10 Product Specifications
10-3. Detection principle
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SD-2600
A
Y
X
B
SW
VR
E
10-3. Detection principle
When a combustible gas burns on the surface of a highly active oxidation catalyst in catalytic combustion,
the contact burning-type sensor measures resultant temperature changes by measuring the resistance
changes in the heat-resistant alloy wire coil.
The sensor consists of two elements: A detecting element having a heat-resistant alloy wire coil with an
ultrafine particle oxidation catalyst sintered on it together with a carrier and a temperature-compensating
element with a mixture of gas-inert alumina and glass sintered on it.
When a combustible gas comes into contact with the surface of the detecting element with oxidation
catalyst sintered on it, the gas burns, causing the temperature to rise. In accordance with this temperature
change, there occurs a change in the resistance of a heat-resistant alloy wire coil that constitutes the
element. These resistance values are approximately proportional to gas concentrations. From the changes
in the resistance values, potential differences are obtained using a bridge circuit and displayed as gas
concentrations on the meter.
[Structure]
[Principle]
Heat-resistant alloy wire coil
1.3 - 1.8 mm
Oxidation catalyst
Alumina
1.4 - 1.6 mm
C: Compensating
element
D: Detecting element
M
Power supply
Variable resistor for bridge
equilibrium adjustment
Switch
Variable resistor for bridge
voltage adjustment
Fixed
resistance
Fixed
resistance
