EP0479009B1 - Temperature sensor - Google Patents
Temperature sensor Download PDFInfo
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- EP0479009B1 EP0479009B1 EP91115573A EP91115573A EP0479009B1 EP 0479009 B1 EP0479009 B1 EP 0479009B1 EP 91115573 A EP91115573 A EP 91115573A EP 91115573 A EP91115573 A EP 91115573A EP 0479009 B1 EP0479009 B1 EP 0479009B1
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- temperature
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- 230000001419 dependent effect Effects 0.000 claims abstract description 15
- 239000003990 capacitor Substances 0.000 claims description 11
- 238000011156 evaluation Methods 0.000 claims description 11
- 229910004670 OPV1 Inorganic materials 0.000 claims description 7
- 238000005259 measurement Methods 0.000 claims description 3
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- 230000004044 response Effects 0.000 abstract description 3
- 238000001514 detection method Methods 0.000 description 8
- 230000003321 amplification Effects 0.000 description 6
- 238000003199 nucleic acid amplification method Methods 0.000 description 6
- 230000005855 radiation Effects 0.000 description 6
- 238000001228 spectrum Methods 0.000 description 4
- 229910004667 OPV2 Inorganic materials 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 230000036561 sun exposure Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B17/00—Fire alarms; Alarms responsive to explosion
- G08B17/12—Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
Definitions
- the invention relates to a heat sensor with a resistor arrangement containing at least one temperature-dependent resistor and connected to a voltage supply, and with a first amplifier circuit which is connected on the input side to the resistor arrangement and on the output side to a first measuring and evaluation circuit.
- DE-A1-28 52 971 describes a fire detector in the form of an optoelectric flame detector which is followed by a feedback amplifier which has a P behavior.
- a D-element with a downstream evaluation circuit is connected downstream of the amplifier.
- This known arrangement enables both the detection of flames and sparks.
- the circuit-related features that are made are particularly suitable for an optoelectric flame detector, and are not suitable for a heat sensor that has to detect a rise in temperature or a change in temperature in general, because the heat sensor shows a different behavior.
- a fire detection system in which a heat sensor is arranged in a turbulent gas flow (e.g. tunnel) in order to separate the so-called AC signal component from the so-called DC signal component of the heat sensor with a downstream circuit arrangement and because of a rapid Temperature rise to detect a fire.
- the known circuit arrangement has an operational amplifier, the output signal of which is fed to a high-pass filter, so that only the AC component of the signal can pass through. This is led to another operational amplifier.
- the so-called AC component of the heat sensor signal varies with a frequency between one and a few hundred Hertz.
- the further amplifier amplifies this frequency-dependent signal, the degree of amplification being adjustable with appropriately arranged components. An automatic, frequency-dependent setting of the gain is not described there.
- DE-A1-1 960 218 describes a thermal radiation detector for automatic fire detection or flame monitoring, which has at least one thermal radiation receiver (e.g. photocell).
- the electrical AC voltage signal of the temperature radiation receiver which corresponds to the flickering of the flame, is amplified in an electrical filter, for example in an active bandpass amplifier with a double-T network in the feedback branch, and then further processed, for example rectified and smoothed. This output signal is fed to an electronic comparator.
- the received signal of the detector can be sent in parallel through two bandpass filters with different amplification and band center frequency and then rectified, smoothed or low-pass filtered and one electronic comparator can be supplied.
- This comparator only emits a defined signal if the difference or the ratio of the output voltages from the two low-pass filters corresponds to the evaluated power density spectrum of flames or fires.
- the DC component of the received signal can also be amplified in one of the two filters.
- a fire detector for example an optoelectric temperature radiation detector
- two filters in the form of a respective bandpass amplifier, wherein different amplification levels and band center frequencies can be provided in order to compensate for the drop in the power density spectra of the irradiance over the frequency.
- the degrees of amplification and the band center frequencies are designed such that a comparator arranged downstream of the rectifier and low-pass filter circuits only emits a signal if the difference or quotient of the rectified and smoothed output voltages of the filters, taking into account the amplifications of the band-pass filters, corresponds to the course of the Power density spectrum corresponds to the temperature radiation imitated by flames, whereby the band center frequencies can be selected between 1 and 20 Hertz.
- This circuit arrangement is typically designed for an optoelectric temperature radiation detector and is not readily transferable for a heat sensor as a fire detector.
- the object of the invention is to provide a circuit arrangement for a heat sensor with a temperature-dependent resistor for rapid detection of the room temperature without sacrificing known and proven properties and without significantly increasing the effort compared to conventional heat detectors, which circuit arrangement makes it possible to partially reduce the frequency response of the temperature-dependent resistor compensate.
- a second amplifier is also connected on the input side, but via a high-pass circuit to the resistor arrangement.
- a second measuring and evaluation interface is connected on the output side.
- a coupling capacitor is arranged in the second amplifier circuit, so that an increase in the gain is achieved with increasing frequency.
- the resistor arrangement is designed as a voltage divider, a resistor being connected in series with the temperature-dependent resistor and the first amplifier circuit having its first input at the connection point of this resistor with the temperature-dependent resistor and with its second input at the connection point of the temperature-dependent resistor is connected to the negative pole of the power supply.
- the temperature-dependent resistor is expediently formed by a thermistor.
- the first and the second amplifier circuit are each formed with a negative feedback operational amplifier, these being preferably designed as non-inverting amplifiers.
- the output of the operational amplifier is connected to its inverting input via a resistor and the inverting input is connected to the negative pole of the voltage supply via a capacitor connected in parallel with a capacitor.
- the high-pass circuit is preferably formed with a capacitor connecting the center tap of the voltage divider with the first input of the second amplifier circuit and a resistor connecting the first input of the second amplifier circuit with the negative pole of the supply voltage.
- a voltage divider formed from a resistor R1 and a thermistor HL is connected to the terminals + Ub and -Ub of a voltage supply.
- the power supply is located in a control center, not shown, to which the heat sensor is connected via a primary signal line, also not shown.
- the first input E11 is connected to the connection point of the thermistor HL with the resistor R1 and the second input E12 of an amplifier circuit V1 is connected to the connection point of the thermistor HL with the terminal -Ub of the voltage supply.
- the amplifier circuit V1 consists of an operational amplifier OPV1, the inverting input E1- of which is connected on the one hand via a resistor R3 to its output Av1 and on the other hand forms the second input E12 of the amplifier circuit V1 via a resistor R2.
- the non-inverting input E1 + of the operational amplifier OPV1 forms the first input E11 of the amplifier circuit V1.
- the OPV1 operational amplifier is also connected to the two terminals + Ub and -Ub of the power supply.
- the output Av1 of the operational amplifier OPV1 simultaneously forms the output of the amplifier circuit V1 and is connected to the input of a first measuring and evaluation circuit M1 + A1.
- the output of this measuring and evaluation circuit M1 + A1 is connected to a terminal MA1.
- the first input E21 of an amplifier circuit V2 is also connected to the connection point of the thermistor HL with the resistor R1 via a capacitor C1.
- This first input E21 is also connected via a resistor R4 to the connection point of the thermistor HL to the terminal -Ub, to which the second input E22 of the amplifier circuit V2 is also connected.
- the amplifier circuit V2 is constructed similarly to the amplifier circuit V1, the operational amplifier OPV2 corresponding to the operational amplifier OPV1, the resistor R6 to the resistor R3 and the parallel connection of a resistor R5 with a capacitor C2 to the resistor R2.
- the output Av2 of the operational amplifier OPV2 is connected to the input of a second measuring and evaluation circuit M2 + A2, the output of which is connected to a terminal MA2. It is here too possible to connect the output to terminals + Ub and -Ub via a transmission device, not shown.
- the voltage drop across the thermistor HL is temperature-dependent, the amplitude of this voltage decreasing with increasing frequency.
- the amplification of the amplifier circuit V1 is set via the resistors R2 and R3 in such a way that very slow changes in the voltage can be recognized and processed by the first measuring and evaluation circuit M1 + A1, the signals with frequencies between 5 Hz and However, 20 Hz are not sufficiently amplified to be able to be evaluated. Therefore, the second amplifier circuit V2 is provided, which is preceded by a high-pass circuit consisting of the capacitor C1 and the resistor R4.
- This high-pass circuit sifts out the slow signal components, so that the gain of V2 can be adjusted via the resistors R5 and R6 so that the second measuring and evaluation circuit M2 + A2 e.g. the intensity of the signal components in the desired frequency range between 5 Hz and 20 Hz is recorded and evaluated.
- the measurement values can be evaluated in M1 + A1 as well as in M2 + A2 by one or more threshold switches, or an analog value proportional to the measured amplitude can also be generated and transmitted to the control center.
- the capacitor C2 provided in the amplifier circuit V2 ensures an increase in the gain with increasing frequency, so that the frequency response of the thermistor HL is partially compensated for by the amplifier circuit V2.
- measured value so often that the desired rate of fluctuation can be detected, e.g. 40 times per second and to transfer the measured values thus obtained to the control center for further processing.
- measured values can be both individually, i.e. in the example, one every fortieth of a second, and also combined to form longer telegrams, e.g. 10 measured values are transmitted every quarter of a second.
Abstract
Description
Die Erfindung betrifft einen Wärmesensor mit einer mindestens einen temperaturabhängigen Widerstand enthaltenden, an eine Spannungsversorgung angeschlossenen Widerstandsanordnung, und mit einer ersten Verstärkerschaltung, die eingangsseitig mit der Widerstandsanordnung und ausgangsseitig mit einer ersten Meß- und Auswerteschaltung verbunden ist.The invention relates to a heat sensor with a resistor arrangement containing at least one temperature-dependent resistor and connected to a voltage supply, and with a first amplifier circuit which is connected on the input side to the resistor arrangement and on the output side to a first measuring and evaluation circuit.
Für die automatische Brandentdeckung ist die durch ein Feuer entstehende Wärme ein naheliegendes Kriterium. Jedoch führen auch viele andere Wärmequellen als ein Schadenfeuer zu Temperaturerhöhungen, wie z.B. Sonneneinstrahlung, Heizungen, diverse Arbeitsprozesse und vieles andere mehr, so daß es nicht möglich ist, allein aufgrund einer kleinen Temperaturerhöhung auf ein Schadenfeuer zu schließen und die Feuerwehr zu alarmieren. Dies gilt besonders, wenn man bereits sehr kleine Feuer entdecken, bzw. ein Schadenfeuer bereits im Frühstadium detektieren will. Zu diesem Zweck ist es hilfreich, die Temperaturänderungen detaillierter zu betrachten und zu bewerten, wobei es sich als besonders nützlich herausgestellt hat, rasche und kleine Temperaturschwankungen zu erkennen. Dem steht entgegen, daß rasche Änderungen der Raumtemperatur nur mit sehr aufwendigen Meßeinrichtungen, nicht aber mit den in der Brandschutztechnik gebräuchlichen "Wärmemeldern" ermittelt werden können.The heat generated by a fire is an obvious criterion for automatic fire detection. However, many heat sources other than damage fire also lead to temperature increases, e.g. Sun exposure, heating, various work processes and much more, so that it is not possible to conclude that a fire is due to a small temperature increase and to alert the fire department. This is especially true if you already discover very small fires, or if you want to detect a damage fire at an early stage. For this purpose, it is helpful to examine and evaluate the temperature changes in more detail, and it has proven particularly useful to detect rapid and small temperature fluctuations. This is opposed to the fact that rapid changes in the room temperature can only be determined with very complex measuring devices, but not with the "heat detectors" used in fire protection technology.
Es ist üblich, eine automatische Feuermeldung mittels sogenannter "Wärme-Maximalmelder" erst dann auszulösen, wenn die Raumtemperatur wesentlich über der unter normalen Umständen erreichbaren Raumtemperatur von z.B. 40°C liegt. Es ist weiterhin bekannt, mittels sogenannter "Wärme-Differentialmelder" lineare Temperaturanstiege von z.B. mehr als 10 K/min zur Alarmgabe zu nutzen. Beide Melder reagieren daher erst bei relativ großen Bränden. Zur Früherkennung von Bränden müssen daher andere Brandentdeckungsverfahren, z.B. mittels Rauchmeldern, herangezogen werden.It is customary to only trigger an automatic fire alarm by means of so-called "maximum heat detectors" when the room temperature is significantly higher than the room temperature of, for example, 40 ° C. which can be achieved under normal circumstances. It is also known to use linear temperature increases of, for example, more than 10 K / min for so-called “heat differential detectors”. Both detectors therefore only react to relatively large fires. Other fire detection methods, for example using smoke detectors, must therefore be used for the early detection of fires.
In der DE-A1-28 52 971 ist ein Feuermelder in Form eines optoelektrischen Flammendetektors beschrieben, dem ein rückgekoppelter Verstärker nachgeschaltet ist, der ein P-Verhalten aufweist. Dem Verstärker ist ein D-Glied mit nachgeordneter Auswerteschaltung nachgeschaltet. Diese bekannte Anordnung ermöglicht sowohl die Erfassung von Flammen als auch von Funken. Die dabei getroffenen schaltungstechnischen Merkmale sind insbesondere für einen optoelektrischen Flammendetektor ausgelegt, für einen Wärmesensor, der einen Temperaturanstieg oder ganz allgemein eine Temperaturänderung zu detektieren hat, nicht geeignet, weil der Wärmesensor eine andere Verhaltensweise zeigt.DE-A1-28 52 971 describes a fire detector in the form of an optoelectric flame detector which is followed by a feedback amplifier which has a P behavior. A D-element with a downstream evaluation circuit is connected downstream of the amplifier. This known arrangement enables both the detection of flames and sparks. The circuit-related features that are made are particularly suitable for an optoelectric flame detector, and are not suitable for a heat sensor that has to detect a rise in temperature or a change in temperature in general, because the heat sensor shows a different behavior.
Aus der GB-A-2 001 764 ist ein Feuerdetektionssystem bekannt, bei dem ein Wärmesensor in einem turbulenten Gasstrom (z.B. Tunnel) angeordnet ist, um mit einer nachgeordneten Schaltungsanordnung den sog. Wechselstromsignalanteil vom sog. Gleichstromsignalanteil des Wärmesensors zu trennen und aufgrund eines raschen Temperaturanstiegs ein Feuer zu detektieren. Die bekannte Schaltungsanordnung weist einen Operationsverstärker auf, dessen Ausgangssignal einem Hochpaßfilter zugeführt ist, so daß nur die Wechselstromkomponente des Signals passieren kann. Dieses ist auf einen weiteren Operationsverstärker geführt. Die sog. Wechselstromkomponente des Wärmesensor-Signals variiert mit einer Frequenz zwischen einem und einigen Hundert Hertz. Der weitere Verstärker verstärkt dieses frequenzabhängige Signal, wobei der Verstärkungsgrad mit entsprechend angeordneten Bauelementen einstellbar ist. Eine selbsttätige, von der Frequenz abhängige Einstellung des Verstärkungsgrads ist dort nicht beschrieben.From GB-A-2 001 764 a fire detection system is known, in which a heat sensor is arranged in a turbulent gas flow (e.g. tunnel) in order to separate the so-called AC signal component from the so-called DC signal component of the heat sensor with a downstream circuit arrangement and because of a rapid Temperature rise to detect a fire. The known circuit arrangement has an operational amplifier, the output signal of which is fed to a high-pass filter, so that only the AC component of the signal can pass through. This is led to another operational amplifier. The so-called AC component of the heat sensor signal varies with a frequency between one and a few hundred Hertz. The further amplifier amplifies this frequency-dependent signal, the degree of amplification being adjustable with appropriately arranged components. An automatic, frequency-dependent setting of the gain is not described there.
In der DE-A1-1 960 218 ist ein Temperaturstrahlungsdetektor zur automatischen Brandentdeckung oder Flammenüberwachung beschrieben, der zumindest einen Temperaturstrahlungsempfänger (z.B. Fotozelle) aufweist. Dabei wird das elektrische Wechselspannungssignal des Temperaturstrahlungsempfängers, das dem Flackern der Flamme entspricht, in einem elektrischen Filter, z.B. in einem aktiven Bandpaßverstärker mit einem Doppel-T-Netzwerk im Rückkopplungszweig, verstärkt und anschließend weiterverarbeitet, beispielsweise gleichgerichtet und geglättet. Dieses Ausgangssignal wird einem elektronischen Komparator zugeführt. Um den Abfall der Leistungsdichtespektren über der Frequenz zur Erhöhung der Entdeckungswahrscheinlichkeit eines Brandes bei gleichzeitiger Verbesserung des Abstands gegenüber Störgrößen auszunutzen, kann das empfangene Signal des Detektors parallel durch zwei Bandpaßfilter mit unterschiedlicher Verstärkung und Bandmittenfrequenz geschickt und anschließend gleichgerichtet, geglättet bzw. tiefpaßgefiltert werden und einem elektronischen Komparator zugeführt werden. Dieser Komparator gibt nur dann ein definiertes Signal ab, wenn die Differenz oder das Verhältnis der Ausgangsspannungen von den beiden Tiefpaßfiltern dem bewerteten Leistungsdichtespektrum von Flammen oder Bränden entspricht. Dabei kann in einem der beiden Filter auch der Gleichanteil des empfangenen Signals verstärkt werden. Aus diesem bekannten Stand der Technik ist zu entnehmen, einem Branddetektor, z.B. einem optoelektrischen Temperaturstrahlungsdetektor, parallel zwei Filter in Form eines jeweiligen Bandpaßverstärkers nachzuschalten, wobei unterschiedliche Verstärkungsgrade und Bandmittenfrequenzen vorgesehen sein können, um den Abfall der Leistungsdichtespektren der Bestrahlungsstärke über der Frequenz auszugleichen. Dazu werden die Verstärkungsgrade und die Bandmittenfrequenzen so ausgelegt, daß ein den Gleichrichter- und Tiefpaßfilter-Schaltungen nachgeordneter Komparator nur dann ein Signal abgibt, wenn die Differenz oder Quotient der gleichgerichteten und geglätteten Ausgangsspannungen der Filter unter Berücksichtigung der Verstärkungen der Bandpaßfilter dem Verlauf des Leistungsdichtespektrums der von Flammen imitierten Temperaturstrahlung entspricht, wobei die Bandmittenfrequenzen zwischen 1 und 20 Hertz gewählt werden können.
Diese Schaltungsanordnung ist typischerweise für einen optoelektrischen Temperaturstrahlungsdetektor ausgelegt und für einen Wärmesensor als Branddetektor nicht ohne weiteres übertragbar.DE-A1-1 960 218 describes a thermal radiation detector for automatic fire detection or flame monitoring, which has at least one thermal radiation receiver (e.g. photocell). The electrical AC voltage signal of the temperature radiation receiver, which corresponds to the flickering of the flame, is amplified in an electrical filter, for example in an active bandpass amplifier with a double-T network in the feedback branch, and then further processed, for example rectified and smoothed. This output signal is fed to an electronic comparator. In order to take advantage of the drop in the power density spectra above the frequency to increase the probability of detection of a fire while at the same time improving the distance to disturbance variables, the received signal of the detector can be sent in parallel through two bandpass filters with different amplification and band center frequency and then rectified, smoothed or low-pass filtered and one electronic comparator can be supplied. This comparator only emits a defined signal if the difference or the ratio of the output voltages from the two low-pass filters corresponds to the evaluated power density spectrum of flames or fires. The DC component of the received signal can also be amplified in one of the two filters. From this known prior art it can be seen that a fire detector, for example an optoelectric temperature radiation detector, is connected in parallel to two filters in the form of a respective bandpass amplifier, wherein different amplification levels and band center frequencies can be provided in order to compensate for the drop in the power density spectra of the irradiance over the frequency. For this purpose, the degrees of amplification and the band center frequencies are designed such that a comparator arranged downstream of the rectifier and low-pass filter circuits only emits a signal if the difference or quotient of the rectified and smoothed output voltages of the filters, taking into account the amplifications of the band-pass filters, corresponds to the course of the Power density spectrum corresponds to the temperature radiation imitated by flames, whereby the band center frequencies can be selected between 1 and 20 Hertz.
This circuit arrangement is typically designed for an optoelectric temperature radiation detector and is not readily transferable for a heat sensor as a fire detector.
Aufgabe der Erfindung ist es, eine Schaltungsanordnung für einen Wärmesensor mit einem temperaturabhängigen Widerstand zur raschen Erfassung der Raumtemperatur ohne Verzicht auf bekannte und bewährte Eigenschaften und ohne wesentliche Erhöhung des Aufwandes gegenüber gebräuchlicher Wärmemelder anzugeben, welche Schaltungsanordnung es ermöglicht, den Frequenzgang des temperaturabhängigen Widerstandes teilweise zu kompensieren.The object of the invention is to provide a circuit arrangement for a heat sensor with a temperature-dependent resistor for rapid detection of the room temperature without sacrificing known and proven properties and without significantly increasing the effort compared to conventional heat detectors, which circuit arrangement makes it possible to partially reduce the frequency response of the temperature-dependent resistor compensate.
Diese Aufgabe wird erfindungsgemäß mit den Merkmalen des Anspruchs 1 gelöst.
Erfindungsgemäß ist noch ein zweiter Verstärker eingangsseitig direkt, jedoch über eine Hochpaßschaltung mit der Widerstandsanordnung verbunden. Ausgangsseitig ist eine zweite Meß- und Auswerteanschaltung angeschlossen. Dabei ist in der zweiten Verstärkerschaltung ein Kopplungskondensator angeordnet, so daß eine Zunahme der Verstärkung mit zunehmender Frequenz erreicht wird.This object is achieved with the features of
According to the invention, a second amplifier is also connected on the input side, but via a high-pass circuit to the resistor arrangement. A second measuring and evaluation interface is connected on the output side. A coupling capacitor is arranged in the second amplifier circuit, so that an increase in the gain is achieved with increasing frequency.
In einer möglichen Ausführungsform des Erfindungsgegenstandes ist die Widestandsanordnung als Spannungsteiler ausgebildet, wobei ein Widerstand in Serie zum temperaturabhängigen Widerstand geschaltet ist und die erste Verstärkerschaltung mit ihrem ersten Eingang am Verbindungspunkt dieses Widerstands mit dem temperaturabhängigen Widerstand und mit ihrem zweiten Eingang am Verbindungspunkt des temperaturabhängigen Widerstands mit dem Minuspol der Spannungsversorgung angeschlossen ist. Zweckmäßigerweise ist der temperaturabhängige Widerstand von einem Heißleiter gebildet.In one possible embodiment of the subject matter of the invention, the resistor arrangement is designed as a voltage divider, a resistor being connected in series with the temperature-dependent resistor and the first amplifier circuit having its first input at the connection point of this resistor with the temperature-dependent resistor and with its second input at the connection point of the temperature-dependent resistor is connected to the negative pole of the power supply. The temperature-dependent resistor is expediently formed by a thermistor.
In weiterer Ausgestaltung der Erfindung sind die erste und die zweite Verstärkerschaltung jeweils mit einem gegengekoppelten Operationsverstärker gebildet, wobei diese vorzugsweise als nicht-invertierende Verstärker ausgebildet sind.In a further embodiment of the invention, the first and the second amplifier circuit are each formed with a negative feedback operational amplifier, these being preferably designed as non-inverting amplifiers.
In einer weiteren Ausführungsform ist in der zweiten Verstärkerschaltung der Ausgang des Operationsverstärkers über einen Widerstand mit seinem invertierenden Eingang und der invertierende Eingang über die Parallelschaltung eines Widerstands mit einem Kondensator mit dem Minuspol der Spannungsversorgung verbunden.In a further embodiment, in the second amplifier circuit, the output of the operational amplifier is connected to its inverting input via a resistor and the inverting input is connected to the negative pole of the voltage supply via a capacitor connected in parallel with a capacitor.
Die Hochpaßschaltung ist vorzugsweise mit einem den Mittelabgriff des Spannungsteilers mit dem ersten Eingang der zweiten Verstärkerschaltung verbindenden Kondensator und einem den ersten Eingang der zweiten Verstärkerschaltung mit dem Minuspol der Versorgungsspannung verbindenden Widerstand gebildet.The high-pass circuit is preferably formed with a capacitor connecting the center tap of the voltage divider with the first input of the second amplifier circuit and a resistor connecting the first input of the second amplifier circuit with the negative pole of the supply voltage.
Die Erfindung soll anhand eines Ausführungsbeispiels mit Hilfe der einzigen Figur näher beschrieben werden.
Bei dem in der Figur dargestellten Wärmesensor ist ein aus einem Widerstand R1 und einem Heißleiter HL gebildeter Spannungsteiler mit den Klemmen +Ub und -Ub einer Spannungsversorgung verbunden. Die Spannungsversorgung befindet sich dabei in einer nicht dargestellten Zentrale, mit der der Wärmesensor über eine ebenfalls nicht dargestellte Meldeprimärleitung verbunden ist.The invention will be described in more detail using an exemplary embodiment with the help of the single figure.
In the heat sensor shown in the figure, a voltage divider formed from a resistor R1 and a thermistor HL is connected to the terminals + Ub and -Ub of a voltage supply. The power supply is located in a control center, not shown, to which the heat sensor is connected via a primary signal line, also not shown.
An den Verbindungspunkt des Heißleiters HL mit dem Widerstand R1 ist der erste Eingang E11 und an den Verbindungspunkt des Heißleiters HL mit der Klemme -Ub der Spannungsversorgung ist der zweite Eingang E12 einer Verstärkerschaltung V1 angeschlossen.The first input E11 is connected to the connection point of the thermistor HL with the resistor R1 and the second input E12 of an amplifier circuit V1 is connected to the connection point of the thermistor HL with the terminal -Ub of the voltage supply.
Die Verstärkerschaltung V1 besteht dabei aus einem Operationsverstärker OPV1, dessen invertierender Eingang E1- einerseits über einen Widerstand R3 mit seinem Ausgang Av1 verbunden ist und andererseits über einen Widerstand R2 den zweiten Eingang E12 der Verstärkerschaltung V1 bildet. Der nicht-invertierende Eingang E1+ des Operationsverstärkers OPV1 bildet den ersten Eingang E11 der Verstärkerschaltung V1. Der Operationsverstärker OPV1 ist außerdem an die beiden Klemmen +Ub und -Ub der Spannungsversorgung angeschlossen. Der Ausgang Av1 des Operationsverstärkers OPV1 bildet gleichzeitig den Ausgang der Verstärkerschaltung V1 und ist mit dem Eingang einer ersten Meß- und Auswerteschaltung M1+A1 verbunden. Der Ausgang dieser Meß- und Auswerteschaltung M1+A1 ist mit einer Klemme MA1 verbunden. Es ist allerdings auch möglich, den Ausgang der Meß- und Auswerteschaltung M1+A1 mittels einer nicht dargestellten Übertragungseinrichtung an die Klemmen +Ub und -Ub anzuschließen.The amplifier circuit V1 consists of an operational amplifier OPV1, the inverting input E1- of which is connected on the one hand via a resistor R3 to its output Av1 and on the other hand forms the second input E12 of the amplifier circuit V1 via a resistor R2. The non-inverting input E1 + of the operational amplifier OPV1 forms the first input E11 of the amplifier circuit V1. The OPV1 operational amplifier is also connected to the two terminals + Ub and -Ub of the power supply. The output Av1 of the operational amplifier OPV1 simultaneously forms the output of the amplifier circuit V1 and is connected to the input of a first measuring and evaluation circuit M1 + A1. The output of this measuring and evaluation circuit M1 + A1 is connected to a terminal MA1. However, it is also possible to connect the output of the measuring and evaluation circuit M1 + A1 to the terminals + Ub and -Ub by means of a transmission device, not shown.
An den Verbindungspunkt des Heißleiters HL mit dem Widerstand R1 ist auch der erste Eingang E21 einer Verstärkerschaltung V2 über einen Kondensator C1 angeschlossen. Dieser erste Eingang E21 ist außerdem über einen Widerstand R4 mit dem Verbindungspunkt des Heißleiters HL mit der Klemme -Ub verbunden, an der auch der zweite Eingang E22 der Verstärkerschaltung V2 angeschlossen ist. Die Verstärkerschaltung V2 ist ähnlich aufgebaut wie die Verstärkerschaltung V1, wobei der Operationsverstärker OPV2 dem Operationsverstärker OPV1, der Widerstand R6 dem Widerstand R3 und die Parallelschaltung eines Widerstands R5 mit einem Kondensator C2 dem Widerstand R2 entspricht. Der Ausgang Av2 des Operationsverstärkers OPV2 ist mit dem Eingang einer zweiten Meß- und Auswerteschaltung M2+A2 verbunden, deren Ausgang an eine Klemme MA2 angeschlossen ist. Auch hier ist es möglich, den Ausgang über eine nicht dargestellte Übertragungseinrichtung an die Klemmen +Ub und -Ub anzuschließen.The first input E21 of an amplifier circuit V2 is also connected to the connection point of the thermistor HL with the resistor R1 via a capacitor C1. This first input E21 is also connected via a resistor R4 to the connection point of the thermistor HL to the terminal -Ub, to which the second input E22 of the amplifier circuit V2 is also connected. The amplifier circuit V2 is constructed similarly to the amplifier circuit V1, the operational amplifier OPV2 corresponding to the operational amplifier OPV1, the resistor R6 to the resistor R3 and the parallel connection of a resistor R5 with a capacitor C2 to the resistor R2. The output Av2 of the operational amplifier OPV2 is connected to the input of a second measuring and evaluation circuit M2 + A2, the output of which is connected to a terminal MA2. It is here too possible to connect the output to terminals + Ub and -Ub via a transmission device, not shown.
Die am Heißleiter HL abfallende Spannung ist temperaturabhängig, wobei die Amplitude dieser Spannung mit zunehmender Frequenz abnimmt. Die Verstärkung der Verstärkerschaltung V1 ist über die Widerstände R2 und R3 so eingestellt, daß sehr langsame Änderungen der Spannung von der ersten Meß- und Auswerteschaltung M1+A1 erkannt und verarbeitet werden können, die für einen entstehenden Brand charakteristischen Signale mit Frequenzen zwischen 5 Hz und 20 Hz jedoch nicht genügend verstärkt sind, um ausgewertet werden zu können. Deshalb ist die zweite Verstärkerschaltung V2 vorgesehen, der eine aus dem Kondensator C1 und dem Widerstand R4 bestehende Hochpaßschaltung vorgeschaltet ist. Diese Hochpaßschaltung siebt die langsamen Signalanteile aus, so daß die Verstärkung von V2 über die widerstände R5 und R6 so eingestellt werden kann, daß die zweite Meß- und Auswerteschaltung M2+A2 z.B. die Intensität der Signalanteile im gewünschten Frequenzbereich zwischen 5 Hz und 20 Hz erfaßt und auswertet. Die Auswertung der Meßwerte kann dabei sowohl in M1+A1 als auch in M2+A2 durch einen oder auch mehrere Schwellwertschalter erfolgen oder es kann aber auch ein der gemessenen Amplitude proportionaler Analogwert erzeugt und der Zentrale übermittelt werden. Der in der Verstärkerschaltung V2 vorgesehene Kondensator C2 sorgt für eine Zunahme der Verstärkung mit zunehmender Frequenz, so daß der Frequenzgang des Heißleiters HL durch die Verstärkerschaltung V2 teilweise kompensiert wird.The voltage drop across the thermistor HL is temperature-dependent, the amplitude of this voltage decreasing with increasing frequency. The amplification of the amplifier circuit V1 is set via the resistors R2 and R3 in such a way that very slow changes in the voltage can be recognized and processed by the first measuring and evaluation circuit M1 + A1, the signals with frequencies between 5 Hz and However, 20 Hz are not sufficiently amplified to be able to be evaluated. Therefore, the second amplifier circuit V2 is provided, which is preceded by a high-pass circuit consisting of the capacitor C1 and the resistor R4. This high-pass circuit sifts out the slow signal components, so that the gain of V2 can be adjusted via the resistors R5 and R6 so that the second measuring and evaluation circuit M2 + A2 e.g. the intensity of the signal components in the desired frequency range between 5 Hz and 20 Hz is recorded and evaluated. The measurement values can be evaluated in M1 + A1 as well as in M2 + A2 by one or more threshold switches, or an analog value proportional to the measured amplitude can also be generated and transmitted to the control center. The capacitor C2 provided in the amplifier circuit V2 ensures an increase in the gain with increasing frequency, so that the frequency response of the thermistor HL is partially compensated for by the amplifier circuit V2.
Besonders einfach und zweckmäßig ist es, den Meßwert so häufig abzufragen, daß die gewünschte Schwankungsgeschwindigkeit erfaßt werden kann, z.B. 40 mal pro Sekunde und die so gewonnenen Meßwerte zur weiteren Bearbeitung in die Zentrale zu übertragen. Dabei können diese Meßwerte sowohl einzeln, d.h. im Beispiel, je einer jede vierzigstel Sekunde, als auch zu längeren Telegrammen zusammengefaßt, also z.B. je 10 Meßwerte jede Viertel Sekunde, übertragen werden.It is particularly simple and expedient to query the measured value so often that the desired rate of fluctuation can be detected, e.g. 40 times per second and to transfer the measured values thus obtained to the control center for further processing. These measured values can be both individually, i.e. in the example, one every fortieth of a second, and also combined to form longer telegrams, e.g. 10 measured values are transmitted every quarter of a second.
Claims (6)
- Heat sensor having a resistor arrangement (R1,HL) which contains at least one temperature-dependent resistor (HL) and is connected to a voltage supply (+Ub-Ub), and having a first amplifier circuit (V1), which is connected on the input side directly to the resistor arrangement (R1,HL) and on the output side to a first measurement and evaluation circuit (M1+A1), characterized in that a second amplifier circuit (V2) is connected on the input side directly via a high-pass circuit (C1,R4) to the resistor arrangement (R1,HL) and on the output side to a second measurement and evaluation circuit (M2+A2), a coupling capacitor (C2) arranged in the second amplifier circuit effecting an increase in the gain with increasing frequency.
- Heat sensor according to Claim 1, characterized in that the resistor arrangement (R1,HL) is constructed as a voltage divider, one resistor (R1) being connected in series with the temperature-dependent resistor (HL) and the first amplifier circuit (V1) being connected by its first input (E11) to the junction point of this resistor (R1) with the temperature-dependent resistor (HL) and by its second input (E12) to the junction point of the temperature-dependent resistor (R1) with the negative pole (-Ub) of the voltage supply.
- Heat sensor according to one of Claims 1 or 2, characterized in that the first and the second amplifier circuit (V1,V2) are in each case formed by an operational amplifier (OPV1,OPV2) having negative feedback.
- Heat sensor according to Claim 3, characterized in that the operational amplifiers (OPV1,OPV2) having negative feedback are constructed as non-inverting amplifiers.
- Heat sensor according to Claim 4, characterized in that, in the second amplifier circuit (V2), the output (Av2) of the operational amplifier (OPV2) is connected via a resistor (R6) to its inverting input (E2-) and the inverting input (E2-) is connected via the parallel circuit of a resistor (R5) and a capacitor (C2) to the negative pole (-Ub) of the voltage supply.
- Heat sensor according to one of Claims 2 to 5, characterized in that the high-pass circuit is formed using a capacitor (C1) connecting the centre tap of the voltage divider (R1,HL) to the first input (E21) of the second amplifier circuit (V2), and a resistor (R4) connecting the first input (E21) of the second amplifier circuit (V2) to the negative pole (-Ub) of the supply voltage.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4031621 | 1990-10-05 | ||
| DE4031621 | 1990-10-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0479009A1 EP0479009A1 (en) | 1992-04-08 |
| EP0479009B1 true EP0479009B1 (en) | 1996-11-27 |
Family
ID=6415696
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP91115573A Expired - Lifetime EP0479009B1 (en) | 1990-10-05 | 1991-09-13 | Temperature sensor |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0479009B1 (en) |
| AT (1) | ATE145745T1 (en) |
| DE (1) | DE59108378D1 (en) |
| ES (1) | ES2094177T3 (en) |
| GR (1) | GR3021795T3 (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2001764A (en) * | 1977-07-27 | 1979-02-07 | Coal Ind | Detecting fires in ducts |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2911540A (en) * | 1955-02-14 | 1959-11-03 | Gen Controls Co | Flame detection system |
| DE1960218A1 (en) * | 1969-12-01 | 1971-06-03 | Rainer Portscht | Temperature radiation detector for automatic fire detection or flame monitoring |
| CH519761A (en) * | 1971-03-04 | 1972-02-29 | Cerberus Ag | Flame detector |
| DE2631454C3 (en) * | 1976-07-13 | 1979-05-03 | Preussag Ag Feuerschutz, 2060 Bad Oldesloe | Flame detector |
| DE2852971C2 (en) * | 1978-12-07 | 1985-02-14 | Preussag Ag Feuerschutz, 2060 Bad Oldesloe | Fire alarm |
-
1991
- 1991-09-13 ES ES91115573T patent/ES2094177T3/en not_active Expired - Lifetime
- 1991-09-13 EP EP91115573A patent/EP0479009B1/en not_active Expired - Lifetime
- 1991-09-13 AT AT91115573T patent/ATE145745T1/en not_active IP Right Cessation
- 1991-09-13 DE DE59108378T patent/DE59108378D1/en not_active Expired - Fee Related
-
1996
- 1996-11-28 GR GR960402965T patent/GR3021795T3/en unknown
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2001764A (en) * | 1977-07-27 | 1979-02-07 | Coal Ind | Detecting fires in ducts |
Also Published As
| Publication number | Publication date |
|---|---|
| GR3021795T3 (en) | 1997-02-28 |
| DE59108378D1 (en) | 1997-01-09 |
| ES2094177T3 (en) | 1997-01-16 |
| ATE145745T1 (en) | 1996-12-15 |
| EP0479009A1 (en) | 1992-04-08 |
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