- 141 - GD-70D
<Hot-Wire Semiconductor Type>
The hot-wire semiconductor type sensor detects a change in resistance of the platinum wire coil integrated in
a metal oxide semiconductor whose resistance value changes by contact with a gas as gas concentration.
This is a highly sensitive gas detection sensor suitable for low concentrations.
Special precautions for this principle
1. This detector may be interfered by gases other than the gas to be detected and vapors.
Please note that the alarm may be triggered by interference. 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 detector can be ensured.
In facilities compliant with the High Pressure Gas Safety Act, an alarm setting below our standard alarm
setpoint may trigger a false alarm.
3. This is a safety unit, not a control unit.
The alarm contact output of the detector 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. The gas sensing part of the gas detection sensor installed in the detector is made of porous sintered
alloy. If silicon or sulfide compounds are accumulated on the surface of porous sintered alloy, the area
of the gas sensing part becomes smaller, which may result in serious deterioration of its sensitivity.
For safety reasons, do not use the detector under the presence of silicon or sulfide compounds even
though their amount is very small.
5. It is recommended that a regular maintenance and sensitivity calibration are performed for every six
months.
Basic Circuit
0.4 - 0.8 mm
Metal oxide sintered alloy
0.5 - 1.0 mm
Fixed
resistance
Fixed
resistance
C: Compensating
element
Variable resistor for bridge
equilibrium adjustment
Variable resistor for bridge
voltage adjustment
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