Wheatstone Bridge Circuit

Charles Wheatstone was the developer of the Wheatstone Bridge Circuit. This is a circuit designed to measure an unknown resistance or a change in resistance by comparing it to known resistances. There is a catalytic combustion censors used which contains a heated filament that makes up a portion of the Wheatstone Bridge Circuit. “The filament is coated with a catalyst that reacts with a combustible gas and generates heat.” This meaning that the filaments electrical resistance creates an imbalance in the circuit. 

The Wheatstone Bridge Circuit is one of the most precise ways of measuring changes in resistance. There are many reasons one might be sampling air quality. With there being multiple methods of sampling air, knowing what to sample for can ultimately help pick what method to use.  There are many limitations when it comes to sampling air, and many factors that should be taken into consideration. When testing the quality of the air it is important to do multiple testings to come up with the overall average. 

"Air sampling data are often accepted as an indication of the actual level of exposure of the workers and are assumed to be an indication of an absorbed dose." It is important to take into account the different variables that can affect the amount of containment that workers face on a daily basis. Some of these factors are: gender, age, health status, the nature of the work that is being done and the persons breathing rate. Sampling air can be done for a variety of reasons, when sampling it is important to know if what you are sampling for is in any way hazardous. Also, when sampling the air they need to know if workers have been overexposed in any way and if so how to take immediate precaution. Since the Wheatstone Bridge Circuit is such a precise method, it is used well in correlation with measuring the quality of air. "The Wheatstone bridge comprises the detection circuit in many direct reading instruments used for evaluating the presence of combustible gases."

Basics of Industrial Hygiene by Debra Nims