KR101307922B1 - Calibration of an electro-optical signal path of a sensor device by means of online signal level monitoring - Google Patents

Abstract

A sensor device for detecting certain objects, in particular optically detecting smoke particles, is described. The sensor device comprises (a) transmission devices 120, 220 for emitting transmission radiation 120a, (b) reception radiation having scattered radiation generated by at least partial scattering of the transmission radiation by the subject. Receiving devices (130, 230) for receiving (130a) and for receiving a measurement signal indicative of the received radiation (130a), (c) for modifying the measurement signal and for outputting a changed measurement signal; Signal changing devices 140, 240, wherein the level of the changed measurement signal increases after the transmitting device 120, 220 is switched on; (d) a calibration device 150 for monitoring the changed measurement signal; 250). The calibration device 150, 250 may detect the arrival of a predefined signal level Uref for the changed measurement signal and switch on the transmission device 120, 220 and the arrival of the predefined signal level. It is implemented so that the time interval Δt _c can be determined. A risk detector having a sensor device of this kind and a method for calibrating a sensor device of that kind are also described.

Description

CALIBRATION OF AN ELECTRO-OPTICAL SIGNAL PATH OF A SENSOR DEVICE BY MEANS OF ONLINE SIGNAL LEVEL MONITORING}

The present invention relates generally to the technical field of building safety. In particular, the present invention relates to sensor devices for detecting certain objects, in particular for optically detecting smoke particles. In addition, the present invention relates to a hazard detector for detecting a dangerous situation, in particular for detecting smoke in a monitored space. In addition, the present invention relates to a method for calibrating sensor devices of this kind.

Optical or optoelectronic smoke detectors usually operate according to well-known scattered light principles. Such devices take advantage of the fact that clean air reflects virtually no light. However, if smoke particles are present in the measurement chamber, the illumination light emitted by the light source will be at least partially scattered by the smoke particles. A portion of the scattered light impinges on a photo detector arranged relative to the light source such that it is not directly touched by the illumination light. Therefore, the illumination light does not reach the photo detector when there are no smoke particles in the measurement chamber.

The photo detector of the optical smoke detector is typically a photodiode that supplies only very small measurement signals. The photodiode supplies an output current whose intensity depends on the incident light intensity. The intensity of the light that strikes the photodiode depends in particular on the intensity of the illumination light emitted by the light source, on the geometry of the smoke detector and on the density of the smoke particles in the measurement chamber.

An electronic amplification circuit that converts the current provided by the photodiode into a voltage and amplifies the voltage so that the signal can be further processed by a subsequent system is typically connected downstream of the photodiode. The subsequent system includes, for example, an analog-to-digital converter and a microcontroller for further signal processing.

In order to ensure reliable triggering of the alarm on the one hand and low false alarm rate of the optical smoke detector on the other hand, the electronic smoke detector of the optical smoke detector is generally used before the service of the smoke detector. There is a need to calibrate the optical signal path. In addition, the calibration of the electro-optical signal path of this kind must be carried out at constant holding intervals so that reliable alarm triggering and low false alarm rate can also be ensured even during a delayed period of operation of the optical smoke detector. have.

Inevitable changes from the nominal behavior of the components of the electro-optic signal path, for example characterized by specific tolerances, can be compensated for by calibration, sometimes referred to as fine adjustment. Changes of this kind actually occur especially with regard to the efficiency of the light source, the control of the light source, and / or the amplification of the amplifier circuit.

The electro-optical path signal of the optical smoke detector is (a) a light source, such as a light emitting diode for emitting illumination light, (b) a measuring chamber through which scattered smoke particles can pass, (c) a light detector, such as through the chamber A photodiode for detecting illumination light scattered by the smoke particles, (d) an amplifier circuit connected downstream of the light detector, and (e) for analyzing the detected scattered light signals and the light source And a microcontroller coupled downstream of the amplifier circuit to control or adjust the voltage.

To calibrate an optical smoke detector, or in some cases, the use of the electro-optical signal path of the optical smoke detector consists of scatterers introduced into the measuring chamber, the scatterers corresponding to smoke particles Simulate their defined density. Thereafter, a pulse of illumination light pulses emitted by the light source, for example, until a predefined signal swing necessary for tripping an alarm of the optical smoke detector is reached by the amplifier circuit. The adjustment of the durations changes the intensity of the illumination light. The use of a dispersion body of this kind is described for example in EP 0 658 264 B1.

Typically, at least 3-4 pulse periods are repeatedly applied to the light source to achieve precise calibration. However, the pulse periods cannot be repeated arbitrarily and quickly, because the corresponding light source needs to be cooled again in the middle and the amplifier circuit used must be stabilized back to a stable state. As a result, the calibration of the electro-optical signal path of the optical smoke detector is time-consuming. This results in longer manufacturing time and an increase in manufacturing cost for optical smoke detectors.

The primary object of the present invention is to improve the calibration of optical risk detectors.

This object is achieved by the content of each independent claim. Preferred embodiment modifications of the invention are described in the dependent claims.

According to a first aspect of the invention, a sensor device for detecting a constant object, in particular for detecting smoke particles, is described. The sensor device receives and receives received radiation having (a) a transmitting device for emitting transmit radiation, and (b) scattered radiation generated as a result of at least partial scattering of the transmit radiation by the subject. A receiving device (b1) for outputting a measurement signal indicative of radiation, (c) a signal changing device for modifying the measurement signal and for outputting a changed measurement signal, wherein the level of the changed measurement signal is switched on Then increase,-(d) a calibration device for monitoring the modified measurement signal, wherein the calibration device can be detected: (d1) the arrival of a predefined signal level for the modified measurement signal, And (d2) the time between switching on of the transmitting device and reaching the predefined signal level. It is implemented so that this interval may be determined.

The sensor device described is based on the recognition that the calibration of the electro-optical signal path of the sensor device can be carried out in a particularly simple manner by the "online" monitoring of the changed measurement signal level. According to the invention, i.e., the time interval for activation of the transmission radiation necessary to reach a certain minimum level at the output of the electro-optic signal path is simply determined, the output being reliably detected and in particular reliable It is needed during operation of the sensor device for smoke detection. During the actual operation of the sensor device, the transmitting device is activated and controlled in a pulsed manner and the duration of activation of the transmitting device corresponds to a determined time interval between the switching on of the transmitting device and the arrival of a predefined signal level. do. The electro-optical signal path can therefore be calibrated in a preferred manner already with one-time activation of the transmitting device. Preferably, the time-consuming and cost-intensive repetitive procedures necessary for switching on and off the transmitting device several times are no longer needed.

The term "activation" is to be understood in this context as the transmitting device in a switched-on state during the time of the activation and thus emitting transmitting radiation.

The electro-optical signal path of the sensor device according to the invention can therefore be calibrated by a method which can be carried out simply and quickly. As a result, the sensor device can be manufactured faster and the manufacturing cost can be significantly reduced. Thus, in the case of known sensor devices requiring time-consuming calibration, it is no longer necessary for mass production of sensor devices according to the present invention to use multiple calibration stations simultaneously, as is necessary for sufficiently high speed manufacturing. Not. This means that at least some of the calibration stations operated simultaneously or in parallel can be saved and acquisition costs for the setting up of the mass production facility for the sensor devices can be reduced. The reduction of acquisition costs of this kind obviously has a beneficial effect in terms of manufacturing costs, since the acquisition costs must be amortized as the product price charged for the sensor devices.

The measurement signal output by the receiving device may, for example, indicate the intensity of the measuring radiation that impinges on the receiving device.

The term "radiation" is to be understood as meaning electromagnetic radiation with arbitrary wavelengths in the context of this document. In particular, the electromagnetic radiation may be light in the visible, infrared (IR), or ultraviolet (UV) spectral region. In addition to the relatively narrowband spectral range or even monochromatic radiation, the electromagnetic radiation can also have different wavelengths representing continuous spectrum or different narrowband and / or wideband spectral ranges that are separated from one another. The electromagnetic radiation can also have wavelengths assigned to the far-infrared and / or far-ultraviolet spectral range. Microwave radiation or any type of electromagnetic radiation can basically be used as transmit radiation and thus as receive radiation. In a similar manner, the term “optical” is intended to refer to all mentioned spectral ranges of electromagnetic radiation, not just the visible spectral range.

According to an exemplary embodiment of the present invention, the signal modification device has an integrating entity.

For example, the signal changing device may be an integrated photomultiplier in which the receiving radiation is integrated over the entire pulse length of the transmitting radiation pulse emitted by the transmitting device. This has the advantage that a significantly lower amplification factor can be selected compared to using a known transimpedance amplifier, which allows the overall signal processing of the optical sensor device to be more robust and / or more resistant to interference. That means it can be executed to be less affected.

The integral entity can be executed by an integral electronic circuit, for example. However, it is pointed out that the integrating entity may also be implemented by a software component that calculates an output signal that represents the time integration of the changed measurement signal when executed by the processor. In addition, the integration can also be executed in hybrid form, ie by software components and hardware components.

Using an integral entity also means that after the transmitting device has been switched on, the changed measurement signal representing the output signal of the signal changing device rises exactly monotonously until at least the specified readout time, or if the receiving radiation is on the receiving device if possible. Should not immediately affect, at least has the advantage of monotonous rise. This means that a predefined signal level can be reliably detected by the calibration device and that a reliable calibration of the electro-optic signal path is a corresponding reliable determination of the time interval between the switching on of the transmitting device and the arrival of the predefined signal level. Has the advantage that it can be implemented by.

In accordance with a further exemplary embodiment of the present invention, the integrating entity has a capacitor or capacitance. This has the advantage that the integral entity can be easily implemented by a simple electronic circuit with very cheap electronic components. This in turn lowers the material costs for producing the entire sensor device.

In addition, the use of a capacitor enables in a simple manner the continuous integration of the modified measurement signal, which is typically an analog signal.

The possible temperature dependence of the integrated electronic circuit implemented by the capacitor can lead to a modified measuring signal, in particular reaching a signal level or signal maximum depending on the current temperature. However, temperature effects of this kind can be compensated for by close-meshed monitoring of the altered measuring signal over time, and the maximum signal level is always reliably detected.

The capacitor may be a separate capacitor, for example, separate from other electronic components of the integrated electronic circuit, so that the separate capacitor and the other electronic components are not implemented together in an integrated circuit. This in turn reduces the material costs for producing the entire sensor device.

Capacitors or capacitances can also be implemented in microcontrollers with ASICs and / or analog functions.

According to a further exemplary embodiment of the invention the signal changing device has an amplifying electronic circuit. Although only small amplification is necessary due to the above-mentioned use of the integrated electronic circuit, this allows signal processing to be performed at amplified signal levels allowing reliable (additional) signal processing by their signal amplitude.

According to a further exemplary embodiment of the invention the calibration device has an analog-to-digital converter in which the modified measurement signal can be sampled.

Using an analog-to-digital converter (ADC) has the advantage that the arrival of a predefined signal level can be checked using digital data. This allows particularly reliable determination of the time interval between the switching on of the transmitting device and the arrival of a predefined signal level and consequently also particularly reliable calibration of the electro-optic signal path.

In a sensor device suitable for optically detecting smoke particles, the time interval between the switching on of the transmitting device and the arrival of a predefined signal level may amount to approximately 10 to 200 ms, for example.

As already described above, the time interval corresponds to the pulse duration that the transmitting device should be operated during the operation of the sensor device to allow reliable object detection. The sampling rate of the ADC must be high enough so as to not miss the arrival of the predefined signal level even when the modified measurement signal rises relatively steeply. In the case of a sensor device used in a smoke detector, the sampling rate may be, for example, approximately 1 MHz.

According to a further exemplary embodiment of the invention, the calibration device has a control unit coupled to the transmitting device and implemented such that the transmitting device can be operated by a pulsed control signal, the respective pulse durations being switched by the transmitting device. It correlates to a specific time interval between on and arrival of a predefined signal level.

The control unit may, for example, have a driver circuit for converting the voltage curve of the pulsed control signal into a suitable current profile of the pulsed control signal, the corresponding current being passed through the transmitting device during operation of the sensor device. Flow.

According to a further exemplary embodiment of the invention the transmitting device has a light emitting diode.

The use of light emitting diodes (LEDs) has the advantage that the transmission device can be implemented using inexpensive optoelectronic components which further exhibit a high degree of energy efficiency. This means that light emitting diodes can emit high intensity transmit radiation or transmit light even at low levels of electrical power consumption. Therefore, the described sensor device can be operated with low energy requirements. For battery operation this can provide long battery life.

The light emitting diode is preferably a light emitting diode that emits light in the infrared spectral range (IRED). Using IRED has the advantage that the transmitting radiation can be produced with a particularly high degree of energy efficiency and in addition has infrared light which is very well scattered by many objects, especially smoke.

The light emitting diode may in particular be configured such that pulsed transmit radiation can be emitted.

Advantageously, only one drive pulse is required for calibration to calibrate the electro-optical signal path for the sensor device described later. In this case the LED or optionally IRED is switched on and the modified measurement signal output by the signal changing device, which can be, for example, a typical photomultiplier, is periodically sampled. This occurs in any event until the time when the modified measurement signal reaches the required target signal swing. Thereafter the LED or IRED can be switched off. The required duty cycle or switch-on time of the LED or IRED then corresponds to the calibrated pulse length of the LED or IRED.

It is pointed out that the transmission device can also have multiple light emitting diodes. In this case each of the light emitting diodes may contribute to the emission of particularly strong or intensive transmission radiation as a whole.

According to a further exemplary embodiment of the invention, the receiving device has a photodiode. This has the advantage that the receiving device can be implemented using a simple and especially inexpensive optoelectronic component. Therefore, the receiving device described above represents an optical device with a high degree of electromagnetic compatibility which is also suitable for being referred to as "low cost" applications.

The photodiode may have a spectral sensitivity that is optimized for the requirements present in a particular case. In particular, in order to use the sensor device for an optical smoke detector, the photodiode can have high sensitivity within the near-infrared spectral range, where simple light emitting diodes commonly used as light sources are In particular, it exhibits a high degree of efficiency.

It is pointed out that the receiving device may also have a plurality of photodiodes, each of which is coupled to the signal changing device described above.

According to a further aspect of the invention, a hazard detector for detecting a dangerous situation, in particular for detecting smoke in a monitored space, is described. The hazard detector described above has a sensor device of the type described above.

The risk detector described above is also based on the knowledge that the calibration of the electro-optical signal path can be carried out in a simple and particularly rapid manner through the "online" monitoring of the signal level of the altered measuring signal. In this case the time interval is simply determined, and in order for the predefined target signal swing to reach the output of the electro-optic signal path, within the time interval, the transmitting radiation must be emitted by the transmitting device. The target signal swing is required for reliable object detection and in particular for reliable smoke detection during operation of the sensor device.

According to a further aspect of the invention, a method is described for detecting a certain object, in particular for calibrating a sensor device for optically detecting smoke particles. The method described above comprises (a) switching on a transmitting device to emit transmit radiation, and (b) receiving received radiation having scattered radiation generated by at least partial scattering of the transmit radiation by the subject. (C) outputting a measurement signal indicative of the received radiation, (d) modifying the measurement signal such that the level of the modified measurement signal is increased, (e) monitoring the modified measurement signal, the modified The arrival of a predefined signal level is detected for the measurement signal, comprising determining a time interval between the switching on of the transmitting device and the arrival of the predefined signal level.

The method described above is based on the knowledge that the electro-optic signal path can be calibrated in a simple, efficient and rapid manner by determining the time interval, and within the time interval, the received radiation or in some cases the scattering The transmitted radiation must impinge on the radiation receiver to reach a predefined signal level of the constantly increasing modified measurement signal. Advantageously, only one switch-on pulse is required for the radiation source to carry out the calibration method described above, which, in comparison with known calibration methods for optical smoke detectors, calibrates the electro-optical signal path. This means it can be completed much faster. By known calibration methods, in other words it is generally necessary to use a number of eg three to four iterative pulse cycles, in order to achieve a reliable calibration of the electro-optic signal path. The radiation source is activated and controlled by repetitive pulse periods.

According to a further exemplary embodiment of the invention, the method further comprises introducing the reference object into the measurement space of the sensor device such that a scattering reference object is impinged by the transmitting radiation and generates the received radiation. .

The reference object may generally be any arbitrary scattering body that causes the transmitted radiation to be scattered, thereby causing the received radiation to be generated. In the case of the calibration of the electro-optical signal path of the smoke detector, the reference object may have a scattering behavior for electromagnetic radiation corresponding to a defined amount of scattering behavior or in some cases a concentration of smoke particles.

It is pointed out that embodiments of the invention have been described with reference to different objects of the invention. In particular, some embodiment variations of the present invention are described by the device claims and other embodiment variations of the present invention are described by the method claims. Unless explicitly stated otherwise, when reading this specification, in addition to one type of combination of features belonging to the object of the present invention, any combination of features belonging to different types of object of the present invention is also possible. It will be immediately apparent to those skilled in the art.

Further advantages and features of the present invention will come from the following illustrative description of presently preferred embodiment modifications. The individual drawings of the drawings of the present application will be regarded as merely schematic and will not be considered to have been scaled.

1 shows a smoke detector based on the optical scattered light principle in accordance with an exemplary embodiment of the present invention.
FIG. 2 shows a schematic of the overall electro-optic signal path in the optical smoke detector shown in FIG. 1.
3 shows the time characteristics of different signals during the on-line calibration of an optical smoke detector with a single light pulse.

The features and / or components of different embodiment variations that are the same or at least functionally identical to the corresponding features and / or components of the embodiment change are first labeled from the same reference numerals or from the corresponding reference of the corresponding component. It is pointed out that only the first digit is labeled by different reference signs. In order to avoid unnecessary repetition, the features and / or components already described with reference to the above-described embodiment change will not be described in detail again in the following points.

In addition, it is pointed out that the embodiment changes described below represent only a limited selection of possible embodiment changes of the present invention. In particular, it is possible for a combination of individual embodiment modifications with other embodiment modifications in an appropriate manner so that a number of different embodiment modifications are deemed to be clearly disclosed from the point of view of those skilled in the art by the embodiment modifications explicitly set forth herein. Do.

1 shows a smoke detector 100 based on the scattered light principle of optics. For example, the smoke detector has a measurement chamber 110 through which smoke passes during a fire. The measurement chamber is also referred to as scattering volume 110. Included in the measurement chamber 110 is a light source or radiation source 120, which is implemented as a photodiode and receives control pulses by a control line 170a, thereby illuminating the pulsed light. Induced to emit light 120a. Also in the edge region of the measurement chamber 110 is a photo detector 130, which is embodied by a photodiode and at least partially scatters the illumination light 120a by smoke particles. Then, the measurement light 130a that hits the photo detector 130 is received. The optical barrier 111 prevents the illumination light 120a from hitting the photo detector 130 directly, ie without scattering.

Connected downstream of the photo detector 130 is a signal change device 140 that converts the photocurrent resulting from the light incident on the photo detector 130 into a voltage signal. According to an exemplary embodiment presented herein, the signal changing device is an amplifier circuit 140 that integrates the photocurrent provided by the photo detector. The modified measurement signal provided by the amplifier circuit 140 is further processed by the control device 150.

As can be seen from FIG. 1, an analog-to-digital converter (ADC) 156 is integrated into the control device 150. The analog-to-digital converter serves to convert the analog output signal of the amplifier circuit 140 into a digital measurement value 156a, the digital measurement value 156a can be further processed (as described herein) In a manner not shown), for example, if a certain limit value is exceeded, the fire alarm signal may be initiated.

The control device 150 additionally comprises a driver circuit 170 for the light source 120 that is connected to the control device 150 or more precisely to the driver circuit 170 by a control line 170a. Include.

As can also be seen from FIG. 1, the control device 150 furthermore has a suitable temperature of the entire smoke detector 100 can also be measured, the internal temperature measuring diode 158 by the temperature of the control device 150. ). Alternatively or in combination, the temperature may also be measured by external temperature sensor 168. The external temperature sensor 168 may be, for example, what is called a hot-carrier thermal resistor or an NTC thermistor.

In order to ensure trouble-free operation of the smoke detector 100, calibration is performed before the smoke detector 100 is serviced. A scatterer (not shown in FIG. 1), which is defined in this case, is introduced into the measurement chamber 110 and a response value in which the digitized output signal 156a of the analog-to-digital converter 156 is recorded and predefined Is compared with By virtue of the use of defined scatterers, the entire electro-optical signal path inside the smoke detector is automatically registered.

According to an exemplary embodiment described herein, the calibration of the electro-optic signal path can be made by a single light pulse. As described in more detail below with reference to FIG. 3, the signal level of the modified measurement signal output by the amplifier circuit 140 is monitored online at the progress of a single illumination pulse and at a determined time interval, wherein the time interval A predefined reference level within is reached following the onset of the illumination pulse.

2 shows a schematic representation of the entire electro-optic signal path in the optical smoke detector 100, indicated by reference numeral 200. The signal path is in particular the control and activation of the light source 220 by the control device 250, the efficiency of the light source 220, the optical scattering conditions inside the measurement chamber 210, the light detector 230 Efficiency, amplification of the amplifier circuit 240 and signal conversion of the analog-to-digital converter in the control device 250.

If it is realized that the digitized output signal of the analog-to-digital converter during the calibration may be smaller than planned, for example as a result of the relatively low-luminosity light source 220, which is the light Compensation is made by the extension corresponding to the pulse duration of the pulses. If the output signal of the analog-to-digital converter is larger than planned, for example, especially as a result of the high-brightness light source 220, this can be compensated for by shortening the pulse duration of the light pulses.

This is the case in the case of the smoke detector 100 described herein, wherein the calibration is not due to the adjustment of the amplification of the amplifier circuit 240 but of the pulse durations of the illumination pulses emitted by the light source 220. It means that it is affected by the adjustment.

In order to maintain the switch-on time of the light source 220 within predetermined limits, the light source 220 has a defined light outputs, possibly a different light source with a difference in terms of their illumination efficiency. Can be derived from their preselection.

3 shows the time characteristic of different signals during on-line calibration of optical smoke detector 100 with a single light pulse. Diagram 381 shows the time characteristic of the current I _IRED flowing through the light emitting diode 120. Diagram 382 shows the time characteristic of the modified measurement signal U _amp provided by the amplifier circuit 140. Diagram 383 shows sampling by the analog-to-digital converter 156. The scaling of the time axis of the three diagrams 381, 382 and 383 is the same; There is no offset between the time axes of the three diagrams 381, 382 and 383. Scatters with scattering reactions defined during the calibration described above are included in the measurement chamber 110.

As can be seen from diagram 381, the described calibration of the electro-optical signal path begins by online monitoring of a single light pulse that is switched _on at time t _on . The corresponding illumination light emitted by the light emitting diode 120 then impinges on the photodiode 130 as measurement light scattered and scattered by the scatterer. The photodiode 130 generates a measurement signal indicating the intensity of the measurement light.

The amplifier circuit 140 now begins to integrate the measurement signal. At the same time, the ADC 156 periodically samples the output signal of the amplifier circuit 140. This is indicated by "S2" in diagrams 382 and 383, respectively.

After a certain amount of time, the output signal of the amplifier circuit 140 sampled by the ADC 156 reaches a predefined target voltage swing U _ref . This is indicated by "S3" in diagrams 382 and 383, respectively. Immediately after reaching the target voltage swing U _ref , the light emitting diode 120 is switched _off again at time t _off . The integration process also ends with the result that the signal level of the modified measurement signal U _amp provided by the amplifier circuit 140 falls back. This is indicated by "S4" in the diagram 381.

It is pointed out that the sampling of the modified measurement signal U _amp by the ADC 156 continues until at least a time that ensures that the predefined target voltage swing U _ref is also reliably reached.

The control device 150 as shown in FIG. 2 also handles the calibration, t _off and t _on Calculate the time difference Δt _c between. This is indicated by "S5" in diagram 381. The time difference Δt _c corresponds to the calibration duration Δt _c .

During operation of the smoke detector 100, a current pulse of duration Δt _c may then be applied to the light emitting diode 120 at regular intervals. This allows smoke particles to penetrate into the measurement chamber 110 to be detected with a high degree of reliability. If a predefined minimum smoke density is exceeded, an appropriate alarm signal can then be output.

100 smoke detector
110 measuring chamber / scattering volume
111 barrier
120 radiation sources / light sources / light emitting diodes
120a illuminated radiation / illuminated light
130 radiation detector / photo detector / photodiode
130a measuring radiation / measuring light
140 Signal Change Device / Amplifier Circuit
150 control devices
156 Analog-to-Digital Converters (ADCs)
156a measured value
158 internal temperature measuring diode
168 External Temperature Measurement Sensor / NTC
170 driver circuit
170a control line
200 smoke detectors
210 measuring chamber / scattering volume
220 radiation sources / light sources / light emitting diodes
230 radiation detector / photodetector / photodiode
240 amplifier circuit
250 control device
270a control line
381 LED Through Current
382 modified measuring signals
Sampling by 383 Analog-to-Digital Converters
I _IRED IR LED Through Current
Δt _c calibration duration
t _on switch-on time
t _off switch-off time
Output voltage of U _amp amplifier circuit
U _ref swing target voltage

Claims (14)

A sensor device for detecting a fixed object,
A single transmitting device 120, 220 for emitting the transmitting radiation 120a,
Receiving devices 130, 230 for receiving received radiation 130a having scattered radiation generated by at least partial scattering of the transmitted radiation by the subject and outputting a measurement signal indicative of the received radiation 130a ),
A signal changing device 140, 240 for changing the measurement signal and outputting a changed measurement signal, wherein the level of the changed measurement signal increases after the transmitting device 120, 220 is switched on;
Calibration device 150, 250 for monitoring the modified measurement signal
Lt; / RTI >
The calibration device 150, 250,
The arrival of a predefined signal level U _ref for the modified measurement signal can be detected,
Such that a time interval Δt _c between the switching on of the transmitting device 120, 220 and the arrival of the predefined signal level may be determined.
Implemented
Sensor device. The method of claim 1,
The signal change device 140, 240 has an integrating entity,
Sensor device. The method of claim 2,
The integrating entity has a capacitor,
Sensor device. 4. The method according to any one of claims 1 to 3,
The signal changing device 140, 240 having an amplifying electronic circuit,
Sensor device. 4. The method according to any one of claims 1 to 3,
The calibration device 150, 250 has an analog-to-digital converter 156, wherein the modified measurement signal can be sampled using the analog-to-digital converter 156.
Sensor device. 4. The method according to any one of claims 1 to 3,
The calibration device 150, 250 has a control unit coupled to the transmission device 120, 220, the control unit being operated by a control signal in which the transmission device 120, 220 is pulsed. Implemented in a capable manner, the respective pulse durations being correlated with the determined time interval Δt _c between the switching on of the transmitting device 120, 220 and the arrival of the predefined signal level,
Sensor device. 4. The method according to any one of claims 1 to 3,
The transmitting device has light emitting diodes 120, 220,
Sensor device. 4. The method according to any one of claims 1 to 3,
The receiving device has photodiodes 130 and 230,
Sensor device. As a hazard detector for detecting dangerous situations,
The risk detector (100, 200) comprises a sensor device according to any one of claims 1 to 3,
Risk detector. A method for calibrating a sensor device for detecting a constant object, the method comprising:
Switching on the single transmitting device 120, 220 such that the transmitting radiation 120a is emitted,
Receiving received radiation 130a having scattered radiation generated by at least partial scattering of the transmitted radiation by the subject,
Outputting a measurement signal indicative of the received radiation 130a,
Modifying the measurement signal such that the level of the changed measurement signal is increased,
Monitoring the modified measurement signal, wherein the arrival of a predefined signal level Uref for the modified measurement signal is detected;
Determining a time interval Δt _c between the switching on of the transmitting device 120, 220 and the arrival of the predefined signal level
/ RTI >
Method for calibrating a sensor device. The method of claim 10,
Introducing the scattering reference object into the measurement spaces 110, 210 such that a scattering reference object is impinged by the transmitting radiation 120a and generates the receiving radiation 130a.
≪ / RTI >
Method for calibrating a sensor device. The method of claim 1,
Wherein the sensor device is for optically detecting smoke particles,
Sensor device. 10. The method of claim 9,
The risk detector is for detecting smoke in the monitored space,
Risk detector. The method of claim 10,
Wherein the sensor device is for optically detecting smoke particles,
Method for calibrating a sensor device.

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