O2 ANALYSER IS USED TO READ THE CINCENTRATION OF O2 IN THE INERT GAS COMING OUT OF THE BOILER UPTAKE TO BE SENT TO THE IG MAIN LINE. THERE ARE 2 TYPEA OF MOST COMMON OXYGEN ANALYSERS:-
- PARAMAGNETIC SENSORS:– O2 IS A HIGHLY PARAMAGNETIC GAS THAN OTHER COMMON GASES. IN THIS TYPE OF ANALYSER THERE IS A SAMPLE CELL IN WHICH A LIGHTWEIGHT BODY IS SUSPENDED IN A MAGNETIC FIELD. WHEN SAMPLE GAS IS DRAWN THROUGH THE CELL THE SUSPENDED BODY EXPERIENCES A TORQUE PROPORTIONAL TO THE MAGNETIC SUSCEPTIBILITY OF THE GAS. AN EQUAL AND OPPOSING TORQUE IS PRODUCED BY AN ELECTRIC CURRENT PASSING THROUGH A COIL WOUNDED ROUND THE SUSPENDED BODY. THE EQULISING CURRENT IS A MEASURE OF THE MAGNETIC FORCE AND IS THUS A MEASURE OF THE MAGNETIC SUSCEPTIBILITY OF THE SAMPLE I.E RELATED TO ITS OXYGEN CONTENT.
- ELECTROCHEMICAL SENSORS :- THIS DETERMINES THE O2 CONTENT OF A GAS MIXTURE BY MEASURING THE OUTPUT OF AN ELECTROCHEMICAL CELL. O2 DIFFUSES THROUGH A MEMBRANE INTO THE CELL CAUSING CURRENT TO FLOW BETWEEN 2 SPECIAL ELECTRODES SEPERATED BY A LIQUID OR GEL ELECTROLYTE. THE CURRENT FLOW IS RELATED TO THE O2 CONCENTRATION IN THE SAMPLE AND THE SCALE IS ARRANGED TO GIVE A DIRECT INDICATION OF O2 CONTENT.