Leakage detection and compensation system

• US 8,659,437 B2
• Filed: 07/06/2010
• Issued: 02/25/2014
• Est. Priority Date: 05/12/2005
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Chian, Brent
• Primary Examiner(s): La, Anh V
• Application Number:
  US12/831,016
• Publication Number:
  US 20100265075A1
• Time in Patent Office: 1,330 Days
• Field of Search: 340577-584, 340/693.5, 340/511, 340/507, 340660-664, 340/593, 431/6, 431/24, 431/75, 431/76, 431/77, 327/113, 327/512, 327/518, 361/253
• US Class Current: 340/577
• CPC Class Codes: F23N 2229/12 with flame rectification current detecting means
• CPC Class Codes: F23N 5/123 using electronic means
• CPC Class Codes: F23N 5/24 Preventing development of abnormal or undesired conditions, i.e. safety arrangements F23N5/02 - F23N5/18 take precedence

Abstract

A flame sensing system having a flame rod, a signal generator, a signal measurement circuit, and a controller, where the frequency and/or amplitude of the excitation signal may be variable. The signal measurement circuit may include a bias circuitry that references the flame signal to a voltage, a capacitor that varies the filtration, an AC coupling capacitor, a current limiting resistor, and a low-pass filter. The system may determine the flame-sensing rod contamination, the stray capacitance of the flame sensing system, and compensate for stray capacitance in the flame sensing system. The flame model may include a circuit that simulates a flame in the presence of the sensing rod, and another circuit that simulates a contact surface between the flame and the sensing rod.

Claims

1. A flame sensing system comprising:

a flame rod;

a signal generator that generates an excitation signal for the flame rod;

a signal measurement circuit connected to the signal generator and the flame rod; and

a controller to control frequency and/or amplitude of the excitation signal; and

wherein the signal measurement circuit comprises;

a bias circuitry, connected to the controller and signal measurement circuit, that references a flame signal to a voltage;

a low pass filter that varies a filtration of the flame signal, connected to the bias circuitry and the flame rod; and

an AC coupling capacitor connected to the signal generator and the flame rod.

2. The system of claim 1, further comprising a current limiting resistor connected in series with the AC coupling capacitor.

3. The system of claim 1, further comprising a capacitor coupled between the controller and a node disposed between the low pass filter and the bias circuitry, wherein the capacitor may be attached or unattached electrically as controlled by the controller.

4. A flame sensing system comprising:

a flame rod;

a signal generator that generates an excitation signal for the flame rod;

a signal measurement circuit connected to the signal generator and the flame rod; and

a controller to control frequency and/or amplitude of the excitation signal; and

wherein the signal measurement circuit comprises;

a bias circuitry, connected to the controller and signal measurement circuit, that references a flame signal to a voltage;

a low pass filter that varies a filtration of the flame signal, connected to the bias circuitry and the flame rod;

an AC coupling capacitor connected to the signal generator and the flame rod; and

a current limiting resistor connected in series with the AC coupling capacitor.