Wheatstone Bridge

The Wheatstone bridge is a circuit in a sensor used in recording air quality, specifically for combustible gases like carbon monoxide.  This type of sensor is also called a catalytic combustion sensor, and the Wheatstone bridge is the circuit inside the sensor that detects the combustible gases.  So how is the Wheatstone bridge used in air sampling?  Well, these sensors contain a Wheatstone bridge circuit which contains a catalyst that reacts with the combustible gas.  Once the gas reacts with the catalyst in the sensor, there is a noticeable difference in heat.  This changes the electrical resistance inside the sensor on the catalyst.  Once there's a change in the electrical resistance, there is a level in the circuit that is directly proportional to the level of combustible gas present.  So this change in the level of the circuit is measured, which then gives the reading of the level of combustible gas that is present.  It is obviously a lot more complex than this, but that is just a short summary of how a Wheatstone bridge circuit is actually used in air sampling because once the sensors react with a gas, there are readings for the level of gas present.  Also, Wheatstone bridge circuits are used in sensors that record thermal conductivity.  So, what exactly is a Wheatstone bridge? Well, it is a circuit inside a sensor used in measuring combustible gas levels, and also thermal conductivity.  It contains a lot of pipes and valves and meters needed to be used in the detection of a combustible gas in the area being recorded.  Once there is a reaction inside the circuit, levels and signals begin to change in the sensor and this change in the sensor is the level of combustible gas being recorded.  I hope this blog gave you a little more information about what a Wheatstone bridge actually is and how it is used in air sampling.  (Nims, 132-133)

Source- Basics of Industrial Hygiene by Debra K. Nims