5

Description of sample switching system

The measured gas is divided into two, and in one of the

flow paths, a high performance converter is provided to con-

vert carbon monoxide into carbonic acid gas. Here, the

carbon monoxide in the measured gas is eliminated and the

gas is led into one cell of the high-sensitivity infrared ana-

lyzer. In the other flow path, the gas is led directly into the

other cell of the analyzer.

These flow paths are changed over via changeover valves

SV

valve drive signal transmitted from the analyzer. By carry-

ing out this changeover cyclically, the output of the ana-

lyzer varies with the concentration of the carbon monoxide

in the measured gas. Use of the obtained variation width

as a measured value enables improving the S/N ratio and

eliminating the effect of interfering components plus zero

drift.

Infrared light source

(single light source)

Motor

Rotary sector

(one-point chopper)

Sector synchronous

signal

Alarm output

Range identification signal

Calibration output

SV drive signal

Remote range input

External hold input

(Option)

Output,

0 to 1V or

4 to 20mA

DC

Operating key

Sample

gas inlet

Sample cell

AC voltage

amplifier

Sample

gas outlet

Gain

changeover

A/D

CPU

Relay drive signal

Indicator

Indication

D/A

Contact input,output

RAM

ROM

Distribution cell

(interference filter)

Interference compensating

detector

Trimmer

Reference cell

Reference

gas inlet

Reference

gas outlet

CO

measured

gas

1ry filter

Pump

Reference gas

Temperature

controller

converter

Flowrator

2ry filter

ZRG3

Reference

cell

Sample

cell

Sample

switching

type analyzer

Relay

Output signal