COMBUSTIBLE GAS SENSORS. CATALYTIC BEAD GAS SENSORS (CiTipeLs) FOR MEASURING THE CONCENTRATION OF COMBUSTIBLE GASES. THE SENSORS OPERATE ON THE CATALYTIC BEAD PRINCIPAL, WHEREBY TWO BEADS ARE USED. EACH CONSISTS OF A PLATINUM WIRE COIL COATED IN A CATALYST MATERIAL. ONE BEAD IS REACTIVE TO COMBUSTIBLE GASES (DETECTOR) AND THE SECOND IS INERT (COMPENSATOR) AND PROVIDES A REFERENCE TO ENVIRONMENTAL CONDITIONS, WHICH CAN EFFECT THE OUTPUT. WHEN MOUNTED IN A WHEATSTONE BRIDGE ELECTRICAL CIRCUIT WITH AN INSTRUMENT, THE ELECTRICAL POWER HEATS THE ELEMENTS TO A POINT WHERE COMBUSTIBLE GASES CAN BE OXIDISED ON THE DETECTOR. WITH NO GAS PRESENT, THE RESISTANCES OF THE TWO ELEMENTS ARE IN BALANCE, BUT IN THE PRESENCE OF GAS, THE TEMPERATURE AND HENCE THE RESISTANCE OF THE DETECTOR CHANGES. THIS CAN BE MEASURED AND IS PROPORTIONAL TO THE GAS CONCENTRATION. THE GAS SENSORS ARE SOLD AS A COMPONENT TO OEM EQUIPMENT, THAT INCORPORATE THE SENSOR FOR GAS MONITORING AND MEASURING APPLICATIONS.

GIR1 TERMS OF HEADING 9026 INCLUDES INSTRUMENTS AND APPARATUS FOR MEASURING OR CHECKING THE FLOW, LEVEL, PRESSURE OR OTHER VARIABLES OF LIQUIDS OR GASES. GIR6 TERMS OF ONE DASH SUBHEADING 902680, OTHER INSTRUMENTS AND APPARATUS. CN CODE 90268080, OTHER THAN ELECTRONIC.