2.2. Sensing head
The sensing element of the DAT 420 gas detector is an electrochemical sensor operating accord-
ing to the amperometry principle. The sensor detects gas by producing a chemical reaction be-
tween gas and oxygen contained in the sensor. This reaction produces a small current which is
proportional to the concentration of the gas. That small current is then measured and converted by
the 4-20 mA transmitter of the DAT 420.
The sensing head of the DAT 420 consists of:
▪ A flameproof “d” sensor housing (base + body + top).
▪ A sintered metal filter.
▪ A sensor gasket.
▪ An electrochemical sensor.
▪ A 4-20 mA transmitter.
The sensor housing is a stainless steel assembly (base, body and top) which can be dismantled to
allow plug-in sensor or sintered metal filter replacement.
Figure 3: sensing head
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