DE102008001067A1 - Radiometric sensor device for non-contact temperature measurement and method for radiometric, non-contact temperature monitoring of a detection range - Google Patents

Abstract

The invention relates to a radiometric sensor device for non-contact temperature measurement in a detection area (5), comprising: an antenna (2) for receiving radio and / or microwave radiation (R) and outputting a microwave signal (S1) and means (3, 4, 8) for receiving and evaluating the microwave signal (S1) and outputting an output signal (S2). According to the invention, it is provided that the means for receiving and enhancing the microwave signal (S1) from the microwave signal (S1) determine successive discrete reference values (Tbi) and determine from temporal changes of the discrete reference values (Tbi) whether a relevant temperature change in the detection range (5) is done. For this purpose, the means preferably comprise: a radiometer device (3) for receiving the microwave signal (S1) and outputting an analog band signal (B) and a detection device (4) for receiving and evaluating the band signal and determining the discrete reference values (Tbi) and a temporal temperature behavior in the detection area (5). Furthermore, a corresponding method is provided.

Description

State of the art

sensor devices for non-contact temperature measurement are for used different tasks, especially for fire protection or for the detection of persons.

In Car alarm systems or interior monitoring of vehicles be ultrasound, radar, infrared sensors or video cameras used. In building alarm systems come in particular Infrared sensors or Doppler radar measuring devices are used. As a protection sensor for power tools, z. B. as a saw stop in particular to avoid injury to the user are capacitive Known method; This is often the saw when triggered destroyed the protection sensor. When car pedestrian protection in particular radar, ultrasonic or infrared sensors are used.

Farther it is known for comfort adjustments in the vehicle, z. B. a comfort entry-Go adjustment, proximity sensors to be used as capacitive sensors or radar sensors.

Radar- and enable ultrasound, video camera and capacitive measurements here distance and differential speed measurements. Touchless Temperature measurements, however, are generally radiometric, d. H. by measuring the irradiance.

infrared sensors enable temperature measurements by recording the heat radiation in the IR range, the electromagnetic Radiation of the temperature radiator in this wavelength range However, it can be easily shielded.

Next Photonic temperature measurements by infrared sensors are still radiometric millimeter wave measurements known, in particular for Detection of mines, for surface analysis and known in astronomy. Here, the temperature radiation of the observed body in the long-wave range of the spectrum, in particular millimeter wavelength range or megahertz frequency range, recorded, wherein a noise signal is generally determined. Unlike the photonic infrared measurements by photodiodes or similar sensors, the recording of the radio radiation takes place as frequency measurement via antennas or dipole antennas. It also results in higher frequencies a signal that does not drop as much as a photonic one Measurement.

Radiometric Temperature determinations point towards temperature sensors in the infrared range some advantages. So the radiation can be from deeper Areas of the considered object or the detection area be recorded. A shielding of the radio wave radiation is in usually only by metal surfaces, but not by Clothing or other thinner objects possible.

These Millimeter radiometers are generally discreet and constructed must be calibrated consuming, since an absolute noise temperature measurement is required. This is for the calibration in general a switch in the receiver required.

The US 2005/0053118 A1 describes a system and method for non-contact temperature measurement of an object using microwave radiometry, which can be used in particular for building surveillance. In this case, comparative measurements are carried out in which the radio-wave radiation of the object is recorded alternately in a transmission mode and subsequently blocked in a blocking mode, with the recording of a comparison object taking place in the blocking mode as comparison value. From this comparison, a calibration can thus be carried out for determining the temperature of the object under consideration.

The calibration of the measurement signal by comparison measurements according to US 2005/0053118 A1 However, it is relatively expensive, so that the use of radiometric measurements is limited.

Farther active measurements in the radar wavelength range are known, however, these are usually restricted to narrow ones ISM tapes are required that increase the performance restrict the radar system and tedious and costly Authorization procedures require. Furthermore, classic radar sensors under transmission of radar radiation due to electrosmog not unproblematic.

Disclosure of the invention

According to the invention a passive detection system or surveillance system under Measurement of the temperature-dependent radio emission and / or Microwave radiation, in particular of millimeter or microwaves, sought. Advantageously, this millimeter waves be detected by an antenna or radiometrically, since such radiometric antennas with respect to microwave sensors with Lower costs can be produced in large quantities are.

The invention is based on the idea of a radiometric measurement of the temperature radiation tion in the radio wave range and / or microwave range, in particular in the millimeter wavelength range, by taking successive measured values or discrete reference values formed from measurements and considering the differential changes. In principle, the received wavelength range can only be in the microwave range or even only in the radio wave range, or extend over both wavelength ranges. In the following, the signal output from the antenna will always be referred to as a microwave signal in all cases.

According to the invention thus changes in the measured thermal noise power detected. The noise power depends on the temperature the considered material surfaces and the material properties from. A fast change of the measured noise power can thus according to the invention the appearance of new Objects within the detection range of the sensor or very fast temperature changes be assigned. By detecting changes in the Noise temperature are inventively no consuming Calibration procedure required in the reception branch.

The discrete reference values can in particular through integration over predetermined time intervals are formed. This is advantageously done after an analog-to-digital conversion. Thus, by temporal Integration of the measurement signal or one formed from the measurement signal Signal reference values formed and relevant changes over time examined. The result is a differential measurement, the respective Events can be assigned.

in this connection can the temporal change of successive reference values be compared with a predetermined threshold, and when exceeding the Threshold on a significant change as well as falling below of the threshold to a non-relevant change detected become.

There According to the invention, a passive method without a transmitted electromagnetic waves If no EMVU problem occurs.

According to the invention an antenna with a suitable antenna diagram selected become a spot measurement of a relevant coverage area to enable. Furthermore, according to the invention no Switch required in the reception branch for the calibration. Thus, the sensitivity of the invention Sensor device increases.

According to the invention this particular car alarm systems, building alarm systems or monitoring sensors or motion detectors formed become. Furthermore, protection sensors can be used to prevent accidents are created by A user or a body part of a user in a hazardous area, z. B. in front of the saw blade of a circular saw detected becomes. According to the invention, humans can also or body parts with clothing or protective clothing, eg. B. a thicker glove, by measuring the noise power of the radio waves be recorded.

Farther can according to the invention vehicle pedestrian protection measurements, an environmental sensor and a proximity sensor for Comfort adjustments are made possible on vehicles.

Brief description of the drawings

1 shows a block diagram of a radiometric sensor device according to the invention;

2 shows a flowchart of a method according to the invention.

Embodiment of invention

A radiometric sensor device 1 has an antenna or dipole antenna 2 for receiving radio waves and / or microwaves R and outputting a microwave signal S1, a radiometer 3 for receiving the microwave signal S1 and outputting a baseband signal B, a detection device 4 for receiving the baseband signal B and detection and a control device 8th for the output of control signals S2.

The radiometric sensor device 1 serves according to the embodiment shown the 1 for monitoring a detection area 5 in the vicinity of the sensor device 1 , z. B. on a building 6 ,

The antenna 2 is designed as an arbitrarily designed directional antenna, z. B. dipole or patch antenna, and takes incident radio waves R from the detection area 5 on. Optionally, apertures may be used to limit their detection angle 7 be used.

The antenna 2 is for receiving radio waves R or microwaves R, advantageously in the microwave to millimeter range with an arbitrarily selected bandwidth, z. 1 MHz to 10 GHz, out of the detection range 5 designed. The antenna 2 gives the microwave signal S1 as a noise signal to the radiometer 3 from that converts the microwave signal S1 in a conventional manner into a baseband signal B, which indicates the amplitude of the noise power of the microwave signal S1. The baseband signal B is sent to the detection means 4 output.

The radiometer 3 can optionally also generate an intermediate frequency signal (IF signal); However, this is basically not required according to the invention and depends on the available bandwidths.

The determination device 4 is in 1 with their elements 4.0 to 4.9 en taillierter explained. The determination device 4 Optionally has a modeling device 4.0 for generating the IF signal IF and a bandpass filter 4.1 receiving the signal ZF and outputting a band-pass filtered IF signal B1. Below is an RF amplifier 4.2 provided either by the dotted line directly from the radiometer 3 output baseband signal B or that of the bandpass filter 4.1 output band-pass filtered IF signal B1 and amplified, for. B. with 40-80 dB, and thus generates the signal B2: The signal B2 is on a device 4.3 which multiplies the signal B2 by itself and generates the rectified signal B3 as an equivalent DC signal; the device 4.3 can z. B. be a diode rectifier or frequency mixer. The signal B3 is in a subsequent device 4.4 low-pass filtered and as signal B4 an analog-to-digital converter 4.5 which supplies a digital signal B5 to a digital integrator 4.6 outputs, as a low-pass a temporal integration over a predetermined period of time or time difference .DELTA.t performs.

wobei Δt = t1 – t0.In the digital integrator 4.6 the voltage u _OBJ recorded as the digital signal B5 is integrated over the predetermined time difference Δt. This is based on the following consideration:
A temperature T _{OBJ of} the detection area 5 (or via the coverage area 5 averaged temperature) is proportional to the voltage U _OBJ , which results as a time averaged over .DELTA.t value of the signal B5 corresponding voltage u _OBJ , ie

where Δt = t1 - t0.

According to the invention directly from the integrator 4.6 output time Liche integral are used as uncalibrated temperature or temperature reference value Tb and in a first memory 4.7 be filed. When using the same time intervals .DELTA.t for the successive measurements in principle, the division with .DELTA.t can be omitted and can be compared directly the integrals.

This results in a sequence of discrete reference values Tb _i with i = 1, 2, 3,... A comparison device 4.8 determines a differential temperature of two consecutive values Tb _i , Tb _{i + 1} and compares this difference value with a reference value N × ΔTs, where ΔTs is the minimum temperature increase detectable by the system and can be determined experimentally or theoretically estimated. N gives this a safety factor in the range of z. B. 1.2 to 2.

In the comparison device 4.8 Thus, the comparison ΔTb _i = Tb _{i + 1} - Tb _i , <N · ΔTs is formed.

If the difference ΔTb _i , that of the temperature change in the detection range 5 is equal to or proportional to two consecutive measurements, less than the Reerenzwert N · .DELTA.Ts, so is in a second memory 4.9 as the determined temperature change ΔTi a 0 is stored; If the difference ΔTb _{i is} greater than or equal to N · ΔTs, then in the second memory 4.9 the measured differential temperature ΔTb _i stored.

Thus, in the second memory 4.9 successive difference values are stored, the measured differential temperatures in the detection area 5 correspond. The second memory 4.9 is from a controller 8th which subsequently performs a rating. Thus, due to the difference formation and the consideration according to the invention of not carrying out any calibration or normalization of these values, changes can be directly deduced from the sequence of the difference values ΔTb _i .

In this case, the determination device 4 with their elements 4.0 to 4.9 and the controller 8th be implemented in hardware, z. B. as a fixed wiring, or purely by software, so that the detection device 4 and the controller 8th can also be realized with a program.

According to the invention in the control device 8th Statements about the temperature changes are made, such. B. the emergence of a fire or the passage of a person 10 through the detection area 5 or the detection angle 7 (Solid angle). If the detection area 5 a safety area in a machine to be handled, z. B. represents a hazardous area in front of the saw blade of a circular saw, also a sufficiently rapid increase in the temperature can be detected as entering or going into the danger zone. Sufficiently fast temperature changes can thus be assigned to a respective event, whereupon the control device 8th a control signal S2 outputs, the z. B. a warning signal upon detection of a fire or entering the detection area 5 , or a switching signal z. B. can be for a circular saw.

By the inventive differential Measuring principle are drift effects of the circuit according to the invention as well as temporally slow changes in room temperature in the detection area, as they are z. B. when turning on and off of radiators or by changes in the temperature of the day, not recorded. However, rapid temperature changes or sufficiently large temperature differences within the defined integration time Δt can be detected.

in this connection Δt as well as the other values N and ΔTs adapted to the particular needs of the application.

In 1 are thus at the entrance of the person 10 in the coverage area 5 and at the exit of the person 10 out of the coverage area 5 each changes in the average temperature T of the detection range 5 be recognized when the values .DELTA.t, N and .DELTA.Ts are selected accordingly.

In order to be able to carry out integration times Δt = 50 to 200 ms as economically as possible, the integration according to the invention is advantageously implemented digitally. To the sampling frequency of the analog-to-digital converter 4.5 To keep low, is advantageously a low-pass NF 4.4 after the diode modulator 4.1 provided, the z. B. a suitable cutoff frequency, z. B. 1 KHz to 20 KHz, and thus higher-frequency noise components removed from the rectified baseband signal. This is based on the idea according to the invention that such higher frequencies are not relevant for the detection according to the invention and the subsequent digitization or analog-digital conversion with the low-pass filtering is simplified. The cutoff frequency TP can in this case in particular also in the acoustic range of z. B. 20 KHz.

In the method according to the invention is in accordance with the flowchart of 2 after a start in step St0, the microwave radiation R is subsequently recorded in step St1 and taken to the radiometer as the microwave signal S1 or the noise signal 3 In step St2, the base band is optionally transformed into an IF band or ZF signal ZF. In step St3, this IF signal is band-pass filtered and passed as signal B1. In step St4 to St8, the subsequent evaluation of the original bandpass signal B or of the modulated IF signal B1 takes place, the analogue signal being amplified in step St4, and then the analogue noise signal being converted into the equivalent direct voltage signal B3 in step St5. In step 6 when the DC signal B3 is low-pass filtered to the signal B4, in step St7, the analog-to-digital conversion of the analog signal B4 and output of B5 are performed, which is subsequently integrated in step St8, thereby producing the discrete reference values Tbi. In step St9, the comparison of the reference value determined by the temporal integration with the comparison value and the determination as to whether the difference is smaller than N × ΔTs or not, whereupon in step St10 corresponding statements about the averaged temperature change can be made and subsequently possibly the control signal S2 is output.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 2005/0053118 A1 [0009, 0010]

Claims (16)

Radiometric sensor device for non-contact temperature measurement in a detection area ( 5 ) comprising: an antenna ( 2 ) for receiving radio radiation and / or microwave radiation (R) and outputting a microwave signal (S1), means ( 3 . 4 . 8th ) for receiving and evaluating the microwave signal (S1) and outputting an output signal (S2), characterized in that the means ( 3 . 4 . 8th ) for recording and evaluating the microwave signal (S1) from the microwave signal (S1) determine successive discrete reference values (Tb _i ) and determine from temporal changes of the discrete reference values (Tb _i ) whether a relevant temperature change in the detection range ( 5 ) is done. Radiometric sensor device according to claim 1, characterized in that the means ( 3 . 4 . 8th ) for receiving and evaluating the microwave signal (S1): a radiometer device ( 3 ) for receiving the microwave signal (S1) and outputting an analog band signal (B), and a determination device ( 4 ) for receiving and processing the band signal (B) and for determining the successive discrete reference values (Tb _i ) from the band signal (B) or from signals (B1, B2, B3, B4, B5) determined from the band signal (B), and a control device ( 8th ) for evaluating the discrete reference values (Tb _i ) determined by the determining device and for outputting the output signal (S2). Radiometric sensor device according to claim 2, characterized in that the detection device ( 4 ) comprises: an integrator ( 4.6 ) for time-integrating or summing the band signal or a signal (B5) formed from the band signal (B) and outputting the successive discrete reference values (Tb _i ), and a comparison device ( 4.8 ) for comparing successive reference values (Tb _i ). Radiometric sensor device according to claim 3, characterized in that the comparison device ( 4.8 ) compares the change or difference of successive reference values (Tb _i ) with a threshold value (N · ΔTs). Radiometric sensor device according to claim 4, characterized in that in the case that the determined difference value (ΔTb _i ,) of two successive discrete reference values (Tb _i , Tb _{i + 1} ) is smaller than the threshold value (N · ΔTs), to a constant temperature is detected, and in the case that the detected difference value exceeds the threshold value (N · ΔTs), a relevant temperature change is detected. Radiometric sensor device according to claim 5, characterized in that the last discrete reference value (Tb _i ) in each case in a first memory ( 4.7 ) and stored by the comparator ( 4.8 ) and, when a relevant temperature change is detected, the differential temperature (ΔTb _i ) in a second memory ( 4.9 ) is stored. Radiometric sensor device according to one of claims 3 to 6, characterized in that in the detection device ( 4 ) an analog-to-digital converter ( 4.5 ) is provided for converting the band signal (B) or an analog signal (B4) generated from the band signal (B), and that of the analog-to-digital converter ( 4.5 ) output digital signal (B5) to the integrator ( 4.6 ) is output. Radiometric sensor device according to claim 7, characterized in that the detection device ( 4 ) an analog low-pass filter ( 4.4 ) for removing noise, which sends a signal (B4) to the integrator ( 4.6 ). Radiometric sensor device according to one of the preceding claims, characterized in that the control device ( 4 ) on detection of a rapid change in temperature as the output signal (S2) outputs a control signal (S2). Radiometric sensor device according to claim 9, characterized in that the control signal (S2) is a warning signal or shutdown signal is. Radiometric sensor device according to one of the preceding claims, characterized in that the antenna ( 2 ) is a directional antenna and / or aperture devices to limit their detection angle ( 7 ) for the microwave radiation (R). Radiometric sensor device according to one of the preceding claims, characterized in that the antenna ( 2 ) is designed for receiving microwave radiation (R) in the millimeter wavelength range. Method for radiometric, non-contact temperature monitoring of a detection area ( 5 ), comprising at least the following steps: recording of radio radiation and / or microwave radiation (R) from the detection area ( 5 ) and output of an analog microwave signal (S1) (St1), determining successive discrete references values (Tb _i ) from the microwave signal (S1) or a signal (B, B1, B2, B3, B4, B5) generated from the microwave signal (St7), determining changes over time of the discrete reference values (Tb _i ), determining from the temporal Changes in the discrete reference values (Tb _i ), whether a relevant temperature change in the detection area ( 5 ), and outputting an output signal (S2) as a function of the determined time changes. Method according to claim 13, characterized by the further step: generating a band signal (B) from the microwave signal (S1) (St2), wherein further signals (B1, B2, B3, B4, B5) the temporal changes of the discrete reference values (Tb _i ) are determined. A method according to claim 14, characterized in that the successive discrete reference values (Tb _i ) are formed by time-integrating or summing the band signal (B) or a signal (B5) formed from the band signal (B), and changes or differences successive reference values (Tb _i ) are compared with a threshold value (N · ΔTs). A method according to claim 15, characterized in that in the case that the determined difference value (ΔTb _i ,) of two consecutive discrete reference values (Tb _i , Tb _{i + 1} ) is smaller than the threshold value (N · ΔTs) to a constant Temperature is detected, and in the event that the determined difference value exceeds the threshold value (N · ΔTs), a relevant temperature change is detected.