Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 17)

<1. Overview>
1-3
IM 11M12A01-02E 8th Edition : Jan.13,2012-00
1.1.3 System 3
This example, System 3, represents typical applications in 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.
System 3 uses the ZR40H automatic calibration unit, with auto-switching of the calibration gas.
A “combustible gas detected” contact input turns off power to the heater. There’s also contact
output from the converter that can be used to operate a purge gas valve to supply air to the
sensor.
F1-3E.ai
ZR22G Separate type
Zirconia Oxygen Analyzer, Detector
ZR402G Converter
Signal
(6-core shield cable)
Heater (2-core)
Reference gas
Calibration gas
Flowmeter Needle
valve
Zero gas cylinder
100 to 240 V AC
*3
Check valve
Contact input
Analog output, contact output
Digital output (HART)
Air Set
lnstrument air
Pressure
reducing
valve
EXA ZR402G
*1
*2
~
Calibration gas
unit case
ZR40H
Automatic Calibration Unit
*1 Shield cable ; Use shielded signal cables, and connect the shield to the FG terminal of the converter.
*2 Select the desired probe from the Probe Configuration table on page 1-4.
*3 When a zirconia oxygen analyzer is used, 100% N2 gas cannot be used as the zero gas. Use approximately 1% of O2 gas
(N2-based).
Figure1.3