Leakage current noise reduction for ionization chamber based alarms
AssigneeMicrochip Technology Incorporated
InventorsArthur Eck, Patrick McFarland, Jonathan Corbett
Life of this patent
Estimating the term…
Abstract
As an example, an apparatus may include: an ionization chamber, a voltage source to drive the ionization chamber; a voltage sensor to measure an ionization chamber output voltage; a calibration circuit to compensate the ionization chamber output voltage based on a correction factor; and a monitoring circuit to trigger an alarm if the compensated output voltage meets a predetermined condition. The calibration circuit may determine the correction factor to compensate for any leakage current affecting the ionization chamber output voltage.
Claims25
An apparatus comprising:
- an ionization chamber;
- a voltage source to drive the ionization chamber;
- a voltage sensor to measure an ionization chamber output voltage;
- a control sense driver to drive a floating control sense line electrically isolated from the ionization chamber;
- a current sensor to measure output current through the control sense driver;
- a calibration circuit to compensate the ionization chamber output voltage based on a correction factor;
- and
- a monitoring circuit to trigger an alarm if the compensated output voltage meets a predetermined condition;
- wherein the calibration circuit is operable to determine the correction factor to compensate for any leakage current affecting the ionization chamber output voltage, wherein the correction factor is based at least in part on the measured output current through the control sense driver.
A smoke detector comprising:
- an ionization chamber;
- an inlet to provide a sample to the ionization chamber;
- a voltage source to drive the ionization chamber;
- a voltage sensor to measure an ionization chamber output voltage;
- a control sense driver to drive a floating control sense line electrically insulated from the ionization chamber;
- a current sensor to measure output current through the control sense driver;
- a calibration circuit to compensate the ionization chamber output voltage based on a correction factor;
- and
- a monitoring circuit to trigger an alarm if the compensated output voltage meets a predetermined condition;
- wherein the calibration circuit is operable to determine the correction factor to compensate for any leakage current affecting the ionization chamber output voltage, wherein the correction factor is based at least in part on the measured output current through the control sense driver.
A method comprising:
- driving an ionization chamber with a voltage source;
- measuring an ionization chamber output voltage with a voltage sensor;
- driving a lead to a second voltage different from the ionization chamber output voltage, the lead electrically insulated from the ionization chamber;
- measuring a reaction to the second voltage;
- analyzing the reaction and based on the reaction, determining a correction factor to compensate for any leakage current affecting the ionization chamber output voltage, wherein the leakage current includes current across a printed circuit board (PCB) from the voltage source to the voltage sensor;
- applying the correction factor to the signal with a calibration circuit;
- comparing the compensated signal to a predetermined criterion, wherein the predetermined criterion includes an alarm condition;
- and
- responding to the alarm condition if the compensated signal meets the predetermined criterion.
Dependencies are inferred from the claim text.