| abstract |
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. n 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. n 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). n 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. n 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. |