Gas Sensor in General

QWhat is gas?
AGenerally, home use gas such as propane and methane are associated. But "gas" means all the gaseous bodies including odorless gases such as oxygen, hydrogen, carbon dioxide, and smelling gases such as ammonia.
QWhat can gas sensors do?
ASome gases can explode at certain concentration and/or influence the human body. To avoid that, it is necessary to check gas existence or detect the gas concentration. Gas sensors are used as a component for such prevention equipment.
QWhat are gas sensors used for?
ASafety and security: Gas leak alarms, carbon monoxide alarms, various measurement equipment.
Comfort: Air conditioners, air purifiers.
Health: Alcohol checkers, halitosis measuring device.

Fuel cell vehicle (FCV) uses our hydrogen detectors.
QWhat kind of gas can be detected?
QWhat kind of gas sensors exist?
AThere are several types such as semiconductor, hot-wire, electro-chemical, solid electrolyte, and infrared.
QWhat is "noise gases"?
AAll the gases except the target detection gas. Such noise gases may exist in usual ambient air.
QWhat is "gas response"?
AIt is the time for the sensor to respond after the gas reaches the sensor.

Semiconductor Gas Sensor

QWhat is the detection principle of semiconductor gas sensors?
QWhat are strengths and weaknesses of semiconductor gas sensors?
AStrengths: High sensitivity to low concentration gas, low cost, long life.
Weaknesses: Influenced by ambient temperature and humidity, and low selectivity.
QIn what range of concentration can Nissha FIS sensors measure the gas?
AThough it depends on the kind of gas, our gas sensors can measure gas in the range of tens ppb to tens of thousands of ppm.
QWhat is the life of the semiconductor gas sensor?
AThe life is semi-permanent if used under usual ambient atmospheric conditions. The sensitivity may change from a long-term view point.
QWhat is "gas sensitivity"?
AIt is (Rs in clean air)/(Rs in gas), where Rs means Sensor Resistance. Since Rs generally decreases in gas, the gas sensitivity is below 1.
QWhat is "initial action"?
AIt is the sensor behavior from power-on to the ready status.
QCan your gas sensor detect inactive gas such as helium?
AUnfortunately, semiconductor gas sensor cannot detect inactive gases.
QThe humidity has an effect on the sensor. Why?
AAmbient humidity (water vapor) can be considered as a kind of gas.
QCan your gas sensors be used without oxygen?
AOxygen is required. Use the sensor under usual ambient atmosphere.
QWhat is the sensing material?
ABasically, tin oxides. Other materials are tungsten oxides, indium oxides, etc.
QDoes your sensor have intrinsically safe construction?
ANo, you need such construction housing separately.

How to Use Gas Sensor

QCan pins of the sensor be bend or cut?
ADo not bend or cut the pins because the sensor will be mechanically shocked.
QCan the sensor be soldered on the printed circuit board with a soldering bath?
AManual soldering is recommendable to avoid the solder's flux from influencing the sensor.
QThe sensor is warm or hot. Should we cool it down?
AThe sensor should be heated to detect gases. Cooling down with fans, etc. will change the sensitivity.
QIf the specified heater voltage is changed, what will happen?
AThe sensing element temperature will be changed, then the cross sensitivity will also be changed.
QWhat happens if the sensor is exposed to very high concentration gas?
AThe heater may deteriorate so that the sensor temperature cannot be controlled. Avoid it.
QDo you have the cross-sensitivity data?
ARefer to PDF sensor leaflet in "Gas Sensors".