11 Appendix
11-1. Detection principle of galvanic cell type
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11
11
Appendix
11-1. Detection principle of galvanic cell type
By immersing precious metal and lead in electrolyte and connecting them with a lead wire, a battery can be
made (galvanic cell).
When oxygen passes through the barrier, deoxidizing reaction occurs at the precious metal electrode while
oxidizing reaction occurs at the lead electrode.
The electric current generated by this reaction goes through load resistance (thermister), where it is
converted into voltage so that it can be read. When the oxygen concentration is decreased, deoxidizing
reaction at the precious metal electrode is also decreased, thus lowering the voltage at both ends of the
thermister.
<Structure Diagram>
Important precautions
1. The readings of the monitor fluctuate slightly in response to changes in the air pressure. In particular,
be careful of alarm activation when a low air pressure is brought in by typhoon, etc.
In addition, it may be fluctuated by environmental (temperature, humidity, etc.) changes in the
installation site.
2. The alarm must be set within a range where the performance of the monitor can be ensured. The
standard alarm setpoint values are 18 vol% for the first and 19 vol% for the second.
3. This is a safety unit. This is not a control unit.
The alarm contact output of the monitor must be used for an external alarm lamp/buzzer, while the
analog signal output must be used for an indicator or external recorder. If these outputs are used to
control other units, we shall not be responsible for any malfunctions.
4. For maintenance of the monitor, it must go through a regular maintenance, including replacement and
adjustment of the regular replacement parts as specified in the operating manual. In addition, because
this is a safety unit, it is recommended that a regular maintenance and span adjustment are performed
every six months.
Barrier
Negative
electrode
Electrolyte
Output terminal
Thermister
Positive
electrod
