User's Manual for CM6G - Yokogawa

Principle of Measurement< Principle of Measurement> 1The instrument is to detect the temperature difference, using a thermocouple, between the exhaustcombustion gas made after sample gas is burnt in the burner, and the feed air at the inlet of theburner, then amplify and add the compensating calculation to the output signal and measure thecalorific value of WI.DIFFERENTIALPRESSUREDETECTIONBURNINGMIXINGGASBLOWAIRPRIMARYSECONDARYTERTIARYCOMPENSATINGCALCULATIONAIRDIVIDINGOUTPUTSIGNALFigure 1.1 Measurement principle diagramWhen the sample gas is burnt by the air, the formula of the increased temperature is as follows:K • Fg∆θ = (1.1)Cps • Fswhere K:Fg:Fs:Cps:Calorific value of the sample gasFlow rate of the sample gasAir-diluted combustion exhaust gas flow rateConstant pressure heat ratio of air-diluted combustion exhaust gasAir flow rate Fa is big enough compared with the sample gas flow rate Fg (Fa:Fg=50-200:1) andCps ─~ Cpa, Fs ─~ Fa+Fg=Fa ( 1 + g ), therefore, the formula (1.1) is as follows:K • Fg∆θ = (1.2)Cpa • Fa (1 + g)where Fa:Cpa:Air flow rateAir constant pressure heat ratiog: Fg/FaIM 11R02A01-02E