The present invention provides very small low cost apparatus and method for determining the concentration and / or
hazard from a target gas by means of optically monitoring one or more sensors that responds to
carbon monoxide. The apparatus comprises a
photon source optically coupled to the sensor and the
photon intensity passing through the sensor is quantified by one or more
photodiode(s) in a
system, so that the
photon flux is a function of at least one sensor's response to the target gas, e.g., transmits light through the sensor to the
photodiode. The
photocurrent from the
photodiode is converted to a sensor reading value proportional to the optical characteristics of the sensors and is loaded into a
microprocessor or other logic circuit. In the
microprocessor, the sensor readings may be differentiated to determine the rate of change of the sensor readings and the total photons absorbed value may be used to calculated the CO concentration.There are a number of methods to compute the CO
hazard and these is subject of another patent to be filed. In addition, a preferred method to meet the BSI and European CO Standards is described using two sensor systems with two different sensors each having different sensitivity within one housing. The single housing
dual sensor uses one LED and two photodiodes. The novel two sensors method to meet the European (BSI) CO standard is similar to the method developed to meet the Japanese standard.The major advantages of MICROSIR over SIR are: 1. Lower cost (estimates saving of US$1.25 per sensor, 2. Better controlled gas path therefore more accurate and more precision, 3. Better
getter system therefore longer life (as shown by
ammonia accelerated age tests), and 4. Better
RESERVOIR SYSTEM THEREFORE BETTER
humidity CONTROL AT BOTH LOW AND HIGH (as shown by sensor response curves).5. The MICROSIR Edgeview is faster and meets the Japanese standard for CO and the
European Standard for CO enhanced
smoke, 6. More easily automated as the board of alarms use surface
mount and MICROSIR is a surface
mount part that attaches over surface mounted
optics after the
soldering, 7. small size, and 8. approved UL recognized component.The MICROSIR device can also be used to detect the CO, which may be combined with temperature and
smoke in a very small
package. The detection of one or more indicators such as
smoke and CO; increases the sensitivity of the other indicators. Combining signals produces an improved
fire detector comprising a CO sensor and a smoke sensor in one unit. The smoke detection sensor may be either
ionization or photoelectric either or both may be combined with the CO sensor to provide earlier warning to fire and reduce false alarms.