Multiplexed Monitoring – To be Doubt or Not?

There are several types of continuous emissions monitoring (CEM) systems. The technical designs may be very different, but they usually have a few things in common. The instruments providing the measurement results do not come cheap, and the systems require maintenance. However, if monitoring is to be done in more than one gas duct, then there might be a way to save costs, multiplexing. But there’s multiplexing, and there’s multiplexing. Let’s have a look at the principles and explain why optical multiplexing is straight-forward while gas multiplexing has its issues.