DETECTOR

• US 20100027583A1
• Filed: 11/20/2007
• Published: 02/04/2010
• Est. Priority Date: 02/06/2007
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Thorn Security Limited (Johnson Controls International plc)
• Inventors: Randall, Dave John, James, Timothy Andrew
• Granted Patent: US 9,134,180 B2
• Time in Patent Office: Days
• US Class Current: 374/164
• CPC Class Codes: G01J 1/0252 Constructional arrangements for compensating for fluctuations caused by, e.g. temperature, or using cooling or temperature stabilization of parts of the device; Controlling the atmosphere inside a photometer; Purge systems, cleaning devices protection against electromagnetic interferences G01J2001/0276
• CPC Class Codes: G01J 2005/063 Heating; Thermostating
• CPC Class Codes: G01J 5/0014 for sensing the radiation from gases, flames
• CPC Class Codes: G01J 5/0018 Flames, plasma or welding
• CPC Class Codes: G01J 5/061 by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
• CPC Class Codes: G01J 5/064 Ambient temperature sensor; Housing temperature sensor; Constructional details thereof
• CPC Class Codes: G01J 5/34 using capacitors, e.g. pyroelectric capacitors

Abstract

A detector comprises a housing (1), a pyroelectric array sensor (2) mounted within the housing, a heater (4) associated with the pyroelectric array sensor, and control means (6) for varying the power supplied to the heater to control the temperature of the pyroelectric array sensor relative to the ambient temperature in order to minimise the rate of change of temperature of the pyroelectric array sensor and to keep a predetermined difference between the temperature of the pyroelectric array sensor and the ambient temperature.

Claims

1-17. -17. (canceled)

18. A detector comprising:

a housing;

a sensor mounted within the housing;

a heater positioned adjacent to the sensor; and

control means for varying power supplied to the heater to control the temperature of the sensor relative to ambient temperature in order to minimize a rate of change of temperature of the sensor.

19. A detector as claimed in claim 18, wherein the control means controls the power supplied to the heater in such a manner as to adjust the temperature of the sensor to establish a predetermined difference above ambient temperature at a controlled rate, while minimizing power consumption of the detector.

21. A detector as claimed in claim 19, wherein the control means is such as to vary the predetermined temperature difference according to the ambient temperature.

22. A detector as claimed in claim 21, wherein the control means is such that the predetermined temperature difference reduces to zero when the ambient temperature is sufficiently high that the sensor is able to cope with expected variations in the ambient temperature without power being supplied to the heater.

23. A detector as claimed in claim 18, wherein the heater is fixed to one surface of the sensor.

24. A detector as claimed in claim 23, wherein the heater is constituted by at least one thick film resistive element printed onto said surface of the sensor.

25. A detector as claimed in claim 18, wherein the control means is constituted by a microcontroller which controls the supply of power to the heater via a heater drive circuit.

26. A detector as claimed in claim 25, further comprising a first temperature sensing element for sensing the temperature of the sensor, and a second temperature sensing element mounted in the housing remote from the heater for sensing the ambient temperature, both temperature sensing elements providing output signals to the microcontroller.

27. A detector as claimed in claim 26, wherein the first temperature sensing element is integrated within the sensor.

28. A detector as claimed in claim 25, wherein the microcontroller is programmed with software which permits the microcontroller to track the ambient temperature, to compare the ambient temperature with the temperature of the sensor, and to control the heater drive circuit to supply sufficient power to the heater to control the temperature of the sensor relative to the ambient temperature in order to minimize the rate of change of temperature of the sensor.

29. A detector as claimed in claim 25, wherein the microcontroller is programmed so as to apply a nominal power level to the heater to maintain the temperature of the sensor at the predetermined temperature difference.

30. A detector as claimed in claim 25, wherein the microcontroller is programmed so as to minimize the power required by the heater in comparison to the power that would be required to keep the sensor at a fixed temperature.

31. A detector as claimed in claim 18, wherein the sensor is a flame detector sensor which is positioned within the housing adjacent to a window through which the sensor can detect an external flame.

32. A detector as claimed in claim 23, wherein the sensor is a flame detector sensor which is positioned within the housing adjacent to a window through which the sensor can detect an external flame, and wherein said one surface of the sensor faces away from the window, the opposite surface of the sensor constituting means for sensing an external flame.

20. A detector as claimed in claimed 19, wherein the predetermined temperature difference is dependent upon the largest temperature change that the detector has been designed to sustain in its intended operating environment.

33. In a detector comprising a housing, and a pyroelectric array, a sensor mounted within the housing, a method comprising the steps of:

sensing ambient temperature within the housing;

sensing temperature of the pyroelectric array sensor; and

varying power supplied to a heater positioned adjacent to the pyroelectric array sensor to control the temperature of said sensor relative to ambient temperature while minimizing a rate of change of temperature of said sensor.