An electro-optic hybrid methane sensor

A novel electro-optic hybrid instrument for methane concentration measurements is presented. Compared with conventional fiber optic instruments for methane concentration using infrared absorption in the 1.3 mum and 1.66 mum bands, this instrument overcomes the spectral limitations of optical fibers allowing for the absorption measurements in the 3.3 mum band. Since 3.3 mum is the wavelength corresponding one of the two fundamental frequencies of the methane infrared spectrum, the absorption in this band is significant and consequently the sensorpsilas sensitivity is higher. Furthermore using the higher wavelength decreases the scattering factor so that the influence of the hard impurities in the atmosphere is decreased also. Since the application of the sensor is expected to be in the hazardous and explosive atmospheres some investigations to define the maximum optical power level were performed. Due to the relatively low power level allowed for the explosion safety some special low power consumption algorithms of the signal processing were implemented. Owing to these algorithms the need of ADC and microcomputer is discarded in the remote module. Thus power consumption of the remote module is minimized allowing for the use of cost effective components for optical powering and providing the explosion safety in hazardous areas.