In current technology scenario, monitoring of gases produced is very
important. From home appliances such as air conditioners to electric
chimneys and safety systems at industries monitoring of gases is very
crucial. Gas sensors are very important part of such systems. Small
like a nose, gas sensors spontaneously react to the gas present, thus
keeping the system updated about any alterations that occur in the
concentration of molecules at gaseous state.
Gas sensors are available in wide specifications depending on the
sensitivity levels, type of gas to be sensed, physical dimensions and
numerous other factors. This Insight covers a methane gas sensor that
can sense gases such as ammonia which might get produced from methane.
When a gas interacts with this sensor, it is first ionized into its
constituents and is then adsorbed by the sensing element. This
adsorption creates a potential difference on the element which is
conveyed to the processor unit through output pins in form of current.
What is this sensing element? Is it kept in some chamber or is kept
exposed? How does it get current and how it is taken out? Let’s find out
in this Insight!!!
The gas sensor module consists of a steel exoskeleton under which a
sensing element is housed. This sensing element is subjected to current
through connecting leads. This current is known as heating current
through it, the gases coming close to the sensing element get ionized
and are absorbed by the sensing element. This changes the resistance of
the sensing element which alters the value of the current going out of
it.
Image 01 shows externals of a standard gas sensor module: a steel mesh,
copper clamping ring and connecting leads. The top part is a stainless
steel mesh which takes care of the following:
{C}{C}{C}{C}1. {C}{C}{C}{C}Filtering out the suspended particles so
that only gaseous elements are able to pass to insides of the sensor.
{C}{C}{C}{C}2. {C}{C}{C}{C}Protecting the insides of the sensor.
{C}{C}{C}{C}3. {C}{C}{C}{C}Exhibits an anti explosion network that
keeps the sensor module intact at high temperatures and gas pressures.
In order to manage above listed functions efficiently, the steel mesh is
made into two layers. The mesh is bound to rest of the body via a
copper plated clamping ring.
The connecting leads of the sensor are thick so that sensor can be
connected firmly to the circuit and sufficient amount of heat gets
conducted to the inside part. They are casted from copper and have tin
plating over them. Four of the six leads (A, B, C, D) are for signal
fetching while two (1,2) are used to provide sufficient heat to the
sensing element.
The pins are placed on a Bakelite base which is a good insulator and
provides firm gripping to the connecting leads of the sensor.
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