*1 Teflon tubing is recommended. However, this may differ if the unit is to be used to detect highly adsorbent
gases. Contact your authorized dealer for information and assistance. For product improvement purposes,
the preceding specifications may be subject to change without notice. Any specifications issued separately
take precedence over those stated above.
Chapter 12 – Warranty
New Cosmos Electric Company Limited, warrants its gas detection products against any defects in materials
and workmanship under normal use and operating conditions, for a period of one year from the date of
purchase. (Except toxic and oxygen sensor unit)
All obligations and liabilities under this product warranty are limited to repairing or replacing at the
manufacturer’s option of the allegedly defective items returned to us, with carrier charges prepaid. All repairs
and replacements are made subject to our factory inspection of the returned items.
No liability is accepted for the consequential damages or reinstallation labor. Defects as defined in the above
shall not include decomposition by chemical reaction (including corrosion).
New Cosmos Electric Company Limited, shall not assume responsibility for contingent liability arising from
alleged failure of any of its products and accessories.
Chapter 13 – Detection Principles
13.1 Electrochemical Sensor
In an electrochemical method, electrolytic reactions are carried out selectively on target composite gases,
and the ensuing electrolytic current is measured by a gas sensor.
The gas sensor consists of three electrodes (active, reference, and counter electrodes), electrolyte, and a
potentiostat circuit. The electrode is a gas permeable membrane (to permeate gas and not electrolyte)
treated with a catalyst. When SiH4 contacts the active electrode, the following reaction occurs on the
electrode:
SiH
4
+4H
2
O→H
4
SiO
4
+8H
+
+8e
−
(1)
while the following reaction occurs on the counter electrode:
2O
2
+8H
+
+8e
−
→4H
2
O (2)
and current flows to the external circuit. To make the reaction selective and the generated current
porportional to the concentration of SiH4, the potential of the active electrode is detected by the reference
electrode and, during the electrolysis reaction, the active electrode is maintained at a constant potential by
the potentiostat circuit. (Refer to the following illusration.)
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