Instruction manual

SM425 INSTRUCTION MANUAL 1.0 OVERVIEW
Figure 1-1 System 1
1.1.2 System 2
This system is for monitoring and controlling oxygen concentration in the combustion gases of a large-
size boiler or heating furnace. Clean (dry) air (21% O
2
) is used as the reference gas and the span gas for
calibration. Zero gas is fed in from a cylinder during calibration. The gas flow is controlled by the ZA8F
flow setting unit (for manual valve operation).
Figure 1-2 System 2
1.1.3 System 3
System 3 represents a typical analyzer configuration application for large boilers and heating furnaces,
where there is a need to monitor and control oxygen concentration. The reference gas and calibration-
time span gas are (clean, dry) instrument air. Zero gas is supplied from a gas cylinder.
Figure 1-3 shows the SM425CAL autocalibration unit, with auto-switching of the calibration gas. An
external “combustible gas detected” signal is conncected to one of the converter input contacts to turn off
power to the heater. A converter output contact is used to operate a purge gas valve to supply air to the
sensor prior to warm-up.
2 42500001 REV A