molecules or atoms at their characteristic wavelength (e.g., the typical maximum absorption wavelength of the target gas). A detector downstream of the target environment is illuminated by the radiation propagating through it. At the detector, an electrical signal indicating the propagated radiation is measured. The amount or concentration of the target fluid in the target environment is obtained from the electrical signal.

[0007] In some cases, the detector is a photoacoustic detector that includes a microphone. The microphone includes a microphone diaphragm, which is located inside the target environment or within a sealed environment filled with a reference fluid. In either case, the pressure of the target fluid and / or the reference fluid changes due to the photoacoustic effect, i.e., due to pressure variations (either within the target environment or the sealed environment) caused by the interaction of radiation (at a specific wavelength) with the molecules of the target fluid and / or the reference fluid. These pressure variations are acoustic waves that deform the microphone diaphragm, resulting in the generation of an electrical signal indicating the acoustic waves. The acoustic waves are associated with impact radiation, which in turn is associated with the amount or concentration of the target fluid. Therefore, by analyzing the electrical signal generated by the microphone, information related to the amount or concentration of the target fluid can be obtained.

[0008] In other cases (e.g., for nondispersive infrared, NDIR, sensors), the detector can be a thermal detector and perform thermal measurements associated with impact radiation of a specific wavelength, or it can measure the quantity or concentration of the target fluid.

[0009] The transmitter may include an electrical conductor that dissipates electrical power through the Joule effect, irradiating the target environment with radiation of different wavelengths depending on the temperature reached at the conductor. The temperature of the conductor follows... The law of light states that the power of emitted radiation is proportional to the fourth power of temperature. Even if the same law does not apply, wavelength is still a function of temperature. The temperature T of a conductor can be directly measured. CONDUCTOR .

[0010] However, this is not an easy task: the temperature T of the conductor... CONDUCTOR It's easy to exceed 900℃, which is not a temperature that is easily measured or directly controlled (especially for MEMS devices). Furthermore, the transition conductor temperature T... CONDUCTOR The transducer may output voltages that are difficult for the microcontroller to manage. This often requires the use of Zener diodes to save the microcontroller and frequently involves the use of static converters (e.g., DC / DC, DC / DC converters) to reduce the voltage.

[0011] Therefore, they sought technologies to reduce equipment usage.

[0012] In addition, there are some problems with the measurements performed by the detector. In some implementations, the transmitter does not send radiation discontinuously, but rather in a periodic manner (pulse train). For example, the transmission could follow a squared signal, such that "hot" periods (where the Joule effect causes the temperature to reach the temperature required to emit radiation at a specific wavelength) alternate with "cold" periods (where no power is supplied to the conductor, i.e., there is no Joule effect, and the conductor temperature decreases).

[0013] However, it has been noted that this method of measurement is suboptimal. Measurements obtained from electrical signals (e.g., those obtained via a microphone or as part of subsequent processing) are affected by errors caused by thermal phenomena, making it difficult to obtain accurate measurements. For example, thermoacoustic waves may be generated that carry unwanted heat, but this heat reaches the detector and introduces errors into the detection.

[0014] They are also seeking techniques to reduce errors caused by thermal phenomena.

[0015] Specifically, it preferably has an emitter that generates radiation without producing an undesirable correlation with voltage and ambient temperature. Summary of the Invention

[0016] According to one aspect, a transmitter for emitting radiation of a specific wavelength is disclosed, the transmitter comprising:

[0017] The emitting conductor, heated by Joule, is configured to emit radiation of a specific wavelength at its emission temperature.

[0018] The controller is configured, during operation, to control a variable voltage affected by a Joule-heated transmitting conductor and modulated according to a duty cycle, the duty cycle being variable among the following:

[0019] The high average power duty cycle during the thermal cycle causes the Joule-heated transmitting conductor to reach and maintain its emission temperature under the influence of the high average power; and

[0020] The low average power duty cycle during the cold cycle, which alternates with the hot cycle, causes the Joule-heated transmitting conductor to reach a temperature below the emission temperature due to the low average power. This low average power duty cycle is less than the high average power duty cycle.

[0021] At least one of the high average power duty cycle and the low average power duty cycle is defined based on at least one temperature indication measurement, which indicates the measured ambient temperature.

[0022] Therefore, it is not necessary to have a sensor that directly measures the temperature of the transmitting conductor heated by Joule.

[0023] According to one aspect, for at least one thermal cycle, the controller can limit the high average power duty cycle to a duty cycle that allows the emission temperature to be reached and maintained at the Joule-heated emission conductor.

[0024] Therefore, the negative impacts of changes in ambient temperature are avoided.

[0025] According to one aspect, the controller can limit the duty cycle for at least one hot or cold cycle based on the following:

[0026] At least one temperature indication measurement is provided so that high ambient temperatures are compensated for by a low duty cycle, and vice versa.

[0027] According to one aspect, the controller can limit the duty cycle for at least one hot or cold cycle based on the following:

[0028] At least one voltage indication measurement indicates the voltage applied to the Joule-heated transmitting conductor, such that a high voltage is compensated by a small duty cycle, and vice versa.

[0029] Therefore, the voltage change at the emitting conductor heated by Joule is compensated.

[0030] According to one example, the controller (250) can be configured to limit the low average power duty cycle to a duty cycle that causes a reduction in electrical power relative to the high average power for at least one cold cycle, wherein the reduction is constant regardless of the ambient temperature.

[0031] Therefore, the sensed values ​​are more reliable and the negative effects of thermoacoustic phenomena are compensated.

[0032] According to one aspect, during the initialization process, the controller can be configured to control a variable voltage affected by a Joule-heated transmitting conductor and modulated according to a duty cycle, the duty cycle being variable among:

[0033] The high average power duty cycle during the thermal cycle causes the Joule-heated transmitting conductor to reach and maintain its emission temperature under the influence of the high average power; and

[0034] The low average power duty cycle during the cold cycle, which alternates with the hot cycle, causes the Joule-heated transmitting conductor to reach a temperature below the emission temperature due to the low average power. This low average power duty cycle is less than the high average power duty cycle.

[0035] During the initialization process, the decrease between high and low average power remains constant, and the ambient temperature also remains constant.

[0036] The controller is configured to limit the low average power duty cycle during operation such that the decrease between the high and low average power is the same as the decrease between the high and low average power experienced during the initialization process.

[0037] This also allows for compensation of negative thermoacoustic phenomena.

[0038] According to one aspect, a sensor for determining fluid properties is provided, comprising:

[0039] As described above, the specific wavelength of the transmitter is a characteristic of the fluid's wavelength; and

[0040] The detector is configured to detect electrical signals associated with the radiation emitted by the transmitter.

[0041] The transmitter and detector are configured such that the radiation emitted by the transmitter propagates through the target volume containing the target fluid, thereby correlating the electrical signal with the properties of the fluid.

[0042] The sensor can operate according to an initialization process that uses a detector to provide multiple emission and detection for different known fluid volumes to personalize the detection rule, which maps the fluid volume to a reading unit to be converted into a fluid volume. The sensor is configured to limit the low average power duty cycle during operation such that the reduction between the high and low average power is the same as the reduction between the high and low average power experienced during the initialization process.

[0043] According to one aspect, a method for emitting radiation of a specific wavelength is provided, including:

[0044] Radiation is emitted at a specific emission temperature using a Joule-heated emitting conductor.

[0045] The transmission is affected by modulation based on the duty cycle, which can vary among the following:

[0046] The high average power duty cycle during the thermal cycle causes the Joule-heated transmitting conductor to reach and maintain its emission temperature under the influence of the high average power; and

[0047] The low average power duty cycle during the cold cycle, which alternates with the hot cycle, causes the Joule-heated transmitting conductor to reach the secondary emission temperature under the influence of low average power, where the low average power duty cycle is smaller than the high average power duty cycle.

[0048] At least one of the high average power duty cycle and the low average power duty cycle is defined based on at least one temperature indication measurement, which indicates the measured ambient temperature.

[0049] According to one aspect, a sensing method for determining fluid properties is provided, including:

[0050] Perform the above method;

[0051] Allowing radiation to propagate through a target volume containing the target fluid; and

[0052] Detect the electrical signal associated with the radiation emitted by the transmitter, and then correlate the electrical signal with the fluid properties.

[0053] According to one aspect, a non-transitory storage unit is provided for storing instructions that, when executed on a computer, cause the computer to perform the methods described above. Attached Figure Description

[0054] Figure 1a and Figure 1b Two schemes based on an example fluid sensor are shown.

[0055] Figure 2 It shows that it can be Figure 1a or Figure 1b The transmitter shown is the transmitter of the transmitter.

[0056] Figure 3 It shows that it can be Figure 1a or Figure 1b A schematic diagram of a fluid sensor.

[0057] Figure 4 illustrates pulse width modulation (PWM) associated with a transmitter, which can be... Figure 2 The transmitter.

[0058] Figure 5 shows a diagram illustrating the advantages of this technology.

[0059] Figure 6 The method is shown based on an example. Detailed Implementation

[0060] Throughout the instruction manual, even when intended to be effective for fluids, the term "gas" is generally used.

[0061] Figure 1a A schematic example of a fluid sensor 100 is shown. Sensor 100 may include an emitter 200 (e.g., an optical emitter, light emitter, IR emitter, etc.) and a detector 300 (e.g., an optical detector, light detector, IR detector, etc.). Sensor 100 may be, for example, a non-dispersive infrared (NDIR) sensor or a photoacoustic (PAS) sensor. Sensor 100, emitter 200, and detector 300 may be MEMS devices.

[0062] Emitter 200 can emit radiation 201 at a specific wavelength λ0 (which can be selected, for example, a characteristic wavelength of a specific fluid to be measured). Radiation 201 can be or includes light. Radiation 201 can be or includes infrared (IR) radiation (e.g., MIR radiation). Radiation 201 can include laser radiation. Radiation 201 can be at a specific wavelength λ0, and in the sense that it is in a narrow band, it includes the specific wavelength λ0. The narrow band can be approximated as the interval [λ0-δλ, λ0+δλ], where δλ is a small increment wavelength.

[0063] Sensor 100 may include detector 300 for receiving radiation 203 emitted by transmitter 200. Detector 300 may be, for example, a light intensity detector or a photoacoustic detector. If detector 200 is a photoacoustic detector, it includes a microphone that converts pressure changes (sound waves, sound) into electrical signals.

[0064] An optical filter 202 can be inserted between the transmitter 200 and the detector 300. The optical filter 202 may include a photonic crystal structure. Alternatively, the optical filter 202 may be a Fabry-Perot optical filter. The optical filter 202 can be understood as a wavelength-selective structure that provides radiation 203 in a more restricted narrow band (still containing a specific wavelength λ0). For example, the band becomes [λ0-dλ, λ0+dλ], where dλ << δλ. It should be noted that even for clarity, in Figure 1a The optical filter 202 is clearly shown in the schematic diagram, but the optical filter 202 can also be considered as part of the transmitter 200.

[0065] Therefore, optical paths 201 and 203 are defined between the transmitter 200 and the detector 300. In optical paths 201 and 203, radiation 203 passes through the target volume 204 (the target environment), in which a target gas (or more generally, a target fluid) is present. The target gas absorbs and emits photons of specific wavelengths (each gas is characterized by a specific wavelength, i.e., wavelength 201 or 203 intended to be emitted by the transmitter 200). Thus, after propagating through the target volume 204 (and after exciting molecules or atoms of a specific gas intended to be measured in quantity or concentration), radiation 203 is used, for example, to determine the properties of the fluid by measuring its quantity or concentration. Specifically, an electrical signal can be processed at a decoder, indicating the radiation reaching the detector 300.

[0066] In some examples, detector 300 is enclosed within a sealed volume in which a reference gas is present, thus allowing measurement of the amount or concentration of a target gas placed outside the closed volume (within target volume 204). In other examples, the target gas reaches directly into the interior of detector 300, and its amount or concentration is measured directly by detector 300.

[0067] Figure 1b The image shows sensor 100 (which can be connected to...). Figure 1a Another diagram (same as above) (can also be referenced) Figure 2 Sensor 100 includes a Joule-heated emitting conductor (heater) 260. The Joule-heated emitting conductor 260 can be in the form of a suspended heating film anchored to a support element. The heating film can be heated via the Joule effect. With its temperature, the Joule-heated emitting conductor 260 generates radiation according to Planck's law (the hotter the heater 260, the smaller the wavelength λ0).

[0068] The Joule-heated emitting conductor (heater) 260 can be heated by the Joule effect at the temperature of radiation 201 (or its filtered version 203, optical filter 202 not shown) that results in an emission wavelength of λ0. After propagating through the target volume 204a (which is supplemented with the target gas to be measured), the light radiation reaches the sealed volume (e.g., PAS volume) 204b. The sealed volume 204b contains a fixed, known amount of reference gas. The radiation excites molecules or atoms of the target gas in the target volume 204a and the reference gas in the sealed volume 204b. The radiation 203 passes through the transparent window 302 and the sealed volume 204b, and causes a temperature change within the sealed volume 204b, which in turn changes the pressure and causes the diaphragm 310 of the microphone 312 to deform accordingly. An electrical signal 314 can thus be generated. The electrical signal 324 can provide information related to the amount or concentration of the target gas in the target volume 204a.

[0069] The PAS detector can be replaced by a detector that directly converts the radiation entering via window 302 into an electrical signal. In this case, there will be no microphone 312 and membrane 310, but in any case, an electrical signal indicating the amount of target gas will be obtained. It should also be noted that in any case, the volume of detector 300 is not necessarily closed, but can also be an open volume sensor, with no reference gas inserted into the closed volume.

[0070] from Figure 1b As can be seen, the Joule-heated emitting conductor 260 can be structurally and structurally made such that:

[0071] -At the emission temperature T HOT At temperatures of 950°C or above 400°C or above 600°C, the Joule-heated emitting conductor 260 emits radiation including a specific wavelength λ0 (which may be the wavelength characteristics of the specific gas to be measured).

[0072] -At least the sub-emission temperature T COLD (For example, 85°C), for example at T COLD < <T HOT (For example, the secondary emission temperature T) COLD Equal to or greater than ambient temperature T AMBIENT For example, T COLD >T AMBIENT In the case of Joule heating, the emitting conductor 260 does not emit (or emits a negligible amount of radiation) radiation of a specific wavelength λ0 (it can radiate in different frequency bands according to Planck's law), or it can radiate to it in a negligible amount.

[0073] Note that, according to Planck's law, at the secondary emission temperature TCOLD At this temperature, some negligible emission may occur at wavelength λ0. For example, at the secondary emission temperature T... COLD Under these conditions, the radiation intensity can be reduced to less than 5%, or even less than 1%, or less than 0.1%. Here, when referring to the sub-emission temperature, it is assumed that the emission at wavelength λ0 is negligible and approximately zero. Note that when referring to the sub-emission temperature (T... COLD When this is the case, the sub-emission temperature range can be referenced (e.g., T). AMBIENT ≤T COLD ≤T COLD,MAX <T HOT ).

[0074] It should also be noted that the secondary launch temperature T COLD It is not necessarily a single predefined temperature value. The range of secondary emission temperatures can therefore be limited (i.e., the temperature range in which radiation at wavelength λ0 is not generated or can be ignored). Therefore, in the following paragraphs, "secondary emission temperature" is generally used to indicate that the secondary emission temperature is not necessarily at a single temperature value.

[0075] Conversely, as shown below, the emission temperature T HOT (Ideally, for a specific gas, this could be a single value) and can be controlled with high precision using techniques discussed below. Therefore, in the following paragraphs, "emission temperature T" is generally referred to in the sense of aiming to achieve a specific emission temperature value. HOT ".

[0076] Specifically, the emission at the Joule-heated emitting conductor 260 can be controlled such that:

[0077] - During certain cycles (e.g., "thermal cycles"), the Joule-heated emitting conductor 260 actually emits a large amount of radiation 201, 203 with wavelength λ0, and

[0078] - During other cycles (“cold cycles”) that alternate with the thermal cycle, the Joule-heated emitting conductor 260 is maintained at a sub-emission temperature T where the radiation does not include a specific wavelength λ0 or includes a negligible amount of wavelength. COLD (For example, below the emission temperature T) HOT ) place.

[0079] The variable voltage v at the Joule-heated emitting conductor 260 DD (See also) Figure 2 (And Figure 4) is also indicated here as signal 270. Signal 270 can be understood as a combination of the effects of the following two signals:

[0080] -Low-frequency (LF) signal 272 (in Figure 1bThe signal is indicated as "PAS to microphone alternating signal", but it can also be used with non-PAS devices.

[0081] - High frequency (HF) signal 274 (in Figure 1b (It is indicated as "PWM control voltage source").

[0082] Signals 272 and 274 can be understood as PWM signals, and the resulting signal 270 can be understood as a modulated combination of the two PWM signals 272 and 274. A pulse train is thus generated. As will be explained later, signals 272 and 274 modulate each other, causing the Joule-heated conductor 260 to operate according to two different modes:

[0083] - In the high average power mode during the thermal cycle, the Joule-heated emitter conductor 260 is affected by high average power, reaching and maintaining the emitter temperature T. HOT ;as well as

[0084] - In the low average power mode during the cold cycle, the Joule-heated emitter conductor 260 is affected by low average power, reaching and maintaining the sub-emission temperature T. COLD (Low average power is less than high average power.)

[0085] As will be shown later, HF signal 274 is responsible for reaching and maintaining the emission temperature T during the thermal cycle. HOT And during the cold cycle, it remains at the secondary launch temperature (below the launch temperature T). HOT At this location, LF signal 272 is responsible for timing the alternation of the hot and cold cycles.

[0086] In some examples, the LF signal 272 can be a bi-state periodic signal divided into two half-cycles, each half-cycle having a time length equal to half the period of signal 272. Figure 4 shows the period 472 of the LF signal 272 divided into two half-cycles 472h (i.e., the hot period) and 472c (i.e., the cold period). However, note that the period 472 does not necessarily need to be precisely divided into two half-cycles of equal length, but different subdivisions are possible. Generally, it can be understood that the period 472 is subdivided into a hot sub-period 472h (i.e., the hot period) and a cold sub-period 472c (i.e., the cold period), the reciprocals of which can vary depending on the specific implementation.

[0087] The LF signal 272 may have a frequency between 10 Hz and 40 Hz or 100 Hz (e.g., 25 Hz). This frequency is suitable for allowing the transmission of radiation pulses of a specific wavelength λ0 (during a hot cycle) to alternate with radiation of a wavelength λ0 that is not present (during a cold cycle). The frequency range between 10 Hz and 40 Hz or 100 Hz is particularly suitable for allowing effective detection at detector 300 (e.g., when detector 300 is a photoacoustic detector, microphone 312 can reliably detect sound in the range between 10 Hz and 10 Hz or 100 Hz).

[0088] HF signal 274 can be understood, for example, as digitally controlled PWM, which modulates the voltage of the Joule-heated transmitting conductor 260 between the following:

[0089] -High voltage value V DD (Where the voltage amplitude is greater than 0, for example, greater than 5V, or in other cases greater than 12V, for example, V) DD =12V); and

[0090] -0 voltage or low voltage value (where the voltage amplitude is less than that of a high voltage value).

[0091] The PWM of HF signal 274 has a high duty cycle during the hot cycle 472h (thus providing high average power to the Joule-heated transmitting conductor 260) and a low duty cycle during the cold cycle 472c to reduce the average power supplied to the Joule-heated transmitting conductor 260. The PWM duty cycle is typically a dimensionless positive number (or percentage) between 0 and 1 (or 0% and 100%). The duty cycle indicates the relative proportion between the duration of a high voltage value and the duration of a 0 or low voltage value over a given entire cycle: for example, if the duty cycle is 0, a high voltage value is never reached; if the duty cycle is 1 (or 100%), a high voltage value is continuously applied; if the duty cycle is 0.5 (or 50%), high and 0 or low voltage values ​​alternate for the same duration, and the average voltage applied to the heater 260 is V. DD / 2. However, in this case, the high duty cycle of 472h in the thermal cycle is limited to reaching the launch temperature.

[0092] Figure 2 The transmitter (e.g., is shown) Figure 1a and / or Figure 1b Example 200 of a transmitter. The transmitter 200 includes a Joule-heated transmitting conductor (heater) 260 as a transmitter operating at a variable voltage v. DD The element that generates radiation 201 is activated by the action of the controller 250. Under the control 210 applied by the controller 250, the voltage v DD(Signal 270) can be fed to terminals 206 and 207 of the Joule-heated transmitting conductor 260. Terminals 206 and 207 can be connected to conductor lines 208 and 209, respectively. Line 209 can be imagined as a mass, and line 208 can be powered by a constant potential V. DD >0 feed (or lines 208 and 209 are simply at different polarities or potentials). Switch 212 can connect the near-end branch 208b (at a constant potential V). DD >0) and the distal branch 208a (connected to terminal 206) separate, thereby causing V DD Alternating between 0 and 0. Variable voltage V DD It can be supplied to a Joule-heated transmitting conductor as a fixed voltage amplitude V controlled by switch 212 controlled by controller 250. DD The pulse. (In alternative embodiments, different solutions can be used. In some cases, the variable voltage V...) DD (This can be provided directly by controller 250). Switch 212 can be, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET), and control 210 can be connected to the gate of the MOSFET. The terminals associated with switch 212 can be the source and drain of the MOSFET (one of the source and drain is connected to the far end branch 208a, and the other is connected to the near end branch 206).

[0093] Controller 210 can be understood as a PWM for controlling signals 272 and 274. Controller 250 may include or be connected to the input of timer 252, which provides a timing signal 272' to control the LF signal 272: timing signal 272' can control the transition from a hot cycle to a cold cycle and vice versa. Timer 252 may be or include a phase-locked loop (PLL) circuit and / or may be powered by an external clock input (not shown).

[0094] Transmitter 200 may include voltage sensor 230 (which in Figure 2The component is shown as being inside the controller 250 (but it could also be an external component) or connected to the voltage sensor 230 at the input. The voltage sensor 230 can be connected to lines 208 and 209 (e.g., branch 208a and line 209) that feed power to terminals 206 and 207 of the Joule-heated transmitting conductor 260 (specifically, when switch 212 is present, a portion of terminal 208 is positioned downstream of switch 212). In the example, the voltage sensor 230 can be connected to only one of the two conductor lines 208 and 209 (e.g., when line 209 is already connected to the mass, it may not be necessary to also directly connect the voltage sensor 230 to conductor line 209, as the voltage sensor 230 could also be connected to the mass). In the example, the voltage sensor 230 can be replaced by another electrical sensor (e.g., a current sensor) that provides a measurement associated with voltage. In any case, the voltage sensor 230 provides at least a voltage indication measurement 230', which provides information related to the actual voltage experienced by the Joule-heated emitting conductor 260. For example, the voltage indication measurement 230' may be in, for example, the digital domain. It has been noted that even for a variable voltage v... DD Even with extremely precise control by switch 212, some undesirable voltage variations can still occur. Therefore, by sensing the voltage v actually supplied to the Joule-heated transmitting conductor 260... DD This allows for more effective control.

[0095] It is understood that it is not necessary to measure the input voltage V in real time. DD A variable voltage v can be applied to the Joule-heated transmitting conductor 260. DD Previously measured input voltage V DD .

[0096] Transmitter 200 may include temperature sensor 240 (in this case, it is shown as part of controller 250, but it may also be provided as a separate element). Temperature sensor 240 may provide a temperature indication measurement 240' (e.g., in the digital domain), which indicates the ambient temperature T. AMBIENT .

[0097] It is understood that when the Joule-heated emitting conductor 260 is in thermal equilibrium with the environment, the ambient temperature T AMBIENT This can be measured as the initial temperature of the emitting conductor 260, which has been Joule-heated. Therefore, the ambient temperature T AMBIENT This can be easily obtained by measuring the temperature of the Joule-heated emitter 260 before applying a variable voltage to it. Therefore, the ambient temperature T... AMBIENTThe measurement does not require an additional temperature sensor that "senses ambient temperature" in some way. Instead, temperature sensor 240 can be simply applied directly to the Joule-heated emitting conductor 260. It can be simply specified that the Joule-heated emitting conductor 260 is turned off for a predetermined amount of time sufficient to allow thermal equilibrium with the environment to be reached. Essentially, the temperature indication measurement 240' can be read temporally prior to the process of applying a variable voltage to heater 260 and the subsequent emission of radiation with wavelength λ0. Note that instead of T... AMBIENT You can refer to T only. CONDUCTOR,INITIAL .

[0098] Controller 250 may include a PWM controller (duty cycle limiter) 220, which may be input by any one of a voltage indication measurement 230', a temperature indication measurement 240', and a timing signal 272'. Therefore, controller 250 may, depending on the specific implementation of voltage control, limit the duty cycle of the hot cycle and the duty cycle of the cold cycle by applying control 210 (based on at least one of the timing signal 272', the voltage indication measurement 230', and the temperature indication measurement 240'), and determine the transition between the hot and cold cycles (and vice versa).

[0099] However, note that control 210 is not necessarily established in real time: simply put, the input voltage V DD and ambient temperature T AMBIENT The variable voltage can be measured before the Joule-heated transmitting conductor 260 is fed. Therefore, the high and low duty cycles are defined before the pulse train is started and do not change during transmission.

[0100] In some examples, the voltage is controlled in real time.

[0101] The controller 250 may have a chip structure, and all or at least some of its components may be provided within a single structure (e.g., a package structure). At least one of the timer 252, voltage sensor 230, and temperature sensor 240 may be inside or outside the chip structure.

[0102] The controller 250 may also be a component that controls the operation of the detector 300 and, more generally, the operation of the sensor 100. The controller 250 may include a PWM controller 220, which is shown herein as a drive controller 210.

[0103] Figure 4 shows the variable voltage v in scheme (a) and time scheme (b). DD (Signal 270) is a partial amplification scheme for 402.

[0104] It can be seen that, based on the variable duty cycle, the variable voltage v DDIt can be limited to a value of 0 (or another low voltage value) and v DD between.

[0105] Scheme (a) shows a sequence of LF signal 272 with a period of 472. Each period 472 is further subdivided into different sub-periods:

[0106] - At least one sub-cycle of 472 hours corresponding to the thermal cycle; and

[0107] - At least one sub-cycle 472c corresponding to the cold cycle.

[0108] (As mentioned above, Figure 4 shows that sub-cycles 472h and 472c are two half-cycles of exactly the same length, but this is not universal, and different lengths and different subdivisions are possible.)

[0109] The subdivision of the LF signal 272 in the continuous period 472 can be based on, for example, timer 252, and controlled by, for example, timing signal 272'.

[0110] As can be seen from scheme (a) in Figure 4, the characteristics of hot cycle 472h and cold cycle 472c are different duty cycles: the duty cycle is high in hot cycle 472h and low in cold cycle 472c.

[0111] Therefore, during the thermal cycle 472h, a high average power is supplied to the conductor 260, while during the cold cycle 472c, a low average power (greater than 0) is supplied to the conductor 260. The duty cycle during the thermal cycle 472h causes the Joule-heated emitting conductor 260 to reach the emission temperature that generates radiation of the desired wavelength λ0. On the other hand, it is understood that the low average power can also be defined such that the average power reached during the cold cycle 472c is a constant decrease relative to the average power during the thermal cycle 472h (the constant decrease does not change with ambient temperature).

[0112] Scheme (b) in Figure 4 shows the duty cycle during hot cycle 472h. (A similar figure will be obtained for cold cycle 472c, except for the difference in the reciprocal length of the time slots). As shown in scheme (b), during high-voltage time slot 474h, the variable voltage v DD A high voltage value v can be used DD For low-voltage time slot 474l, the variable voltage v DD A value of 0 (or another low voltage value) can be used. The relative lengths of time slots 474h and 474l are determined by the duty cycle (e.g., defined by the PWM controller 220). The duty cycle is based on a time period indicated by 474, which is much smaller than the thermal time constant τ. thermalScheme (b) in Figure 4 shows a more elongated extension of the high-voltage time slot 472h relative to the low-voltage time slot 472l, and this is to be expected since scheme (b) involves the hot cycle 472h. In the cold cycle 472c, the length of time slot 474h is much shorter, while the length of time slot 474l is much longer.

[0113] As described above, the duty cycle can be defined by the controller 250 (specifically the PWM controller 220) based on at least one of the voltage indication measurement 230' and the temperature indication measurement 240'. The time variation 480 of the high-voltage time slot 474h can be modified, for example, according to the specific voltage control being implemented.

[0114] Figure 3 An example configuration of a sensor 100 with a simplified operating block (which can be understood as both the elements and method steps of sensor 100) is shown. On one side of the transmitter 200, a duty cycle calculation block 220 (which can be understood as corresponding to a PWM controller 220) can have a voltage indication measurement value 230' at its input. Temperature indication measurement value 240' PWM controller 220 can output a variable voltage v to subject the Joule-heated transmitting conductor 260 to the voltage. DD Control 210 (intended for use with control signal 270).

[0115] At detector 300, a gas (or fluid) measurement block 310 may be provided. When detector 300 acquires information based on photoacoustic sensing (e.g., it includes a microphone 312), the vibration of the membrane is converted into an electrical signal 314. Signal 314 may be provided to output calculation block 318 in its original analog or digital version.

[0116] The final measurement 316 (e.g., the concentration and / or quantity of the fluid) can be output by the output calculation block 318 (e.g., provided to a display peripheral device or otherwise sent to a user, and / or transmitted or stored in a storage memory, such as flash memory or a register), as the final measurement (or more generally, as a characteristic of the fluid).

[0117] At block 318, transmitter 100 (and sensor 200) can determine the relationship between electrical signal 314 and the actual quantity of gas (or fluid) (e.g., in ppm). In the example provided in graph (a) of Figure 5, the vertical axis shows the reading unit (obtained from signal 314), and the horizontal axis shows the actual ppm quantity of the gas (output as value 316). It is understood that the actual quantity of gas and signal 314 (value u) are bound together by a linear function (the linear detection law), as shown in Figure (a), u = u(ppm) + u(0), where u(ppm) is the expected measurement (proportional to the gas quantity), and u(0) is an unwanted offset related to temperature.

[0118] The slope of the linear function u = u(ppm) + u(0) is related to the ambient temperature: therefore, different ambient temperatures will, in principle, lead to different functions with different slopes. By comparing Figure 5(a)(T)... AMBIENT =25℃) and Figure (b) (T AMBIENT =50℃), this result can be seen. Therefore, in principle, the signal 314 collected by sensor 200 may lead to incorrect measurements.

[0119] Figure (a) also shows the offset u(0) in the linear function. Again, in this case, the offset can, in principle, vary in different measurements. In addition to the expected illumination at a specific wavelength λ0, other unwanted thermal phenomena (e.g., thermoacoustic waves) were observed. These unwanted phenomena could, in principle, alter the offset u(0), leading to different readings at block 318 and incorrect representations of the gas quantity.

[0120] However, this technology allows for the handling of these inconveniences. A detailed explanation is provided below.

[0121] Generally speaking, the temperature of conductor 260 (heater) is T. CONDUCTOR =T AMBIENT +ΔT(during a 472-hour thermal cycle, this temperature becomes T) HOT =T AMBIENT +ΔT HOT ), where ΔT is the temperature increment caused by the electrical power supplied to the Joule-heated emitting conductor 260. General formula T CONDUCTOR =T AMBIENT +ΔT becomes T during the 472h thermal cycle. HOT =T AMBIENT +ΔT HOT And it becomes T during the cold cycle. COLD =T AMBIENT +ΔT COLD (Note that T) COLDIt is not necessarily predefined, and only needs to be the secondary emission temperature, which produces zero or negligible radiation at wavelength λ0. If T AMBIENT =25℃ and the emission temperature required to emit radiation of a specific wavelength λ0 is T HOT =950℃, then during the general thermal cycle of 472h, the electrical power P el，HOT This will provide the temperature increment ΔT HOT =T HOT -T AMBIENT =950℃-25℃=925℃.

[0122] During the general thermal cycle of 472 hours, the average electrical power P el，HOT Due to high average power duty cycle D HOT To adjust (e.g., the length of time slot 474h divided by time) period (length), and can be power along time. period The average length of 474. In practice, the electrical power P el，HOT It can be expressed as average power, which is represented as:

[0123]

[0124] Where V dd It is the high voltage value supplied to terminals 206 and 207 of the Joule-heated transmitting conductor 260, and R el，HOT It is the resistance [Ω] (resistance R) of the emitting conductor 260 Ω heated by Joule. el It typically varies with temperature, and this can be reflected by assuming that the resistance during the hot cycle is different from that during the cold cycle, i.e., R el，HOT ≠R el，COLD ).

[0125] It has indeed been noted that, in general, the temperature increment ΔT is related to the average power P. el Proportional to the thermal resistance by a proportionality constant. and Same]. This provides

[0126]

[0127] (where D is the general duty cycle, R is the duty cycle) th It is a general thermal resistor, R el It is a general purpose resistor, V dd It is a constant high voltage value, which changes to a common thermal cycle of 472 hours.

[0128] Combining the above results, the temperature of the Joule-heated emitting conductor 260 follows the following rule:

[0129]

[0130] During the general thermal cycle of 472 hours, it becomes

[0131] It is conceivable that, in order to limit the high average power duty cycle D HOT The temperature of the Joule-heated emitting conductor 260 should be sensed in real time. However, it has been understood that this is not necessary.

[0132] In fact, it is understood that the ambient temperature can be detected instead of the temperature of the Joule-heated emitting conductor 260. (or another temperature indication measurement 240') and the actual voltage experienced at terminals 206 and 207 of the Joule-heated emitting conductor 260 (or another voltage indication measurement 230'). It is understood that, according to The duty cycle D can be easily obtained. HOT In reality:

[0133] -T HOT It is the temperature to be reached (the emission temperature for obtaining radiation with wavelength λ0), and therefore it is known;

[0134] -T AMBIENT It can be Obtained by measurement (e.g., by measuring a temperature indicator at 240°C);

[0135] -V DD It can be That is, the voltage at terminals 206 and 207 of the Joule-heated transmitting conductor 260, obtained by measurement (e.g., by means of temperature indication measurement 240');

[0136] -R el，HOT and R th，HOT These are the resistance of the Joule-heated emitter conductor 260 and the thermal resistance of the Joule-heated emitter conductor 260 during a thermal cycle (generally, both resistance and thermal resistance change with temperature, i.e., R...). el，HOT ≠R el，COLD And R th，HOT ≠R th，COLD (but all are known).

[0137] The controller 250 (and in particular the duty cycle limiter 220) can therefore calculate D. HoT This provides the power required to emit radiation with wavelength λ0 during a thermal cycle of 472h to the Joule-heated emitting conductor 260.

[0138] Therefore, during the 472-hour thermal cycle, the high average power duty cycle DHOT It can be based on the required emission temperature T HOT Control is achieved using at least one voltage indication measurement (230′) and at least one temperature indication measurement (240′), which, as the acquired measurements, define the duty cycle required to maintain the emission temperature.

[0139] As described below, in this example, at least one voltage indication measurement (230′) and at least one temperature indication measurement (240′) can be obtained before the voltage is supplied to the Joule-heated transmitting conductor 260, and therefore, the high average power duty cycle D HOT The value of can be calculated in advance and then retained without further real-time adjustments. Therefore, for a complete measurement session, D HOT It can remain constant.

[0140] Therefore, during the 472-hour thermal cycle, the ambient temperature T can be maintained. AMBIENT Compensation: Regardless of T AMBIENT Regardless of the value, the expected launch temperature T will be reached and maintained. HOT Similarly, V can be executed. DD Compensation: To reach and maintain the expected launch temperature T HOT .

[0141] During the cold cycle 472c, the Joule-heated emitting conductor 260 does not emit radiation of wavelength λ0 (or should at least emit a negligible amount). Therefore, during the cold cycle 472c, the duty cycle D COLD It should be reduced to decrease the average power (P) supplied to the Joule-heated transmitting conductor 260. el，COLD This lowers the temperature and ideally raises it to avoid firing.

[0142] It is understood that, preferably, during the cold cycle 472c, a high average power P is continuously fed to the Joule-heated emitter conductor 260. el，HOT Low average power quantity P with offset (decrease) el，COLD The offset is constant for all measurements and does not change with ambient temperature. Therefore, during the cold cycle at 472°C:

[0143] ΔP el =P el，HOT -P el，COLD =constant>0.

[0144] Based on the example of this technique, the constant ΔP el This can be defined, for example, during the initialization (calibration) process 610 (discussed below) and does not imply change. It has been noted that, in fact, by always maintaining the same constant reduction ΔP... elThe offset u(0) in Figure 5 does not change with different measurements, even when performed at different ambient temperatures. Therefore, during the cold cycle 472°C, the heat transfer caused by thermoacoustic waves is compensated.

[0145] Therefore, the power reduction during the cold cycle is constant in response to the hot cycle. This effect pre-compensates for any possible offset when reading u(0), so it is known and does not require post-compensation.

[0146] Now let's explain how to define the low average power duty cycle D that will be used in cold cycle 472c. COLD Most interpretations follow those based on thermal cycles (see above).

[0147] During the overall cooling cycle of 472°C, the average electrical low power P el，COLD Due to low average power duty cycle D COLD To adjust. Electrical power P el，COLD It can be expressed as the average power by the following formula:

[0148]

[0149] Where V dd It is a (constant) high voltage value supplied to terminals 206 and 207 of the Joule-heated transmitting conductor 260 during a cold cycle of 472 hours, and R el，COLD It is the resistance temperature of the emitting conductor 260, which has been heated by Joule, at the secondary emission temperature.

[0150] Known

[0151] Combining the above results, the temperature at a cold cycle of 472°C is: T COLD This may vary during the general cold cycle because we are not necessarily using a constant T. COLD interested.

[0152] Here:

[0153] -T COLD It is (not necessarily constant) the secondary emission temperature (e.g., at least at one moment during a cold cycle, it can be 85°C);

[0154] -T AMBIENT It can be Obtained by measurement (e.g., by measuring a temperature of 240°C using a temperature indicator);

[0155] -V DD It can be That is, the voltage at terminals 206 and 207 of the Joule-heated emitting conductor 260, such as by means of measurement (e.g., by means of temperature indication measurement 240');

[0156] -R el，COLD and R th，COLD These are the resistance of the Joule-heated emitting conductor 260 and the thermal resistance of the Joule-heated emitting conductor 260, respectively.

[0157] As described below, in this example, at least one voltage indication measurement (230′) and at least one temperature indication measurement (240′) can be obtained before the voltage is supplied to the Joule-heated transmitting conductor 260, and the low average power duty cycle D COLD The value can therefore be calculated in advance (e.g., with a high average power duty cycle D). HOT The calculations are performed together and then maintained without further real-time adjustments. Therefore, for a complete measurement session, D COLD It can remain constant.

[0158] During the cold cycle, we are not interested in reaching a specific temperature, but we only need to avoid (or ignore) emission at a specific wavelength λ0. However, as will be explained later, regardless of ambient temperature and / or input voltage V... DD How can control be implemented to reduce the power ΔP from the hot cycle to the cold cycle? el Keep it constant.

[0159] Figure 6 A method 600 for explaining how the transmitter 100 can operate is shown (the specific operation of the detector 200 is not shown).

[0160] At step 610, the initialization is performed. Subsequently, at 620, the measurement operation is performed (iteration 621 refers to the fact that multiple measurements may depend on the same initialization 610).

[0161] During initialization 610, transmitter 100 (and typically sensor 300) operates as described above (e.g., by generating pulse trains according to the duty cycle described above and emitting radiation during hot and cold cycles as described above). Therefore, any of operations 631-634 (discussed below) can be performed during initialization 610. It is only required that multiple known fluid volumes be measured at the same ambient temperature, and that the same constant decrease ΔP is used between hot and cold cycles. el At the end of initialization 610, a linear detection law can be obtained for a specific ambient temperature (e.g., a graph such as Figure 5(a)).

[0162] For example, during initialization 610, controller 250 can control a variable voltage affected by the Joule-heated transmitting conductor 260 and modulated according to a duty cycle, which is variable among the following:

[0163] The high average power duty cycle during the 472-hour thermal cycle ensures that the Joule-heated transmitting conductor 260 reaches and maintains its emission temperature under the influence of the high average power; and

[0164] The low average power duty cycle during the cold cycle 472c, which alternates with the thermal cycle 472h, causes the Joule-heated transmitting conductor 260 to reach a temperature below the emission temperature due to the low average power. The low average power duty cycle is less than the high average power duty cycle.

[0165] During the initialization process, the decrease between the high average power and the low average power can remain constant, and the ambient temperature also remains constant. Controller 250 can be configured to limit the low average power duty cycle during measurement operation 620 (i.e., after initialization 610) such that the decrease between the high average power and the low average power is the same as the decrease between the high average power and the low average power experienced during the initialization process.

[0166] Similarly, sensor 300 can be understood as being configured to perform an initialization process 610, which, with the aid of detector 300, provides multiple emission and detection for different known fluid quantities to personalize the detection rule, which maps the fluid quantity to a readout unit to be converted into a fluid quantity. In operation, sensor 300 can be configured to limit the low average power duty cycle such that the decrease between high and low average power is the same as the decrease between high and low average power experienced during the initialization process.

[0167] The initialization process 610 can be operated similarly to that in normal measurement operation 620. For example, temperature measurement 240' and / or voltage measurement 230' can be performed in the same manner. In some examples, the initialization process 610 can, for example, use high-precision machinery at a predefined ambient temperature and a predefined power supply voltage V. DD Execute below.

[0168] During measurement operation 620, the results obtained at initialization 610 will be used. Specifically, in operation, transmitter 100 limits the duty cycle such that at any possible ambient temperature, there exists the same constant decrement ΔP used in initialization. el .

[0169] like Figure 6 As can be seen from Figure 4, the launch (step 634) can actually be performed before at least one of the following:

[0170] - Pause step 631, during which no voltage is supplied to heater 260 (e.g., switch 212 remains open); the pause time allows heater 260 to reach thermal equilibrium with the environment;

[0171] - At step 632, a temperature measurement (to reach value 230') and / or a voltage measurement (to reach value 240') are measured;

[0172] - At step 633, the high average power duty cycle and the low average power duty cycle are defined based on the measured values ​​230' and 240'.

[0173] Iteration 635 refers to the fact that several pulses can be generated using the same pre-calculated duty cycle.

[0174] Even if not in Figure 6 As shown, during initialization 610, detector 200 also detects signal 314 and provides an output based on a previously defined linear law.

[0175] In some examples, initialization 610 is not required and can be performed using other methods (e.g., reference data obtained through simulation). In other examples, initialization 610 can be performed multiple times (e.g., when the transmitter is intended to be reinitialized).

[0176] Figure 5 shows four graphs (a), (b), (c), and (d) that allow for an understanding of the advantages of the present invention.

[0177] Graph (a) shows a linear function u [ordinate] that maps to the actual gas quantity [horizontal axis: ppm]. In principle (e.g., the technique discussed here), this graph only applies to T... AMBIENT = 25℃ (which can be the ambient temperature at which initialization 610 has been performed). It can be seen that u(ppm) linearly follows the actual gas quantity, but is affected by a shift at 0ppm (i.e., u(0) > 0). As mentioned above, the shift is related to the decrease in average power ΔP from the hot cycle to the subsequent cold cycle. el Proportional (i.e., u(0)∝ΔP) el The slope of u(ppm) is related to the emission (thermal) temperature (T is used here). max，25 (to indicate) proportionally, that is (where T) max，25 (This refers to the thermal temperature reached from an initial temperature of 25°C without the thermal cycle compensation discussed above). Sensor 300 can view the curve (a).

[0178] Figure (b) shows the output at an ambient temperature of 50°C (without using the techniques described above, such as those for compensating for ambient temperature during the thermal cycle). If different ambient temperatures are not compensated, and the duty cycles for the cold and hot cycles are not modified relative to the case in Figure (a), then by means of T... max，50 >T max，25 (where T) max，50 This is the thermal temperature reached starting from 50℃ (without the thermal cycle compensation discussed above), slope Addendum: The new relationship is shown in Figure (b), but at this point the sensor 300 is unaware of the relationship and may provide incorrect measurements 316.

[0179] However, this inconvenience can be addressed at the transmitter using this technique. Figure (c) illustrates the advantages of this technique (particularly in thermal cycle compensation). Here, T is used. AMBIENT =50℃ (as shown in Figure (b)), we have that at any ambient temperature, the transmitter is subjected to the same emission temperature T. HOT =T max，25 The effect, and the slope can be reported as This is achieved by modifying the duty cycle to account for ambient temperature and voltage at heater 260 to compensate for the effect of a 472-hour thermal cycle. This result is obtained by assuming that conductor 260 is permanently disconnected during the cold cycle (D...). COLD =0). However, undesirably, the offset u(0) is not kept constant but is reduced. This may also lead to incorrect gas quantity readings.

[0180] It is understood that, through use in a cold cycle of 472c, a low average power duty cycle D COLD It is constrained to ensure that the power reduction is constant during measurement (e.g., the same as in initialization) and that the offset reduction is compensated. The favorable effect is depicted in Figure (d). By comparing Figure (a) and Figure (d), it can be seen that at an ambient temperature of 50°C, the function u(ppm) appears to be the same as at an ambient temperature of 25°C (i.e., no change in slope and no offset error relative to the case in Figure (a)).

[0181] Another example can be obtained by comparing T. AMBIENT，1st scenario The first scene at 25℃ and T AMBIENT，2nd scenario Let's understand this from the second scenario at 50℃. First, we need to consider the thermal cycle here:

[0182] Scene 1 (T) AMBIENT，1st scenario =25℃), thermal cycle:

[0183] Peak (emission) temperature T HOT =950℃,

[0184] ΔTHOT =T HOT-TAMBIENT，1st scenario =950℃ - 25℃ = 925℃

[0185] Reaching ΔT HOT，1st scenario Average power P el，HOT，1st scenario It is 400mW (to be provided during the thermal cycle);

[0186] Second Scene (T) AMBIENT =50℃), thermal cycle:

[0187] Peak (emission) temperature T HOT =950℃ (it should be kept constant to allow emission at the necessary wavelength λ0),

[0188] ΔTHOT=T HOT-TAMBIENT，2nd scenario =950℃ - 50℃ = 900℃

[0189] Reaching ΔT HOT，1st scenario Average power P el，HOT，2nd scenario It is 390mW.

[0190] Therefore, the difference between the electrical power in the first scenario and the electrical power in the second scenario is determined to be ΔP. el，HOT，1st scenario-2nd scenario =P el，HOT，1st scenario -P el，HOT，2nd scenario =400mW - 390mW = 10mW. The ΔP of this 10mW during the thermal cycle. el，HOT，1st scenario-2nd scenario This causes an offset drift at the detector, which treats the absolute power as the baseline u(0) (due to thermoacoustic phenomena).

[0191] It must be passed through ΔP el Select the following constant value of 380mW to adjust the average power during the cold cycle to address thermoacoustic phenomena:

[0192] Scene 1 (T) AMBIENT， 1 st scenario =25℃, see above, P has been calculated el，hot，1st scenario =400mW), cooling cycle:

[0193] "Preheating" to a certain power level, for example, 20mW (e.g., given T). COLD =85℃)

[0194] ΔPel=P el，HOT，1st scenario -P el，COLD，1st scenario =400mW - 20mW = 380mW (ΔP) el It should remain constant!

[0195] Scene 2 (T) AMBIENT，2nd scenario =50℃, see above, P has been calculated el，hot，1st scenario =390mW), Cooling cycle:

[0196] "Preheating" at 10mW (T is given) COLD =85℃, because conductor 260 starts hotter than ambient temperature, but uses less power.

[0197] ΔP el =P el，HOT，2nd scenario -P el，COLD，2nd scenario =390mW - 10mW = 380mW (ΔP is the same as that of a 25℃ environment) el Goal achieved!

[0198] Therefore, ΔP el，HOT，1st scenario-2nd scenario ≠0 will result in unwanted offset drift, which means a deviation between the input power and the input power that needs to be kept stable (380mW in this case). By maintaining ΔP el =P el，HOT -P el，COLD The case can be shifted from that in Figure (c) to that in Figure (d): the offset and slope endpoints are the same as in Figure (a), and the amount of gas can be easily measured.

[0199] For example, we can imagine the first scenario as the initialization scenario 610, and the second scenario as the scenario during the measurement operation 620: we have the electrical power ΔP supplied to the heater 260. el The same, constant reduction.

[0200] For general measurements, the following duty cycle can be defined as:

[0201] - During the 472-hour thermal cycle, by taking into account the measured ambient temperature and / or input voltage, resistance and thermal resistance (e.g., based on the formula...) Where T HOT T AMBIENT R th，HOT V DD R el，HOT Given and D HOT (Ignore), the duty cycle is limited to achieve the launch temperature T. HOT ; and / or

[0202] - During the cold cycle 472c, the duty cycle is limited to the implied reduction in electrical power ΔP. el Constant (e.g., constrained in initialization 610), while considering the formula

[0203] For example, it can be used to calculate the low average power duty cycle D. COLD (For example, according to) When ΔP is completed, elThe compensation (to keep it constant). ΔP el The compensation can be performed online by increasing (or decreasing) the input power by the same absolute power during the cold and hot cycles.

[0204] In one example, from the general formula We can get Furthermore, by applying a pre-calculated ΔP el =costant and D HOT You can get D COLD (For example, at step 633).

[0205] The above often refers to dynamically controlled duty cycles (e.g., in cold and hot cycles). However, it should be noted that several techniques exist for selecting the duty cycle. For example, the duty cycle does not necessarily need to change abruptly (e.g., from hot to cold cycles, or based on voltage ripple detection, etc.). Furthermore, the duty cycle can be smoothed, filtered, etc., which also applies to signals 230' and 240' considered for dynamically limiting the duty cycle. Other different modulations based on the same duty cycle can be selected, but this is known.

[0206] Significant progress has been made at the transmitter because the generated radiation is essentially independent of ambient temperature and input voltage. Therefore, the invention is also effective for transmitters used for emission generation but not for gas sensing (and, for example, independently of the results associated with the graph in Figure 5): a transmitter is obtained that emits at a precisely specific wavelength without being negatively affected by ambient temperature and power supply voltage. A stable emission source independent of ambient temperature and power supply voltage is generated.

[0207] Especially for fluid (gas) sensors, the effects of thermoacoustic waves are greatly reduced. The detector 300, placed in the same housing as the transmitter 200, would otherwise be affected by thermoacoustic waves. However, by defining a stable ΔP... el The effects of thermoacoustic waves can be compensated for.

[0208] In addition, the use of DC / DC converters and Zener diodes can be avoided in principle, as changes in power supply voltage are compensated for.

[0209] Although some aspects have been described in the context of the apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method step also represent a description of the corresponding block or item or feature of the corresponding apparatus. Some or all of the method steps can be performed by (or using) hardware means, such as a microprocessor, a programmable computer, or an electronic circuit. In some examples, one or more of the most important method steps can be performed by such means.

[0210] Depending on the implementation requirements, examples of this technology can be implemented in hardware or software. The implementation can be performed using a digital storage medium such as a floppy disk, DVD, Blu-ray, CD, ROM, PROM, EPROM, EEPROM, or flash memory. The digital storage medium has electronically readable control signals stored thereon that cooperate (or are capable of cooperating with) a programmable computer system to cause the corresponding method to be executed. Therefore, the digital storage medium can be computer-readable.

[0211] Some examples of this technology include data carriers having electronically readable control signals that can cooperate with a programmable computer system to enable the execution of one of the methods described herein.

[0212] Typically, an example of this technology can be implemented as a computer program product with program code that, when run on a computer, operates to perform a method within a method. The program code may, for example, be stored on a machine-readable medium.

[0213] Other examples include a computer program stored on a machine-readable medium for performing one of the methods described herein.

[0214] In other words, an example of this technique is therefore a computer program with program code that, when run on a computer, performs one of the methods described herein.

[0215] Another example of a method is therefore a data carrier (or digital storage medium, or computer-readable medium) on which a computer program for performing one of the methods described herein is recorded. Data carriers, digital storage media, or recording media are typically tangible and / or non-transitory.

[0216] Another example of this technique is therefore a data stream or signal sequence, which represents a computer program for performing one of the methods described herein. The data stream or signal sequence can, for example, be configured to be transmitted via a data communication connection, such as via the Internet.

[0217] Another example includes a processing device, such as a computer or programmable logic device, which is configured or adapted to perform one of the methods described herein.

[0218] Another example includes a computer on which a computer program is installed to perform one of the methods described herein.

[0219] Another example of the present technology includes an apparatus or system configured to transmit (e.g., electronically or optically) to a receiver a computer program for performing one of the methods described herein. For example, the receiver may be a computer, mobile device, storage device, etc. The apparatus or system may, for example, include a file server for transmitting the computer program to the receiver.

[0220] In some examples, programmable logic devices (e.g., field-programmable gate arrays) can be used to perform some or all of the functions of the methods described herein. In some examples, field-programmable gate arrays can cooperate with a microprocessor to perform one of the methods described herein. Generally, these methods are preferably performed by any hardware device.

[0221] The apparatus described herein can be implemented using hardware devices, computers, or a combination of hardware devices and computers.

[0222] The apparatus described herein, or any component thereof, may be implemented, at least in part, in hardware and / or software.

[0223] The methods described in this article can be performed using hardware devices, computers, or a combination of hardware devices and computers.

[0224] The methods or any component of the apparatus described herein may be performed, at least in part, by hardware and / or software.

[0225] The examples above are merely illustrative of the technical principles herein. It should be understood that modifications and variations to the arrangements and details described herein will be readily apparent to those skilled in the art. Therefore, the scope is intended to be limited only by the appended patent claims, and not by the specific details presented through the description and interpretation of the examples herein.

Claims

1. A transmitter (200) for emitting radiation (201, 203) of a specific wavelength, said specific wavelength being a characteristic wavelength of a specific fluid, said transmitter comprising: The Joule-heated emitting conductor (260) is configured to emit radiation (201) of the specified wavelength at the emission temperature, wherein the radiation at the specified wavelength is emitted at the emission temperature. The controller (250) is configured, in operation, to control the variable voltage (Vo) applied to the Joule-heated transmitting conductor (260) and modulated according to the duty cycle. DD The duty cycle can vary among the following: The high average power duty cycle during the thermal cycle (472h) causes the Joule-heated emitting conductor (260) to be affected by the high average power to reach and maintain the emission temperature to emit radiation of the specific wavelength; as well as The low average power duty cycle during the cold cycle (472c) alternating with the thermal cycle (472h) causes the Joule-heated transmitting conductor (260) to be affected by the low average power to reach a temperature lower than the transmitting temperature, wherein the low average power duty cycle is less than the high average power duty cycle. The transmitter is configured to acquire at least one temperature indication measurement, which indicates the ambient temperature provided by a temperature sensor. The high average power duty cycle and the low average power duty cycle are defined based on the at least one temperature indication measurement (240'), which indicates the measured ambient temperature.

2. The transmitter of claim 1, wherein the controller (250) is configured to limit the high average power duty cycle for at least one thermal cycle (472h) to a duty cycle that allows the emission temperature to be reached and maintained at the Joule-heated emission conductor (260).

3. The transmitter according to claim 1 or 2, wherein the controller (250) is configured to define the high average power duty cycle and the low average power duty cycle according to at least the following: At least one temperature indication measurement (240') such that a high ambient temperature is compensated by a low duty cycle; and a low ambient temperature is compensated by a high duty cycle, wherein the high ambient temperature is higher than the low ambient temperature and the high duty cycle is higher than the low duty cycle.

4. The transmitter according to claim 1 or 2, wherein the controller (250) is configured to define the high average power duty cycle and the low average power duty cycle according to: At least one voltage indication measurement (230') indicates the measured voltage applied to the Joule-heated transmitting conductor (260), such that a high voltage is compensated by a small duty cycle and a small voltage is compensated by a high duty cycle, wherein the high voltage is higher than the small voltage and the high duty cycle is higher than the small duty cycle.

5. The transmitter according to any one of claims 1 or 2, wherein the controller (250) is configured to limit the low average power duty cycle to a duty cycle that causes a power reduction relative to the high average power for the cold cycle (472c), wherein the reduction is constant regardless of the ambient temperature.

6. The transmitter according to any one of claims 1 or 2 is configured to obtain the at least one temperature indication measurement (240') as a value indicating the temperature of the Joule-heated transmitting conductor (260) before the variable voltage is applied to the Joule-heated transmitting conductor (260).

7. The transmitter according to claim 6 is configured to obtain the temperature indication measurement (240') when the Joule-heated transmitting conductor (260) is in thermal equilibrium.

8. The transmitter of claim 6, configured to define the high average power duty cycle and the low average power duty cycle before the variable voltage is applied to the Joule-heated transmitting conductor (260).

9. The transmitter according to any one of claims 1, 2, 7 and 8, wherein the controller (250) is configured to limit the low average power duty cycle and the high average power duty cycle such that a pre-fixed reduction in electrical power from the high average power to the low average power causes power loss in the Joule-heated transmitting conductor (260), wherein the pre-fixed reduction is constant regardless of the ambient temperature.

10. A method for use with a transmitter according to any one of claims 1-9, the method comprising an initialization process and an operation process, the method comprising: During the initialization process, a variable voltage is controlled and applied to the Joule-heated transmitting conductor (260) according to a duty cycle that varies among the following: The high average power duty cycle during the thermal cycle (472h) causes the Joule-heated emitting conductor (260) to be affected by the high average power to reach and maintain the emission temperature to emit radiation of the specific wavelength; as well as The low average power duty cycle during the cold cycle (472c) alternating with the thermal cycle (472h) causes the Joule-heated transmitting conductor (260) to be affected by the low average power to reach a temperature lower than the transmitting temperature, wherein the low average power duty cycle is less than the high average power duty cycle. During the initialization process, the decrease between the high average power and the low average power remains constant, and the ambient temperature also remains constant. The method includes, during the operation process, limiting the low average power duty cycle such that the reduction between the high average power and the low average power is the same as the reduction between the high average power and the low average power experienced during the initialization process.

11. A sensor (100) for determining fluid properties, comprising: The transmitter (200) according to any one of claims 1-9, wherein the specific wavelength is the characteristic wavelength of the fluid; as well as The detector (300) is configured to detect an electrical signal (314) associated with the radiation (201, 203) emitted by the transmitter (200). The transmitter (200) and detector (300) are configured such that the radiation (201, 203) emitted by the transmitter (200) propagates through a target volume (204, 204a) containing the target fluid, such that the electrical signal (314) is associated with the properties of the fluid.

12. A method for the sensor of claim 11, the method comprising an initialization process and an operation process, the initialization process, by means of the detector (300), providing multiple emission and detection for different known fluid volumes to personalize a detection rule that maps the fluid volume to a reading unit to be converted into a fluid volume. The method includes limiting the low average power duty cycle during the operation process such that the reduction between the high average power and the low average power is the same as the reduction between the high average power and the low average power experienced during the initialization process.

13. A method for emitting radiation (201, 203) of a specific wavelength, said specific wavelength being a characteristic wavelength of a fluid, the method comprising: Radiation of a specific wavelength (201) is emitted at a specific emission temperature using a Joule-heated emitting conductor (260). Radiation at the specific wavelength is emitted at the emission temperature. The transmission is affected by modulation based on the duty cycle, which varies among the following: The high average power duty cycle during the thermal cycle (472h) causes the Joule-heated emitting conductor (260) to be affected by the high average power to reach the emission temperature in order to emit radiation of the specific wavelength; as well as The low average power duty cycle during the cold cycle (472c) alternating with the thermal cycle (472h) causes the Joule-heated transmitting conductor (260) to be affected by the low average power to reach a temperature lower than the transmitting temperature, wherein the low average power duty cycle is lower than the high average power duty cycle. The high average power duty cycle and the low average power duty cycle are defined based on at least one temperature indication measurement (240'), which indicates the measured ambient temperature.

14. A sensing method for determining fluid properties, comprising: Perform the method according to claim 13, The radiation is allowed to propagate through the target volume (204, 204a) containing the target fluid. as well as Detect an electrical signal (314) associated with the radiation (201, 203) such that the electrical signal (314) is associated with the properties of the fluid.

15. A non-transitory storage unit for storing instructions, which, when executed on a computer, cause the computer to perform the method according to any one of claims 12-14.

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