EP0535029B1 - Status-reporting device for reporting a temperature, with a suitable temperature sensor and method of manufacture of said sensor - Google Patents

Abstract

PCT No. PCT/DE91/00507 Sec. 371 Date Dec. 21, 1992 Sec. 102(e) Date Dec. 21, 1992 PCT Filed Jun. 19, 1991 PCT Pub. No. WO91/20065 PCT Pub. Date Dec. 26, 1991.The invention is directed to a status-reporting device with a plurality of sensors which send output signals whose values depend on the status monitored by the sensors and with an evaluating device which is connected to the sensors and responds by sending an alarm signal when a preselected value of the output signals is reached. According to the invention, the evaluating device has an individual threshold switch (IC51) which generates the alarm signal and is connected with the output (3) of an interrogating device (IC3) which has a plurality of inputs (1, 2, 5, 12-15) connected to each sensor, respectively, and means (IC2) which connect the inputs (1, 2, 5, 12-15) with the output (3) periodically and one after the other. Also described is a temperature sensor which is particularly suitable for fire detection and fire extinguishing systems, as well as a process for the production thereof (FIG. 4).

Description

The invention relates to a condition reporting device of the type specified in the preamble of claim 1, a temperature sensor suitable therefor according to the preamble of claim 12 and a method for its production according to the preamble of claim 14.

Known status reporting devices of the above-mentioned type serve the purpose of emitting an alarm signal when an extreme temperature condition occurs and at the same time making it clear which of the temperature sensors involved has triggered the alarm signal (US-A-4,340,886, EP-A-0 004 911, GB -A-2 174 525, Electronics Weekly No. 778, August 13, 1975, Electronic Design, Volume 13, No. 1, January 10, 1985, DE-A-31 28 811). The temperature is monitored e.g. for fire detection or temperature monitoring e.g. of motors, bearings, ovens or cooling systems. Thermocouples, resistance temperature sensors, temperature-sensitive diodes, mercury switches or the like serve as temperature sensors, but also e.g. Common fire detectors or glass break detectors, all of which are characterized by relatively slow response times, low sensitivity and large dimensions.

According to an object of the invention, the condition reporting device described at the outset should be suitable not only for temperature monitoring, but also for automatically triggering an extinguishing system, as is the case, for example, in aircraft, tanks, dangerous goods tankers or the like. because of the often explosive fires there is desirable and necessary. For this purpose, not only very small and therefore very quickly responding temperature sensors that can be scanned at high frequencies, but also methods are available by means of which such temperature sensors can be manufactured with such a high mechanical and thermal stability that they can also be used in highly sensitive fire detection and fire fighting systems on moving vehicles without the risk of mechanical or thermal damage. The invention is therefore also based on the object of proposing a temperature sensor which is particularly suitable for such a status reporting device and a method for its production.

The characteristic features of claims 1, 12 and 14 serve to achieve this object.

The invention has the advantage that it enables sensible use of thermistors and thereby their known advantages such as e.g. uses small dimensions, short response times and high sensitivity. In addition, temperature sensors are proposed which enable a temperature measurement of the air surrounding them, but at the same time are kept very small and can nevertheless be effectively protected against mechanical damage and are therefore particularly suitable for use in confined spaces. Finally, the method according to the invention creates a possibility of manufacturing such temperature sensors in such a way that the casting compound on the one hand also at temperatures to be measured of e.g. 300 - 900 ° C does not become liquid, but on the other hand does not become so hard that the crucial sensor part, namely the thermistor bead, bursts as a result of internal stresses during manufacture or use and is therefore unusable. Finally, since the thermistor bead remains directly exposed to the air in spite of its mechanical protection in the temperature sensor according to the invention, high reaction speeds of the entire temperature reporting device result, with the result that critical temperature overshoots, fires or the like are not only delayed, but are reported after a fraction of a second.

In view of the advantages and performance of the new sensor described above, but also in view of the considerable cost advantages, there are also additional possible uses for the condition reporting device according to the invention in overheating or fire detection systems, such as in house installations, in the detection of tire overheating in trucks, in power plants or in shipping as well as automatic extinguishing systems in public and private buildings.

In addition to the warning function, the status reporting device can also be used as part of a control system. In connection with the electronics, this results in further additional application options such as in the field of air conditioning or heating control.

Further advantageous features of the invention result from the dependent claims.

• Fig. 1 einen erfindungsgemäßen Temperatursensor etwa im Maßstab 1 : 1 in einer auseinandergezogenen Vorderansicht;
• Fig. 1a den Temperatursensor nach Fig. 1 im gefügten Zustand und in einer teilweise geschnittenen Vorderansicht;
• Fig. 2 ein Netzteil für die erfindungsgemäße Zustandsmeldevorrichtung;
• Fig. 3 eine Sensoreinheit für die Zustandsmeldevorrichtung;
• Fig. 4 eine einen Schwellwertschalter aufweisende Auswerteeinrichtung und eine ihr parallel geschaltete Prüfeinrichtung für die Zustandsmeldevorrichtung;
• Fig. 5 eine Alarm- und/oder Sicherheitseinrichtung für die Zustandsmeldevorrichtung;
• Fig. 6 einen Teil einer Anzeigeeinrichtung für die Prüfeinrichtung nach Fig. 5; und
• Fig. 7 eine standardisierte, an unterschiedliche Sensoren anpaßbare Steckkarte für die erfindungsgemäße Zustandsmeldevorrichtung.

The invention is explained in more detail below in connection with the accompanying drawing on the special embodiment of a fire detection system. Show it:

• 1 shows a temperature sensor according to the invention approximately on a scale of 1: 1 in an exploded front view;
• Fig. 1a, the temperature sensor of Figure 1 in the assembled state and in a partially sectioned front view.
• 2 shows a power supply unit for the status reporting device according to the invention;
• 3 shows a sensor unit for the status reporting device;
• 4 shows an evaluation device having a threshold switch and a test device connected in parallel for the status reporting device;
• 5 shows an alarm and / or safety device for the status reporting device;
• FIG. 6 shows part of a display device for the test device according to FIG. 5; and
• 7 shows a standardized plug-in card which can be adapted to different sensors for the status reporting device according to the invention.

1 shows a temperature sensor according to the invention with a thermistor 1 in the form of a pearl thermistor (eg M 812 from Siemens AG, D-8000 Munich 80) there is a thermistor bead or a semiconductor bead 4 enclosed in a thin, short glass tube 2 and arranged at its tip 3, to which two connecting wires 5 are fastened, which lead out of the glass tube 2. In order to make such a thermistor 1 available on the market useful for the purposes of the invention, it is combined with a preferably cylindrical plug housing 6, which has an intermediate part 7, a hollow end section 8 attached to one side thereof and another on its other side attached, designed as a conventional, 2 or 3-pin connector base 9. The connecting wires 5 are inserted into the hollow cylindrical ends of plugs 10 and firmly connected to the plugs 10 by crimping (crimping) in order to avoid that any soldering mass or the like that is used can melt and run away during the subsequent casting of the end section 8. The plugs 10 are then inserted through bores which are formed in an insert (not shown) which fills the intermediate part 7 in such a way that the arrangement shown in FIG. 1 a results in which the free ends of the plugs 10 protrude into the hollow bottom 9. The connectors 10 are preferably firmly locked in the insert by elements acting in the manner of a snap connection. In addition, the glass tube 2 is preferably arranged so that it is arranged parallel and coaxially to the axis of the connector housing 6 and the thermistor bead 4 is arranged at the end of the end section 8 facing away from the intermediate part 7.

In order to obtain a mechanically stable construction for the extremely sensitive pearl thermistor 1, the hollow end section 8 is now filled with a casting compound 11 so that the entire glass tube 2, with the exception of its tip 3, is embedded in the casting compound 11. After potting, therefore, only the tip 3 with the semiconductor bead 4 protrudes out of the connector housing 6 or the potting compound 11, which on the one hand results in a mechanically stable sensor, and on the other hand creates a very sensitive and very quickly responding temperature sensor which detects the temperature of the surrounding air measures and reacts to temperature changes, the smaller the area of the semiconductor bead 4 to be heated is. When using thermistors 1 of the type described on the market, response times of the order of half a second can be achieved, which is particularly important for rapid fire detection and fighting. There is also the advantage that, in the case of such thermistors 1, by means of circuits which are described below with reference to FIG. 4, the desired triggering temperature is in the range from 80 ° C. to 300 ° C. to approximately ± 1 ° C. can be set.

In order to protect the tip 3 of the thermistor 1 from mechanical damage, for example during assembly of the connector housing 6 at the place of use, a preferably cylindrical protective cap 12 can be screwed onto the end section of the connector housing 6, which is either open at the outer end and / or with a plurality of openings is provided so that the air, the temperature of which is to be monitored, can flow around the tip 3 and thus the semiconductor bead 4. In this case, the thermistor bead 4 is arranged at a preselected location within the protective cap 12 and the sealing compound 11 is filled into the protective cap to such a height h that in turn only the tip 4 with the semiconductor bead 4 protrudes from the sealing compound 11 . After potting, the protective cap 12 forms an inseparable unit with the plug housing 6.

The introduction of the sealing compound 11 into the end section 8 must be done with extreme caution. Otherwise the potting compound 11 will either be too soft with the result that it will be in the temperature range to be monitored, e.g. 80 ° C to 300 ° C flowable and thereby the mechanical stability of the sensor is impaired, or becomes too hard with the risk that the tip 3 of the glass tube 2 jumps off and the sensor becomes unusable.

Casting compounds which have been found to be useful are those which are produced from thermosetting epoxy resins and which have high thermal conductivity and a coefficient of thermal expansion comparable to that of copper. A two-component epoxy casting resin has been found to be particularly suitable, which is available from Grace Electronics Materials Emerson & Cuming (D-6900 Heidelberg) under the name "Stycast 2762 FT" (= sealant) and "Catalyst 17" (= hardener) is distributed. The end section 8 must, however, be filled as follows when using this casting resin:

The sensor is first manufactured in the manner described. A potting compound is then produced by mixing the sealant and the hardener in a mixing ratio (weight ratio) of 10: 1 to 10: 1.1. The potting compound is then filled into the end section 8, which is preferably preheated to approximately 80 ° C., and preheated to 80 ° C. in a heating oven. The subsequent curing takes place in three heating levels in the heating furnace, first for 16 hours at 80 ° C, then for 3 hours at 120 ° C and finally again for 3 hours at 180 ° C. The heater is then reset to 80 ° C and switched off when this temperature is reached. After the oven has cooled to a room temperature of, for example, 20 ° C, the ready-to-use temperature sensor with cast-in thermistor can be removed from the oven. The sensor can be made of different materials. The connector housing is preferably made of metal and the insert is made of an electrically non-conductive plastic with the required resistance to the temperatures that may occur. By using a potting compound 11 made of a non-conductive material, it also provides the necessary insulation.

Depending on the thermistor type, the sensor manufactured according to the method described above can be used anywhere for temperature measurement or temperature monitoring in a temperature range of approximately - 60 ° C to 900 ° C and can either function as a thermometer or thermostat. An excellent application is described below using a fire detection system with a range of e.g. describes seven identical temperature sensors attached to different danger zones.

Fig. 2 shows the circuit of a power supply for operating the circuits shown in the following figures with a constant voltage V _A of, for example, + 5 V ± 1% according to the usual IC technology. The input voltage can be selected between, for example, + 8 V and + 32 V, is applied to an input line 21 provided with a fuse Si 1 and, in the exemplary embodiment, is + 24 V. Between the input line 21 and a ground line 22 are a tens diode ZD 1 (eg BZT 03 / D39), which limits the input voltage to 39 V regardless of any voltage peaks, and a capacitor C₁ for smoothing larger voltage fluctuations. Two in the lines 21 and 22 connected diodes D₁ and D₂ (eg 1 N 4007) serve as polarity protection.

With the lines 21 and 22, the inputs (1 and 2) of a voltage regulator IC 1 (for example MC 78 MO5 BT) are connected, the output (3) of which is connected to an output line 23 on which the constant voltage V _A appears, which is obtained by means of a further filter capacitor C₂ is smoothed. There are different lines 22 and 23 below IC blocks described IC₂ to IC₆ with their inputs 8 and 16 and an IC block IC₅ with its inputs 4 and 8 switched, these inputs in addition the capacitors C₈ (Fig. 3) and C₉ to C₁₂ are connected in parallel according to the respective data sheets to protect the IC chips from smaller stray voltages. However, these capacitors are only shown in FIGS. 2 and 3.

A connected to the input line 21, provided with a fuse Si₂ line 24 leads to a visible from FIG. 5 alarm and / or security device 20 and to a circuit breaker T₁ also visible from FIG. 5. The IC modules IC₂ to IC₆ and IC₅, however, belong to the evaluation device of FIG. 4th

Fig. 3 shows a transmitter unit 25, which contains seven thermistor temperature sensors Rs₁ to Rs₇ (eg M 812-100 k ± 10%) in the exemplary embodiment, which are arranged at any desired locations of an aircraft, truck or the like, preferably 1 and are sensitive in the exemplary embodiment in the range from -55 ° C. to 350 ° C. The ohmic resistance of the sensors Rs₁ to Rs₇ decreases with increasing temperature. The sensors Rs₁ to Rs₇ therefore consist in the exemplary embodiment of resistors, one of whose connections are connected via a line 26 to the output line 23 of the power supply (FIG. 2). The other connections, on the other hand, are connected via resistors R₁₄ to R₂₀ (e.g. 56 Ω) to outputs 27 to 33, which emit output signals, the sizes of which depend on the temperatures monitored by the sensors Rs₁ to Rs₇. Between these outputs 27 to 33 and a line 34 connected to the ground line 22 (FIG. 2), a tens diode ZD₂ to ZD₈ (for example ZPD 6 V 2) is placed in order to subsequently secure the voltages at the outputs of the sensors Rs₁ to Rs₇ Limit circuits to 6.2 V.

4, in which the transmitter unit 25 is only shown schematically, its outputs 27 to 33 are each connected to an input of an evaluation circuit which can emit an alarm signal on an output line 35. In the exemplary embodiment, this always appears when the output signal at any output 27 to 33 of the transmitter unit 25 exceeds a preselected critical variable in the positive or negative direction as desired.

According to the invention, the evaluation device according to FIG. 4 contains a single threshold switch IC₅₁ in the form of an IC chip (eg LT 1017 IN8), the output (7) of which is connected to line 35. This threshold switch IC₅₁ is connected at its inverting input (6) with two adjustable resistors R₆ (eg 10 k) and R₇ (eg 20 k), by means of which a positive voltage can be set as a threshold at the inverting input (6). The non-inverting input (5), on the other hand, is connected by means of a line 36 to which a resistor R₅ (for example 1.62 k) connected to its other terminal is connected to the output (3) of an interrogation device IC₃ in the form of another IC -Block (e.g. HEF 4051 BP) connected, which has seven inputs (1, 2, 5, 12 - 14) connected to an output 27 to 33 each and an input (4) connected to ground. A connected to the line 36 filter capacitor C₄ serves to avoid voltage peaks.

The interrogation device IC₃ are assigned means by means of which the inputs (1, 2, 5, 12-14) mentioned can be connected individually in succession and periodically to the output (3). These means preferably consist of an oscillator in the form of a further IC module (eg HEF 4060 BP), which has three outputs (4, 5, 7), which are connected to three further inputs (9-11) of the interrogation device IC₃ which clock signals appear with three different clock frequencies. On the one hand, these control the inner clock of the interrogation device IC₃ and, on the other hand, determine the repetition frequency with which the inputs (1, 2, 5, 12 - 15) are individually connected to the output (3) one after the other or how quickly these interrogation cycles are to be repeated. To set these clock frequencies, the oscillator IC₂ is provided with an external circuit (e.g. R₃, C₃) according to the data sheet.

If at any time, for example, the input (13) of the interrogation device IC₃ connected to the line 27 of the transmitter unit 25 is connected to its output (3), then the resistance of the sensor Rs₁ and the resistors R₁₄, R₅ form a voltage divider. The voltages and resistances are chosen so that at normal temperatures at the non-inverting input (5) a smaller voltage than at the inverting input (6) of the threshold switch IC₅₁ appears, which is set to + 2.5 V, for example. At the output (7) of the threshold switch IC₅₁ an output signal of 0 V is therefore emitted. On the other hand, the voltage in line 36 rises due to a critical temperature rise in the area of the sensor Rs 1, then the voltage drop in line 36 becomes ever greater until it finally exceeds the set threshold and is greater than the voltage at the inverting one Entrance (6) will. Consequently, the threshold switch IC₅₁ is turned on, so that at its output (7), for example, the 5 V alarm signal (= logical "1") appears. The setting can be selected so that the threshold is exceeded at a critical temperature of 180 ° C or any other temperature.

For the other sensors Rs₂ to Rs₇ the same applies mutatis mutandis, since they, when they are connected via the interrogation device IC₃ with their output (3), always form a voltage divider together with one of the resistors R₁₅ to R₂₀ and the resistor R₅, which the input voltage influenced at the non-inverting input (5) of the threshold switch IC₅₁. In line 35, therefore, the alarm signal appears periodically whenever one of the sensors Rs₁ to Rs₇ is exposed to a temperature which is higher than the set threshold, and this alarm signal is retained until the next sensor by means of the interrogator IC₃ the threshold switch IC₅₁ is placed.

The line 35 of the evaluation device IC₃ is connected to Fig. 4 with an input (4) of a monoflop IC₆ (eg HFF 4538 BP), the output (10) via a series resistor R₁₂ (eg 10 k) and an output line 37 of the evaluation device with the Circuit breaker T₁ according to Fig. 5 is connected. The monoflop IC₆ is set by the appearance of each alarm signal at its output (10) for a preselected period of time, which can be set by means of an external circuit at other inputs (1, 2, 14, 15) according to the data sheet. This ensures that a sufficiently long signal to control the alarm and / or security device 20 is formed in the output line 37 even at a preferably very high polling frequency. In addition, the line 35 is grounded via a high resistance R₂₀ (e.g. 1 M). This ensures that the Monoflop IC₆ in an extreme disturbance situation, e.g. in the event of a voltage drop due to a disconnected battery, is set to zero at the output (10) and does not inadvertently emit an output signal signaling an alarm state.

The interrogation device IC₃ is a test device connected in parallel, which checks the proper functioning of the interrogation device IC₃, in particular the sensors Rs₁ to Rs bei and emits a further alarm signal if it does not function properly. This test device contains a further interrogation device IC₄ (eg HEF 4051 BP) corresponding to the interrogation device IC₃ and one connected to its output (3) another threshold switch IC₅₂ (eg LT 1017 IN 8), which is preferably combined with the threshold switch IC₅₁ in a common housing, which has a further output (1) and two further inputs (2,3), which are assigned to the threshold switch IC₅₂.

Analog to the interrogation device IC₃ are inputs (1, 2, 4, 5, 12, 13, 15) of the interrogation device IC₄ with the output lines 27 to 33 of the transmitter unit 25 and further inputs (9-11) with the outputs of an agent corresponding to the agent IC₂ , preferably connected to the same oscillator IC₂, so that the inputs (1, 2, 4, 5, 12, 13, 15) are connected accordingly to the output 3.

In contrast to the interrogation device IC₃, the output (3) of the interrogation device IC₄ is connected to a line 38 leading to the non-inverting input (3) of the threshold switch IC ,₂, to which a comparatively large resistor R₅ (eg 46.4 k ) and a filter capacitor C₅ are connected. As a result, the voltage normally lying at the non-inverting input (2) of the threshold switch IC auf₂ is set to a larger value than the voltage lying at the inverting input by means of resistors R und, R₉, and the threshold switch IC₅₂ with an operational sensor unit 25 and interrogation device IC₃ has an output signal of e.g. + 5 V gives regardless of whether the monitored temperature corresponds to the preselected room temperature or the temperature preselected with the threshold value of the threshold switch IC₅₁.

If, on the other hand, one of the sensors Rs₁ to Rs₇ is defective, the voltage at the non-inverting input of the threshold switch IC₅₂ falls to zero, with the result that an alarm signal of 0 V appears at the output (1), which is fed to a display device 39. The further alarm signal therefore always appears when a defective sensor Rs₁ to Rs₇ is connected to the output (3) of the further interrogation device IC₄ or another defect, e.g. Power failure, is present.

Each of the monoflop IC₆ for a period of, for example, a few seconds on line 37 maintains the alarm signal in accordance with FIG. 5 through the circuit breaker T 1, for example a field effect transistor, at whose input (3) the 24 V voltage of the power supply (FIG. 2 ) is applied, which passes through the switching process to a control line 40 which leads to the alarm and / or security device 20.

In the simplest case, the alarm and / or security device 20 contains e.g. a warning lamp L₁ connected via a diode D₅ (e.g. IN 4007), which lights up when the alarm signal appears as long as the monoflop IC₆ is set at the output (10). Alternatively or additionally, a warning lamp L₂ can be connected to the control line 40 via a further, corresponding diode D₆, a resistor R₂₁ (e.g. 220 k) and a third diode D₈ (e.g. also IN 4007). This is assigned a holding circuit which contains a switch T₂ designed as a field effect transistor, the control input (2) of which is connected via a resistor R₂₂ (eg 3 k) to the output of the diode D₆ and via a Zener diode ZD₉ to ground and whose voltage input ( 3) via a hand switch 41 on the line 24 coming from the power supply. The output (5) of this switch T₂ is on the one hand at the warning lamp L₂ and on the other hand is fed back via the resistors R₂₁ and R₂₂ to the control input (2). The warning lamp L₂ therefore lights up continuously after triggering the switch T₂, which e.g. has the advantage that a driver who has currently left his vehicle equipped with the condition reporting device described can determine on his return whether an alarm signal has meanwhile appeared or not. By briefly pressing the hand switch 41 to open the holding circuit, the alarm lamp L₂ can be extinguished again.

The alarm and / or security device 20 can be used as security elements e.g. have at least two fire extinguisher bottles HR 1 and HR 2, which are provided with trigger capsules customary in fire protection systems. The voltage input of the fire extinguishing bottle HR₁ is e.g. via a diode D₃ (e.g. 1N 4007) directly on the control line 40, while the voltage input of the fire extinguisher bottle HR₂ is via a normally open switch 22 on line 24 of the power supply. Therefore, the fire extinguisher bottle HR₁ is automatically triggered when an alarm signal appears to initiate a deletion process, while the fire extinguisher bottle HR₂ can be operated manually or additionally by actuating the hand switch 42 when the fire extinguisher bottle HR₁ is used up.

To check the function of the alarm and / or security device 20 finally serve two indicator lights L₃ and L₄, which are switched between the voltage inputs of the fire extinguisher HR₁ and HR₂ and a second fixed contact of the hand switch 41 are, and two diodes D₄ and D₇, which are connected between the second fixed contact of the hand switch 41 and the connection points between the diodes D₅ and D₈ and the associated alarm lamps L₁ and L₂. When the hand switch 41 is switched from its normal position shown in FIG. 4 to the second fixed contact, the alarm lamps L 1, L 2 are therefore connected to the 24 V line 24 and thereby tested. In this position of the hand switch 41 but the indicator lights L₃ and L₄ should light up. For this purpose, their operating voltages are selected so that they are connected to earth with intact fire extinguishers HR 1, HR 2 via their squibs, but no automatic auto-ignition of the fire extinguishers HR 1 and HR 2 takes place via these squibs. If, on the other hand, any primer is defective, the associated indicator lamp cannot be grounded via this primer and therefore cannot light up.

Otherwise, the diodes D₃ to D₈ are each polarized so that the currents flow only in the directions shown in Fig. 5 and no undesirable effects on uninvolved circuit parts can occur.

To check the function of the sensors Rs₁ to Rs₇, the display device 39 is e.g. constructed as follows:

4, it contains on the one hand a ground switch IC₇ (eg CD 4099 BF), whose input (3) is connected to the output (1) of the threshold switch IC₅₂, while three further inputs (5 - 7) of the ground switch IC₇ with the outputs ( 4, 5, 7) of a means are connected, which periodically and individually activates the outputs (1, 9, 11 - 15) of the ground switch IC₇. This means is expediently in turn formed by the oscillator IC₂. Activating the outputs (1, 9, 11 - 15) has the effect that when the usual output voltage of + 5 V (= logical "1") is present at the output (2) of the threshold switch IC₅₂ via a grounded output (4) be grounded. If, on the other hand, a sensor is defective, the voltage fails, a cable is broken or the like, then the relevant output on (1, 9, 11 - 15), if it is activated via the oscillator IC₂, is not connected to ground , which in this case is a voltage of 0V (= logical "0") at the output of the threshold switch IC₅₂.

The outputs (1, 9, 11 - 15) of the ground switch IC₇ are each connected to an input of a keyboard 43 which is only schematically indicated in FIG. 4. Each of these inputs leads over a push button switch TS 1 to TS 7 to the cathode of a control device 44 with its anode connected to the operating voltage, for example a light-emitting diode. If any of the push buttons TS 1 to TS 7 is pressed, then the cathode of the control device 44 is connected to the associated output of the ground switch IC₇ via this push button switch. The control device 44 would therefore always have to respond to the clock determined by the interrogation frequency of the oscillator IC₂, for example light up when the output of the ground switch IC₇ assigned to the actuated key switch is activated. If the control device 44 does not respond, then there is a defect because the associated output of the ground switch ICesch is not periodically connected to ground.

Overall, the alarm and / or security device 20 and the test device with the display device 39 assigned to them result in the advantage that a functional check can be carried out continuously while the entire system is in operation.

7 shows a particularly preferred embodiment of the status reporting device according to the invention. This consists of a standardized plug-in card or circuit board, which is soldered to an IC socket and on which all IC components, cabling and circuits are permanently mounted with the exception of those parts that should be individually changeable. In the exemplary embodiment, the IC components IC₂ to IC₄, IC₅₁ and IC₅₂, IC₆ and IC₇ are combined into a single IC component IC₈, the inputs (1, 4, 5, 33, 34, 39, 51, 52) for connecting the Resistors R₃ and R₅ to R₁₀ and the capacitors C₃ to C₅, further inputs (10, 20, 35 - 37) for applying the operating voltages or ground, further inputs (13 - 19) for applying the encoder unit 25 and outputs (54 - 62) for connecting the keyboard 43 or the like. And an output (2) for emitting the warning signal appearing at the output (7) of the threshold switch IC₅₁ or the signal appearing at the output (10) of the monoflop IC₆. This results in the essential advantage that the IC module IC₈ is used for a multiple number of different status messages or monitoring and can be combined with any encoder units and keyboards or other display devices. Depending on the sensors and display devices used in the individual case, it is only necessary to adapt some external switching elements shown in FIG. 7 accordingly.

The apparent from Fig. 7 IC module IC₈ is otherwise preferably with that for Pour the sealant described temperature sensors and then cured for 16 hours at 80 ° C and 3 hours at 120 ° C. The rest of the procedure can then be carried out as when the temperature sensor is hardening. Due to the universal structure of such a module, it is possible to solve a multitude of monitoring tasks with almost identical means and by means of an optimized device that takes up little space.

The invention is not restricted to the exemplary embodiments described, which can be modified in many ways. This applies in particular to the temperature sensors used, in their place other temperature sensors and also sensors for completely different purposes, e.g. Cold conductors, strain gauges, infrared and other light sensors, voltmeters or the like can be used. It is only necessary to convert the measurement signals obtained in detail into usable signals for the electrical circuits described and to adjust the thresholds set at the threshold switches IC₅₁ and IC₅₂ accordingly. Furthermore, it goes without saying that other alarm and / or security devices and other display devices can be provided, the design of which largely depends on the type of the monitored states. In addition to visual displays, acoustic or other displays can of course also be provided. Furthermore, more or fewer than the seven sensors described can be provided, although it is of course also possible to apply sensors of different types or sensors for monitoring different types of states to the circuit described, in particular the IC module IC₈ according to FIG. 7, wherein only their output signals would have to be adjusted accordingly. Finally, the invention is not limited to the use of the individually specified IC modules, which were only mentioned for example.

Claims (14)

1. Status-reporting device for reporting a predetermined temperature condition, with a plurality of temperature sensors (Rs₁-Rs₇) which deliver output signals whose magnitudes depend on a condition monitored by the sensors, and with an evaluation device connected to the sensors and which, when a preselected magnitude of the output signals is reached, responds by emitting an alarm signal, and has a threshold-value switch (IC₅₁) generating the alarm signal which is connected to the output (3) of an interrogation device (IC₃) which has a plurality of inputs (1, 2, 5, 12-15), each connected to a sensor (Rs₁-Rs₇), and has means (IC₂) periodically and successively connecting the inputs (1, 2, 5, 12-15) to the output (3), characterised in that the temperature sensors (Rs₁-Rs₇) comprise bead thermistors which are embedded in casings (6) in a sealing compound (11) in such a way that their points (3) carrying the thermistor beads (4) project out of the sealing compound, in that the casings (6) have terminal portions (8) with protective caps (12) which have at least one opening intended to maintain an airflow at the point (3), and in that the sealing compound (11) also partly fills the protective cap (12).
2. Status-reporting device according to claim 1, characterised in that one output (7) of the threshold-value switch (IC₅₁) is connected to a monoflop (IC₆) intended for temporary storage of the alarm signal.
3. Status-reporting device according to claim 2, characterised in that the output of the monoflop (IC₆) is connected to the power switch (T₁) of an alarm and/or security device (20).
4. Status-reporting device according to claim 3, characterised in that the alarm and/or security device (20) includes a cancelling device (22) which is triggerable by the alarm signal.
5. Status-reporting device according to claim 3 or 4, characterised in that the alarm and/or security device (20) includes a warning device (L₁) adjustable to the alarm signal and to its duration, and a warning device (L₂) which may be switched on permanently by the alarm signal.
6. Status-reporting device according to one of claims 3 to 5, characterised in that the alarm and/or security device (20) has associated therewith a test device (41, L₃, L₄) for function testing.
7. Status-reporting device according to one of claims 1 to 6, characterised in that there is incorporated in parallel with the evaluation device a testing device testing its proper functioning and responding to improper functioning by emitting a further alarm signal.
8. Status-reporting device according to claim 7, characterised in that the testing device has a further threshold-value switch (IC₅₂) emitting the further alarm signal, and connected to the output (3) of a further interrogation device (IC₄) which has a plurality of inputs (1, 2, 4, 5, 12, 13, 15), each connected to a sensor ((Rs₁-Rs₇), and means periodically and successively connecting the inputs (1, 2, 4, 5, 12, 13, 15) to the output (3).
9. Status-reporting device according to claim 8, characterised in that the output (1) of the further threshold-value switch (IC₅₂) is connected to a display device (39).
10. Status-reporting device according to claim 9, characterised in that the display device (39) includes a keyboard (43) connected to at least one monitoring device (44), and by means of which the sensors (Rs₁-Rs₇) may be individually monitored by key actuation.
11. Status-reporting device according to one of claims 1 to 10, characterised in that the interrogation devices (IC₃, IC₄), the threshold-value switches (IC₅₁, IC₅₂) and the means (IC₂) are combined into a standardised plug-in board (IC₈) which has input connections for individually-selectable thermistors and setting units, display devices, operational voltages or the like selectable or displaceable in dependence on these said thermistors, and at least one output (2) for delivering the alarm signals emitted by the evaluation device.
12. Temperature sensor with a casing having a base with a plug-in means and, facing away therefrom, a hollow terminal portion in which is disposed a thermistor, whose connector wires are connected to the plug-in means, said temperature sensor further being filled by a sealing compound comprising epoxy cast resin, characterised in that the terminal portion (8) is open at its free end, and the thermistor (1) comprises a bead thermistor which is disposed in the terminal portion (8) and embedded in the sealing compound (11) in such a way that its point (3) carrying the thermistor bead (4) projects out of the sealing compound (11), in that the terminal portion (8) is provided with a protective cap (12) which has at least one opening intended to maintain an airflow at the point (3), and in that the sealing compound (11) also partly fills the protective cap (12).
13. Method of producing a temperature sensor according to claim 12, in which the individual parts of the temperature sensor are firstly mechanically assembled, and then the hollow terminal portion is filled with a two-component epoxy cast resin which comprises a resin and a hardener, characterised in that firstly the resin and the hardener are mixed in a ratio of 10 : 1 to 10 : 1.1, producing a sealing compound, which is then filled into the hollow terminal portion (8) of the plug-in portion (6), said hollow terminal portion (8) preferably being pre-heated to approximately 80° C, until only the point (3) of the thermistor (1) carrying the thermistor bead (4) projects out of the sealing compound, hardening thereafter taking place in a heating furnace set firstly for approximately 16 hours at approximately 80° C, thereafter for approximately 3 hours at approximately 120° C, and then for approximately 3 hours at approximately 180° C, and in that the temperature sensor is finally left to cool to room temperature.
14. Method according to claim 13, characterised in that a mixture of Stycast 2762 FT and Catalyst 17 is used as a sealing compound.

Images