OPERATION OF A SENSOR

Description

[0001] The present invention relates to a method for operating a sensor, in particular an optical gas sensor for measuring an analyte, a sensor, in particular an optical gas sensor, and an arrangement.

[0002] Galvanic gas sensors typically have an analog voltage output. Depending on the galvanic oxygen sensor, the voltage is typically between 10 mV and 15 mV at an oxygen partial pressure of 0.21 bar.

[0003] A galvanic gas sensor is an electrochemical cell with a cathode and an anode. In a galvanic oxygen sensor, for example, oxygen is converted at the cathode, and an electric current flows depending on the partial pressure of oxygen. The current is converted into a voltage signal using a small circuit, which usually also includes temperature compensation. A two-pin connector is usually mounted on the circuit, to which a measuring device is connected. A battery or external power supply is not required to operate an analog galvanic sensor. Galvanic oxygen sensors have a short lifespan of a few months to two years and are prone to failure. Nevertheless, this type of sensor is the most commonly used.

[0004] Optical gas sensors are based on a different measuring principle. In an optical oxygen sensor, special color pigments are irradiated with light of a specific wavelength and begin to fluoresce. The intensity or decay time of the fluorescence, after the illumination is switched off, depends on the oxygen partial pressure and is evaluated. Typically, the oxygen partial pressure is calculated using a microcontroller, and the result is output digitally via a digital interface. Therefore, an optical oxygen sensor is generally not compatible with devices designed for an analog galvanic oxygen sensor.

[0005] To enable compatibility between an optical sensor and a galvanic sensor, a digital-to-analog converter can be used, which outputs an analog signal equivalent to that of a galvanic sensor instead of the digital output signal. On the other hand, a digital interface would be preferred in new device developments, as digital transmissions are generally more robust, less susceptible to interference, and less expensive. If the sensor is to be operated in humid environments with high humidity and possibly also salinity, corrosion resistance is necessary. With galvanic sensors, the voltages occurring are very low at just a few millivolts, and thus the risk of corrosion at the contacts of the sensor connection is quite low. In contrast, the voltage levels of conventional serial interfaces are relatively high, at voltages above 1.5 V. Corrosion can occur more frequently at such voltages.An alternative is current interfaces, where the voltage potential is kept low and the digital information is transmitted as different current levels. This makes it possible to minimize the risk of corrosion on the contacts.

[0006] A power supply is required for the operation of an optical gas sensor. In addition to a sensor layer containing the color pigments, components of an optical gas sensor can include a light-emitting diode (LED) with an LED driver circuit, a photodiode with an amplifier, a microcontroller, an analog-to-digital converter, etc. A power supply can be provided to operate the electronics. Power consumption is primarily comprised of the following components: the power consumption for the analog components of the circuit and amplifier, the power consumption for operating the LED and the LED driver, and the power consumption for operating the microcontroller.

[0007] The power consumption for operating an optical gas sensor is typically between 7 mA and 150 mA.

[0008] If an optical gas sensor is to be designed as a direct replacement for a galvanic sensor, which can be used instead of an analog galvanic sensor without modifying an existing device, the optical gas sensor should, on the one hand, be mechanically compatible and, on the other hand, should have a power supply, preferably with a battery, which is ideally housed in the housing of the sensor.

[0009] However, currently known optical gas sensors have such high power consumption that operation with an integrated battery is only possible for a very short period of time and is therefore not practical.

[0010] Patent US 2012 / 192623 A1 discloses a gas detection system in which several different sensor types can be used with a single transmitting device and in which the several different sensor types can be automatically detected, adjusted, calibrated and monitored by the system with reduced user input.

[0011] It is an object of the invention to provide a sensor, in particular an optical gas sensor, with low power consumption. This object is achieved by means of the independent claims. Further embodiments are shown in the dependent claims.

[0012] According to the present invention, a method for operating a sensor, preferably an optical gas sensor, for measuring an analyte (in particular comprising a gas to be sensed), wherein the method comprises an automatic detection of whether the sensor, in particular the optical gas sensor, is connected to a device, (in particular if affirmative) an automatic detection of an interface used for the sensor, in particular for the optical gas sensor, to the device (or the device) and / or a measuring range of the analyte (in particular a partial pressure or partial pressure range of the gas to be sensed), and based on the automatic detection (in particular based on both automatic detections), an automatic adaptation of the operation of the sensor, in particular the optical gas sensor (for example an automatic adaptation of the operation of a microcontroller,an interface and the entire electronics of the optical gas sensor - in particular, a power supply can be separated from an LED and a photodiode and an amplifier).

[0013] According to another exemplary embodiment of the present invention, a sensor, in particular an optical gas sensor, is provided, which has a sensor layer (in particular for interacting with gas to be detected by the sensor), a radiation source (in particular for optically exciting the sensor layer, further in particular for exciting the sensor layer to fluoresce), a radiation detector (in particular for detecting a response signal of the sensor layer after excitation) and a microcontroller (or another control device), wherein the microcontroller is designed to control and / or execute a method with the features described above.

[0014] According to the present invention, an arrangement is provided which comprises a sensor, in particular an optical gas sensor, having the features described above and a device to which the sensor, in particular the optical gas sensor, is connected or connectable.

[0015] According to the invention, an operating method for a sensor (preferably for a gas sensor and more preferably for an optical gas sensor) is created, with which it is automatically detected whether a sensor is connected to a device and, if so, via which interface the sensor is connected. The interface can be, for example, an analog interface, a digital unidirectional or bidirectional serial interface with voltage levels (where high and low are coded as different voltage levels), or a digital unidirectional or bidirectional serial current interface (where high and low are coded as different currents). With such a sensor, in particular a measurement time and / or a sleep time of the microcontroller can be automatically adjusted. This can advantageously be done depending on whether the sensor is installed and / or whether the concentration of the analyte is within a certain range or not.In this way, the power consumption of the sensor can be reduced so much that long operation with one battery is possible.

[0016] Several options are conceivable for reading a sensor signal. In principle, it would be possible to develop a separate sensor with the ideal sensor interface for each application, but this would be costly and time-consuming. It is advantageous to provide a sensor with a configurable interface. It is preferable if the sensor can automatically detect whether it is installed in a device and which interface is available for communication with or in the device. Battery operation may be preferred, as the above measures can significantly reduce power consumption, enabling a reasonable operating time with a small battery.

[0017] The problem solved according to the invention therefore includes that a sensor (preferably a gas sensor) can be operated so that: it is automatically detected whether the sensor is installed in a device it is automatically detected which interface is available for communication with the device analogue and digital communication via current and voltage levels is possible via a single 2-pin interface and the interface is automatically configured the power consumption is greatly reduced and sensible battery operation is possible with a small battery integrated in the housing the external dimensions of the sensor are no larger than those of conventional galvanic gas sensors and thus an optical oxygen sensor can be designed as a direct replacement for a galvanic oxygen sensor.

[0018] Additional embodiments of the method, the sensor (in particular a gas sensor and further in particular an optical gas sensor), and the arrangement are described below. Although the following embodiments are described with reference to an optical gas sensor, all of these embodiments can also be used for other sensors, and in particular for other gas sensors.

[0019] According to one embodiment, the automatic detection may comprise one, several or all of the following measures: (1) automatic detection that the optical gas sensor is not connected to a device if a connection (in particular a sensor output) of the optical gas sensor is open; (2) automatic detection that the optical gas sensor is connected to a device with an analog interface if an input resistance of the device is within an associated predeterminable interval, in particular between 5 kΩ and 1 MΩ, further in particular between 10 kΩ and 1 MΩ; (3) automatic detection that the optical gas sensor is connected to a device with a digital current interface if an input resistance is below an associated predeterminable threshold value, in particular below 100 Ω;(4) automatic detection that the optical gas sensor is connected to a device with a digital interface with voltage levels if an input resistance is above a corresponding predeterminable threshold value and a voltage level, in particular above 1V, is measurable at the input of the optical gas sensor;

[0020] A method for operating an optical gas sensor according to an exemplary embodiment of the invention, which automatically detects whether an optical gas sensor is connected to a device or not, or if so, which interface (in particular of the device or to the device) is available, is based on measuring the voltage level and input resistance of the connected device at the connection (in particular at a sensor output) of the sensor. According to an exemplary embodiment, it may advantageously be possible to automatically distinguish between the following four cases: (1) If the sensor is not connected to a device, the connection (especially a sensor output) of the gas sensor is open and high-impedance. (2) If the sensor is installed in a device with an analog interface, the input resistance of the device is usually between 5 kΩ and 1 MΩ. (3) If the sensor is installed in a device with a digital current interface, the input resistance of the device is usually very low, preferably less than 100 Ω. (4) If the sensor is installed in a device with a digital interface with voltage levels, the input of the device is usually also high-impedance, but has a pull-up resistor, thus a voltage level can be measured at the input or output of the sensor.

[0021] According to one embodiment, the method can perform automatic detection on only two pins of a sensor connection, in particular on a 2-pin connection of the sensor, in particular of the optical gas sensor. By automatically configuring the connection, it is possible to provide various interfaces on just one 2-pin connection. However, 3-pin connectors (or connectors with more than three pins) can also be used, where either only two pins are used or two pins are connected together.

[0022] According to the invention, the sensor performs the automatic detection based on a measurement of voltage level and input resistance of the connected device at a terminal (in particular a sensor output) of the optical gas sensor.

[0023] Using simple metrological means, automatic detection of the electronic environment of the optical gas sensor is therefore possible, which is advantageous as a meaningful basis for energy-saving control or regulation of the optical gas sensor.

[0024] According to one embodiment, the automatic detection of the analyte's measuring range can include detecting whether the analyte concentration is within a predetermined range or not. For example, a measurement of the gas concentration using the optical gas sensor may only be required if the analyte concentration is within a specific range. For example, in diving equipment, the measurement of an oxygen partial pressure may only be necessary or useful if the oxygen partial pressure is within a predetermined range, for example, between 0.6 bar and 1.6 bar. If the oxygen partial pressure is below a predetermined threshold for an extended period of time (for example, below 0.3 bar), it can be assumed that the optical gas sensor is inactive (for example, during storage), so that a measurement is not required. This enables power-saving operation of the optical gas sensor.

[0025] According to one embodiment, the automatic adaptation may comprise one, several or all of the following measures: Automatic configuration of the interface to the device; Automatic adjustment of a measurement time of the optical sensor; Automatic adjustment of a sleep interval of the microcontroller, in particular by means of a timer for waking up the microcontroller after a predeterminable sleep interval has elapsed; Supplying a radiation source and / or a radiation detector of the optical gas sensor with electrical energy only during a measurement cycle, and in particular disconnecting the radiation source and / or the radiation detector from the electrical energy supply during a sleep interval of the microcontroller; If it is automatically detected that the optical gas sensor is not connected to a device, no measurements are carried out.

[0026] Thus, one or more measures are possible to significantly reduce the power consumption of the optical gas sensor. Firstly, a microcontroller of the optical gas sensor can be equipped with one or more sleep modes in which the internal clock generators are switched off, the processor does not execute any commands, and thus the power consumption is reduced to a very low sleep current, for example, less than 5 µA. Using an integrated timer, which itself can have a very low power consumption of, for example, less than 1 µA, the microcontroller can be woken up after a sleep interval and returned to normal operating mode.

[0027] Another measure to reduce power consumption is to supply analog circuits for a radiation source (in particular an LED) and a radiation detector (in particular a photodiode) with power only during the measurement cycle of a certain duration, but to disconnect them from the power supply during a sleep interval.

[0028] According to one embodiment, the automatic adjustment can be performed to reduce, in particular to optimize or minimize, the power consumption of the optical gas sensor. The average power consumption can be further reduced by allowing the sensor to detect whether it is even installed in a device. If the optical gas sensor is simply stored, no measurements are performed at all.

[0029] According to one embodiment, the method can comprise determining a required measurement time with the optical gas sensor to achieve a predeterminable measurement accuracy and performing a measurement with the determined measurement time. In particular, the required measurement time can be determined based on a characteristic curve of the optical gas sensor as a function of a gas partial pressure to be measured, in particular the oxygen partial pressure. The achievable measurement accuracy with an optical gas sensor, for example, with an oxygen sensor, also depends on the measurement time. If only a low measurement accuracy is required, shorter measurement times can be used.Furthermore, with the same measurement accuracy, shorter measurement times can be used at low gas partial pressures (especially oxygen partial pressures) than at high gas partial pressures (especially oxygen partial pressures), since the characteristic curve of optical gas sensors (especially oxygen sensors) is steeper at low gas partial pressures (especially oxygen partial pressures).

[0030] According to one embodiment, the method can trigger a measurement with the optical gas sensor with a predetermined increased measurement accuracy, measurement frequency, and / or measurement time only if a concentration of an analyte to be measured lies within a predetermined range. In particular, before said measurement, the method can perform a pilot measurement with the optical gas sensor with a lower measurement accuracy, measurement frequency, and / or measurement time than the predetermined increased measurement accuracy, measurement frequency, and / or measurement time to determine whether the concentration of the analyte to be measured lies within the predetermined range.Power consumption can be optimized by having the sensor only measure with high accuracy and / or high measurement frequency and transmit data only when the analyte concentration is within a specific range. The measurement time, and thus the measurement accuracy and / or the microcontroller's sleep interval, are adjusted accordingly. It is also possible to conduct pilot measurements with short measurement times and low measurement accuracy to determine whether the analyte concentration is within a range of interest, and only then perform measurements with longer measurement times and high accuracy. This allows power consumption to be further reduced.

[0031] According to one embodiment, the method may include converting an analog measurement signal into a digital measurement signal using an analog-to-digital converter. In particular, the method may include reconverting the converted digital measurement signal into a reconverted analog measurement signal using a digital-to-analog converter if the measurement signal is to be provided to the device in analog form. In this way, the optical gas sensor can provide sensor signals in analog or digital form at its interface to a device, as needed.

[0032] According to one embodiment, the optical gas sensor may have one, several or all of the following features: a battery for supplying the optical gas sensor with electrical energy; an analog-to-digital converter for converting an analog measurement signal into a digital measurement signal; a digital-to-analog converter for reconverting an analog measurement signal converted into a digital measurement signal by an analog-to-digital converter into a reconverted analog measurement signal, if the measurement signal is to be provided to the device in analog form; a circuit for measuring a resistance at a terminal (in particular a sensor output) of the optical gas sensor; at least one digital interface for providing a digital sensor signal, in particular a digital voltage level interface for providing the digital sensor signal as a voltage level and / or a digital current level interface for providing the digital sensor signal as a current level;a voltage measuring device for measuring a voltage at a terminal (in particular a sensor output) of the optical gas sensor, which may in particular comprise an analog-to-digital converter;

[0033] Alternatively or additionally, the optical gas sensor can be equipped with additional components.

[0034] According to one embodiment, the arrangement can comprise a plug connection, in particular a 2-pin plug connection, for connecting the optical gas sensor to the device. Such a plug connection can be provided via a separate connector that can be arranged between the optical gas sensor and a device to be connected to it.

[0035] According to one embodiment, the device can comprise or consist of diving equipment, in particular a rebreather. A rebreather, but also other diving equipment (such as a dive computer, a mouthpiece, or a gas cylinder) can be equipped with an optical gas sensor, particularly designed as an oxygen sensor. When diving, it is important to know the oxygen partial pressure to ensure a sufficient oxygen supply to the diver.

[0036] Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and better understood by reference to the following more detailed description of embodiments taken in conjunction with the accompanying drawings. Features that are substantially or functionally the same or similar are designated by the same reference numerals. Figure 1shows an arrangement of an optical gas sensor and a device connected thereto according to an exemplary embodiment of the invention. Figure 2 shows a circuit of an optical gas sensor according to an exemplary embodiment of the invention.

[0037] The representation in the drawing is schematic. The figures are therefore not exact construction drawings.

[0038] Before exemplary embodiments are described with reference to the figures, some basic considerations will be summarized on the basis of which exemplary embodiments of the invention have been derived.

[0039] A method for operating an optical gas sensor according to an exemplary embodiment of the invention can include automatic detection of whether a sensor is installed, automatic detection of which interface is being used, and / or automatic detection of the measurement range of the analyte. Based on this, automatic configuration of the interface and / or automatic adjustment of the measurement time and / or the sleep interval of the microcontroller can be performed. Through these measures, and especially through a combination of the measures, power consumption can be reduced so significantly that sensible operation with a battery integrated into the sensor is possible.

[0040] In particular, a small lithium button cell battery with a capacity of 500 mAh to 1000 mAh can thus enable many thousands of operating hours and years of storage. Thus, according to an exemplary embodiment of the invention, it is possible to design an optical gas sensor such that, including the battery, it has the same mechanical dimensions and a pin-compatible 2-pole electrical interface as a galvanic sensor. Therefore, according to one embodiment of the invention, such an optical gas sensor can be used as a direct replacement for a galvanic sensor.

[0041] Figure 1 shows an arrangement of an optical gas sensor 1 and a device 2 connected thereto according to an exemplary embodiment of the invention.

[0042] The Figure 1The arrangement shown shows the optical gas sensor 1 in an operating mode in which it is connected to the device 2 via a plug connection 3. The plug connection 3 is advantageously designed as a 2-pin plug connection for connecting the optical gas sensor 1 to the device 2. For example, the device 2 can be diving equipment, for example, a rebreather device. In this application example, the optical gas sensor 1 can be designed to measure an oxygen partial pressure.

[0043] As in Figure 1 As shown, the optical gas sensor 1 comprises a sensor layer 8 with pigments, a radiation source 6, e.g., configured as an LED, a radiation detector 10, e.g., configured as a photodiode, and a microcontroller 4. Said microcontroller 4 can be configured to control or execute a method for operating the optical gas sensor 1. Figure 1further shows that the optical gas sensor 1 can have a battery 12, for example designed as a lithium button cell, for supplying the optical gas sensor 1 with electrical energy.

[0044] The microcontroller 4 can have an analog-to-digital converter (not shown) for converting an analog measurement signal into a digital measurement signal. Alternatively, such an analog-to-digital converter can also be provided separately from the microcontroller 4 but coupled to the microcontroller 4. Furthermore, the optical gas sensor 1 can have a digital-to-analog converter 14 for reconverting an analog measurement signal converted into a digital measurement signal by means of the analog-to-digital converter into a reconverted analog measurement signal if the measurement signal is to be provided to the device 2 in analog form. The optical gas sensor 1 also has a circuit 13 for measuring a resistance at a terminal (in particular at a sensor output 18) of the optical gas sensor 1. Furthermore, digital interfaces 15, 16 for providing a digital sensor signal can be provided in the optical sensor 1.These can include a digital voltage level interface 16 for providing the digital sensor signal as a voltage level and a digital current level interface 15 for providing the digital sensor signal as a current level. Furthermore, a voltage measuring device for measuring a voltage at a terminal (in particular at the sensor output 18) of the optical gas sensor 1 can be provided in the optical gas sensor 1. This voltage measuring device can be designed, for example, as a (particularly further) analog-to-digital converter 21.

[0045] To operate the optical gas sensor 1 to measure an analyte, the operating method described in more detail below can be carried out, in particular by means of the microcontroller 4: First, the method can automatically detect whether the optical gas sensor 1 is connected to device 2. If so, an interface to the device 2 used for the optical gas sensor 1 can then be automatically detected. Alternatively or additionally, a measuring range of the analyte can be automatically detected. Based on the results of the first and / or second automatic detection, the operation of the optical gas sensor 1 can then be automatically adjusted. This can preferably include an automatic adjustment of the operation of the microcontroller 4 of the optical gas sensor 1 for operating the optical gas sensor 1.

[0046] For example, the automatic detection may include determining in which of the following four states the arrangement of optical gas sensor 1 and device 2 with, if present, connector 3 in between is currently in: (1) Automatic detection that the optical gas sensor 1 is not connected to a device 2. This state can be assumed if a connection (in particular sensor output 18) of the optical gas sensor 1 is open. (2) Automatic detection that the optical gas sensor 1 is connected to a device 2 with an analog interface. This state can be assumed if an input resistance of the device 2 lies within an associated predeterminable interval, for example between 5 kΩ and 1 MΩ. (3) Automatic detection that the optical gas sensor 1 is connected to a device 2 with a digital current interface (in particular with current levels). This state can be assumed if an input resistance is below an associated predeterminable threshold, for example below 100 Ω. (4) Automatic detection that the optical gas sensor 1 is connected to a device 2 with a digital interface with voltage levels.This state can be assumed if an input resistance is above a corresponding predeterminable threshold value and a voltage level is measurable at the input of the optical gas sensor 1.

[0047] Advantageously, said automatic detection can be performed on a single 2-pin connection of the optical gas sensor 1. The automatic detection can be performed simply based on a measurement of the voltage level and input resistance of the connected device 2 at a connection of the optical gas sensor 1. In particular, the automatic detection of the analyte measurement range can include detecting whether the analyte concentration is within a predetermined range or not. Preferably, a measurement can only be performed if the current analyte concentration is of interest within a predetermined range.

[0048] The automatic adjustment of the operation of the optical gas sensor 1 based on the preceding automatic detections may in particular comprise the following measures: An automatic configuration of the interface is carried out .

[0049] Furthermore, a measurement time can be automatically adjusted. It is also possible to automatically adjust a sleep interval of the microcontroller 4. This can advantageously be done using a timer to wake up the microcontroller 4 after a predeterminable sleep interval has elapsed. In particular, the radiation source 6 and the radiation detector 10 of the optical gas sensor 1 can be supplied with electrical energy from the battery 12 only during a measurement cycle. However, the radiation source 6 and the radiation detector 10 can be disconnected from the electrical energy supply by the battery 12 during a sleep interval of the microcontroller 4. If it is automatically detected that the optical gas sensor 1 is not connected to a device 2, measurements can be omitted to save power.

[0050] In summary, the automatic adjustment can be carried out with the control objective of reducing, optimizing or minimizing the power consumption of the optical gas sensor 1 during operation.

[0051] The operating method can advantageously comprise determining a required measurement time with the optical gas sensor 1 to achieve a predeterminable measurement accuracy and performing a measurement with the determined measurement time. The required measurement time can be determined based on a characteristic curve of the optical gas sensor 1 as a function of an oxygen partial pressure to be measured. At certain, particularly low, oxygen partial pressures, the characteristic curve can be steeper and the optical gas sensor 1 can therefore be more sensitive than at other, particularly high, oxygen partial pressures. In areas with a steeper characteristic curve, a shorter measurement time can be sufficient to achieve a certain measurement accuracy than in areas with a flatter characteristic curve.

[0052] To save power, the operating method can also be triggered to perform a measurement with the optical gas sensor 1 with a predetermined increased measurement accuracy, measurement frequency, and / or measurement time only when a concentration of an analyte to be measured lies within a predetermined range of interest, which, for example, indicates an active functional state of the optical gas sensor 1 (and not, for example, merely its current storage). Preferably, before said measurement, the operating method can perform a pilot measurement with the optical gas sensor 1 with a lower measurement accuracy, measurement frequency, and / or measurement time than the predetermined increased measurement accuracy, measurement frequency, and / or measurement time to determine whether the concentration of the analyte to be measured lies within the predetermined range.

[0053] Figure 1shows the optical gas sensor 1, designed, for example, as an optical oxygen sensor, which is connected to the device 2 via the plug connection 3. Likewise, the optical gas sensor 1 can be designed as a gas sensor for other analytes.

[0054] In the illustrated embodiment, the plug connection 3 is two-pin and consists of a sensor output 18 and a ground output 17. The optical gas sensor 1 has a sensor layer 8 with color pigments, which can be attached to the outside of a transparent housing. These color pigments of the sensor layer 8 are illuminated with light from a radiation source 6 designed as an LED for a specific measurement duration. The radiation source 6 is controlled by a driver 5 designed here as an LED driver. The color pigments fluoresce with a wavelength greater than that of the light emitted by the radiation source 6. The excitation light of the radiation source 6 is separated from the fluorescence light with an excitation filter 7 and an emission filter 9. After the radiation source 6 is switched off, the fluorescence decays within a characteristic decay time. The intensity of the fluorescence and the decay time depend on the partial pressure of oxygen.more generally, from the sensor-detected gas partial pressure. The higher the oxygen partial pressure, the more strongly the fluorescence is quenched, and the smaller the amplitude of the fluorescence signal, or the shorter the decay time. A radiation detector 10, embodied, for example, as a photodiode, receives the emitted fluorescent light. The signal from the radiation detector 10 is amplified by an amplifier 11. The output of the amplifier 11 is connected to an analog-to-digital converter in the microcontroller 4.

[0055] Using a switch 8, the output of the optical gas sensor 1, designed, for example, as sensor output 18, can be connected to various hardware. In the uppermost position of switch 8, the sensor output 18 is connected to a circuit 13 for measuring the resistance at the sensor output 18. Alternatively, the sensor output 18 can be connected to a digital-to-analog converter 14 if an analog signal is to be output at the sensor output 18. In a further switch position, the sensor output 18 can be connected to a first serial digital interface 16, in which bits are encoded as voltage levels. Interface 16 can preferably be TTL (transistor-transistor logic) and CMOS (complementary metal-oxide-semiconductor) compatible. Interface 16 can be used unidirectionally for transmitting only or bidirectionally for transmitting and receiving data.With a further switch position, the sensor output 18 can be connected to a second serial interface 15, where, unlike the first serial interface 16, the levels are coded as current levels rather than voltage levels. This is particularly advantageous when the oxygen sensor is operated in an environment with high humidity and possibly even salinity. Together with a very small input resistance 20 (preferably less than 100 Ω), the voltage level at the sensor output 18 and thus the risk of corrosion at the contacts of the connector 3 can be minimized. The electrical potential corresponding to the voltage at the sensor output 18 can be measured with a further analog-to-digital converter 21.

[0056] One, some or all of the components 13, 14, 15, 16 and 21 may also be integrated in the microcontroller 4.

[0057] The optical gas sensor 1 is powered by the built-in battery 12. For simplified illustration, Figure 1 No connections to ground terminal 17 or to the battery supply 12 are shown. A power supply 24 for the radiation source 6, the driver 5, and the amplifier 11 for the radiation detector 10 can be disconnected via a switch 25 connected to a digital output of the microcontroller 4.

[0058] As already described, the optical gas sensor 1 is connected to the device 2 via the connector 3. The device 2 has an internal resistance of 20 Ω.

[0059] In the described embodiment, an interface 19 of device 2 is one of the following three: If device 2 is designed as an analog device for an analog oxygen sensor with a voltage output, then in this case, interface 19 is an analog or analog / digital circuit. The internal resistance 20 of device 2 in this case is preferably between 5 kΩ and 1 MΩ. A pull-up resistor 23 is not present in this case.

[0060] In another case, device 2 is designed as a digital device with a unidirectional serial receiver or a bidirectional serial interface with voltage levels. Reference numeral 19 denotes a unidirectional or bidirectional interface. The internal resistor 20 is high-impedance, and the input 22 of device 2 is connected to the pull-up resistor 23. The pull-up resistor 23 is preferably between 1 kΩ and 100 kΩ.

[0061] In another case, device 2 is designed as a digital device with a unidirectional serial power interface. In this case, reference numeral 19 denotes a unidirectional serial power interface. The internal resistance 20 in this scenario is preferably less than 100 Ω.

[0062] In Figure 1 For simplicity, only the input circuit 19 and the two resistors 20 and 23 are shown in device 2. Device 2 typically includes additional components such as a microcontroller, analog and digital circuits, a display, etc.

[0063] In the following, the functionality of an automatic state machine is described, which is used in the Figure 1 illustrated arrangement or in the optical gas sensor 1.

[0064] The method for operating the optical gas sensor 1 can be implemented in the microcontroller 4 as an automatic state machine or state machine in order to automatically configure the output (in particular sensor output 18) according to the connected device 2 and to automatically adjust, in particular to optimize, the power consumption of the optical gas sensor 1 depending on the operating conditions or storage.

[0065] State 1 is described below: If the optical gas sensor 1 is not installed in a device 2, the circuit 13 for measuring the resistance is connected to the output. If the optical gas sensor 1 is not installed, the output has a high impedance. A high-impedance output is detected via the circuit 13. No potential is measured via the analog-to-digital converter 21. The switch 25 is open. No oxygen measurements are performed. The analog circuits are disconnected from the power supply, and the microcontroller 4 is put into sleep mode for a predefined interval. After the interval has elapsed, the microcontroller 4 wakes up. The same function is now performed to check whether the optical gas sensor 1 is connected to a device 2 or not.

[0066] If the optical gas sensor 1, preferably designed as an oxygen sensor, is connected to a device 2 with a unidirectional or bidirectional serial interface with a pull-up resistor 23, an electrical potential, preferably greater than 1 V, is detected at the output during the check in state 1 with the analog-to-digital converter 21 and the state machine changes to state 2.

[0067] If the optical gas sensor 1 is installed in a device 2 designed for galvanic oxygen sensors with an analog voltage output, the resistance measurement circuit 13 measures a resistance at the output between, for example, 1 kΩ and 1 MΩ. The state machine then switches to state 3.

[0068] If the optical gas sensor 1 is installed in a device 2 designed for oxygen sensors with a digital serial current output, the resistance measurement circuit 13 measures a resistance at the output, for example, between 0 and 100 Ω. The state machine then transitions to state 4.

[0069] State 2 is described below: Microcontroller 4 uses switch 8 to connect the second digital serial interface 15 to the sensor output 18. Measurement data is transmitted serially. Interface 15 is preferably configured as a bidirectional single-duplex interface, thus enabling bidirectional communication.

[0070] The radiation source 6, the driver 5, and the amplifier 11 for the radiation detector 10 are supplied with power via the switch 25 for a predefined measurement time, and the oxygen partial pressure is measured. The measured value is output digitally via the second digital serial interface 15. Subsequently, the microcontroller 4 is put into sleep mode for a predefined sleep interval, after which it performs the next measurement.

[0071] State 2 can be used for measurement data transmission, but also for configuration and a firmware update of the optical gas sensor 1. If the optical gas sensor 1 is removed from the device 2 or the pull-up resistor 23 is deactivated, no potential is measured at the sensor output 18 via the analog-to-digital converter 21, and the optical gas sensor 1 goes into state 1.

[0072] State 3 is described below: The microcontroller 4 uses switch 8 to connect the digital-to-analog converter 14 to the sensor output 18.

[0073] The radiation source 6, the driver 5, and the amplifier 11 for the radiation detector 10 are supplied with power via the switch 25 for a predefined measurement time, and the oxygen partial pressure is measured. The measured value is output as an analog voltage signal via the digital-to-analog converter 14. Subsequently, the microcontroller 4 is put into sleep mode for a predefined sleep period, after which it performs the next measurement.

[0074] At regular intervals, preferably greater than 1 minute, switch 8 is briefly connected to the output resistance measurement circuit 13 to check whether the optical gas sensor 1 is still installed in a device 2. If an open and / or high-impedance output is then detected, the state machine changes to state 1.

[0075] State 4 is described below: The microcontroller 4 uses switch 8 to connect the digital serial current interface 16 to the sensor output 18.

[0076] The radiation source 6, the driver 5, and the amplifier 11 for the radiation detector 10 are supplied with power via switch 25 for a predefined measurement time, and the oxygen partial pressure is measured. The measured value is output digitally via the digital serial current interface 16. Subsequently, the microcontroller 4 is put into sleep mode for a predefined sleep interval, after which it performs the next measurement.

[0077] At regular intervals, switch 8 is briefly connected to the output resistance measurement circuit 13 to check whether the optical gas sensor 1 is still installed in a device 2. If an open and / or high-impedance output is then detected, the state machine changes to state 1.

[0078] Advantageously, the power consumption can be reduced significantly with the described state machine because: Oxygen measurements are only carried out in states 2-4 and thus the radiation source 6, the driver 5 and the amplifier 11 for the radiation detector 10 do not need to be supplied with power. The said sleep interval can be set depending on the state. For example, the said sleep interval for state 1 can be longer than 10 s, preferably longer than 1 min, while the said sleep interval in states 2-4, corresponding to the time between two oxygen measurements, is preferably 0.5 s to 10 s. The said measurement time can be set depending on the oxygen partial pressure. At low oxygen partial pressures, a shorter measurement time can be used than at high oxygen partial pressures with the same accuracy. For example, with an oxygen partial pressure of 0.2 bar and a measurement time of 2 ms, the same accuracy can be achieved as with an oxygen partial pressure of 1.5 bar and a measurement time of 10 ms.Due to the shortened measuring time, only a fifth of the energy is used for the measurement at 0.2 bar. In many applications, oxygen partial pressures only occur in a certain measuring range. For example, in rebreather diving devices in which oxygen sensors can be used to regulate the oxygen supply, an oxygen partial pressure of 0.6 bar to 1.6 bar can usually be used. During storage of such a rebreather diving device, when the device is not in use, the oxygen supply is closed and the circuit is open, and so the device only contains air with 21% oxygen. If the oxygen sensor measures an oxygen partial pressure below a certain threshold, for example 0.3 bar, the device is apparently not in use, and the sleep interval can be extended, for example to 1 minute.

[0079] Figure 2shows a circuit of an optical gas sensor 1 according to an exemplary embodiment of the invention.

[0080] Figure 2 shows a simple implementation of the interface and state machine with a low-cost microcontroller 4, in which a digital-to-analog converter 13 and a serial USART interface are integrated. The input and output pins of the microcontroller 4 can be configured as outputs or as high-impedance inputs. Likewise, the output of the digital-to-analog converter 13 and the combined transmit / receive pin 33 of a USART interface can also be configured as high-impedance inputs. If they are configured as high-impedance, there is a switching threshold above which a signal is detected as high—or, if the level is below this—as low.

[0081] In state 1, the output pin of the digital-to-analog converter 13, output pin "1" 32, output pin "2" 31, and output pin "3" 30 are initially configured as high-impedance inputs. The internal pull-up resistor 34 is off. If a device 2 with a unidirectional or bidirectional serial interface with a pull-up resistor 23 is connected to the sensor output 18, the transmit / receive pin 33, configured as a high-impedance input, is high. The state machine transitions to state 2.

[0082] Otherwise, output pin "1" 32 is configured as an input again, and output pin "2" 31 is configured as an output and set to high. If the optical gas sensor 1 is not connected to a device 2, output 18 is high impedance and the transmit / receive pin 33, configured as an input, is high. The state machine remains in state 1.

[0083] Otherwise, output pin "1" 32 is configured as an output and set to high. If sensor output 18 is connected to a device 2 designed with a digital serial current output and an input resistance 20 of less than 100 Ω, the input resistance 20 of device 2, together with resistor R5 with a value of, for example, 3.3 kΩ, acts as a voltage divider. The voltage at the transmit / receive pin 33 configured as an input is below the threshold and is thus detected as low, and the state machine transitions to state 4.

[0084] Otherwise, the state machine switches to state 3, since sensor 1 is obviously connected to a device 2, but this is not a device 2 with a digital interface. Thus, a device 2 with an analog interface is present, for example, with an input resistance between 10 kΩ and 500 kΩ.

[0085] In state 2, the output of the digital-to-analog converter 13, output "1" 32, output "2" 31, and output "3" 30 are configured as high-impedance inputs, and the digital interface 33 is configured as a one-wire unidirectional or bidirectional single-duplex serial interface (USART). The output of the serial interface is configured as an open collector output. The internal pull-up resistor 34 is deactivated. The optical gas sensor 1 is connected to a device 2 with a high-impedance input and pull-up resistor 23, thus enabling signal transmission with different high and low voltage levels.

[0086] In state 4, the output of the digital-to-analog converter 13, output "1" 32, output "2" 31, and output "3" 30 are configured as high-impedance inputs, and the digital interface 33 is configured as a one-wire unidirectional or bidirectional single-duplex serial interface (USART). The output of the serial interface is configured as an open collector output. The interface's internal pull-up resistor 34, typically 10 kΩ to 50 kΩ, is switched on, and resistor R4 is in series with a low-impedance input resistor 23, preferably less than 100 Ω. For example, if the microcontroller 4 is supplied with a voltage of 2 V, a current of approximately 200 µA flows at high and no current flows at low. Only at high is there a small electrical potential of less than 20 mV at the sensor output 18 of the optical gas sensor 1, which is however too low to accelerate corrosion on the connector even in humid and saline environments.

[0087] In state 3, output "1" 32, output "2" 31, and the digital interface 33 are configured as high-impedance inputs. The internal pull-up resistor 34 is off. Output 3 is configured as an output and is set to high. Thus, the drain of the N-FET T1 is connected to the ground terminal 17. The output voltage from the digital-to-analog converter 13 is divided by a voltage divider consisting of R1 and R2 to the typical output voltage range of analog galvanic sensors.

[0088] It should be noted that the term "have" does not exclude other elements and that "a" does not exclude a plural.

Claims

1. Method for operating a sensor, in particular an optical gas sensor (1), having a connection (3) with at least 2 poles, for measuring an analyte, wherein the method comprises: automatic detection of whether the sensor, in particular the optical gas sensor (1), is connected to a device (2); automatic detection of an analog interface and / or digital serial interface with current level (15) and / or digital serial interface with voltage level (16) used for the sensor, in particular the optical gas sensor (1), to the device (2); and based on the automatic detection, automatic adaptation of the operation of the sensor, in particular of the optical gas sensor (1), wherein the method comprises the automatic detection via the 2 poles of the connection (3) of the sensor, in particular of the optical gas sensor (1), by measuring an input resistance of the device (2) connected to the 2 poles and / or by measuring a voltage level of the device (2) connected to the 2 poles; wherein the automatic detection comprises the following measure: automatic detection that the sensor, in particular the optical gas sensor (1), is connected to the device (2) with an analog interface if an input resistance of the device (2) lies in an associated predefinable interval; and / or is connected to the device (2) with a digital serial interface with current level (15) if an input resistance lies below an associated predefinable threshold value; and / or is connected to the device (2) with a digital serial interface with voltage level (16) if a voltage level can be measured at an input of the sensor, in particular of the optical gas sensor (1); wherein the automatic adaptation comprises one, several or all of the following measures: automatic configuration of the 2 poles of the connection (3) according to the detected device as: analog interface, serial digital interface with current level (15), serial digital interface with voltage level (16).

2. Method according to claim 1, wherein the automatic detection comprises one, several or all of the following measures: automatic detection that the sensor, in particular the optical gas sensor (1), is not connected to the device (2) if a connection of the optical gas sensor (1) is open; automatic detection that the sensor, in particular the optical gas sensor (1), is connected to the device (2) with the analog interface if an input resistance of the device (2) lies between 5 kΩ and 1 MΩ; automatic detection that the sensor, in particular the optical gas sensor (1), is connected to the device (2) with the digital current interface with current level (15) if an input resistance lies below 100 Ω; automatic detection that the sensor, in particular the optical gas sensor (1), is connected to the device (2) with a digital interface with voltage level (16) if a voltage level greater than 1 V can be measured at an input of the sensor, in particular of the optical gas sensor (1).

3. Method according to claim 1 or 2, comprising the following feature: wherein an automatic detection of the measuring range of the analyte comprises the detection whether or not the concentration of the analyte is in a predetermined range.

4. Method according to one of claims 1 to 3, wherein the automatic adaptation comprises one, several or all of the following measures: in the case of automatic detection that the sensor, in particular the optical gas sensor (1), is not connected to the device (2), no performance of measurements.

5. Method according to one of claims 1 to 4, wherein the automatic adaptation is performed for reducing, in particular for optimizing or for minimizing, a power consumption of the sensor, in particular of the optical gas sensor (1).

6. Method according to one of claims 1 to 5, wherein the method triggers a performance of a measurement with the sensor, in particular the optical gas sensor (1), with a predetermined increased measuring accuracy only if a concentration of the analyte is in a predetermined range.

7. Method according to claim 6, wherein the method performs, before said measurement, a pilot measurement with the sensor, in particular the optical gas sensor (1), with a lower measuring accuracy compared to the predetermined increased measuring accuracy for determining whether the concentration of the analyte to be measured is in the predetermined range.

8. Method according to one of claims 1 to 7, wherein the method comprises converting an analog measuring signal into a digital measuring signal by means of an analog-to-digital converter.

9. Method according to claim 8, wherein the method comprises back-converting the converted digital measuring signal into a back-converted analog measuring signal by means of a digital-to-analog converter (14) if the measuring signal is to be provided to the device (2) in an analog manner.

10. Sensor, in particular optical gas sensor (1), comprising a sensor layer (8), a radiation source (6), a radiation detector (10) and a microcontroller (4), characterised in that the microcontroller (4) is designed to control and / or carry out a method according to one of claims 1 to 9.

11. Sensor, in particular optical gas sensor (1), according to claim 10, comprising one, several or all of the following features: a battery (12) for supplying the sensor, in particular the optical gas sensor (1), with electrical energy; an analog-to-digital converter for converting an analog measuring signal into a digital measuring signal; a digital-to-analog converter (14) for back-converting an analog measuring signal converted into a digital measuring signal by means of an analog-to-digital converter into a back-converted analog measuring signal if the measuring signal is to be provided to the device (2) in an analog manner; a circuit (13) for measuring a resistance at a connection of the sensor, in particular of the optical gas sensor (1); at least one digital interface (15, 16) for providing a digital sensor signal, in particular a digital voltage level interface (16) for providing the digital sensor signal as voltage level and / or a digital current level interface (15) for providing the digital sensor signal as current level; a voltage measuring device for measuring a voltage at a connection of the sensor, in particular of the optical gas sensor (1), in particular formed by means of an analog-to-digital converter (21).

12. Arrangement, comprising: a sensor, in particular an optical gas sensor (1), according to claim 10 or 11; and a device (2) to which the sensor, in particular the optical gas sensor (1), is connected or can be connected.

13. Arrangement according to claim 12, comprising at least one of the following features: comprising a plug connection (3), in particular a 2-pole plug connection, for connecting the sensor, in particular the optical gas sensor (1), to the device (2); wherein the device (2) comprises or consists of immersion equipment, in particular a circulation immersion device.