CA2203447A1 - Aircraft temperature monitoring - Google Patents
Aircraft temperature monitoringInfo
- Publication number
- CA2203447A1 CA2203447A1 CA 2203447 CA2203447A CA2203447A1 CA 2203447 A1 CA2203447 A1 CA 2203447A1 CA 2203447 CA2203447 CA 2203447 CA 2203447 A CA2203447 A CA 2203447A CA 2203447 A1 CA2203447 A1 CA 2203447A1
- Authority
- CA
- Canada
- Prior art keywords
- loop
- switch
- switches
- monitor unit
- supply line
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B25/00—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems
- G08B25/01—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems characterised by the transmission medium
- G08B25/018—Sensor coding by detecting magnitude of an electrical parameter, e.g. resistance
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- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Emergency Alarm Devices (AREA)
- Testing Electric Properties And Detecting Electric Faults (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
Aircraft leading edge overheat systems have temperature-responsive switches connected along the wing and a monitor to detect when any of the switches closes because of overheating. In the present invention, two constant-current sources are connected to opposite ends of a first loop having several series-connected resistors. One terminal of each switch is connected to a junction between different ones of the resistors, the other terminal being connected to a second loop at ground potential. The monitor measures the voltage across opposite ends of the first loop. When overheating is detected, a switch closes and causes a change in the monitored voltage. The monitor provides an alarm to indicate the overheating and identifies the closed switch from the voltage produced. A store records which switch was closed.
Description
AIRCRAFT TEMPERATURE MONITORING
Background of the Invention This invention relates to aircraft temperature monitoring.
In some aircraft, hot gases from the engine are supplied along tubes extending within the leading edge of the wing, to warm its edge and prevent ice formation. Temperature-responsive switches spaced along the wing, are used to detect overheating. A display on the flight deck warns the pilot that overheating is occurring, so that the pilot can take remedial action, such as by reducing the flow of gases along the heating tube. Overheating is usually caused by leakage of gas from the heating tubes. This leakage may occur only during flight, when the wings are bent by the aerodynamic forces on the wing, and may not be apparent when the aircraft is on the ground. Present leading-edge overheat detection systems do not enable the location of the overheating to be identified, so it can be difficult to detect the source of the leak. This can mean that the aircraft is out of service for lengthy periods while the leak is located and rectified, leading to an appreciable loss of revenue for the aircraft operator.
Brief Summary of the Invention It is an object of the present invention to provide an improved aircraft temperature monitoring system.
According to the present invention there is provided an aircraft temperature monitoring system including an electrical supply unit, a plurality of temperature-responsive switches connected at one terminal to a supply line connected with said supply unit and at another terminal to a location at a potential different from said supply line such that closing of a switch causes current flow through the switch, and monitor means for monitoring the effect of closing of a switch, each switch having associated therewith a respective resistor such that closing each switch causes a different voltage to be applied to the monitor means, such that the monitor means can determine the identity of the closed switch.
The supply line is preferably formed in a first loop, the resistors being connected in series in the loop. Each end of the first loop may be connected to a respective source of constant current, the monitor means being connected to monitor the voltage at opposite ends of the loop. The system may include an even number of switches, two resistors being connected between the middle two switches around the first loop. Each resistor may have the same value. The other terminal of the switches is preferably connected to a second loop, which may include a manually-operated test switch that normally closes the second loop but can be switched to open the second loop and connect it to the supply line.
Alternatively, the ends of the first loop may be connected across a voltage source, the monitor means being connected to the other terminal of the switches so that closing of each switch causes a different voltage to be applied to the monitor means. The voltage source may be an ac source.
Each of the switches may be responsive at the same temperature, or some may be responsive at different temperatures. The system may include a store arranged to store an indication of which switch has been closed.
An aircraft leading-edge overheat detection system, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings.
Brief Description of the Drawings Figure 1 is a schematic diagram showing a conventional system;
Figure 2 shows another conventional system;
Figure 3 is a schematic diagram showing the system of the present invention:
and Figure 4 shows a modification of the system shown in Figure 3.
Detailed Description of the Preferred Embodiments With reference to Figure 1 there is shown a simplified form of a conventional circuit including a warning panel unit 1 with a lamp 2 connected between a voltage source 3 and one end of a supply line 4, which extends along one of the aircraft wings and engine pylon. The other end of the supply line 4 is normally floating but can be connected to ground by means of a "Test" switch 5. Three heat-responsive switches 6 to 8 are spaced along the wing and engine pylon and have one terminal connected to the supply line 4; the other terminal is connected locally to ground. The switches 6 to 8 are normally open so that no current flows through them, but they close, to produce a low impedance, when the temperature rises ahove a predetermined value. In normal operation, no current flows through the lamp 2, because the supply line 4 is at the same potential as the voltage source. If, however, the temperature at one of the switches 6 to 8 should rise sufficiently for it to close, the supply line 4 would be connected to ground by the closed switch, so a current would flow through the switch and the lamp 2 causing it to light. This provides a warning to the pilot that one of the switches has closed, so that he can take remedial action to reduce the leading edge temperature and thereby open the closed switch. The system can be tested by closing the "Test" switch S on the panel unit 1, which connects the floating end of the supply line 4 to earth. Any break in the supply line 4 would prevent the lamp 2 lighting. The problem with this system is that it does not provide any indication of which switch has closed and hence it does not indicate the location of the fault. When inspected on the ground, the engineer may have to inspect the entire length of the wing. In some cases, the fault may only appear during flight, making its detection even more difficult.
An alternative arrangement is shown in Figure 2, where the switches 6' to 8' are connected to an earth loop 9', instead of being locally earthed. This arrangement suffers from the same problems as the circuit shown in Figure 1.
With reference now to Figure 3, there is shown a system according to the present invention, which identifies the location of any closed switch. Figure 3 shows an overheat detector 10 with ten temperature-responsive switches 11 to 20, each having one terminal connected to an earth line 21 and another terminal connected to a supply line 22. Both lines 21 and 22 extend in a loop within the aircraft wing leading edge and engine pylon, from an overheat detection panel unit 23. The switches 11 to 20 may each close at the same temperature or at selected different temperatures. The supply line 22 includes twelve resistors 25 to 36 connected in series in the line, two of the resistors 25 and 36 being located in the panel 23 and the other ten resistors 26 to 35 being connected between adjacent ones of the switches 11 to 20, with two resistors 30 and 31 being connected between the middle two switches l S and 16 in the loop. The resistors 25 to 36 are of the same resistance (typically between about 150Q and 200Q), they are encapsulated and have a low temperature coefficient of resistance. The two ends 37 and 38 of the supply line loop 22 are connected to the collectors of respective transistors 40 and 41 acting as two constant current sources. The emitters of the transistors 40 and 41 are connected together and the bases are connected to the output of a power supply unit 42 via zener diodes 43 and 44, which m~int~in a constant voltage at the bases. The ends 37 and 38 of the supply line 22 are also connected to respective inputs of a comparator 45 via transistor amplifiers 46 and 47. A Test switch 39 normally connects one end of the earth loop 21 to the other end but, when actuated, connects the left end 37 of the supply line 22 to the end of the earth line remote from earth.
~ CA 02203447 1997-04-23 , The system has separate detectors 10 and 10' for each wing and may also have separate detectors in the same wing for redundancy purposes, as is usual with leading edge overheat detection systems.
The output of the comparator 45 is connected to an input of a multiplexer 46, the other inputs of which are connected to similar overheat detectors in different wings, or in different parts of wings, or duplicated within the same wing. The output of the multiplexer 46 is connected to a microprocessor 50 via an A/D converter 51. The microprocessor 50 has outputs connected to switches 52 by which respective warning lamps 53 are illllmin~ted. The microprocessor 50 is also connected to a numerical display 54 on which an indication is provided of the location of a closed switch. Various stores 55 and buffers 56 enable an historical record to be m~int~ined and accessed by maintenance engineers so that the site of any overheating during a flight can be checked later on the ground. The units 45 to 54 together form a monitor that monitors the effect of closing of the switches 11 to 20.
When the leading edge of the wing is at normal temperatures, all the switches 11 to 20 are open so that the current supplied to opposite ends of the supply line loop 22 is balanced.
The voltages at opposite ends 37 and 38 of the loop 22 are equal and hence the inputs to the comparator 45 are equal. In this condition, the lamps 53 are not illl]min~ted.
If the leading edge of the wing should overheat sufficiently to cause one of the switches 11 to 20 to close, a warning will be provided. For example, if switch 11 should close, the junction between the two resistors 25 and 26 would go to ground so that the current from transistor 40 only flows through one resistor 25, whereas that from the other transistor 41 flows through eleven resistors 36 to 26. This thereby causes the voltage across the left- .
hand end 37 of the supply line 22 to fall, and the voltage across the other end 38 of the supply line to rise. The effect of closing any one of the switches 11 to 30 is illustrated by the table below, where R is the value of each resistance, VL is the voltage at the left-hand end 37 of the loop, VR is the voltage at the right-hand end 38 of the loop, and i is the current flow along each side of the loop:
Closed Switch VL VR
None 6iR 6iR
11 iR lliR
12 2iR lOiR
13 3iR 9iR
14 4iR 8iR
5iR 7iR
16 7iR 5iR
17 8iR 4iR
18 9iR 3iR
19 lOiR 2iR
lliR iR
It can be seen, therefore, by measuring the difference between the two voltages and the sense of difference, that the identity of the closed switch can be determined. As soon as there is a change in voltage on the two ends 37 and 38 of the loop 22, the microprocessor 50 .
causes the appropriate warning lamp 53 to be illllmin~ted depending on which detector 10 is overheated. The identity of the closed switch is shown on the display 54.
When the test switch 39 is operated, the voltage at the left end 37 of the supply loop 22 should drop to zero and that at the right hand end 38 should rise to 12iR. If this fails to occur, the processor 50 determines that a fault has occurred.
It is also possible to identify uniquely the location of a second switch to close. For example, if switch 13 were closed first and then switch 12 were to close, the voltage at the left end 37 of the line 22 would change from 3iR to 2iR, whereas the voltage at the right end 3 8 would remain at 9iR. Depending on the order in which other switches close, it may be possible to detect the location of these, although any switch closing between two already closed switches could not be identified. In general, however, it will only be adjacent switcl1es that close because of the localised heating effect of a leakage.
When the pilot is notified that overheating is occurring, he takes action to rectify this, which should lead to the temperature falling and the tripped switch opening again. The pilot may note the identity of the previously closed switch from the numerical display 54 or he may rely on the ground engineers interrogating the stored log of closed switches contained in the stores 55. This makes it considerably easier to identify the location of any leakage, because the location of the closed switch is known.
~, . 9 The arrangement described above can be installed in an aircraft having a conventional leading edge overheat detection system of the kind shown in Figure 2, without the need to rewire extensively. The modification can be effected easily by replacing the existing warning panel unit with one of the kind shown in Figure 3 and by inserting resistors in the supply loop. The resistors can either be inserted at the terminal blocks to which the heat-responsive switches are connected, or by breaking the line and inserting the resistors using in-line junctions having an encapsulated resistor. This arrangement enables closed switches to be identified without the need for each switch to be connected separately to a monitor by its own cable, thereby avoiding the increased weight and space of additional cabling.
It will be appreciated that the system of the present invention can also be used where the switches are locally grounded, as shown in Figure 1.
Figure 4 shows an alternative arrangement that can be used to enable the identification of a closed switch. In this arrangement, only three switches 141 to 143 are shown, for simplicity. These switches have one terminal connected to a supply line 144, which is modified, as above, by the insertion of four resistors 145 to 148. The other terminals of the switches 141 to 143 are connected to a loop 150. In a conventional installation, this loop 150 would be an earth loop but in the present arrangement, it is disconnected from earth and instead is connected to a voltage-measuring and processmg unit 151. A voltage source 152, which is preferably an ac source, but could be a dc source, is connected across the supply line 144. In this arrangement, the four resistors 145 to 148 act as a potentiometer so that, when one of the heat-responsive switches closes, it applies a different voltage to the loop l SO and hence to the processing unit 151. The processing unit 151 measures the voltage and, from this, determines which switch is closed.
Background of the Invention This invention relates to aircraft temperature monitoring.
In some aircraft, hot gases from the engine are supplied along tubes extending within the leading edge of the wing, to warm its edge and prevent ice formation. Temperature-responsive switches spaced along the wing, are used to detect overheating. A display on the flight deck warns the pilot that overheating is occurring, so that the pilot can take remedial action, such as by reducing the flow of gases along the heating tube. Overheating is usually caused by leakage of gas from the heating tubes. This leakage may occur only during flight, when the wings are bent by the aerodynamic forces on the wing, and may not be apparent when the aircraft is on the ground. Present leading-edge overheat detection systems do not enable the location of the overheating to be identified, so it can be difficult to detect the source of the leak. This can mean that the aircraft is out of service for lengthy periods while the leak is located and rectified, leading to an appreciable loss of revenue for the aircraft operator.
Brief Summary of the Invention It is an object of the present invention to provide an improved aircraft temperature monitoring system.
According to the present invention there is provided an aircraft temperature monitoring system including an electrical supply unit, a plurality of temperature-responsive switches connected at one terminal to a supply line connected with said supply unit and at another terminal to a location at a potential different from said supply line such that closing of a switch causes current flow through the switch, and monitor means for monitoring the effect of closing of a switch, each switch having associated therewith a respective resistor such that closing each switch causes a different voltage to be applied to the monitor means, such that the monitor means can determine the identity of the closed switch.
The supply line is preferably formed in a first loop, the resistors being connected in series in the loop. Each end of the first loop may be connected to a respective source of constant current, the monitor means being connected to monitor the voltage at opposite ends of the loop. The system may include an even number of switches, two resistors being connected between the middle two switches around the first loop. Each resistor may have the same value. The other terminal of the switches is preferably connected to a second loop, which may include a manually-operated test switch that normally closes the second loop but can be switched to open the second loop and connect it to the supply line.
Alternatively, the ends of the first loop may be connected across a voltage source, the monitor means being connected to the other terminal of the switches so that closing of each switch causes a different voltage to be applied to the monitor means. The voltage source may be an ac source.
Each of the switches may be responsive at the same temperature, or some may be responsive at different temperatures. The system may include a store arranged to store an indication of which switch has been closed.
An aircraft leading-edge overheat detection system, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings.
Brief Description of the Drawings Figure 1 is a schematic diagram showing a conventional system;
Figure 2 shows another conventional system;
Figure 3 is a schematic diagram showing the system of the present invention:
and Figure 4 shows a modification of the system shown in Figure 3.
Detailed Description of the Preferred Embodiments With reference to Figure 1 there is shown a simplified form of a conventional circuit including a warning panel unit 1 with a lamp 2 connected between a voltage source 3 and one end of a supply line 4, which extends along one of the aircraft wings and engine pylon. The other end of the supply line 4 is normally floating but can be connected to ground by means of a "Test" switch 5. Three heat-responsive switches 6 to 8 are spaced along the wing and engine pylon and have one terminal connected to the supply line 4; the other terminal is connected locally to ground. The switches 6 to 8 are normally open so that no current flows through them, but they close, to produce a low impedance, when the temperature rises ahove a predetermined value. In normal operation, no current flows through the lamp 2, because the supply line 4 is at the same potential as the voltage source. If, however, the temperature at one of the switches 6 to 8 should rise sufficiently for it to close, the supply line 4 would be connected to ground by the closed switch, so a current would flow through the switch and the lamp 2 causing it to light. This provides a warning to the pilot that one of the switches has closed, so that he can take remedial action to reduce the leading edge temperature and thereby open the closed switch. The system can be tested by closing the "Test" switch S on the panel unit 1, which connects the floating end of the supply line 4 to earth. Any break in the supply line 4 would prevent the lamp 2 lighting. The problem with this system is that it does not provide any indication of which switch has closed and hence it does not indicate the location of the fault. When inspected on the ground, the engineer may have to inspect the entire length of the wing. In some cases, the fault may only appear during flight, making its detection even more difficult.
An alternative arrangement is shown in Figure 2, where the switches 6' to 8' are connected to an earth loop 9', instead of being locally earthed. This arrangement suffers from the same problems as the circuit shown in Figure 1.
With reference now to Figure 3, there is shown a system according to the present invention, which identifies the location of any closed switch. Figure 3 shows an overheat detector 10 with ten temperature-responsive switches 11 to 20, each having one terminal connected to an earth line 21 and another terminal connected to a supply line 22. Both lines 21 and 22 extend in a loop within the aircraft wing leading edge and engine pylon, from an overheat detection panel unit 23. The switches 11 to 20 may each close at the same temperature or at selected different temperatures. The supply line 22 includes twelve resistors 25 to 36 connected in series in the line, two of the resistors 25 and 36 being located in the panel 23 and the other ten resistors 26 to 35 being connected between adjacent ones of the switches 11 to 20, with two resistors 30 and 31 being connected between the middle two switches l S and 16 in the loop. The resistors 25 to 36 are of the same resistance (typically between about 150Q and 200Q), they are encapsulated and have a low temperature coefficient of resistance. The two ends 37 and 38 of the supply line loop 22 are connected to the collectors of respective transistors 40 and 41 acting as two constant current sources. The emitters of the transistors 40 and 41 are connected together and the bases are connected to the output of a power supply unit 42 via zener diodes 43 and 44, which m~int~in a constant voltage at the bases. The ends 37 and 38 of the supply line 22 are also connected to respective inputs of a comparator 45 via transistor amplifiers 46 and 47. A Test switch 39 normally connects one end of the earth loop 21 to the other end but, when actuated, connects the left end 37 of the supply line 22 to the end of the earth line remote from earth.
~ CA 02203447 1997-04-23 , The system has separate detectors 10 and 10' for each wing and may also have separate detectors in the same wing for redundancy purposes, as is usual with leading edge overheat detection systems.
The output of the comparator 45 is connected to an input of a multiplexer 46, the other inputs of which are connected to similar overheat detectors in different wings, or in different parts of wings, or duplicated within the same wing. The output of the multiplexer 46 is connected to a microprocessor 50 via an A/D converter 51. The microprocessor 50 has outputs connected to switches 52 by which respective warning lamps 53 are illllmin~ted. The microprocessor 50 is also connected to a numerical display 54 on which an indication is provided of the location of a closed switch. Various stores 55 and buffers 56 enable an historical record to be m~int~ined and accessed by maintenance engineers so that the site of any overheating during a flight can be checked later on the ground. The units 45 to 54 together form a monitor that monitors the effect of closing of the switches 11 to 20.
When the leading edge of the wing is at normal temperatures, all the switches 11 to 20 are open so that the current supplied to opposite ends of the supply line loop 22 is balanced.
The voltages at opposite ends 37 and 38 of the loop 22 are equal and hence the inputs to the comparator 45 are equal. In this condition, the lamps 53 are not illl]min~ted.
If the leading edge of the wing should overheat sufficiently to cause one of the switches 11 to 20 to close, a warning will be provided. For example, if switch 11 should close, the junction between the two resistors 25 and 26 would go to ground so that the current from transistor 40 only flows through one resistor 25, whereas that from the other transistor 41 flows through eleven resistors 36 to 26. This thereby causes the voltage across the left- .
hand end 37 of the supply line 22 to fall, and the voltage across the other end 38 of the supply line to rise. The effect of closing any one of the switches 11 to 30 is illustrated by the table below, where R is the value of each resistance, VL is the voltage at the left-hand end 37 of the loop, VR is the voltage at the right-hand end 38 of the loop, and i is the current flow along each side of the loop:
Closed Switch VL VR
None 6iR 6iR
11 iR lliR
12 2iR lOiR
13 3iR 9iR
14 4iR 8iR
5iR 7iR
16 7iR 5iR
17 8iR 4iR
18 9iR 3iR
19 lOiR 2iR
lliR iR
It can be seen, therefore, by measuring the difference between the two voltages and the sense of difference, that the identity of the closed switch can be determined. As soon as there is a change in voltage on the two ends 37 and 38 of the loop 22, the microprocessor 50 .
causes the appropriate warning lamp 53 to be illllmin~ted depending on which detector 10 is overheated. The identity of the closed switch is shown on the display 54.
When the test switch 39 is operated, the voltage at the left end 37 of the supply loop 22 should drop to zero and that at the right hand end 38 should rise to 12iR. If this fails to occur, the processor 50 determines that a fault has occurred.
It is also possible to identify uniquely the location of a second switch to close. For example, if switch 13 were closed first and then switch 12 were to close, the voltage at the left end 37 of the line 22 would change from 3iR to 2iR, whereas the voltage at the right end 3 8 would remain at 9iR. Depending on the order in which other switches close, it may be possible to detect the location of these, although any switch closing between two already closed switches could not be identified. In general, however, it will only be adjacent switcl1es that close because of the localised heating effect of a leakage.
When the pilot is notified that overheating is occurring, he takes action to rectify this, which should lead to the temperature falling and the tripped switch opening again. The pilot may note the identity of the previously closed switch from the numerical display 54 or he may rely on the ground engineers interrogating the stored log of closed switches contained in the stores 55. This makes it considerably easier to identify the location of any leakage, because the location of the closed switch is known.
~, . 9 The arrangement described above can be installed in an aircraft having a conventional leading edge overheat detection system of the kind shown in Figure 2, without the need to rewire extensively. The modification can be effected easily by replacing the existing warning panel unit with one of the kind shown in Figure 3 and by inserting resistors in the supply loop. The resistors can either be inserted at the terminal blocks to which the heat-responsive switches are connected, or by breaking the line and inserting the resistors using in-line junctions having an encapsulated resistor. This arrangement enables closed switches to be identified without the need for each switch to be connected separately to a monitor by its own cable, thereby avoiding the increased weight and space of additional cabling.
It will be appreciated that the system of the present invention can also be used where the switches are locally grounded, as shown in Figure 1.
Figure 4 shows an alternative arrangement that can be used to enable the identification of a closed switch. In this arrangement, only three switches 141 to 143 are shown, for simplicity. These switches have one terminal connected to a supply line 144, which is modified, as above, by the insertion of four resistors 145 to 148. The other terminals of the switches 141 to 143 are connected to a loop 150. In a conventional installation, this loop 150 would be an earth loop but in the present arrangement, it is disconnected from earth and instead is connected to a voltage-measuring and processmg unit 151. A voltage source 152, which is preferably an ac source, but could be a dc source, is connected across the supply line 144. In this arrangement, the four resistors 145 to 148 act as a potentiometer so that, when one of the heat-responsive switches closes, it applies a different voltage to the loop l SO and hence to the processing unit 151. The processing unit 151 measures the voltage and, from this, determines which switch is closed.
Claims (15)
1. An aircraft temperature monitoring system comprising: an electrical supply unit; a plurality of temperature-responsive switches each having two terminals; a monitor unit; a supply line connected with said supply unit; a connection between one of said terminals of each said switch and said supply line; a connection between another of said terminals of each said switch and a potential different from said supply line; a connection between said monitor unit and said switches; and a resistor associated with each said switch such that closing of a switch causes current flow through the switch and a different voltage to be applied to said monitor unit, such that said monitor unit can determine the identity of the closed switch.
2. A system according to Claim 1, wherein said supply line is formed in a first loop having two opposite ends, and wherein said resistors are connected in series in said loop.
3. A system according to Claim 2, wherein said supply unit includes two sources of constant current, wherein the system includes a connection between each said source and respective ends of said first loop, and wherein the monitor unit is connected to monitor the voltage at opposite ends of said first loop.
4. A system according to Claim 2 including an even number of switches, wherein two of said resistors are connected between a middle two of said switches around said first loop.
5. A system according to Claim 1, wherein each said resistor has the same value.
6. A system according to Claim 1 including a second loop at said potential different from said supply line, and wherein the other terminal of each of said switches is connected to said second loop.
7. A system according to Claim 6, wherein said second loop includes a manually-operated test switch that normally closes said second loop but can be switched to open said second loop and connect it to said supply line.
8. A system according to Claim 2, wherein said supply unit includes a voltage source, wherein the opposite ends of said first loop are connected across said voltage source, and wherein said monitor unit is connected to the other terminal of said switches so that closing of each switch causes a different voltage to be applied to said monitor unit.
9. A system according to Claim 8, wherein said voltage source is an ac source.
10. A system according to Claim 1, wherein each of said switches is responsive at the same temperature.
11. A system according to Claim 1, wherein some of said switches are responsive at different temperatures.
12. A system according to Claim 1 including a store arranged to store an indication of which switch has been closed.
13. An aircraft temperature monitoring system comprising: an electrical supply unit; a monitor unit; a plurality of temperature-responsive switches having two terminals; a supply line loop having two ends and a plurality of series-connected resistors; a connection of opposite ends of said loop to said supply unit; a connection of one of said terminals of each said switch to a junction between two of said resistors in said loop; a second line at a different potential from said supply line; a connection of said monitor unit with said switches; a connection of the other of said terminals of each said switch to said second line such that closing of a switch causes current flow through the switch and a different voltage to be applied to said monitor unit, such that said monitor unit can determine the identity of the closed switch.
14. An aircraft temperature monitoring system comprising: an electrical supply unit including two constant current sources; a monitor unit; a plurality of temperature-responsive switches having two terminals; a supply line loop having two ends and a plurality of series-connected resistors; a connection of opposite ends of said loop to respective ones of said constant current sources; a connection of one of said terminals of each said switch to a different location between said resistors in said loop; a second line at a potential different from said supply line; a connection of opposite ends of said supply line loop with said monitor unit; and a connection of the other of said terminals of each said switch to said second line such that closing of a switch causes current flow through the switch and a different voltage to be applied to said monitor unit, such that said monitor unit can determine the identity of the closed switch.
15. An aircraft temperature monitoring system comprising: a voltage source; a monitor unit; a supply line loop having opposite ends connected with said voltage source; a plurality of resistors connected in series in said supply line loop; a plurality of temperature-responsive switches having one terminal connected to said supply line loop at locations between different ones of said resistors and another terminal connected with said monitor unit such that closing of a switch causes current flow through the switch and a different voltage to be applied to said monitor unit, such that said monitor unit can determine the identity of the closed switch.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9609046 | 1996-05-01 | ||
| GBGB9609046.9A GB9609046D0 (en) | 1996-05-01 | 1996-05-01 | Aircraft temperature monitoring |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2203447A1 true CA2203447A1 (en) | 1997-11-01 |
Family
ID=10792960
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2203447 Abandoned CA2203447A1 (en) | 1996-05-01 | 1997-04-23 | Aircraft temperature monitoring |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA2203447A1 (en) |
| DE (1) | DE19717767A1 (en) |
| FR (1) | FR2748324A1 (en) |
| GB (1) | GB9609046D0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT201800006157A1 (en) * | 2018-06-08 | 2019-12-08 | TEMPERATURE SENSOR TAPE |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20230287802A1 (en) * | 2022-01-27 | 2023-09-14 | Rohr, Inc. | Leak detection system for anti-ice ducts |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4037463A (en) * | 1974-07-10 | 1977-07-26 | Showa Denko Kabushiki Kaisha | Temperature-detecting element |
| US4514619A (en) * | 1982-09-30 | 1985-04-30 | The B. F. Goodrich Company | Indirect current monitoring via voltage and impedance monitoring |
| EP0164838B1 (en) * | 1984-06-07 | 1990-08-08 | RAYCHEM CORPORATION (a Delaware corporation) | Event location using a locating member containing discrete impedances |
| DE3719988A1 (en) * | 1987-06-15 | 1988-12-29 | Total Feuerschutz Gmbh | INDIVIDUAL IDENTIFICATION |
-
1996
- 1996-05-01 GB GBGB9609046.9A patent/GB9609046D0/en active Pending
-
1997
- 1997-04-23 CA CA 2203447 patent/CA2203447A1/en not_active Abandoned
- 1997-04-26 DE DE1997117767 patent/DE19717767A1/en not_active Withdrawn
- 1997-04-28 FR FR9705433A patent/FR2748324A1/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT201800006157A1 (en) * | 2018-06-08 | 2019-12-08 | TEMPERATURE SENSOR TAPE | |
| WO2019234704A1 (en) * | 2018-06-08 | 2019-12-12 | Tenet S.R.L. Con Unico Socio | Temperature sensing tape |
Also Published As
| Publication number | Publication date |
|---|---|
| DE19717767A1 (en) | 1997-11-06 |
| FR2748324A1 (en) | 1997-11-07 |
| GB9609046D0 (en) | 1996-07-03 |
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| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |