Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B19/00—Alarms responsive to two or more different undesired or abnormal conditions, e.g. burglary and fire, abnormal temperature and abnormal rate of flow
  • G08B19/02—Alarm responsive to formation or anticipated formation of ice

Definitions

• the invention relates to a snow and ice alarm device with a moisture sensor, to which a heating circuit is assigned, and an evaluation circuit controlled as a function of a moisture sensor measured variable, which generate a switching and / or control signal at predetermined moisture values.
• the invention further relates to a method for operating the snow and ice detection device. From DE 40 32 73 Cl a snow and ice alarm device for controlling a heating system is known. This device prevents snow and ice formation on limited lane areas, access ramps or roofs. Moisture is determined via at least two exposed electrodes by measuring a resistance between the electrode arrangement and signaling moisture when the resistance falls below a predetermined value.
• a heating element had to be arranged in or on the moisture electrodes in this known moisture sensor arrangement so that an adjacent layer of ice and snow was melted off and converted into electrically conductive water .
• a temperature sensor that detects the ambient or surface temperature is required. If the humidity sensor develops a humidity signal after falling below a "critical" temperature value (close to 0 ° C), the switching or control signal is generated and the associated heating system ⁇ switched on, since snow or ice formation can be assumed.
• This known device is characterized by high accuracy and has proven itself in practice.
• the operational The reliability of the known ice and snow detector therefore depends on periodic maintenance and cleaning work. Under certain circumstances, such work can only be carried out by specialist personnel and is particularly complex if the moisture sensor is relatively difficult to access, for example in a gutter. A tight encapsulation of the electrical components of the known moisture sensor is also not easy to achieve, since the metallic electrodes must be exposed.
• the invention has for its object to provide a snow and ice alarm device in which a reliable function is guaranteed with significantly reduced maintenance and low production costs.
• an ambient temperature sensor is arranged in a control circuit which activates the humidity sensor when a temperature is detected 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 arranged at a mutual distance in an elongated sensor cartridge such that the temperature sensor is thermally decoupled from the PCT heating element.
• 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 depends not only on its ambient temperature, but also on its energy output to the environment. As is known, the heat transfer between fixed solids and gaseous media are significantly worse than those between solids 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.
• FIG. A 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. The following currents were recorded at an operating voltage of 12V. Sensor dry, no wind 100 ... 120mA
• a considerable advantage of the invention also lies in the special design of the entire sensor combination in an elongated sensor cartridge.
• the sensor cartridge has small dimensions overall and can be easily installed at a suitable point in the zone to be monitored for snow and ice formation.
• the humidity sensor is always arranged in the so-called distal area of the elongated sensor cartridge, while the ambient temperature sensor is spaced from the humidity sensor and thermally decoupled.
• the heating effect of the PTC heating element does not affect the ambient temperature detection of the temperature sensor; nevertheless, both sensors can be combined into a compact unit in the sensor cartridge.
• the sensor cartridge is designed as a plastic tube, at one end of which a cable entry and in the opposite end region of which the PTC heating element is arranged in a metal or glass sleeve.
• the plastic tube has an opening at the distal end at which the thermally conductive sleeve or shell of the PTC heating element is exposed to the environment and offers the possibility of heat dissipation.
• the ambient temperature sensor is located near the cable entry, i.e. away from the PTC heating element in the plastic tube.
• the switching and / or control signal of the snow and ice alarm device according to the invention is generally used to control a defrosting heating device.
• This can be installed in a roof, for example, and ensure that the roof is reliably kept clear of large amounts of snow.
• the advantage of such a roof heating is in addition to the avoidance of dangerous ice and snow roof avalanches, the possibility of permanent relief of the
• the control circuit which is effective as a function of the ambient temperature, closes the measuring circuit of the moisture sensor in a preferred embodiment of the invention.
• the humidity sensor is therefore only subjected to a current if the ambient temperature is in a critical area close to 0 ° C, if there is any risk of snow and ice formation.
• the latter After switching on the current to the PTC heating element, the latter initially has a very high current consumption, which is largely independent of the humidity.
• a lead time lock activated by the control circuit is effective, which blocks the triggering of the switching and / or control signal over a predetermined period of time until the PTC heating element has reached a steady operating state.
• the temperature windows of both the ambient temperature sensor and the humidity sensor are preferably adjustable.
• the method for snow and ice reporting according to the invention uses the snow and ice reporting device described above and is characterized according to the invention by the characterizing features of patent claim 12.
• FIG. 1 shows a block diagram with the electrical components of an exemplary embodiment of the snow and ice detection device according to the invention
• FIG. 2 shows a schematic side view of an exemplary embodiment of a sensor cartridge for the
• Snow and ice reporting device according to FIG. 1.
• the device 1 serves to activate a load relay 3.
• the latter closes the operating circuit 5 of a heating device, for example a panel heater, when activated to defrost a roof or gutter.
• the heating device is fed from a mains power source, which is also an operating power source 10 for the snow and ice cream de adopted 1 supplied.
• the operating voltage generated by the operating current source 10 is a low voltage of 12Vac or de.
• An essential component of the new snow and ice alarm device 1 is a sensor arrangement 11 with an ambient temperature sensor 12 and a moisture sensor 13 designed as a PTC heating element or resistor.
• the configuration of the sensor arrangement is explained below with reference to FIG. 2.
• the sensor arrangement 11 is installed in an elongated, tubular sensor cartridge 14.
• the sensor cartridge 14 consists of a poorly heat-conducting material, preferably of plastic.
• a connecting cable 15 is inserted into the interior of the sensor cartridge 14 via a cable entry 16 at a pipe end.
• the ambient temperature sensor is designed as a PTC resistor and is arranged on the end region of the sensor cartridge 14 adjacent to the cable entry 16 in such a way that it can detect the ambient temperature relatively quickly and accurately through its thin wall.
• the moisture sensor 13 designed as a PTC heating element is arranged at the end of the elongated sensor cartridge 14 opposite the cable entry 16, and at such a distance from the ambient temperature sensor 12 that the latter is unaffected by the heating energy of the PTC heating element, that is to say thermally decoupled from the heating element is.
• PTC heating element is arranged moisture-tight in a metal or glass sleeve.
• the latter is open to the outside through a window-like opening 17 in the plastic tube 14.
• the heat generated by the PTC heating element in the activated state of the moisture sensor can therefore be dissipated to the environment without significant transition losses through the metal or glass sleeve receiving the heating element.
• the ambient temperature measurement by the temperature sensor 12 is the primary measurement and control variable in the described ice and snow detection device 1. Only close if the temperature falls below a "critical" ambient temperature 0 ° C there is a risk of snow and ice formation. However, it can also be assumed that below a very low temperature, which in the exemplary embodiment described is in a setting range of -5 ° C to -20 ° C, there is no longer any ice formation.
• a temperature evaluation device 20 is provided with two adjustable limit transmitters 21 and 22, one of which is used to set an upper limit temperature between -3 ° C. and + 5 ° C. and the other 22 is used to set a lower limit temperature between -20 ° C and -5 ° C is used.
• the ambient temperature signal is fed to the temperature evaluation device 20 via a line 24 and compared with the temperature window set on 21 and 22. Outside the temperature window, the temperature evaluation device 20 remains inactive.
• the PTC heating element 13 forming the moisture sensor remains switched off as long as the ambient temperature is outside the set temperature window and no switching signal is present at the output 25 of the temperature evaluation device 20. If the ambient temperature falls below the upper limit temperature set by the limit indicator 21 and lies within the preset temperature window, the temperature evaluation device 20 develops a switching signal on the line 25. This switching signal closes the operating circuit 30 of the PTC heating element via a PTC control switch 26 starts to heat up immediately.
• the current consumption of the PTC heating element can be recorded via a current evaluation device 31 and, taking into account the diagram according to FIG. A, can be used as a measure of the moisture in the environment of the moisture sensor 13.
• a lead time block 33 activated by the signal on line 25 is therefore required in the exemplary embodiment shown in FIG. 1 planned hen, which is coupled to the current evaluation device 31 and blocks the latter for a predetermined time after the generation of the signal on line 25.
• the lead time lock 33 is therefore set to 4 minutes in the described embodiment.
• the current consumption is a reliable measure for humid or dry environmental conditions.
• the moisture sensitivity of the current evaluation device 31 can be set with the aid of an actuator 32.
• the evaluation device 31 develops a switching and / or control signal on the output line 35.
• the load relay 3 and thus the surface heating 7 are activated with this switching or control signal.
• a holding circuit 36 is arranged between the output of the current evaluation device 31 and the control input 38 of the load relay 3, with the aid of which the control input 38 of the load relay 3 is kept activated for an adjustable minimum time as soon as a switching or control signal is present at the output of the current evaluation device 31 .
• a short activation pulse via line 35 leads to a preset activation time of control input 38 and thus to a corresponding heating time of surface heating 7.
• This heating time can be entered via a suitable heating timer 37 of holding circuit 36.
• display means in the form of light-emitting diodes are connected to the temperature and current evaluation devices 20 and 31 as well as to the load relay 3, the lead time block 33 and the operating current source 10, which indicate the activation of the associated components.
• the temperature indicator lights up if the ambient temperature is within the temperature interval specified by the limit switches.
• the moisture indicator lights up when a switching or control signal is developed on line 35.
• the lead time indicator lights up as long as the lead time lock is in effect.
• the network display indicates the operational state of the overall system, and the heating display shows the activation of the load relay 3 and thus the surface heating 7.
• the measured value recording can take place even in places that are difficult to access, such as in gutters or in the area of high antennas or parabolic mirrors.
• the sensor arrangement requires practically no maintenance, since the sensor connections and electrical components are encapsulated corrosion-free and moisture-proof.
• 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 there is a possibility of snow and ice formation.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
• Defrosting Systems (AREA)
• Buildings Adapted To Withstand Abnormal External Influences (AREA)
• Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
• Geophysics And Detection Of Objects (AREA)
• Cleaning Of Streets, Tracks, Or Beaches (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (7)

Cited By (1)

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• 1997
  • 1997-03-19 DE DE19711371A patent/DE19711371C1/de not_active Expired - Fee Related
  • 1997-10-09 DE DE29717945U patent/DE29717945U1/de not_active Expired - Lifetime
• 1998
  • 1998-02-25 EP EP98912386A patent/EP0970457B1/fr not_active Expired - Lifetime
  • 1998-02-25 US US09/381,587 patent/US6276202B1/en not_active Expired - Fee Related
  • 1998-02-25 DK DK98912386T patent/DK0970457T3/da active
  • 1998-02-25 AT AT98912386T patent/ATE217110T1/de not_active IP Right Cessation
  • 1998-02-25 DE DE59803984T patent/DE59803984D1/de not_active Expired - Lifetime
  • 1998-02-25 WO PCT/EP1998/001055 patent/WO1998041958A1/fr active IP Right Grant
  • 1998-02-25 CA CA002284258A patent/CA2284258C/fr not_active Expired - Fee Related

Non-Patent Citations (1)

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