Leakage detection and compensation system
View Patent ↗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.
1. A method of operating a flame sensing system comprising:
providing a flame sensing system, the flame sensing system comprising:
a signal generator; and
a controller;
providing a flame excitation signal from the signal generator, the signal having a frequency set at a first frequency;
determining at least one characteristic of the flame signal;
adjusting the frequency of the flame excitation signal to a next frequency;
determining the at least one characteristic of the flame signal at the next frequency;
applying a compensated value to the at least one characteristic at the next frequency;
comparing the at least one characteristic at the first frequency to the compensated value of the at least one characteristic at the next frequency;
storing a change and/or ratio between the at least one characteristic at the first frequency to the compensated value of the at least one characteristic at the next frequency in a memory; and
using the controller to control the flame sensing system if the change and/or ratio in the at least one characteristic of the flame signal stored is outside a threshold range.
2. The method of claim 1 , wherein the at least one characteristic of the flame excitation is an amplitude of a flame current.
3. The method of claim 1 , wherein the storing a change stores a ratio of the at least one characteristic of the flame signal at different frequencies in a history file to monitor contamination of a sensing rod.
4. The method of claim 1 , wherein the controller controls the flame sensing system by varying an excitation signal strength.
5. The method of claim 1 , wherein the controller controls the flame sensing system by providing a warning signal.
6. The method of claim 1 , wherein an effect of contamination is indicated by a change of the ratio of the at least one characteristic at different frequencies.
7. The method of claim 1 , wherein the controller compensates the effect of rod contamination by varying an excitation signal strength.
8. The method of claim 1 , wherein the at least one characteristic of the flame signal is a flame current.
9. The method of claim 1 , further comprising connecting at least one additional component to the flame sensing system.
10. The method of claim 9 , further comprising:
storing a change and/or ratio between the at least one characteristic at the first frequency to the at least one characteristic at the next frequency after calibration in a memory.
11. The method of claim 10 , wherein the storing a change stores a ratio of the at least one characteristic of the flame signal at different frequencies in a history file to monitor contamination.
12. The method of claim 10 , wherein the controller controls the flame sensing system by varying an excitation signal strength.
13. The method of claim 10 , wherein the controller controls the flame sensing system by providing a warning signal.
14. The method of claim 10 , wherein an effect of contamination is indicated by a change of a ratio of the at least one characteristic at different frequencies.
15. The method of claim 10 , wherein the controller compensates the effect of rod contamination by varying an excitation signal strength.
16. The method of claim 10 , wherein the at least one characteristic of the flame signal is a flame current.
17. The method of claim 1 , wherein the at least one characteristic of the flame signal is stored in memory.
18. The method of claim 1 , wherein the at least one additional component connected to the flame signal system is a capacitor that varies filtration and response time of the system.
19. The method of claim 1 , wherein a frequency that produces the higher flame current is used for flame sensing.
20. The method of claim 1 , wherein a frequency that produces the acceptable flame current and fast system response time is used for flame sensing when fast response is needed.