EP0970457B1 - Device and method for detecting snow and ice - Google Patents

Abstract

A device for detecting snow and ice which has a humidity sensor and an ambient temperature sensor. An evaluator switch is controlled according to a humidity sensor-measured variable, producing a control signal at set humidity values for defrosting a surface which is being monitored for snow and ice. The ambient temperature sensor activates the humidity sensor within a temperature range of between +2° C. and -12° C. The humidity sensor itself has a PTC (positive temperature coefficient) heating element. The current consumption of the heating element is used as a measure of humidity. Both the ambient temperature sensor and the humidity sensor are positioned at a mutual distance in a longitudinally extended sensor cartridge made of plastic. The temperature sensor is thermally decoupled from the PTC heating element. The PTC heating element is built into a metal sleeve in such a way that it is corrosion and humidity proof.

Description

The invention relates to a snow and ice alarm device with a humidity sensor to which a heating circuit is assigned and one as a function of a moisture sensor measured variable controlled evaluation circuit that at predetermined Humidity values a switching and / or control signal produce. The invention further relates to a method for Operation of the snow and ice alarm system.

DE 40 32 734 C1 describes a snow and ice detection device known for controlling a heating system. This Facility prevents snow and ice formation on limited Road areas, ramps or roofs. Moisture is at least two exposed electrodes thereby found that there is a resistance between the electrode assembly measured and when falling below a predetermined Resistance value moisture is signaled. Because water in the solid state (in the form of ice or snow), is not conductive, had to be in this known moisture sensor arrangement a heating element in or on the moisture electrodes be arranged so that an adjacent layer of ice and snow melted and converted into electrically conductive water becomes. In addition to the humidity sensor is a Temperature sensor that detects ambient or surface temperature required. The humidity sensor develops after falling below a "critical" temperature value (close to 0 ° C) Moisture signal, so the switching or control signal is generated and the associated heating system switched on because of snow or Ice formation can be assumed. This well-known establishment is characterized by high accuracy and has proven in practice. However, it has not been easy so far possible to be exposed to constant environmental influences metallic moisture electrodes from corrosion. pollution and / or to protect short circuits from the outside. The operational Reliability of the well-known ice and snow detector therefore depends on periodic maintenance and cleaning work from. Such work may only be of Specialist personnel can be carried out and, above all, complex if the humidity sensor is relatively difficult to access, for example in a gutter. Also a tight encapsulation the electrical components of the known humidity sensor is not easy to implement because of the metallic Electrodes must be exposed.

The invention has for its object a snow and To provide ice reporting facilities at the a reliable function with significantly reduced maintenance and low production costs guaranteed is.

Starting from a snow and ice reporting facility of type mentioned above, this object is inventively solved in that an ambient temperature sensor in a Control circuit is arranged, which at the humidity sensor Detection of a temperature within a specified temperature range activated; that the humidity sensor is a PTC heating element has, whose current consumption as a measure of the Moisture is used; and that the two sensors in mutual distance in an elongated sensor cartridge are arranged such that the temperature sensor of the PCT heating element is thermally decoupled.

The invention is based on the use of a moisture sensor with maintenance-intensive exposed moisture electrodes. The invention uses the temperature-dependent current consumption of a PTC resistor or heating element for moisture measurement. This PTC heating element can be produced very inexpensively in the form of a pill which is installed in a heat-conducting capsule, for example a metal or glass sleeve. The current consumption of a PTC heating element or resistor is dependent not only on its ambient temperature, but also on its energy output to the environment. As is known, the heat transfer between solid bodies and gaseous media is significantly worse than that between solid bodies and liquid media. The heat dissipation from the PTC heating element by air (with a dry sensor) is significantly worse than through a damp or even liquid ambient atmosphere. In the case of the humidity sensor with PTC heating element used according to the invention, the diagram according to FIG. A was recorded in an ambient temperature window between + 5 ° C. and -20 ° C. Data were recorded at an operating voltage of 12V the following currents Feeler dry, calm 100 ... 120mA Feeler dry, strong wind 140 ... 170mA / Feeler moist 190 ... 200mA Feeler very wet 200 ... 250mA.

These relatively clear differences in current consumption of the PTC sensor influenced by the environmental conditions are easily and reliably detectable. The evaluation can clearly between dry feeler and damp Differentiate sensors. Because of the complete encapsulation of the new PTC sensor and the low current consumption values the system works practically maintenance-free.

A significant advantage of the invention also lies in the special training of the entire sensor combination in one elongated feeler cartridge. The sensor cartridge has overall small dimensions and can be easily on one suitable location of the area to be monitored for snow and ice formation Install zone. The humidity sensor is always there in the so-called distal area of the elongated sensor cartridge arranged while the ambient temperature sensor is spaced from the moisture sensor and thermally decoupled. The heating effect of the PTC heating element influences the detection of the ambient temperature the temperature sensor not; nevertheless, both sensors can be admitted in the sensor cartridge unite in a compact unit.

Precisely because of the compact design of the sensor cartridge and their maintenance-free operation result for the new Ice reporting device extended areas of application. This includes difficult to access gutters, roofs, of ice and Antenna arrangements to be kept clear of snow, in particular parabolic mirrors, Exterior doors as well as pavement ceilings, ramps, House entrances or the like ..

In a preferred development of the invention, the sensor cartridge formed as a plastic tube on one End a cable entry and in its opposite End area the PTC heating element in a metal or glass sleeve is arranged. The plastic tube has at the distal end an opening at which the thermally conductive sleeve or Shell of the PTC heating element is exposed to the environment and the Possibility to dissipate heat. The ambient temperature sensor is close to the cable entry, i.e. away from the PTC heating element arranged in the plastic tube.

With the switching and / or control signal of the invention Snow and ice reporting facilities are usually one Defrosting heater controlled. This can for example, be installed in a roof and ensure that the roof is reliable from larger masses of snow is kept free. The advantage of such roof heating is in addition to avoiding dangerous ice and snow roof avalanches the possibility of permanent relief of the Roof construction and thus for the lighter and cheaper Roof design.

The effective one depending on the ambient temperature In a preferred embodiment, the control circuit closes the Invention the measuring circuit of the moisture sensor. The humidity sensor is therefore only subjected to current if the Ambient temperature is in a critical range close to 0 ° C, if there is any danger of snow and ice formation consists. After switching on the power to the PTC heating element the latter initially has a very high and of the moisture consumption is largely independent of the humidity. In this The first phase is according to an advantageous development of the invention a lead time lock activated by the control circuit effective which triggers the switching and / or Control signal over a predetermined period of time locks until the PTC heating element is a steady Has reached operating state.

The temperature windows of both the ambient temperature sensor are preferably as well as the humidity sensor.

The method according to the invention for snow and ice reporting uses the snow and ice reporting system described above and is characterized by the invention characterizing features of claim 12.

Other advantageous developments of the invention are characterized in the subclaims.

Fig. 1

ein Blockschaltbild mit den elektrischen Komponenten eines Ausführungsbeispiels der erfindungsgemäßen Schnee- und Eismeldeeinrichtung; und

Fig. 2

eine schematische Seitenansicht auf ein Ausführungsbeispiel einer Fühlerpatrone für die Schnee- und Eismeldeeinrichtung gemäß Fig. 1.

The invention is explained in more detail below with reference to an embodiment shown in the drawing. The drawing shows:

Fig. 1

a block diagram with the electrical components of an embodiment of the snow and ice detection device according to the invention; and

Fig. 2

2 shows a schematic side view of an exemplary embodiment of a sensor cartridge for the snow and ice detection device according to FIG. 1.

1 shows an embodiment the snow and ice reporting device according to the invention 1. The device 1 is used in the illustrated embodiment to activate a load relay 3. The latter closes the operating circuit 5 when activated Heating device, for example surface heating, the to defrost a roof or gutter. The Heater is powered from a mains power source that also an operating current source 10 for the Schr.ee and ice reporting device 1 supplied. As can be seen, it is from the Operating current source 10 generated operating voltage a low voltage of 12Vac or dc.

An essential part of the new snow and ice alarm system 1 is a sensor arrangement 11 with an ambient temperature sensor 12 and one as a PTC heating element or -Resistance trained moisture sensor 13. Training the sensor arrangement is explained below with reference to FIG. 2.

The sensor arrangement 11 is in an elongated, tubular sensor cartridge 14 installed. The sensor cartridge 14 consists of a poorly heat-conducting material, preferably made of plastic. A connecting cable 15 is over a cable entry 16 at one end of the pipe into the interior the sensor cartridge 14 introduced. The ambient temperature sensor is designed as a PTC resistor and on the cable entry 16 adjacent end region of the sensor cartridge 14 arranged so that the ambient temperature through its thin wall can record relatively quickly and accurately. The Moisture sensor 13 designed as a PTC heating element is on the the cable entry 16 opposite end of the elongated Sensor cartridge 14 arranged, in one such a distance from the ambient temperature sensor 12 that the latter unaffected by the heating energy of the PTC heating element, is thermally decoupled from the heating element. The PTC heating element is moisture proof in a metal or Glass sleeve arranged. The latter lies through a window-like Opening 17 in the plastic tube 14 open to the outside. The from the PTC heating element when the humidity sensor is activated generated heat can therefore without significant transition losses through which the heating element receiving metal or Glass sleeve are discharged to the environment.

The ambient temperature measurement by the temperature sensor 12 is in the ice and snow reporting device described 1 the primary measurement and control variable. Only when falling below close to a "critical" ambient temperature value 0 ° C there is a risk of snow and ice formation. But it can also be assumed that below one very low temperature in the described embodiment in a setting range from -5 ° C to -20 ° C no ice formation takes place. A temperature evaluation device 20 is in the described embodiment with two adjustable limit switches 21 and 22 provided, one of which for setting an upper Limit temperature between -3 ° C and + 5 ° C and the other 22 for Setting a lower limit temperature between -20 ° C and -5 ° C is used. The ambient temperature signal is the temperature evaluation device 20 fed via a line 24 and with the temperature window set on 21 and 22 compared. The temperature evaluation device remains outside the temperature window 20 inactive. The humidity sensor forming PTC heating element 13 remains off as long as the ambient temperature outside the set temperature window is and no switching signal at the output 25 of the Temperature evaluation device 20 is present.

If the ambient temperature is that of the limit indicator 21 falls below the set upper limit temperature and within of the preset temperature window is so developed the temperature evaluation device 20 a switching signal on line 25. This switching signal closes a PTC control switch 26 the operating circuit 30 of the PTC heating element, which starts to heat up immediately. The current consumption of the PTC heating element can be via a current evaluation device 31 recorded and taking into account the A as a measure of the humidity in the environment of the moisture sensor 13 can be used. The Current draw of the PTC heating element is during an initial Swing-in phase not a reproducible measure for the Humidity environment of the PTC sensor 13. To avoid Incorrect measurements or falsifications are therefore described Embodiment of FIG. 1 one of the signal on the line 25 activated lead time block 33 is provided, which is coupled to the current evaluation device 31 and. the latter over a predetermined time after generation of the signal on line 25 blocks. Experiments have shown that the PTC heating element in a period of 3 to 5 minutes. usually at the latest after 4 minutes, his steady Operating status reached. The lead time lock 33 is therefore in the described embodiment to 4 minutes set. After that, the current consumption is reliable Measure for damp or dry environmental conditions.

The moisture sensitivity of the current evaluation device 31 can be set with the aid of an actuator 32.

In the steady state of the PTC heating element 13 is whose power consumption is characteristic of a dry or moist environment of the moisture sensor. When detecting a high Current consumption (in the described embodiment > 190mA), the evaluation device 31 develops a switching and / or Control signal on the output line 35. With this Switching or control signal is the load relay 3 and thus the surface heating 7 activated. Between the output of the current evaluation device 31 and control input 38 of the load relay 3 a holding circuit 36 is arranged, by means of which the Control input 38 of the load relay 3 via an adjustable Minimum time is kept activated as soon as at the exit of the Current evaluation device 31 a switching or control signal pending. As a result, even a short drive pulse leads via line 35 at a preset activation time of the control input 38 and thus to a corresponding one Heating time for surface heating 7. This heating time can be set using a suitable heating timer 37 entered the holding circuit 36 become.

In the described embodiment, the Temperature and current evaluation devices 20 and 31 as well as with the load relay 3, the lead time lock 33 and the Operating current source 10 display means in the form of light emitting diodes connected, which is the activation of the associated Show components. The temperature indicator lights up if the ambient temperature in that by the limit switch predetermined temperature interval. The moisture indicator lights up when there is a switching or control signal on the Line 35 is developed. The lead time indicator lights up as long as the lead time lock is in effect. The network display denotes the operational state of the overall system, and the heating indicator shows the activation of the Load relay 3 and thus the surface heating 7.

Because of the compact design and the relatively insensitive Configuration of the sensor assembly 11 can Measured value recording even in hard to reach places, such as in gutters or in the area of high antennas or parabolic mirrors respectively. The sensor arrangement requires practically none Maintenance because of the sensor connections and electrical components encapsulated corrosion-free and moisture-proof are. The current consumption of the temperature sensor is extremely low; the PTC sensor 13 also has a low energy consumption and is only switched on when the possibility there is snow and ice formation.

Claims (18)

1. Device for detecting snow and ice including a humidity sensor, associated with which is a heating current circuit, and an evaluating circuit, which is controlled in dependence on a humidity sensor measured variable and produces a switching and/or control signal at predetermined humidity values, characterised in that an ambient temperature sensor is arranged in a control circuit which activates the humidity sensor on detection of a temperature within a predetermined temperature range; that the humidity sensor has a PTC heating element, the current consumption of which is used as a measure of the humidity; and that the two sensors are so arranged mutually spaced in an elongate sensor cartridge that the temperature sensor is thermally decoupled from the PTC heating element.
2. Device as claimed in claim 1, characterised in that the sensor cartridge is constructed in the form of a plastic tube, arranged at one end of which there is a cable inlet and in the opposite end region of which the PTC heating element is arranged in a metal or glass sleeve.
3. Device as claimed in claim 2, characterised in that the temperature sensor is arranged in the plastic tube close to the cable inlet and remote from the PTC heating element.
4. Device as claimed in one of claims 1 to 3, characterised in that the control circuit controls a switch which closes the measuring current circuit of the humidity sensor.
5. Device as claimed in one of claims 1 to 3, characterised in that associated with the measuring current circuit there is a current consumer with a threshold value transmitter and that the switching and/or control signal may be triggered at a current consumption of the PTC heating element which exceeds the threshold value.
6. Device as claimed in claim 5, characterised in that connected after the current absorber there is an adjustable timer which holds the switching and/or control signal for a predetermined period of time.
7. Device as claimed in one of claims 1 to 6, characterised in that the switching and/or control signal controls a heating; device for thawing and/or a warning device by means of a switch, preferably constructed in the form of a load relay.
8. Device as claimed in claim 6 or 7, characterised in that the control circuit additionally activates a lead time lock which blocks the triggering of the switching and/or control signal for a predetermined period of time until the PTC heating element reaches steady state operation.
9. Device as claimed in one of claims 1 to 8, characterised in that the ambient temperature sensor has means for setting an upper and/or lower threshold temperature and that the humidity sensor may be activated when the temperature falls below an upper threshold.
10. Device as claimed in one of claims 1 to 9, characterised in that visual indicating means are coupled to an output of at least the control circuit and the evaluation circuit.
11. Device as claimed in claim 10, characterised in that visual indicating means are additionally coupled to an operating current source and to a heating controller.
12. Method of detecting snow and ice using a device as claimed in one of claims 1 to 11, characterised in that a humidity sensor including a PTC heating element and an ambient temperature sensor are arranged mutually spaced and thermally decoupled in an elongate sensor cartridge, that the sensor cartridge is immersed in a monitored zone at risk of snow and ice, whereby the ambient temperature sensor detects the ambient temperature, that the heating current circuit of the PTC heating element is activated in dependence on the temperature falling below a preset threshold temperature; and that the current in the heating circuit of the PTC humidity sensor is sensed and a switching and/or control signal is triggered when the current exceeds a predetermined threshold current.
13. Method as claimed in claim12, characterised in that a temperature window of between +5°C and -20°C is set and the heating current circuit of the heating element is activated only within this window.
14. Method as claimed in claim 12 or 13, characterised in that a heating device, which heats a roof, one or more roof gutters and/or one or more parabolic mirrors, or a warning signal is activated! with the switching and/or control signal.
15. Method as claimed in claim 14, characterised in that a minimum activation time of the surface heater is preset.
16. Method as claimed in one of claims 12 to 15, characterised in that the current flowing through the PTC heating element is measured and the switching and/or control signal is triggered, when the humidity sensor is activated, in dependence on a current intensity threshold value.
17. Method as claimed in one of claims 12 to 16, characterised in that when the temperature falls below an upper threshold temperature value, a lead time lock is triggered with which the output of the switching and/or control signal is blocked for a predetermined time until the temperature or current consumption of the PTC heating element has reached steady state.
18. Method as claimed in one of claims 12 to 17, characterised in that the operational states of the ambient temperature sensor and/or the humidity sensor and/or a heater and/or a lead time and the presence of the mains voltage are indicated visually.

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