What is the difference between Real Time particle monitoring and Sequential particle monitoring?


Using Real Time particle monitoring involves placing a single cleanroom particle counter or particle sensor at a specific location in your cleanroom. The sensor is committed to monitor particles only at a designated location, where every event is detected and counted. There are no gaps in the particle counting data and particles are monitored in particles per cubic foot or per cubic meter. The Real Time system is well suited for use at critical locations where sensitive processes can be adequately monitored. You can use a stand-alone particle counter that is a dedicated counter with a built-in vacuum pump. Another option is a remote particle counter. This instrument has no display; a process vacuum is provided for sampling or you can use a separate pump dedicated to particle counting.

Sequential Particle Monitoring is also referred to as Pneumatically Multiplexed Particle Counting or a Manifold Monitoring System. This system involves using a single particle counter to monitor multiple points. This can be accomplished by adding a Sequential Manifold Sampler that connects the particle counter to different sampling tubes. Each individual tube is sampled in sequential order; when a tube is sampled, the manifold moves to the next tube to be sampled.

During this tube change, the particle counter stops counting particles until the change is complete, then it delays to allow any air from the prior sample to be purged. A blower continuously pulls air through all the sample tubes, avoiding any “air hammering” that may free particles in the sample tubing from the start and stop of the airflow. The number of monitoring points determines the frequency of each sample. In a typical application, each location is sampled for 60 seconds then purged for 10 seconds as the sampling arm moves to the next location.